AUTOMOBILE

NEW SUV FOR MAHINDRA PRICE JUST START FROM Rs. 5.82 - Rs. 7.36 lakhs

2012-09-21T23:11:00.001-07:00

Mahindra Quanto

Promotion video

Mahindra Quanto Overview

Engine	Specifications
	Displacement (cc)	1493
	Technology	1.5 litre 3-cylinder mCR100 Common Rail
	Fuel	Diesel
Brakes	Front	Disc
	Rear	Drum
Tyres	Tyres	Tubeless 205/65R 15
Steering	Power Steering type	Power and tilt steering
	Minimum Turning radius	5.4 metre
Suspension	Front	Independent double wishbone with coil spring suspension anti-roll bar
	Rear	Five bar link and coil springs
Transmission	Type	5-speed 5MT320 Indirect transmission

Mahindra Quanto Overview

Mahindra Quanto is a compact SUV from Mahindra and Mahindra (M&M), which was introduced on September 20, 2012 in the Indian auto industry. Quanto happens to be the first compact vehicle in the company's product portfolio and thus, launch of the model was surrounded by a buzz. In a first look, it can be clearly said that the model resembles Mahindra Xylo to a great extent, which is known as the company's iconic Multi Purpose Vehicle (MPV). M&M is the most reputed Utility Vehicle (UV) maker of the country and is known for meeting up the demands of Indian buyers; evidently seen in its new 2012 Quanto. The compact SUV has derived its name from the word Quantum, which stands for ample space. A thing to notice is that M&M has followed its long term tradition of ending the name of its models with 'O' as all its vehicles like Scorpio, Bolero, XUV500, (pronounced as XUV five double O), Xylo and Genio ends up with an 'O'.

Mahindra Quanto 2012 has been innovatively designed and is built on the Ingenio platform, the same on which its popular Xylo MUV is based. What makes Quanto a 'people’s car' is that it has been designed by taking customer feedback at various stages of the development process. The response from customers helped M&M to give the car a fine tuning and a strong value proposition.

Mahindra Quanto's exteriors are just fine as the model somehow delivers a boxy outlook, while its interiors are quite appealing. The key USP of the model is its mileage, which stands around 13 kmpl in the normal city driving conditions, whereas on highways the vehicle covers a distance of around 17 kmpl. The SUV is powered by a 1493 cc diesel engine, which has the potential to belt out a maximum power of 100 bhp, quite impressive for a compact SUV.

Mahindra Quanto car, despite being a sub-4 metre length vehicle, offers ample space, more power, comfortable seating arrangement and an at par performance. As Quanto has been built on the Mahindra SUV architecture, its compact size provides the model an edge over sedans and stereotypical hatchbacks. Quanto being a compact and versatile SUV, is offered at a competitive price, which has turned fortunes for the company in the Indian auto industry.

Mahindra Quanto Variants

Mahindra Quanto is available in four different variants, namely C2, C4, C6 and C8. C8 happens to be the top-of-the-line variant and thus, comes with a large number of features for comfort, convenience and safety. The company has offered a handful of features in C8 model, including Anti-lock Braking System (ABS), dual SRS airbags, 6-spoke alloy wheels, steering mounted audio controls, Bluetooth connectivity, height adjustable driver's seat, reverse parking sensors, adjustable lumbar support for front row seats and centre armrest for driver as well as co-driver. Interior of all the variants are almost the same and comes packed with similar designs for the centre console, door pads and steering wheel. Also the buttons to control the air conditioner and power windows are similar within all the four variants of Mahindra Quanto in India.

Mahindra Quanto car is diesel powered and all its variants, including the base variant, come laden with a host of features, which makes them a good value for money.

Mahindra Quanto Pricing

Mahindra Quanto comes as a perfect blend of handful of features with an appealing posture at an affordable price. Given the comfort level of the car and the smart designing of interiors, it certainly can not be said that the all new Quanto car is overpriced. The best thing about the compact SUV that entices buyers is its mileage and the economical price.

Mahindra Quanto Review

At a first glance, the 2012 Mahindra Quanto appears a little boxy due to its flat rear side and with its a bit subdued exterior appearance, the car looks just like a perfect little brother to the Xylo MPV. The latest addition to M&M's Indian portfolio seems like a well thought blend of a SUV and a hatchback, while its sub-4 metre length definitely justifies its compact design.

The engine incorporated in the Mahindra Quanto is responsive and belts out a rugged and robust output. The tall riding height and high ground clearance gives the driver of the compact Quanto, the confidence of driving a proper SUV in a shrunk avatar. The five-speed indirect transmission seems to be of similar make, like the one installed in the Xylo and ensures smooth manoeuvring and driving ergonomics. However, the car does have a little body roll due to its tall height and stance, on which the company should have worked more. The new product from the stables of Mahindra delivers good performance and its seating capacity of seven people, completes the overall package as a compact SUV, which entails the Quanto to be a genuine crowd puller in the Indian market.

Mahindra Quanto Specifications

The 2012 Mahindra Quanto holds a 3-cylinder mCR100 Common Rail, Bharat Stage-IV compliant diesel powertrain with a displacement of 1493 cc, under its hood. The power-mill is mated with a 5-speed indirect transmission system and delivers performance in tricky and demanding city traffic situations.

Mahindra Quanto Exteriors

Exterior Appearance

Mahindra Quanto shares a lot of credentials with Xylo MUV; however, it can be said that the overall look of Quanto is superior or proportionate to its elder cousin. Front fascia of the model is aggressively designed, which enables it to create dominance over the Indian roads. In order to provide the model a sporty and stylish look, its rear end has a spare tyre mounted over the boot, which looks classy. The new 2012 Quanto car has been packed with new tail lamps, which are placed over the boot and have a vertical design.

Exterior Dimensions

Mahindra Quanto has a sub-four metre length and therefore, it can be easily driven through the busy city traffic. The exterior dimensions of Mahindra Quanto are mentioned below in a tabular form:

Criteria Dimensions

Length (mm) 3998

Width (mm) 1850

Height (mm) 1895

Seating Capacity 07

Tyre Size 215/75 R15

Fuel Tank Capacity (Litre) 45

Ground Clearance (mm) 186

Mahindra Quanto Interiors

Interior Comfort

The 2012 Mahindra Quanto scores well on its interiors and the Indian UV maker has rigged the models with several standard features like sun visor, courtesy lamp, Heating, Ventilation and Air Conditioning system (HVAC), power steering with tilt function and floor console. The top-end variants like Quanto C6 and C8 have been laced with the sleek Digital Drive Assist System (DDAS), Micro Hybrid technology, and brand new roof console with sunglasses holder. Other catchy interior add-ons include power windows with driver side express up/down with anti-pinch and a remote controlled Central Locking System.

Mahindra Quanto in India also ensures superior driver comfort with the height adjustable driver seat and capacious leg room. The UV maker has also very thoughtfully installed a foldable snack tray, cup holders in the front, mobile charging points in the middle and rear seats along with a useful rear window demister in the top models. An integrated music system is available on the C6 and C8 variants of Quanto, which can play the favourite MP3, WMA and Audio CD tracks of the driver, further ensuring music inspired driving pleasure.

Mahindra Quanto Fuel Economy

Mahindra Quanto is packed with a performance oriented engine under its hood and thus, the model delivers an impressive fuel economy. The compact SUV offers a mileage of around 13 kmpl in city and runs around 17.30 kmpl on highways. As the fuel prices in country are continuously rising, mileage is a big positive point that 2012 Quanto drives home. It is believed that the car's impressive fuel efficiency has lured those buyers who were either looking for a premium hatchback or an entry-level sedan.

Mahindra Quanto Power

Mahindra Quanto has been assimilated with a 1493 cc common rail mCR100 diesel engine, which has the potential to create wonder on-roads. Before its launch, speculations taking rounds stated that the company was planning to incorporate a 2.5 litre engine in Mahindra Quanto car; however the actual model featured a 1.5 litre powertrain. In the trimming process, the auto major reduced the number of cylinders from 4 to 3 and also trimmed down the bore and stroke of the power mill. With these changes, the company came up with a brand new diesel engine, which belts out a maximum power of 100 bhp at 3750 rpm with a peak torque of 240 Nm at a fairly low 1600-2800 rpm. As 2012 Quanto car is much lighter than the fully-grown Mahindra Xylo, the outputs of this compact SUV are more than sufficient.

Mahindra Quanto Performance

The 2012 Mahindra Quanto packs a powerful punch in its 1.5 litre engine and delivers a respectable power-torque performance. The driving ergonomics seems to be compliant with the necessities of daily commuting individuals and the fuel efficiency also works in the Quanto's favour. The car scores good points in the performance regard but leaves the driver asking for more.

Mahindra Quanto Acceleration and Pick-u

Mahindra Quanto provides a decent acceleration and pick-up, in-line with the Mahindra products in the country. The latest Mahindra car is significantly lighter than the Xylo and outruns other vehicles in the city conditions quite easily, which make it an expert choice for the daily commuters who love driving but have to toil in traffic jams on a routine basis.

Mahindra Quanto Safety and Security

Mahindra Quanto car, as anticipated, has been incorporated with state-of-the art safety features, which assures complete safety of its passengers. C6 and C8 variants are packed with Anti-lock Braking System and fog lamps in front, which are not present in the lower two models, while features like child lock on middle and rear door and digital immobiliser are standard in all the four variants. The top-end variant, C8, is exclusively provided with airbags for front row passengers and intelligent reverse assist, whereas rear washer and wiper are provided in all the variants except the base model, C2.

Mahindra Quanto Comfort and Convenience

Mahindra Quanto is a seven seater model, which boasts off a large number of features regarding comfort and convenience requirements of its passengers and driver. The car is being provided with remote fuel filler for added convenience. Air conditioner of Quanto, despite not having climate controller, keeps the passenger unknown from the unfavourable outside weather as it feature heater and ventilator. The driver seat can be manually adjusted, while the option of folding the rear seats is also present. Door mirrors are also available on both the sides of the compact SUV.

Mahindra Quanto Stereo and Accessories

Mahindra Quanto has been designed with a great emphasis on the infotainment section. The compact SUV comes with dashboard integrated music player; something similar to what was offered in the higher variants of Mahindra Xylo. The car has a single CD player system, which is compatible with AUX input and USB support.

Mahindra Quanto Dealers

Mahindra Quanto 2012 is available at all the official dealerships of the company in India. The Indian auto maker has maintained a vast network of dealers across the length and breadth of the country. A brief review of its few dealerships in some of the major regions of the country is mentioned below in a tabular form:

Location	Dealers
Bangalore	· India Garage · SKS Automobiles India Pvt. Ltd. · Sireesh Auto Pvt Ltd
Chennai	· India Garage · MPL Motors Pvt. Ltd. · Rajarajan & Sons
Kolkata	· Mohan Motors Dealers Pvt Ltd. · Royal Motors · Shree Automobiles (P) Ltd.
Mumbai	· Avis Motors Pvt Ltd. · G3 Motors Pvt Ltd · Miracle Motors India Pvt. Ltd. · NBS International Ltd
Delhi	· Bhasin Motors(I) Pvt Ltd · Indraprastha Automobiles Pvt Ltd. · SHRI DURGA AUTOMOBILES · Skyline Automobiles, Sri Durga Automobiles
Hyderabad	· Automotive Manufacturers Ltd.
Pune	· Kundan Motors · Sahyadri Motors Pvt Ltd · Silver Jubilee Motors

Mahindra Quanto Company Quotes

In a statement, the company regarding Quanto's catchy name had said, "(Quanto) derived from the word 'Quantum', the name has an association with the product promise of more space, more power, more seats and superior performance. The Quanto has the tough and rugged DNA of Mahindra SUVs, thus offering a distinctive advantage over hatchbacks and sedans."

Days before the launch of Quanto, Pawan Goenka, President, Automotive, M&M, was quoted as saying, “With the Quanto, Mahindra is aiming to fill a need gap in the Indian automotive market for a versatile and compact SUV. We are confident that with its unique value proposition, the Quanto will carve out a segment for itself in the market. We expect the Quanto to offer an exciting upgrade at a premium to customers who are otherwise looking for premium diesel hatchbacks or entry level diesel sedans.”

Talking about the initial production of Quanto, Goenko said, “Initially, we expect higher orders for the Quanto, but it should stabilize at 1,500-2,000 units per month.”

Speaking on the Quanto, Dr Pawan Goenka, President, Automotive & Farm Equipment Sectors, Mahindra & Mahindra Ltd, “Customer centric Innovation has always been at the heart of any product development at the Mahindra Group. With the Quanto, Mahindra is aiming to fill a need gap in the Indian automotive market for a versatile and compact SUV. We are confident that with its unique value proposition, the Quanto will carve out a segment for itself in the market. The Quantowill cater to the needs of young urban India which enjoys an active lifestyle. We expect the Quanto to offer an exciting upgrade at a premium to customers who are otherwise looking for premium diesel hatchbacks or entry level diesel sedans”

Mahindra Quanto Competitor Analysis

The 2012 Mahindra Quanto has currently only two direct competitors in the market, such as the Renault Duster and Premier Rio. At present, the Renault Duster is the undisputed market leader in the compact SUV segment and has been termed as the French auto maker's flagship product in the country. Mahindra Quanto does not have the bullish and voluptuous exterior appearance of the Duster but carries a gentler pricing along with the much more dependable Mahindra and Mahindra lineage. Besides, the Quanto holds a bigger engine at 1493 cc that churns out peak power-torque output of 100 bhp and 240 Nm, as compared to the 1461 cc engine of Duster, which could manage only 84 bhp of power and 200 Nm torque turnout. The Quanto also outscores the compact SUV Duster in terms of availability of spare parts and components in the country, a fact that is taken as a great concern with the Indian car enthusiasts. Further, the last row seats are installed by the company in case of the Quanto, while there's no such undertaking by the French auto maker and the dealers are paid extra, in order to get the third row seats in Duster compact SUV.

Mahindra Quanto in India also has another direct rival in the guise of Premier Rio compact SUV. The Mahindra product carries higher pricing and accordingly, delivers better engine performance, superior interior attributes and premium electronic add-ons than the Premier Rio. Further, the Rio car failed to inspire the Indian car buyers in luring them towards the Premier showrooms, largely due to its below par build and low quality features. Coming to the engine performance and power-torque output, the Premier Rio fails miserably in comparison and could deliver a meagre 64 bhp power and 152 Nm torque. The 2012 Mahindra Quanto has also been supplied with a bigger fuel tank than its two closest rivals at 55 litres, as against the fuel tanks of capacity 46 litre and 50 litre installed in Premier Rio and Renault Duster.

The 2012 Mahindra Quanto seems more reliable than the Duster and Rio compact SUVs, and considering the aggressive pricing, the car is even capable of snatching the sales away from the hands of major hatchback and entry-level sedan players in the country. Mahindra has already revealed intentions to market its brand new towards the premium hatchback and entry-level sedan buyers in the domestic market, and the Quanto seems more than capable to accomplish that feat.

Mahindra Quanto Pros

Mahindra Quanto car is built with great innovation and thus, the model boasts of appealing looks. The model happens to be a seven seater with a reasonable price, containing magnitude of features. Incorporated with a brand new diesel engine, which delivers impressive fuel economy is the key USP of this compact SUV.

Mahindra Quanto Cons

Mahindra Quanto has been provided with cramped seats in the last row, which is a negative point of the car. Moreover, the overall build quality of the SUV is also not very impressive.

Mahindra Quanto Conclusion

Mahindra Quanto, a seven seater compact SUV, is available at a competitive price, which appears as a tick in the car's favour. The outer looks of the car are fine, while the interiors have a host of comfort facilities. Although the seats in the last row of the car are cramped a bit, the overall comfort level is not bad at this price range. Having disk brakes in front, while drums at the rear end, the safety features have been nicely addressed in the all new 2012 Mahindra Quanto. Powered by a three cylinder mCR100 diesel engine, Quanto's overall performance is quite impressive, which helped the auto maker introduce its new vehicle aggressively. The best feature of the car is its mileage, which stands around 17.30 kmpl on highways, while the city mileage ranges somewhere around 13 kmpl. The ratings delivered by industry experts to Quanto totals at 4 out of 5, which makes it a good option to go for in compact SUV segment.

ENGINE Chapter 12. Performance, Fuel consumption, Noise, Vibration

2012-09-20T00:25:00.003-07:00

ENGINE

Chapter 12.

Performance, Fuel consumption, Noise, Vibration

1. Required Performances

Various performances are required for the engine. Each performance is related with each other in complex manner, so these affect to the performance of the vehicle. Furthermore, as time is going, which performance is more important has been changed. However, the output power is the most important item because the purpose of the engine is developed making a power for the vehicle. Conventionally, to operate engine for more work should need more fuel to be used. Recently, by enhancing the engine efficiency, better fuel efficiency and better output can be acquired.

To develop the combustion efficiency of the engine is concerned to the purification of the exhaust gas. The carbon monoxide and the hydrogen carbon among the three major harmful materials in the exhaust gas may not be exist if the gasoline can be completely combusted, in ideal. The one, the nitrogen oxide is also one of the important problems.

Considering that the engine weight is 10∼15% of whole weigh of the vehicle, another method for acquiring better output and fuel efficiency at the same time is to make engine be compact and light. With the same output, the power of vehicle having lighter engine will be higher. The lighter and compact engine enhances the fuel consumption. Also, to ensure the good steering, the vehicle should be light and the weigh balance is distributed 50:50 at the front and the rear or similarly.

Engine also should have the features to be driven by the driver’s willingness. For example, when the driver presses the accelerator pedal, if the engine output is too high, then it is not so good for the safety. The response, how to act according to the pressed amount of the accelerator pedal, can make a big affect to the drive condition.

As the engine get the driving force by the combustion of the fuel, the noise and vibration can not be avoided. It is important to prevent these noises and vibrations from transmitting to the passenger.

Additionally, as the engine is one mechanical part of the vehicle, how to maintain the engine is also an important factors.

2. What is Output?

The engine is the device converting the heat energy to the force. The basic performance is represented by the three major factors such as the fuel consumption indicating how much gasoline is combusted, the torque indicating how much force is generated thereby, and the power indicating how much work is performed per unit time.

Among them, the fuel consumption is easy to be notified because it is easily detected by measuring used fuel amount. Then, what are the others, the power and the torque?

As we have explained frequently, the working principle of the gasoline engine is that the expansion force by the combustion of the gasoline is converted into the force pressing the piston to rotate the crankshaft.

When ascending up to the inclined road, we press the accelerator pedal to get high power. When running constantly in the even road, we just press the accelerator a little. As connecting to the throttle valve controlling the amount of intake air, the pressed depth of the accelerator pedal directly affects to the open amount of the throttle valve.

The fuel injection amount is decided by the amount of the intake air. When the air is inhaled with little amount by little pressing the pedal, the gasoline injection amount will be small. When the air amount is large by pressing deeply, then the fuel injection amount will be increased.

That is, the ratio between the air amount and the fuel amount is already preset, so the accelerator pedal controls only the inhale air amount. So, pressing the pedal little, the mixture amount is small and the power of engine, while pressing the pedal more, the power of engine will be increased because the mixture amount is increased.

Generally, the engine performance is decided by the engine force. The force is represented in unit of kg. In the vehicle, as the ultimate force is the rotating force driving the wheel, it is prefer to represent in unit of torque, i.e. kg·m, acquired by multiple the magnitude of force with the distance between the center of rotate to the force applying point.

In another aspect of engine performance, how much work is possible within certain time period is also important. This work amount is the power represented by horse power.

3. Representing Method for Power

Generally, the most important element of the engine performance is the output (power). When a new engine is installed, some one says “What horse power has it?” This horse power is the work efficiency, that is, the unit indicating the work amount during specific time period, so called the dynamic output (power).

This concept was suggested by the James Watts who invented the steam engine in England. To compare the dynamic performances of the some kinds of the steam engines, as the horse power used for water pumping works in the coal mine, the one horse power is 550 ft·lbf/s. Converting into the metric system, it will be 75 kg·m/s. This is the power for pulling up the 75kg weight per 1m in one second.

For the unit of the Horsepower, it will be represented HP in abbreviation, or the PS Pferdestarke from Germany. The PS is more usually used. In SI unit system, representing with W (watt), 1 PS is about 735.4W. So, 100PS is 73.5kW, 100kW is 136PS.

In the vehicle catalogue, we can see additional word such as (Net) or (Gross) in front of the unit of PS/rpm. As the engine output is generally measured with being set the engine to the measuring equipment, the measured output is changed according to the measuring condition, and there is dispersion in measured values. Therefore, to indicate the output, Net value and Gross value are used. The Gross value is measured value with engine only, and the Net value is measured value with being set the engine to the vehicle. For the gasoline engine, the Net value is 15% less than the Gross value. If there is no notice, the larger value is the Gross one.

The power is the function of the time. The engine power will be increased proportional to the rpm because the work amount per time is increased when the rpm is higher. However, when the engine rpm is increasing, the dynamic parts can not run over the certain value, or the engine can not intake or exhaust faster than limit, or the engine power is excessively wasted for driving engine itself if the rpm is over than certain rpm. That is the engine power has certain limit value. This is the maximum power output. In catalogue, it is indicated with the rpm thereat.

4. What is Torque?

The torque or the twisting force which is applied to a rotational matter such as bolt, axis rod and wheel. It depends not only on the applied force but also on the length of the lever arm upon which the force acts. By definition, torque is equal to force multiplied by the leverage; the length from the center of the rotor to the point which a force is applied.

In engine, the torque is equal to force of which the piston going down force multiplied by the distance from the center of crank pin to the center of crankshaft.

So, the magnitude of the torque of certain engine is decided by the force of which the piston presses the Connecting rod, that is, the combustion force. The performance graph of torque is representing that which piston is pressing the crankshaft with how much force when the engine is rotating at what rpm. As this force will be transmitted to the wheel finally, the impulsive force of the vehicle is small if the engine torque is small, the impulsive force of the vehicle is high if the engine torque is high.

The expansion (exploded) force is determined by many elements, especially, by the amount of the inhaled air into the cylinder. With plentiful of air, it is possible to get high power. Considering the relationship between the inhaled air amount and the rpm of engine, when the engine has low speed of rotation, the movement of piston is also slow and inhaled air amount is low. When the engine has high speed of rotation, the movement of the piston is fast and the inhaled air amount is high. However, if the engine has too high speed, then the intake valve may close before the air is not fully inhaled into the cylinder yet. In this case, the inhaled air amountper stroke (volumetric efficiency) is decreased. Therefore, the engine torque curve has the peak shape.

For example, compare the engine torque between the 2500rpm pick engine and the 5000rpm pick engine. The former engine has the best performance at the 2500rpm but not so good performance at the 5000rpm.

On the contrary, the 5000rpm pick engine has a good performance at high speed but it has low performance at low speed. So, the engine characteristics are different between above engines even though the maximum torques are same.

5. To enhance Power

The engine power is a working amount during a specific time. The engine power can be increased as high as the cylinder volume high, the combustion force high and the rpm high.

The engine size is represented by the displacement volume. The cylinder displacement volume is the exhausted gas amount from certain cylinder during the piston moves from the BDC to TDC. The total displacement volume is the sum of volume of all cylinders. The cylinder displacement volume is calculated from multiple the cross sectional area by the stroke of the cylinder. It is represented by unit of cc or ℓ.

When the total displacement volume is bigger, the engine output will be also higher. To compare the engine performance, the PS/ℓ is used. The PS/ℓ means that how much horsepower is generated per 1ℓ of displacement volume. For the passenger car, generally, the more cylinder has higher value of PS/ℓ because volumetric efficiency is higher with multiple cylinder. But the demerit of multiple cylinder is the much complicated structure and the high cost.

The pressing force at the piston is calculated by deviding a work amount per cycle by the displacement volume. By this calculation, the pressing force at the piston is the pressure. But the pressure at the piston is continuously changed by the position of piston and the stroke. So, the the mean pressure per cycle is used for a calculation. This is called as the mean effective pressure, the average pressure in the cylinder.

To enhance the engine power, the main three elements including the total displacement volume, the mean effective pressure, and the rpm should be enhanced. The work per certain time shall be increased by enhancing the rpm. Deciding the total displacement volume of the engine, how the mean effective pressure is increased and how the limitation of the rpm is overcomed are the major focusing point for a developing of an engine to enhance the engine power.

6. S/B Ratio & Output

The displacement volume of cylinder is calculated by the cross sectional area of cylinder and the stroke. Also the cross sectional area is calculated by the daimeter of cylinder (Bore). So, the main factors of displacement are the Bore and the Stroke. The bore and the stroke may differ from each engine even though the same number of cylinder and the same cylinder displacement. That is, some engine have the thin and long cylinder, other engines have the fat and short cylinder. The ratio between the length of stroke and diameter of bore is called Stroke/Bore ratio.

For the passenger car, the Stroke/Bore (S/B) ratio is about 0.7∼1.3. The S/B ratio is less than 1, the stroke is smaller than the bore, it is called Short Stroke. The S/B ratio is higher than 1, the stroke is larger than bore, it is called Long Stroke. The S/B ratio is just 1, the stroke is equal to the bore diameter, it is called Square.

With the same displacement volume, the Short Stroke engine has more potential to have higher power because larger bore engine can make a larger valve diameter and can make a high engine rpm without increasing the piston speed.

First of all, consider about the bore. The gas amount will be larger as the valve diameter or the Valve Lift is larger. With larger gas amount, it is possible to get higher output because more gasoline will be combusted. Additionally, if the valve diameter will be larger, for the same gas amount, the valve lift can be made smaller. So the valve movement will be small at the high speed. However, the larger valve diameter has larger diameter of inteke port, the large intake port engine can not make the fast flow of intake gas at low speed so combustion may be degrade.

Next, considering about the piston speed. With the same rpm of engine, the piston in long stroke should be move as fast as the stroke length. The piston speed has a limitation. When the piston moves in high speed, the lubricant oil may not be properly worked, or the piston inertia force will be too high. The rpm of short stroke engine can be more increased than the long stroke engine, if the engines has same limitation of piston speed. Recently, the limite of the average piston speed is about 15∼22m per second.

In general, the engine for high speed and output such as sports car shall accept Short Stroke or Square type S/B ratio, the engine for commercial car accepts the Long Stroke to increase the torque instead of speed.

7. Compression Ratio & Output

In the previous section, the power can be enhanced by increasing the intake air and increasing the engine rpm. Also there is one more method to increase the engine power. That is the compression ratio.

When the piston is at the TDC, the space which is surrounded by the piston and the cylinder head including the intake-exhaust vlaves is the combustion chamber. The compression ratio is that the cylinder volume is devided by compression chamber volume. The cylinder volume is the total volume of compression chamber volume and the displacement of cylinder.

The compression ratio represents how much the intake mixture is compressed. The compression ratio in the vehicle catalogue is a theoretical value by a calculation. In general, it is about 9 ∼ 10 for normal gasoline engine and about 12 ∼ 13 and for racing engine.

As the compression ratio is high, the mixture is compresses strongly. So the mixture temperature will be high and the combustion will be performed in short time. Then the combustion pressure will be high and the torque and power will also be high. Furthermore, in the combustion stroke, the expansion ratio is also high, so the exhaust gas has not too high temperature. So the fuel efficiency will be good.

However, if the compression ratio is too high, the engine can easily have abnormal combustion such as knocking. So it has limitation. Knocking is related with mixture temperature, flow, chamber wall temperature as well as the compression ratio. So, to increase the compression ratio should be followed by the good cooling system for the cylinder head. Furthermore, the engine should have higher strength for high compression ratio. The high performance engine should be carefully designed.

There are theoretical compression ratio and the actual compression ratio. The actual compression ratio indicates how much the intake air is compressed actually. For example, in the intake stroke, if the air is not inhaled sufficiently, then the actual compression ratio is less than theoretical ratio. In the turbo engine, if the boost pressure is 1atm, then the actual compression ratio will be twice. So, the actual compression ratio is the important factors for the enhancing the power. In above, the knocking is affected by the actual compression ratio.

8. Increasing power by High rpm (rpm limit)

To make a high power engine, the fuel amount of combustion is increased. Even the fuel amount is increased, if the air amount is not increased, then it is no meaning. Therefore, to make a high power engine, the intake air amount be more.

The air flow speed at the intake port is divided the intake air quantity by the cross sectional area. The intake air amount will be increased by the increasing of the engine rpm. So, the engine output is proportion to the rpm.

The flow resistance of the air will be increased as the air flow is fast. By enlarging the duct or volume of air cleaner, the flow resistance can be reduced. However, the resistance around the valve is not controlled. So, over the certain rpm, the power can not be increased any more. Therefore, to get high output at the high speed, the intake air speed should be decreased at the high speed. To do so, there are some methods to be considered.

⑴ Increase the number of cylinder: with the same total displacement volume, if the cylinder number is increased, then the cylinder diameter will be reduced and then valve diameter will do so. Therefore, the intake flow velocity will be reduced.

⑵ Increase the number of intake valve: with the same reason mentioned in ⑴, the air flow velocity will be reduced around the intake valve.

⑶ Enlarge the lift of intake valve and elongate the opening time: The opening time of intake valve is about 240° in terms of crankshaft rotation angle. In the racing engine, it is about 280∼320°.

⑷ Design the SHORT STROKE: with the same displacement volume, the SHORT STROKE is to make the valve be enlarged. So, the opening area is also large and then the intake air speed will be slow.

If the intake air speed is sufficiently slow, the engine rpm can be increased more to make more power.

If the engine rpm is increased, the engine should endure against the high rpm. That is, the engine should be strengthening to ensure the high rpm. Generally, the engine should be lightened to reduce the inertia force, and enhanced the strength of the body and parts of engine.

9. Transient Characteristic & Response

The engine makes large torque but acceleration response is slow, the engine is not a high performance engine. The acceleration performance or the response of the engine can be affected by the weight of the car or gear ratio.

When the driving condition is changed, the intermediate state between before and after is called transient or partial state. The engine characteristic at partial state is called the transient characteristic of the engine. The transient characteristic is basically related with the changing of the rpm and the inertia force. The important things for the response are the weight of the dynamic parts of the engine and the changing ability of the air/fuel while acceleration.

To reduce the inertia force of the dynamic parts of the engine, the dynamic parts should be made as light as possible.

In the fuel injection type engine, an intake collector (surge tank) has a similar volume with the total displacement volume. When the accelerator is pressed to open the throttle valve, the air can not be inhaled into the manifold immediately because of the inertia force of the air.

Therefore, the first movement of the engine torque will be delay. To solve this problem, if the volume of the collector (surge tank) is increased, then the engine output shall be increased.

In some fuel system, the gasoline may not be flown smoothly because the gasoline sprayed from the injector. In this case, when the throttle valve is open quickly, the mixture is leaned and then the initial torque of the engine may be delayed. To solve this problem, there is a method in which the injection amount is selectively increased at that moment.

10. Cylinder Array & Performance

There are three method for arraying the cylinders, in-line type, V-type, and opposed type. What relationship is there between the cylinder array and the engine performance?

The in-line type engine has the cylinder in sequentially arrayed. There are from 2-cylinder type to 6-cylinder type. In the in-line type, the structure of the cylinder block is very simple and the cylinder head is one body, so the engine shall be light and compact. It is used widely from commercial car to racing car.

In the in-line type engine, generally, the cylinder number is 4 when the displacement volume is up to 2ℓ. The cylinder number is 6 more than 2ℓ less than 3.5ℓ. The 4-cylinder engine having the displacement volume of from 1ℓto 1.5ℓ is used for commercial vehicle, and one having more and up to 2ℓ is used for high performance purposed car. Engine for the displacement volume of 2ℓ is generally made into 4-cylinder or 6-cylinder. The 6-cylinder engine has smaller combustion chamber and is easy to be made with SHORT STROKE. So it can be get large maximum output.

The in-line 6-cylinder engine has the long length so it needs somewhat high cost. But, the size is compact in compare with the performance, and the turbocharger can be easily attached. So it can be utilized in high performance engine. Additionally, the inertia force of the piston-crank is well balanced so it shows good features at the anti-vibration. However, it is hard to install widely in the engine room of FF type vehicle; so generally, it is installed at the FR type vehicle in longitudinal direction. The 3-cylinder or 5-cylinder is rarely used in the in-line type.

By dividing 6-cylinder into two set of serial 3-cylinder and facing them to array in parallel, the length is reduced almost half of the in-line 6-cylinder engine is the V-Type 6-cylinder engine. As this engine has the high intake-exhaust efficiency because the bore diameter can be enlarged easily, it is easy to get high power.

If the angle of V array is set to 60°, the feature is closed to the serial 6-cylinder engine. It can be installed at the FF type vehicle. So it is possible for the FF car to be developed into high performance car.

The V-type engine generally consists of 6-cylinder. By combining the serial 4-cylinder and the serial 6-cylinder, the V8 and the V12 engines can be manufactured respectively. They are generally installed at the large vehicle or sports car. The V6 engine is not easy to be utilized because the width of the engine is wider and weight is heavier.

The opposed engine is the same with the V-type engine having the 180° of the angle. The center of engine will be lower than others.

11. Fuel Consumption Ratio

The fuel efficiency of the engine is represented by the fuel consumption rate. The fuel consumption amount for the driving is changed by the driving condition. When the dynamic performance is measured by attaching to the dynamometer to compare with other engine, the consumption amount of the fuel should be considered.

Therefore, the fuel consumption rate is represented by fuel consumption amount per work, and the unit is g/PS·h. Assume that when a engine is rotating with 3000rpm at the dynamometer, the engine outputs 55PS, and 11kg gasoline is used for 1 hour working in this condition, then the fuel consumption rate is 220g/PS·h.

When referring to the graph of fuel consumption rate in the engine performance curve, that the fuel consumption rate is minimized with certain rpm of engine is more concerned than the fuel amount. The actual fuel consumption rate shall be measured in actual driving condition at the vehicle.

Generally to say, the catalogue indicates the fuel consumption rate with the 10-15 mode rate and the 60km/h steady rate. On here, the rate is just concerned to the engine itself.

To reduce the fuel consumption rate, the fuel is used less as possible and the heat should be thoroughly converted into the dynamic force. So, it is related with the heat efficiency. For example, the mixture should be combusted with high temperature and high pressure, completely and fast as possible. And the heat loss to the exhaust gas and to the cylinder wall should be reduced as possible. As well as the mechanical friction should be reduced also.

To calculate how the engine uses the heat from the gasoline in classifying according to the element is the heat balance.

To indicate this heat balance with the graph is the heat balance graph. Generally to say about the heat balance of the gasoline engine. The heat for output, the heat for loss in exhaust gas and the heat for loss through the cylinder wall are 30% separately, and 10% is for others. Until now, the most heat efficiency of the engine is about 35%, that is, in the term of fuel consumption rate, about 170g/PS·h.

12. Output & Fuel Efficiency

As the air amount is increased to enhance the engine output, the fuel amount will be increased, so the fuel efficiency is degraded. However, if the mixture can be completely combusted to increase the heat efficiency and to get higher output, then the high fuel efficiency as well as the high output will be acquired. Additionally, the exhaust gas has less harmful elements.

The engine heat efficiency is the ratio of the heat capacity used for working. To increase the heat efficiency, the expansion of the gas should be as large as possible, at the same time; the loss energy should be as small as possible. The loss energies in the engine are the cooling loss by cooling system, the exhaust loss by being taken out with the hot exhaust gas, and the intake-exhaust loss (pumping loss) used for intake-exhaust operation.

To increase the heat efficiency by increasing the expansion force of the combusted gas is related with to increase the mixture amount and to increase the compression ratio.

To reduce the cooling loss, the temperature of the combustion chamber should be increased. By changing the shape of combustion chamber to enhance the compression ratio, the chamber temperature will be increased at the compression stroke as well as the knocking is prevented. In other hand, the method using the higher cooling water is also concerned.

To reduce the intake-exhaust loss (pumping loss), The intake-exhaust tube should be short and have less bent portion as possible.

To enhance the air flow at the valve, the diameter of the valve may be enlarged or the number of valve may be increased. However, in that case, if the mixture flow is too slow, or if the structure of the chamber is too complicated, then the heat efficiency will be degraded. Therefore, it should be carefully designed.

One more, to enhance the heat efficiency, it should be considered that the friction loss generated when the piston moves. The mechanical energy loss in driving the auxiliary equipments should be reduced.

13. Fuel Efficiency of Vehicle

Even though the fuel consumption rate indicates the engine fuel efficiency, this value is not the exact fuel efficiency of vehicle. With the same engine, the fuel efficiency may differ according that it is installed at heavy and large vehicle or it is installed at light and small vehicle.

Comparing one case that a vehicle includes a small engine having good fuel efficiency and another case that a vehicle includes a large engine having bad fuel efficiency but high power, the actual fuel efficiency will be changed by the driving condition. For example, if a car is usually used in the low rpm condition, then the small displacement volume is more effective. If the car is usually used in high speed or high power condition, then the large displacement volume engine will be more effective.

For the comparing of the fuel efficiency between engines, the specific test mode is required. The specific test mode means that the test method and test conditions are specified. There are many test mode which should be suggested in catalogue, the 10-15 mode running fuel consumption, the 60km/h steady fuel consumption, FTP 75 mode and so on.

In representing the fuel consumption rate, for engine only, the unit of g/PS-h is used, the unit of km/ℓ indicating for vehicle what km the car can run with 1ℓ of fuel is used.

The 10-15 mode fuel efficiency is acquired from dividing the running distance by the amount of the used fuel, the vehicle is tested at the dynamometer according to the predetermined pattern cycle of idling → start acceleration → running with constant speed → deceleration. In the past, the driving pattern had the maximum speed of 40km/h, however, it was not proper to the modern trafic condition. Recently, the maximum speed sets to 70km/h, the 15 mode is added to this test.

The 60km/h steady fuel efficiency is acquired from the used fuel amount when a car is driving with constant speed of 60km/h with the gross weight having full passengers and baggage at the paved plain road without wind. Generally, this value is measured in the ideal state by the manufacturer to suggest to government. The actual value is less than this value.

14. Vibration of Engine

There are many sources to make vibration in engine. There are major three vibrations, one is from the combustion of the engine, one another is from the inertia force of the reciprocal and rotational movement at the dynamic system such as piston, connecting rod, crankshaft, and others.

The vibration from the engine is as much as high pressure of the combustion. And, the engine having high compression ratio and high performance makes more noise. The vibration of the turbo engine makes 20~50% more noise than NA engine. In this case, some devices for preventing from noise are used and the auxiliary devices are attached at the portions less affected by vibration.

Additionally, by changing the engine mounting position or adopting the vibration absorber with the mounting portions, the vibration can not be transmitted to the body directly.

The inertia force is one major source of the vibration. As the piston moves from the highest point to the lowest point with various accelerations. The crankshaft makes a vibration waves and an inertia force from the rotation of the crank pin. The Connecting rod makes an inertia force from the combination of the reciprocal and rotational movement. In the multi cylinder engine, the pistons are connected to the crankshaft, so each inertia will be canceled each other. It is very complicated with the number of cylinders, array of them and each timing of combustion. Therefore, using the counter weight, the inertia force is balanced with the total weight. To match the balance of the inertia force completely is very difficult.

The inertia force is less when the dynamic parts such as piston and Connecting rod have lighter weight. With the same displacement volume, the engine having more number of cylinders has less inertia force because the parts are small and light. When the inertia force is small, the possibility to make a vibration will be few and it will rotate at high speed with the same strength.

By lightening the weight of dynamic part, the inertia force at each part will be small. With the same rpm, the strength of these parts will not be maintained highly. Generally, the device having lower strength is lighter than the device having higher strength. To be lightening is most important point to increase performance as well as to prevent vibration.

15. Noise of Engine

The noises from the engine are the combustion noise and mechanical sounds. The mechanical sounds is caused by the friction between the parts. When the engine rotates with high speed, the noise will be changed and be louder. When a driver changes the shift to up or down, generally, the driver may selects the proper gear by engine noise. So, the sound of engine helps the driver for the driving. Therefore, the engine sound should be noticed but it shall not the noise but the sound.

The mechanical noise is made from the vibration of the cylinder and cylinder head by the combustion force. When the mixture amount is increased or the combustion pressure is higher, then the noise will be louder. Someone may feel that the turbo engine make less noise than the NA engine. The reasons are the turbine absorbs the exhaust energy and the variation of the combustion pressure is smaller.

The mechanical sounds comes from the friction and bump the dynamic parts such as gear, chain, and valves. For example, the cam hits the valve lifter, rocker arm and camshaft hits the valves, the valve bumps with the valve seat and so on.

The resonance noise from the vibration is louder than the direct mechanicla noise. So, the causes of the noise from the engine can not be exactly found. Any way, that there is a noise is not good situation because some parts of the engine shall be hit with others and this is bad for the endurance of parts. If you detect abnormal noise, please check the system as soon as possible.

Comparing the combustion noise with the mechanical noise, at the low speed, the combustion noise is larger. When the rpm is over 3000rpm, the inertial force is larger and the mechanical noise will be larger.

The noise from the engine room will be protected by attaching absorbing materials under the hood and in front of the dashboard, the boundary of the engine room and cabin. The noise absorbing materials are glass wool, felt and so on.

ENGINE Chapter 11 Combustion and Combustion Chamber

2012-09-20T00:20:00.002-07:00

ENGINE

Chapter 11.

Combustion and Combustion Chamber

1. Combustion Process

To get high output and to enhance the fuel efficiency, it is necessary to combust the mixture of fuel and air perfectly as soon as possible while the combustion process. Therefore, to enhance the engine performance is to learn the relationship with the combustion and to study how to increase the fuel efficiency.

The mixture of fuel and air by the carburetor and injector is, at first, inhaled into the cylinder through the intake valve with the swirling flow. And then it is compressed with the swirl flow by the piston going up from the BDC (botton dead center). At this time, the fog state fuel is converted into a vapor state by the heat from the chamber wall and adiabatic compression, and the strong flow of the mixture. Some components may change to the flammable gas.

When a flame is applied to the gas with high temperature, then a flame kernel is made between the electrodes of the plug. This flame kernel is a combusting gas unit having high temperature made from the reaction the fuel gas and the oxygen in the air.

This combusting gas unit immediately heats the mixture there-around. The more mixture surrounding the kernel reacts with more oxygen by this heat and then converts into larger combusting gas unit. Within a short time, this sequence is widely spread so the whole mixture is converted into the combusting gas. This is the combusting process of the mixture.

As the time for being the spark is only about 2/1000 seconds (2 milli seconds: ms), if the temperature around the flame kernel is low or the kernel is blown out by the swirl of the mixture, then the mixture can not be combusted. This phenomenon is called the misfire.

In the process of the combustion, the boundary between the combusting gas and the combusted gas is called the flame surface. The expansion velocity of the flame surface is the flame velocity. The flame velocity is the same mixing the combustion velocity which is the speed of flame developing with statistic fuel gas, the expansion velocity which is the speed of gas expansion by the combusting heat, and the velocity of the gas flow.

The combustion velocity is changed by the component of the fuel and air-fuel ratio which is the weight ratio between the fuel and air. However, it is very slow, i.e. several cm per second, As adding the gas expansion velocity and flow velocity to the combustion velocity, the flame velocity is about 15∼20m per second, even it can be 30m per second. Therefore, the flow of mixture is very important.

2. Air-fuel ratio and Flame Velocity

To enhance the engine performance, the flame velocity should be fast and the amount heat energy which will be converted into the kinetic energy should be as large as possible.

The flame velocity is decided by the three main elements including the combustion velocity, the gas expansion velocity, and the mixture flow velocity. To combust the mixture fast, these elements should be maintained in the best condition.

Considering the combustion velocity and gas expansion velocity, the flame velocity is decided by the mixture ratio which is the ratio between the fuel and air and the temperature and the pressure of the mixture. The temperature and the pressure are decided by the temperature of chamber and compression ratio. To consider the temperature and pressure is very complicated, so here, we assume these conditions are constant. We focus on the fuel component and the mixing ratio.

The gasoline is a liquid consisting of 4∼12 carbon atom in chain link and various molecules including hydrogen atom. If the component ratio is changed or a material is added to accelerate the combustion, then the combustion velocity and the gas expansion velocity shall be faster.

The mixing ratio is a number representing the ratio of fuel amount and the air amount. It can affect to the combustion velocity. So it can be represented by the three indicating number such as the air-fuel ratio (or A/F ratio), the excess air ratio, and the equivalency ratio.

The air-fuel ratio is the value calculated by which weight of air included into the mixture is divided by the weight of fuel included into the mixture. It is called the AIR/FUEL RATIO, or A/F ratio. When the air and fuel are mixed, the A/F ratio for complete combustion theoretically is called the theoretic A/F ratio. The theoretic A/F ratio of the regular gasoline is about 14.7.

If the actual A/F ratio is less than the theoretic A/F ratio, then the amount of the gasoline is more than the theoretic A/F ratio so it is indicated as 『RICH』, otherwise, as 『LEAN』.

For the mixture is combusted in the best condition and for the flame velocity is fastest, the A/F ratio is little smaller than the theoretic A/F ratio, that is 13.5∼14. This means that when the fuel is little more than air, the combustion is better. The combustion velocity has the maximum value at the A/F ratio of 12∼13, with more gasoline amount.

Therefore, the engine power output will be maximum at the A/F ratio of 12∼13. Otherwise, the output will be reduced. In the aspect of fuel consumption ratio, the consumption ratio will be minimum value about the A/F ratio of 16, that is, little lean state has the best fuel efficiency. After combusted, if any oxygen is not remained, then the gasoline is not completely combusted.

3. Ignition Timing

The ignition timing is when the compressed mixture is fired, that is the timing for making a electrical flame at the spark plug. Generally, it can be thought when the mixture is fully compressed and the piston reaches at the TDC (top dead center) is the best timing for the ignition. However, it is too late. The reason is that the combustion velocity of the mixture is changed by the gas flow velocity. As the engine speed is increased, the gas flow will be faster and faster. Therefore, the flame velocity will be faster. So, to ignite when the piston is at the highest point is too late. The best timing is when the piston is almost at the highest point that is, when the area of flame surface is almost half of the combustion chamber.

The ignition timing is represented by the rotation angle of the crankshaft about the TDC of the piston. In terms of the angle, if the ignition timing is set to 40∼30° before the TDC, then the combustion chamber has the maximum pressure at the 15∼20° after the TDC.

If the ignition timing is too early performed, then the combustion is occurred before the piston reaches at the highest point. In this case, the combustion force will press the up rising piston, so the force will be reduced. If the ignition timing is too late, then combustion force will press the downing piston. So the combustion force will not be work effectively.

As the flame velocity is as fast as the engine speed, the ignition timing should be corresponded with the engine speed in order to maximize the pressure of combustion chamber at the TDC of the piston. This operation is to advance the angle of the ignition in considering of the crankshaft rotating angle, so it is called the advance angle.

In the system for performing the advance angle, there are the mechanical type and the electrical type. The mechanical advance angel device is assembled between the distributors applying currents to the spark plug. By detecting the engine speed mechanically, the timing for applying current is controlled according to the engine speed to advance the ignition timing of the spark plug. For example, in the vacuum advance angle device, the advance angle is performed by the operation proportional to the negative pressure of the device connected to the carburetor with pipe using the phenomenon in which the negative pressure in the intake port is increased according to the engine speed.

The electrical advance angle device is that the engine speed and the negative pressure are detected by the sensor, and the best ignition timing is decided by the computer.

4. Swirl Effect

As the flame velocity is fast, more heat energy can be converted into the kinetic energy. Ideally, the mixture should be exploded when the piston just passes the highest point to transmit the expansion force of the combusted gas to the piston most effectively. For full combustion, in terms of crankshaft rotation angle, the time of 40∼60° rotation should be needed. So, the actual situation differs from the ideal situation.

To ensure the fast combusting, the gasoline should be mixed with air well to be enable to perform the chemical react between hydrogen carbon and oxygen.

To do so, the gasoline particle from the injector should be tiny and easy to be vaporized as possible. And the injector orifice should face to the intake valve in order not to adhere the gasoline particles to the intake port wall. For some racing engines, two injectors may be attached at each cylinder.

Additionally, in order to be make the flame velocity be fast, the flow velocity of gas should be faster. When the engine is rotating in slow speed, the flow velocity of the mixture is very important element. When the engine is rotating in high speed, the flow of mixture is high, so the mixing is well and the flame velocity is enough fast. However, when the engine speed starts to be decelerated, the piston downing speed is low, so the mixture flow velocity is lowered and the gasoline fog within the mixture can not be easily vaporized.

Therefore, some researches and developments for direction of intake port, for reducing the size of intake port and for using two intake ports in which one intake port is closed to flow in whirl when the engine works in low speed, to mix the fuel with air enough. The flow of whirl is divided into the swirl of which direction is in horizontal and the tumble of which direction is vertical.

The important thing in the swirl is that the swirl generated at the intake stroke should be remained even should be much stronger in the ignition-combustion stroke.

Swirl Tumble

To do so, one method is that a little gap called squish area is made between the most far position from the plug and the end portion of the piston crown, to blow the mixture by squish area when the piston is near the highest point.

5. Knocking

Even it is rarely occurred in nowadays, the engine makes a noise when the car is accelerated in high load condition.

This is the typical knocking. This comes from that the combustion is not started from the flame kernel of the spark plug and expansion of the flame surface, but from the early combusting of the mixture in the end zone which will be combusted at last.

As the flame surface is a boundary, inside of the surface is filled with the combusted gas and outside of the surface is filled with un-burn gas. That is the combustion is spreading from the flame surface. Before this flame surface is not reached, the un-burn gas is self combusted by the pressure of the gas expansion. This gas with the high pressure and high temperature knocks the cylinder head and piston, so the engine has harmful damages. The knocking is occurred at once, then the piston and cylinder have the abnormally high temperature, so the sequential knockings can be easily following.

Because that the knocking is generated at the end zone of the combusting chamber, the bore will be enlarged by the SHORT STROKE and it is easily generated in the engine having longer flame spread distance. Therefore, the modern engine is equipped with the spark plug, especially the center plug, at the center of the chamber or with a squish area enhancing the mixture flow by making the end zone be narrower.

Nowadays most car doesn’t make any knocking during driving. The engine is developed to prevent from knocking.

On the other hand, there is a research for enhancing the engine performance using the knocking. The knocking, as the firstly concerned, is occurred at the low engine speed in which the combustion of mixture is lag behind of the abnormal combustion. Generally, it is occurred at the ignition timing is advanced when the compression ratio is increase or the flame velocity is high. Therefore, by detecting the knocking, if the engine is run with maximum advance of ignition timing, the best combusting condition can be made.

6. Abnormal Combustion

The all combustion contrary with the normal combustion in which the combustion starts from the spark plug and spread over all chamber are called abnormal combustions. The knocking is the representative example. There are also other types of abnormal combustions.

⑴ PRE-IGNITION & POST-IGNITION

As the PRE is “before” and the POST is “After”, these ignition means that the mixture can be combusted by the other flame before or after the normal ignition is occurred. The PRE-IGNITION is occurred at the compression stroke by any reason sush as remaining at the carbon slug attached at the plug, chamber wall, piston or valves. The POST-IGNITION is that the mixtures not combusted at the normal flame period by misfire, un-burned gas is combusted at the combustion stroke. Both of them are very similar with the knocking, so they can make a great affects at the parts around the chamber.

⑵ RUN ON

As being also called as dieseling, this is the phenomenon that the engine is still working even the ignition switch is off. Very similar with the PRE-IGNITION, the carbon slug works as a flame seed. This is generally occurred when the key is off with the overheated carburetor engine. This is named from that the diesel engine combusts without ignition.

⑶ AFTER FIRE

This is also called as the AFTER BURN. This is that the incompletely combusted gas is exploded at the exhaust system with a big combustion sound. When the accelerator is turn to open or close abruptly, the exceeded gasoline is exhausted into the chamber and then the incompletely combusted mixture is exploded at the catalyst converter or at the muffler. This can make damage to the exhaust system.

⑷ BACK FIRE

In the state that the almost of the combusted gas is taken out at the exhaust stroke, there are some amount of remained gas. The remained gas with high temperature make a ignition the air/fuel mixture at the beginning of intake stroke. In some cases, the fire can reach back to the air cleaner. This is mainly occurred at the carburetor system.

These abnormal combustion is not often occurred in normal driving situations, however, be careful to maintain the engine.

7. Shape of Combustion Chamber

According to the combustion method, the engine performance shall differ. Then, which shape of the combustion chamber is the best for engine performance.

It may be true that the faster flame velocity is the better in order to increase the engine output. With the same gasoline and A/F ratio, we can consider the following five items for the engine power.

⑴ The amount of the inhaled mixture shall be plentiful (More fuel, more heat)

⑵ The flow just before the ignition shall be proper.

(The faster is the better, however, too fast makes a misfire)

⑶ The ignition plug should be installed at the center of the combustion chamber (to ensure fast combustion of mixture)

⑷ The compression ratio should be as high as possible (With high compression, heat efficiency is good)

⑸ Combustion chamber should be compact size to prevent heat from losing.

(to ensure the heat energy converted into kinematic energy)

First of all, concerning the inhalation amount of mixture in ⑴, this is decided by the attaching angle, number, size, lift and shape of the intake valve. It is explained in the intake-exhaust valve section in detail.

In the mixture flow in ⑵, here, how the mixture is taken into the cylinder is the most important point. Even the mixture flow is well, if the shape of valve inside and piston crown are complicated, then the gas will not be expanded smoothly, so it should have the simple shape as possible.

The plug position in ⑶ is decided by the number and position of the intake-exhaust valves. In the 4-valve engine most used nowadays, the plug shall be installed at the center of the combustion chamber, ideally.

As the compression ratio mentioned in ⑷ is higher, the combustion will be faster because the temperature and pressure of the combustion chamber just before ignition is high. However, if the combustion is too fast, then the combustion is performed abnormally. So the chamber can be damaged by this abnormal combustion such as knocking.

To make that the heat can not be lost easily as mentioned in ⑸, consider that; as the inside area of the combustion chamber is bigger, the heat loss when the exploded gas presses the piston will be higher, that is, the heat energy which will be converted into the force energy will be lost. With the same volume of the combustion chamber, as the inside surface area of the chamber is smaller; the heat converting ratio will be higher.

Therefore, when the ratio between the SURFACE and VOLUME of the combustion chamber is the S/V ratio, this ratio represents the combustion efficiency. The smaller S/V ratio is better for the combustion efficiency.

8. Intake-Exhaust Valve & Combustion Chamber

To get better volume efficiency, more amount of intake air is needed, and the flow of intake-exhaust should be made smoother. The size and shape of the intake port is important as well as the attaching angle, diameter and number of the valves should be appropriate to enhance the volume efficiency.

The larger diameter of valve is the better. If the valve is too large, it is heavy so it has large inertia force when it is open and close. Therefore, it will hinder the engine from rotating with high speed. The size of valve should be optimized. The 4-valve engine having two set of intake-exhaust valve is more applied recently than the 2-valve engine having one set of intake-exhaust valve.

The three-valve engine having two intake valves and one exhaust valve was noticed. However, the plug was not installed at the center of chamber, and the exhaust valve was too large so the two intake valve system is worse than 4 valve system.

The chamber types of 4-valve engine are the PENT ROOF type having the roof shaped cylinder head and the Poly-spherical type having the some overlapped spheres. In the both types, a pair of intake-exhaust valve is facing with each other, and the spark plug is located at the center. It satisfies the requirement condition for the excellent volume efficiency.

Big valve angle Small valve angle

The valve inclined angle is the angle of intake-exhaust valve about the center line of the cylinder. The valve angle is the angle between the center lines of each valve. These angles make an important affect to the chamber shape, the S/V ratio, the compression ratio, and the shape of intake-exhaust ports. If the valve angle is to be larger, then the valve diameter can be made widely, and the intake-exhaust gas will be flown more smoothly. However, the chamber is to be larger also, so it has demerits such that the compression ratio will be reduced, and the S/V ratio is to be large. New type engine has the compact combustion chamber of which valve angle is smaller than ever.

The five-valve engine having the three intake valves and two exhaust valves is for high performance by enlarging the cross area of the valve and lightening the valve weight. However, it has more complicated chamber so the S/V ratio will be larger as well as the mechanism around the valve will be more complicated.

9. Piston & Combustion Chamber

The piston head forms the combustion chamber by facing the intake-exhaust valves portion of cylinder head. To combust the mixture fast, the inside surface of the chamber should have fewer extruded or recessed portions to flow the mixture smoothly, and the S/V ratio should be small as possible. Therefore the piston head should be flattened.

In actual, considering other elements such as the valve angle, the cylinder head shall have the recessed shape. Therefore, to increase the compression ratio, the piston head should be extruded, highly. Furthermore, if the engine has high compression ratio, then the gap between the cylinder head and piston head should be narrow so it need to make the valve recess be larger to prevent the valve from abnormally operating. With these limitations in the mechanism, there are many researches for better combustion.

The piston has an important role to transmit the combustion force to the connecting rod effectively, so the other portions except the piston head should be precisely designed.

The combusted gas is sealed with the piston ring. To ensure the sealing, the gap between the piston and cylinder (piston clearance) should be small as possible. The piston will be cooled by the lubricant oil and the heat will be radiated through the piston ring. The thermal expansion coefficient of the aluminum, the main material of the piston, is 23 relatively higher than steel of which thermal expansion coefficient is 12~15, which is the main material of the cylinder. Therefore it is hard to match the piston size to the cylinder size. For example, as the back side of the piston head is reinforced, it is made little smaller than the skirt part and the piston diameter along to the inserting axis of piston pin is little smaller than the perpendicular axis.

As the connecting rod rotates the crankshaft, the piston will press the connecting rod with inclined direction. Therefore, the piston may be trembling along the lateral direction so the skirt will strike the cylinder wall. This is called the piston slap or the sides knock. This is the cause of the noise or power loss by friction.

To minimize this slap, the center of the piston pin is offset about 1∼2.5mm along to the movement direction of the connecting rod. Doing so, the force pressing the piston to the lateral direction will be reduced. It is called the offset piston.

ENGINE Chapter 10 Ignition System

2012-09-20T00:19:00.002-07:00

ENGINE

Chapter 10.

Ignition System

1. Point type Ignition

The ignition system is to fire the mixture compressed in the combustion chamber making a flame with a spark plug.

When the plus and minus poles of the 12V battery is shorted, a spark can be made. However, it is too weak to ignite the mixture. Therefore, this voltage should be boosted up to 10,000∼30,000V. The ignition system consists of a device for boosting the voltage, a device for distributing the ignition timing and a series of spark plug.

To boosting the voltage, an ignition coil, an electric inducer, is used. The ignition coil comprises of a iron core shaped of rod, the secondary coil wound with about 20,000~ 30,000 turns using a hairy thin copper wire around the core and the primary coil wound with 150~300 turns using copper wire of 0.5∼1mm diameter over the secondary coil. When a current is flown at the primary coil, the iron core will be an electromagnet. And at time when the current at the primary coil is broken, a boosted high voltage is induced at the secondary coil.

The distributor has a device for controling the current flowing at the primary coil and a cam having the same number of extruded portions in the middle of it. When this cam presses the arm by rotating, the point attached in front of the arm is opened to cut the current of the primary coil (contact breaker). And the distributor has also a device, overlapping with the contact breaker, for distributing the boosted voltage of the secondary coil to each plugs.

At the cam of the contact breaker, an advancing device for controlling the ignition timing at the variations of engine speed to send the boosted high voltage to the spark plug in time. As the cam should rotate with 1/2 of the engine rpm to match the ignition timing of the plug, it should be attached at the end of camshaft having the same rotation speed. The advancing device shall be explained at the section of 『Ignition Timing』 in detail.

After that, the high voltage generated by the ignition coil is sent to each spark plug through a series of Hihg-Tension Cord.

This ignition system is called contacting or point type. If the driving for the contact breaker is performed by a transistor, then it is called the full transistor type. Furthermore, developing the system, the distributor is driven by a computer in the distributor-less ignition device.

2. Full Transistor type Ignition

In the point type ignition device, the point is opened by the cam, and high voltage is induced at the secondary coil when the current at the primary coil is cut. Similarly, when the switch is turn off, a small unwanted spark will be made at the contact point. As the same of mechanical inertia, the electrical current has the inertia. This unwanted spark will be prevented by inserting a condenser within the ignition circuit.

Furthermore, the point would be burned or not work normally at the high speed. Therefore, for intermitting the current of the primary coil, a transistor is developed instead of the mechanical point.

As being many kinds in the transistor, the application method is various also. When it is used for a switch, NPN type transistor is used. This consists of a base made of P type semiconductor and two N type semiconductors at the both side, one is a collector, and the other is emitter.

In normal state, the current is not transmitted from the emitter to the collector of NPN type transistor. However, if a little current (base current) is applied between the emitter and the base, then an amplified current is induced from the emitter to the collector. Using this characteristic, it can be utilized as a switch.

Instead of the cam and point in the distributor, the signal generator is equipped for detecting the ignition timing, the electrical signal is sent to the igniter including a transistor. Then the base current made by the signal generator is applied to between the emitter and the base, and then an amplified current is generated from the emitter to the collector. Using this current amplifying, the intermittent current is applied to the primary coil, so a boosted voltage can be generated at the secondary coil.

The signal generator consists of a rotor having the same number of extruded portions with that of the cylinder, a permanent magnet, and a pick-up coil detecting the change of magnetic flux. As the signal rotor rotates with the 1/2 speed of the engine speed, the extruded portions passes through the gap between the pick-up coil and the permanent magnet corresponding with the ignition timing. The magnetic flux generated by the permanent magnet will be changed, so an induced current will be flown at the coil. This current is used for the base current of the transistor. Doing so, the trouble from the contact breaker can be resolved.

3. Distributor-less Ignition

In the full transistor ignition system, the primary coil current switching is performed by the signal generator and the transistor, while the advancing and distributing of secondary current is performed by the same device used in point ignition system. The distributor-less ignition system is that the advancing of ignition timing is performed by a computer using an electrical signal from the sensor for ignition timing, and the ignition is performed using generated secondary current from the ignition coil installed near the ignition coil.

The main feature of this ignition device is the high-tension cable connecting the ignition coil – the distributor – the spark plug. As this cable will be short only for connecting the spark plug and the coil just nearby or this cord is not needed in some cases, the troubles from the electromagnetic wave interference from the high current of the high-tension cable or the ignition faults from the electrical resistance of the cable can be prevented. Additionally, the electrical advance device is more compact than the mechanical one.

Inductive type crankshaft position sensor

Optical type crankshaft position sensor

In the sensor for deciding the ignition timing, the crankshaft position sensor or the camshaft position sensor, one type comprises of a timing rotor driven by the camshaft and a pick-up detecting the position of the rotor electrically. Anther type comprises of a LED attached at the rotor blade driven by the camshaft and a photo diode to decide the ignition timing.

In the ignition method, there are the individual ignition method and the bank ignition method.

Individual ignition system

Bank ignition system

In the Individual ignition method, the ignition coil is installed at each cylinder to ignite sequentially according to the order decided by the ECM. In the bank ignition method, the ignition spark is occurred at two cylinders at the same time by one ignition coil. In this time, one cylinder is in the compression stroke and the other cylinder is in the exhaust stroke. The ignition spark at the compression stroke is effectively used, but the spark at the exhaust stroke is meaningless. In this method, the used amount of the transistors and coils is half of individual ignition method, so the cost will be down.

4. Spark Plug

The spark plug ignites at the compressed mixture to fire it according to the spark arc by the high voltage generated from the ignition coil. The spark plug contacts, at first, with the mixture having the similar temperature of outer atmosphere in the intake stroke, After that, it contacts with the exhaust gas over 2000℃ and generates high voltage of 20,000V. Therefore, it is the device working in most severe condition.

The spark plug is used for many kinds of engine in common, and manufactured with a standardizing specification internationally. There are many kinds according to the dimension, structure, performance and characteristic (especially, heat characteristic). This is distinguished by the alpha numerical indicator. This indicating character differs from the manufacturer, so be careful when replacing them. Generally, spark plug is classified as 14mm, 12mm, and 10mm according to the size of attaching screw. To make the combustion chamber compact, the smaller plug is the better. However, the smaller can be the easier to be affected by heat. It is very important to inspect the temperature situation of the engine in order to use the spark plug.

The spark plug, during driving, is affected by the various temperatures. The most affecting temperature is the combusted amount of fuel mixture per time. As the engine is high speed, the temperature of plug will be high. Even in the same driving condition, the temperature differs according to the heat range of the plug.

The heat range is the degrees of which the spark plug radiates the heat acquired from the chamber. As the plug easily radiates the heat, the heat range is high. In racing engine, the cold type having high heat range should be used to prevent the temperature from increasing easily. Contrarily, if the engine is usually used in low speed, the hot type having low heat range should be used to prevent from being cold easily.

The heat range is represented with numeric character on the plug. It differs with the manufacturer. It should be selected according to the used standard plug. If the plug not corresponding with the engine features and driving conditions, for example, if it is used in the low temperature, then carbon slug will be deposited on the end portion of the plug, so it doesn’t work. If the temperature is excessively high, then the mixture is exploded before the ignition is worked, that is pre-ignition will be occurred.

ENGINE Chapter 9 Fuel System

2012-09-20T00:18:00.002-07:00

ENGINE

Chapter 9.

Fuel System

1. Carburetor

In the gasoline engine, the carburetor or the ECM is used for mixing the air and fuel. The most 4-cylinder engine uses the ECM system, only some small engines use the carburetor.

Carburator fuel system

Electronic fuel system

The carburetor uses spraying principle for mixing the gasoline and the air. That is, a fuel spraying hole is made at the venturi and the air flow at the venturi is high. So the pressure at the fuel spraying hole is decreased. So the gasoline will be following the air flow in the fog form and it is mixed with air.

This phenomena is called as the Venturi effect named by the inventor. To enhance this effect, the ventury is made in narrow as possible. This inside diameter is called the main bore size indicating the size of the carburetor. By define the diameter of the venturi about the main bore size, the gasoline amount can be controlled according to the air flow, so the air-fuel ratio can be maintained uniformly.

The pipe for supplying the gasoline is the main jet (fuel spraying hole). By selecting proper jet according to the driving state, it is possible to cover the wide range of rpm. However, when the engine is rotating with low speed such as idling state, the pressure in venturi is lowered so the proper amount of gasoline is not injected. When the engine is rapidly accelerated, the amount gasoline should be larger than normal state. However, it is not so easy to control these variations. To overcome these hindrances, various carburetors have been developed. Especially, in the motor sports, as the displacement volume is determined, the carburetor is most important device for enhancing the engine performance.

The operation of carburetor is like that; at first, the gasoline from the fuel tank is contained into the floating chamber; when the amount of gasoline in the float chamber is reduced then the float goes down and the more gasoline is supplied from the fuel tank. When a driver presses the accelerator pedal, the throttle valve is opened and air flow passing the venturi part so that the gasoline will be taking out from the main jet.

The carburetor has this simple structure, so the cost is low and it has fewer defects. However, for the modern engines which need to enhance the emission, the fuel efficiency and the power output, the carburetor has many problems.

2. Mechanical Fuel Injecting Device

Basically, as regarding the negative pressure as the air amount injected, the carburetor supplies proper amount of gasoline using only mechanical device. Therefore, it can not maintain the air-fuel ratio uniformly. It is need to control the injected fuel amount exactly using the predetermined the air-fuel ratio to prevent from wasting the fuel or to enhance the engine response.

A new system is developed in which the inhaled air amount is measured directly, and the gasoline is sprayed to the intake manifold with the optimized the air-fuel ratio using the mechanical device. This is the K-jetronic invented by Bosch.

By comparing with the carburetor, the fuel injecting device is injecting the fuel to the manifold directly. Therefore, it has good response at the start and at accelerating and decelerating. It is hard for this device to make the vapor lock in which flow of fuel is broken by vaporizing the fuel in the middle of fuel pipe. Additionally, it does not make icing that the carburetor is frozen.

The main feature of the K-jetronic is that installing a circular plate named sensor plate in front of the throttle valve, the gasoline amount is controlled using that the opening state of this plate is changed by the air amount. When the throttle valve is open, the air presses the sensor plate installing in the air flow meter. The lever supporting this plate is connected to the device for controlling the injected fuel amount, and the gasoline is injected to the fuel injecting device by a response to the plate operating.

As a system replacing the carburetor, the K-jetronic has better reliance. However, it sometimes injects the fuel in the same manner of carburetor and controls the fuel amount mechanically. Therefore, it is hard to control the mixture ratio precisely.

In some cases, by accepting an ECM to a portion of the system, the KE-jetronic supplementing these week points is developed. However, step by step, the full ECM system is replacing these mechanical systems in order to regulate the exhaust gas and to enhance the fuel efficiency.

3. Electrical Fuel Injection System

The main part of the electrical fuel injecting system is the fuel injecting device deciding the amount of fuel to make proper mixing ratio by measuring the inlet air amount. This system comprises of the device of measuring the air amount, the device of injecting the fuel, and the device of controlling theses operations.

The representative mechanical fuel injecting device, the K-jetronic, uses the sensor plate for device measuring air amount, and transmits the movement of sensor plate to the valve controlling fuel supplying. Contrarily, the electrical fuel injecting system the measured air amount by the air flow sensor is sent to computer as an electric signal to decide the fuel amount with the result from the sensor for checking the engine status. By these devices, it is possible to control the air-fuel ratio precisely.

The structure of the fuel injector is differed according to the manufacturer and the applied engine type. Except the air flow sensor, most parts are similar. Here, we will explain about the mass air flow type using the air flow meter as the air flow sensor.

The filtered air through the air cleaner is measured its amount at the air flow meter, and taken into the surge tank (intake collector) via the throttle body including throttle valve connecting to the accelerator pedal. This air is distributed to the intake manifold of each cylinder, and inhaled into the cylinder with the gasoline injected from the fuel injecting valve (injector) to the manifold or intake port.

At this time, a controller decides the gasoline amount optimized to the driving status and running condition of the vehicle. This is called as the ECM, Electronic Control Module. The driving status is the electrical signal from the water temperature sensor, the intake air temperature sensor, and the throttle position sensor, and the running condition is the signal from the speed sensor and the signal indicating the air conditioning working status. These signals are sent to the ECM.

By memorizing the data concerning to some combinations of these signals and the control method which indicate what amount of gasoline is injected according to the combination to the computer installed into the ECM, the computer can inject proper amount fuel decided by the computer according to the accelerator operating, from the injector.

4. Fuel Supplying System

The gasoline, the fuel, is contained in the fuel tank and sent to the fuel injecting device after eliminating dust and water by filter.

The fuel tank is made of galvanized steel to prevent rust, as well as the plastic tank is more used. To protect the fuel from leaning one side, there are some partitions, called separator, and level gauge is attached.

The fuel pump has various types. The carburetor uses mechanical pump, ECM system uses electrical pump using electric motor mostly.

A regulator, pressure controller, is attached for sending the gasoline to the injector after controlling the gasoline pressure within the specific range.

For injecting the gasoline, an injector is used. The injector has a needle valve closing the front of the nozzle so the valve is open by flowing an electric current to the solenoid to injecting gasoline.

In the injecting method, there are a Single Point Injection (SPI) injecting gasoline to the collecting portions of manifold, and a Multi Point Injection (MPI) injecting gasoline to each manifold corresponding with each cylinder. The SPI has the injector at the same place as the carburetor does, but this makes the mixture more effectively than carburetor does.

The MPI can be classified to point injection, group injection and bank injection according to the injecting timing. Each manifold has injector. The point injection performs injecting operation at the intake stroke of each cylinder according to the engine rotation. The group injection performs the injecting operation with a group of cylinders which have the sequential intake stroke.

Of course, the point injection can inject the gasoline with most optimized timing and amount. However, the electrical circuit for driving the injector is more complicated. So, some commercial car accepts the group injection.

Simplifying the group injection is the bank injection. At the intake stroke and the combustion stroke in which the piston goes down, the needed gasoline is injected after dividing into two turns and taken into the cylinder after gathering at the intake stroke. Due to the simple structure, it ensures the most efficiency in the gasoline injection. So it is the most used method in the gasoline engine.

ENGINE Chapter 8 Cooling System

2012-09-20T00:17:00.003-07:00

ENGINE

Chapter 8.

Cooling System

1. Cooling system

Of the total heat energy generated by the combustion of fuel mixture in gasoline engine, about 30% is converted into the kinetic energy to push the piston, another about 30% is wasted with exhaust gas, another about 30% is transmitted to coolant through the piston and the other about 10% is lost by friction.

Among them, if the heat transmitted to the combustion chamber wall is not eliminated as quickly as possible, the piston or the cylinder will be deformed by this heat or the film of lubricant oil will be broken.

If this heat is cooled excessively, the much heat energy will be transmitted to the coolant so that the heat efficiency will be degraded. Therefore, cooling system should be controlled to maintain the proper temperature according to the driving situation.

The cooling system for vehicle engine is classified into the water-cooling system and the air-cooling system. The air-cooling system is hard to cool uniformly and easy to make a loud noise, so nowadays almost this system is not used in the vehicle.

According to the flow type of water cooling system, there are the U-turn flow type flowing from one side of the engine to the same side, and the cross flow type flowing from one side to the opposite side. Additionally, according to the flow direction, it can be classified into the longitudinal flowing type flowing along to the longitudinal direction of the engine, and the lateral flowing type along to the lateral direction of the engine.

In the water-cooling system, the cooling water is circulated by water pump from lower portion of the water jacket to the radiator. During running, strong winds can cool the radiator, however, when the car is stopped or slowly driven, a fan should send winds in force. The cooled water shall be returned to the water jacket by the pump. By installing a thermostat between the water jacket and the radiator for sensing the cooling water temperature, if the cooling water has too low temperature, the thermostat blocks the water passage. The most used thermostat is the wax type in which a wax is secured between capsules, and the wax opens and closes the valve using the expansion and shrinking by heat. The thermostat working temperature is about 85℃.

2. Radiator

The radiator is a body radiating heat, in this case, it is a device for radiating the heat into the atmosphere. As the heater is called also as radiator, the cooling device in a car is called as radiator; especially this is called as heat core.

To enhance the efficiency of radiator, the area should be large as possible. Generally, the radiator comprises a radiator core manufactured by welding many metal fins around a tube flowing cooling water therein and two tanks containing the cooling water at both sides of the core.

The tanks are attached at the upper portion and lower portion of the heat core to flow hot water to upper tank and cold water to lower tank using the convection principle.

Down flow type

Cross flow type

U-turn flow type

It is the most used type so called the down flow type. There is the cross flow type in which the tanks are attached at the left and right side to flow in horizontal. In the cross flow type, the height of radiator can be lowered and the design of front grill can be freely changed. However, it has larger flow resistance. For another example, there is an U-turn flow type in which the radiator core is divided in up and down at the center portion, and the cooling water flows into the one side of the upper core and returned from the lower core side.

The aluminum material is more used in both the tube flowing water and the fin colliding with wind. To make be lighter, the resin tank including nylon with glass fiber instead of brass or aluminum is more used.

High temperature

Low temperature

The radiator is equipped with a radiator cap to supplement the cooling water. Conventionally, this cap is just a cover so the cooling water can contact outer atmosphere directly. Nowadays, the cap secures the inside of the radiator that is the pressurized radiator cap. In the atmospheric pressure, the water is boiling at 100℃ and not increasing the boiling point. By pressuring the cooling water, the pressure is increased and the boiling point of water will be higher so the difference with the outer temperature is larger. Therefore, the cooling effect shall be increased.

At the pressurized radiator cap, a pressure valve and a vacuum valve are attached, When the cooling water is about 110∼120℃ and the inside pressure is high, then the pressure valve will be open to take out the cooling water; when the temperature is low and the pressure is lowered, then the vacuum valve will be open to suck the cooling water to the radiator. So the pressure of cooling water is maintained uniformly.

3. Cooling of the Cylinder Head

The most heated part of the engine is the combustion chamber. The heated cylinder and the cylinder head is cooled by the cooling water, the piston is cooled by the engine oil.

This heat affects to the temperature of fuel mixture, the combustion condition, and the temperature of exhaust gas, that is, to the engine performances. How to cool the cylinder head is the most important thing.

The most cylinder head parts are made of aluminum alloys because it has high heat conductivity and light weight. As the intake port having the similar temperature of outer atmosphere and the exhaust port taking out the so hot exhaust gas are nearly installed, they may deformed by the difference of the heat expansion. Therefore, it is very important to cool with balancing the each part temperature.

The cooling water is took into the cylinder head from the water jacket at the cylinder block, and flown around the exhaust port heated by the exhaust gas, and then took out via the intake port. Doing so, the temperature difference among the cylinder head, the exhaust port and the intake port can be minimized. It is possible to prevent the engine parts from being deformed or distorted by the difference of the heat expansion.

Additionally, the each temperature around each cylinder head in the series of cylinder should not have big difference. So the temperature of each cylinder should be similar as possible.

For example, if the cylinders are sequentially cooled from the front to the end, then the later cylinder can not be effectively cooled because the cooling water is already heated. In some cases, the cooling water is distributed to each cylinder at the beginning of the cooling to be cooled equivalently.

The oil can be used for cooling the cylinder head. However, the portions of the cooling effect by the oil is about 20%, the most cooling is performed by the cooling water.

4. Overheat

The water temperature of the engine is decided by the balance between the generated heat capacity from engine and the radiated heat capacity from radiator. If the cooling is not enough, then the cooling water can be boiled. Consequently, water vapor can be ejected from the radiator cap. This is called overheat. If the car is going with overheat state, then the performance will be degraded, at last the engine will be stuck.

If the engine is normal and the thermometer is varying, then it means that overheat will be occurred. The main reasons are four; one is that the wind amount passing the radiator is too small; another is that wind temperature is too high; the third is that amount of cooling water is too small and the last is that the engine is working in hard situation continuously.

When a car has aero parts or large fog lamp so the wind passing is hindered, or when the car runs unpaved road so the radiator covers with dirty thereon, then the cooling water can be easily overheated. In other case, if the fan belt is not tightened or broken then the cooling water can be easily overheated because the wind amount sent to the radiator is reduced.

To tune up the turbo engine, when a large intercooler is installed in front of the radiator, then, then wind amount will be reduced and the cooling water may be overheated.

If the water pipe is old so the cooling water is leaked, or the belt for driving the water pump is loosened, then the cooling water may be easily overheated because the cooling water is deficiency.

ENGINE Chapter 7. Lubrication System

2012-09-20T00:16:00.002-07:00

ENGINE

Chapter 7.

Lubrication System

1. The Role of Engine Oil

The main role of the engine oil is to move the dynamic system such as the piston in the cylinder and the crankshaft smoothly. To do so, the oil forms a oil film at the metal surface to reduce the friction between the metal surfaces. At the same time, the engine oil can secure the combusted gas not to leak to the crankcase, cools the piston and valve, and reduce the shock transmitted from the piston to the crankshaft as well as clean the engine inside.

As the lubrication is already mentioned in the section of 『Journal Bearing』, here, we will explain the other roles of the oil. The first is the sealing role in which the engine oil between the piston ring and cylinder prevents the leaking the compressed air or combustion air.

Oil jet

The cylinder head and the piston crown directly contacts with the hot combusted gas. The cylinder head is cooled not only by the cooling water but also by the oil at the dynamic system. The heat of piston crown is transmitted to the cylinder wall via the piston ring. Also the piston cools down by spraying the engine oil.

Another important role of the oil is to reduce the shock. The combustion force is very strong up to several tons weight force. This force is transmitted from the piston to piston pin, to Connecting rod, to crank pin and to crankshaft. In that process, the oil absorbes shock at the piston pin and the crank pin.

Except that, the engine oil can wipe out the foreign materials such as carbon particle generated by burned oil and metal particles from the wear of metal surfaces.

The oil also prevent inside of the engine from being rusted by chemicals from the combustion.

2. Lubrication Method

In old style engine, the lubrication method was so called the Splash type in which the big end of connecting rod hit and sprayed the oil contained in the oil pan under the connecting rod. Nowadays, the lubrication oil is sent to necessary portion by the oil pump and collects to the oil pan. According to the oil circulation method, there are the dry-sump type and the wet-sump type. The lubrication device consists of the oil pan containing oil, the oil filter purifying the oil, the oil pump sending the oil to each portion.

The wet-sump is equipped in most car. The oil contained in the oil pan is filtered big foreign materials using the oil strainer consisting of steel meshes and sent to the oil filter by oil pump to eliminate any tiny foreign materials. There is a oil gallery in the engine block, it is a oil passage for each dynamic parts such as crankshaft, cylinder head, connecting rod and cylinder wall.

Wet-sump type

Dry-sump type

The oil is returned to the oil pan from the piston, connecting rod, crankshaft and cylinder head. When the car is turned rapidly or accelerated or decelerated abruptly, the oil in the oil pan is leaned one side so it can not be pumped well. Some engines have a separator, a kind of partition in the oil pan to prevent the oil from leaning. For the special engine for racing car, the Scavenging pump takes the oil and air together, and the oil and air are separated by a separator and then oil is contained to the separated oil tank. This is the dry-sump type.

As the dry-sump method does not contain the oil in the pan, the oil pan can be thinner. So, the lower part of engine is smaller and the engine is designed to have lower weight center. However, the device should be complexed. It is applied only to the special case for equipping the opposed engine. Some engine equips a semi-dry-sump type having the oil pump for collecting the oil in the oil pan.

3. Parts of Lubricant System

The 3 main parts consisting of the lubricant system are oil pump, oil filter and the oil cooler cooling the heated oil.

There are many kinds in the oil pump taking up the oil in the oil pan. The passenger car uses a gear pump combined with toothed wheel and linked to the crankshaft directly.

The gear pump comprises of a driven gear in the pump body and the drive gear linked with the tooth of the driven gear. When the drive gear is rotating, the driven gear is also rotating. However, the centers of each gear are departing each other so the oil between them is pumped from the inlet port to outlet port. According to the tooth shape, there is an Involute type, the Trochoidal type, and so on.

Gear type oil pump

The oil sending amount by the oil pump is proportional to the engine rpm. At the high rotation of the engine, the oil pressure is too high. At the low temperature, the degree of viscosity of oil is increased so the oil pressure is too high. The device for maintaining the oil pressure should be equipped. It is called the pressure regulator or the relief valve.

The oil filter purifying the oil from the carbon or metal particles. A folded filter paper is inserted into the cleaner case. There are two types for the replacement the element type and the catridge type. The cartridge type is replaced the filter with case, the element type is replaced only filter element when the filter is replaced.

The proper working temperature of the engine oil is about 80℃. If the temperature is too low, the friction becomes high because of high viscosity. If the temperature is too high, the oil pressure is lowered so lubricating ability will be degraded and also the oil in the high performance engine can be easily deteriorated. So the oil cooler is required for the the high performance engine.

The kinds of oil cooler are divided into the water type and the air type. The water type oil cooler maintains the oil temperature using the engine cooling water, and the air type oil cooler uses the running winds.

The air type has simpler device, but the cooling efficiency is lower than the water type. The water type is more complicated, but it ensures the more stable cooling efficiency.

4. Engine Oil

As we have mentioned, the engine oil works for reducing the wear, cooling the piston and the cylinder head, sealing the gap between the piston and cylinder, releasing the shock, cleaning the engine inside, preventing the knocking and so on.

The required characteristics of the engine oil are as follows,

- Proper viscosity at working condition

- Good lubricant performance

- High heat and corrosion resistances

- Anti-bubble

The most important characteristic is the viscosity. Therefore, the engine oil is classified by two aspects, the viscosity or the quality.

The commercial engine oil is sold in case of 1ℓ, 4ℓ or 20ℓ. At the case, there are name of manufacturer, brand name and oil name with the viscosity class and the quality class.

In the viscosity classification, according to the standard by SAE(Society Automotive Engineers), the lower viscosity has lower number and higher viscosity has higher number. For cold weather, letter “W” is added. For example, certain classification like that the number 30 is for general purpose, and the number 20 is for winter, is the single grade using one number system only. Another classification like that a range is represented such as 5W-30 or 10W-30, is the multi grade. In this case, by comparing the 5W-30 with the 10W-30, the 5W-30 has lower viscosity than 10W-30 at low temperature, but has higher viscosity at the high temperature.

Generally, when the temperature is increased, the viscosity of oil will be decreased. To indicate how the viscosity is changed, the viscosity index is used. If the viscosity is not easily changed, then the viscosity index of the oil is high. The higher viscosity index is easier to use.

In the quality classification, the standard by the API(American Petroleum Institute) is used. For gasoline engine, the letter “S” followed from other alphabet letters is assigned. For the diesel engine, the letter “C” followed from other alphabet letters is assigned. For example, letters from SD to SG are assigned for the gasoline engine.

The kind of engine oil and replacing period are decided by type of engine, driving condition and ambient temperature, so please refer to the manual carefully to select the engine oil. The replacing running time is about 10,000km for SD, and 15,000km for SE, and SF 15,000km for gasoline engine roughly. For turbo engine, the engine oil should be replaced at every 5,000km running time because the driving condition is very tough. The maintenance intervals for each engines are varies, refer the manuals for the each engine.

ENGINE PRINCIPLES Chapter 6. Charger

2012-09-20T00:15:00.002-07:00

Charger

1. Kinds of charger

The basic of increasing the engine power and torque is 『How more oxygen can be inhaled into the engine』. For example, if the density and amount of inlet air is high, then the power and torque shall be high.

Additionally, by developing the intake system and combustion chamber, it is possible to intake more air. One of possible methods is 『to compress the air and to inhale』, that is, to use auxiliary device, the charger.

There are some types in the chargers. Typically, there are a Turbocharger type in which the charger is driven by the exhaust turbine, and a Supercharger type in which the supercharger is driven in mechanically using driving force of some part (such as crankshaft rotation).

Turbocharger

Supercharger

The Turbocharger is, as the “Turbine driving charger”, a system compressing air by the compressor rotating a turbine using the exhaust gas flow. It is possible to get high power output using a small device. However, when the engine is rotating with low speed, the turbine can not rotate with high speed, so the compressing power is not enough and the acceleration will be delayed.

Therefore, even the accelerator is pressed the engine rotation may not be response immediately, that is Turbo Lag. The lag means the time delay.

As driven by the interlocking mechanism with the crankshaft, the Supercharger, the mechanical supercharger, has the well response. However, in the low engine speed, the engine efficiency will be worse by increasing leak air through the gap between the rotor and the housing. In the high engine speed, the driven force loss may be increased. To recover these defects, the structure of supercharger system may be changed or a the Turbocharger and the Supercharger may be combined to new system.

The engine without such supercharger is called as the naturally aspirate engine or NA engine.

2. Turbocharger

As the turbocharger is a combined word of turbo (turbine) and charger, it comprises of a turbine and a compressor directly linked, so that the turbine wheel is rotated by the exhaust gas energy and the inlet air will be compressed by the rotation of the turbine wheel.

The body of turbocharger comprises of turbine wheel, compressor wheel and axis, and attached near the exhaust manifolds.

The heated air by the compressing is cooled by the intercooler and supplied into the engine via the throttle valve. The exhaust gas passes to the turbo charger to rotate the turbine wheel. In order to prevent the over boosting at high speed, when the boost pressure is over the predetermined pressure, a waste gate valve (exhaust bypass valve) of the WGT (waste gate turbocharger) will be opened.

The turbine wheel is rotated 100,000 rpm ~ 160,000 rpm with hot exhaust gas about 900℃ at high speed, the turbine wheel is made of light material having high heat resistance such as ceramics.

The smaller and lighter turbocharger is better for the engine response such as acceleration and deceleration but worse power at high speed. On the contrary, the bigger turbo charger has a high power at high speed but slow response. Therefore, it is important to select the size of turbo wheel according to the displacement volume of the engine. Generally, the compressor wheel is made of aluminum to make lighter turbocharger.

For the supporting of the high speed rotor shaft, lots of the engine oil is supplied to the shaft for the lubrication and the cooling. If the engine is stopped from the high speed abruptly, the turbocharger is rotated without the oil by inertia force of turbocharger until self stopping. So, the rotor shaft may be adhered. For this reason, the turbo engine should be stopped after idling.

3. Boost Pressure and Compression Ratio

The air pressure which is pressurized by the turbocharger is the Boost pressure. If the boost pressure is increased, the intake air amount into the cylinder is also increased and the power output will be increased. However, the boost pressure can not be increased without limitation. As increasing the boost pressure, the actual compression ratio is also increased, so knocking shall be occurred at high compression pressure. The actual compression ratio represents how the inlet air into the cylinder compressed actually is. So, the boost pressure is regulated by waste gate valve.

The knocking is the self ignition phenomena while the flame is spreading after the ignition of the spark plug, the un-burn mixture can be easily self-ignited at high temperature condition by high compression. So, the knocking is occurred as much as the actual compression ratio high.

By this reason, the compression ratio of the turbo engine in specification is smaller than that of the NA engine. For example, if the engine having the represented compression ratio of 10 is supercharged with 1 atm, then the air amount will be 2 times and the actual compression ratio will be 20 and then knocking will suddenly be occurred. Generally, compression ratio of the commercial turbo engine is set lower than that of the NA engine balancing with the power, torque and fuel efficiency.

The knocking can be prevented by controlling the ignition timing in the NA engine but the knocking control by the ignition timing in trubo engine is not easy because the knocking is affected by the boost pressure.

The maximum power and fuel efficiency is made just before the knocking is occurred because the combustion speed is most fast at this situation. By sensing the knocking noise, the ignition timing can be fully advanced by ECM (electronic control modul) until the knocking is occurred. The sensor for detecting the shock noise is the knock sensor.

The knock sensor converts the vibration about 7 kHz into an electrical signal. By attaching at the cylinder block, this signal is treated by computer with the engine rpm, crank angle, and the intake air amount to control the ignition timing for preventing the knocking

4. Turbo Lag

The turbo charger is an air compressor for 『how much air is supplied』. By using the negative pressure acquired when the piston goes down and the flow inertia for intake air, the NA engine can make the charging efficieny of 65∼95%. In the turbo charger, charging amount is 1.2∼1.5 times higher than NA engine if the displacement volumes are same. Therefore, it is possible to make smaller engine than NA engine if the power and the torque are same.

However, it has a defect, so called the turbo lag. The turbo lag is the time delay from starting the acceleration to the actual rpm increasing of the engine. Especially, it is occurred when the car is started, accelerated suddenly, or speed up from the low speed.

The process is like that; at first, the throttle valve is opened, then the air amount is increased, then the combusted gas is increased and the exhaust gas temperature is increased. After that, the rpm of the turbine is increased by the increasing exhaust gas, so that the supplied air amount by the compressor is increased. By this process, the intake air amount is increased more. According to this process, the engine acceleration is delayed from the starting of acceleration to the actual rpm increasing of the engine.

To minimize the turbo lag, there are many researches and developments. For example, as the simplest method, there is a method for increasing the exhaust speed pushed into the turbine wheel. By reducing the diameter of nozzle of exhaust pipe, as the exhaust speed can be increased with the same displacement volume, the turbo lag can be minimized. However, in this case, the maximum power is limited.

To attach small two turbo instead of large one, it is possible to reduce the turbo lag. For example, in the 6-cylinder engine, one turbo is attached at each 3-cylinder. Doing so, it is possible to prevent the exhaust interference as well as to increase the power. This method is called as the twin turbo type. On the other hand, the two way twin turbo type also accepts the two turbo, but just one turbo will be driven at the low speed to maintain better response and two turbo will be driven at the high speed for enhancing torque.

Hybrid turbo

For another example, there is a hybrid turbo type in which the supercharger is used for the low speed, and the turbocharger is used for high speed.

In the electronic control engine, VGT (Variable Geometry Turbocharger) is used to reduce the turbolag and to increase the torque of the engine.

The VGT uses a set of adjustable vanes, or nozzles, to direct flow into the turbocharger turbine. When the vanes are closed, flow is directed tangentially into the turbine wheel. This imparts maximum energy into the turbine, causing the turbocharger to spin faster. Conversely, when the vanes are opened, they direct flow into the turbine in a more radial direction.

VGT (Variable Geometry Turbocharger)

This reduces the angular momentum of the flow going into the wheel, producing less turbine work and ultimately slowing down the turbocharger.

5. Supercharging System and Heat

The turbine shaft of turbocharger is supplied lots of engine oil to cool and to lubricate. Therefore, engine oil in the turbo engine is deteriorited easier than NA engine.

As combusting more mixture, the charging system can not avoid increasing temperature of combustion chamber.

As the turbocharger performs the boosting using the exhaust gas energy, the boosting efficiency will be better at the higher temperature of exhaust. For example, by adopting the heat resistance material to the parts such as the exhaust valve with natrium and the stainless exhaust manifold, and making the supercharger of high heat resistance material, the performance shall be enhanced.

The inlet air should have as lower temperature as possible. Because the air density is lowered as the temperature is higher, the actual compression ratio will be decreased as the temperature is increased with the same volume and the oxygen amount will also be decreased. If the inlet air is hot, the compress mixture at the compressing stroke has higher temperature easy to make a knocking.

When the air is compressed the temperature is increased. This is the same in the charging process. So, the boosting effect is reduced as the amount of increased temperature. Therefore, the heated air should be cooled using a radiator before it reaches at the throttle valve. This cooling device is the intercooler.

There are two types in the interclooler, air cooling and water cooling system.

Air cooling type

Water cooling type

The air type intercooler cools the inlet air temperature using the wind get from the running of the vehicle. The intercooler is attached at the front or side of the radiator. The structure of intercooler is similar with the radiator, but the flow is not the water but the compressed air by the charger.

The water type intercooler cools the compressed hot air using an additional cooling water separated from the engine cooling water. The water has higher heat capacity than air, so the water type is more effective than air type, but it has high cost for parts and maintenance.

6. Supercharger

The supercharger drives the blower and compressor to boost using the engine power. It can make higher torque and not make any response delay such as the turbo lag. However, the driving force for supercharger is from the rotation of the crankshaft, so the engine power shall be consumed. The maximum power output is lower than turbocharger.

There are some kinds in the supercharger, typically, the Roots Blower and the Lysholm Compressor.

The Roots Blower has been used in vehicle engine. The boost control is performed by computer. It is operated when the high output is needed such as for accelerating and driving in high speed.

Roots blower

The structure of the roots blower is, to send the air from one side to other side by rotating two elliptical shaped aluminum rotors coated with special resin, in the oval housing. If the boost pressure is over charged, the valve is opened to return some amount of the charged air.

Lysholm compressor

The Lysholm compressor had been used in industrial field not in vehicle engine. The structure is that two rotors including 3 and 5 screw blades respectively are combined in the elliptical shaped housing. It is driven by a V belt linked with the engine. The rotor is made of aluminum alloy coated with resin of teflon. When it is rotating, airs supplied from one side is accumulated and transmitted to other side so the air is compressed. Consequently, the intake air is compressed up to 2 times.

In the supercharger, the roots blower is not a compressor but a fan as know from the name. In the NA engine, the air is charged by the negative pressure generated when the piston goes down, but the supercharger is additionally equipped the blower for enhancing the charging efficiency by positively sending the air. The Lysholm compressor is a compressor so that it can send the compressed air like the turbocharger.

ENGINE PRINCPLES Chapter 5. Exhaust System

2012-09-20T00:12:00.004-07:00

ENGINE PRINCPLES

Chapter 5.

Exhaust System

1. Exhaust System

By opening exhaust port of the cylinder head, the combusted gas is exhausted through the exhaust manifold, the exhaust pipe gathering the combusted gas from each cylinder, the catalyst converter purifying the used gas and the silencer (muffler) reducing combustion noise.

The most important thing in the exhaust system is the smooth path also. The exhausted gases from each cylinder are bumped at the exhaust pipe gathering the each exhaust manifolds. So, it is important to prevent from hindering each flow or to increase the exhaust efficiency using the exhaust inertia effect having the same principle in the intake inertia effect. However, it is hard to balance between the increasing the exhaust efficiency and the enhancing the engine performance, because there are many weak points from the engine to the muffler.

The exhaust manifold is made of the casting iron having high heat resistance, or the aluminum alloy. Also the exhaust gas temperature is high. So, it is need to make the exhaust system with the material having better heat resistance or to cool the exhaust system with the wind.

The catalyst converter is used for purification of the exhausted gases. There are a manifold catalyst installed near the manifold and a under catalyst installed under the floor. The manifold catalyst is more effective because the exhaust temperature is higher than the other system. However, it can be easily aged by the high temperature so usually two pieces are used. The under catalyst is not easily degraded, however it has high performance of purification.

The muffler is equipped for reducing the temperature and pressure of the exhausted gas as well as the combustion and exhausting sound. Generally, the muffler has many sector walls to make the inside space into maze path for flowing the exhaust gas, so it called as the maze type. There is also a straight muffler type in which a tube having many holes on the surface and silencer such as glass wool inside the tube. The maze type muffler has more effective sound absorption ability but has larger flow resistance. The straight muffler has more enhanced output but has louder sound.

In some cases, these two muffler types are simultaneously equipped using separated two pipes so that the maze type muffler is only used when the engine is working in low speed, and the straight type muffler will be additionally used when the engine is working in high speed and load.

2. Exhaust Inertia Effect and Pulsation Effect

The most important thing determining the performance of the exhaust manifold is the smoothness in the exhausting. The exhaust interference is the main problem hindering the smoothing exhaust. From the each cylinder, the combusted gas is exhausted according to the order of ignition. As they are merged into the manifold, if the exhaust system is not well arranged and combined, then one exhausted gas passing through the manifold can be collided with another exhausted gas from another cylinder or the pressure in the manifold will be increased, so that the exhaust gas can not be exhausted well.

The exhaust interference can be overcome by elongating the distance between the exhaust valves to the collection portion of each cylinder gas or be making the angle of collecting portion into an obtuse angle to ensure the well flow. As increasing the number of cylinder, it is hard to ensure the well exhaust flow by combining the increased manifolds.

In the serial 6-cylinder turbo engine, with not being fully closed the first exhaust valve, the fifth exhaust valve is opened, and with not being fully closed the fifth exhaust valve, the third valve is opened. So, if the all 6 exhaust manifolds are gathered into one collecting pipe, then the sequentially exhausted gases can be collided each other. Therefore, the manifolds are divided into two groups; the one includes the first, the second and the third manifolds and the other includes the fourth, the fifth and the sixth manifolds. Each group has own turbo charger to eliminate the exhaust interference and to enhance the engine output.

The inertia effect and pulsation effect are utilized to exhaust the remained combustion gases in the combustion chamber. As being the same with the intake system, when the exhaust valve is closed, the gas density around the valve shall be reduced to accelerate the exhausting gases from the chamber effectively.

When the exhaust valve is open, the combusted gas having the high pressure is exhausted through the exhaust valve and the remained gases will be exhausted by the following compressing pressure of the piston at the exhaust stroke and then the exhaust valve is closed. Therefore, the exhausted gas flow has high density portion and low density portion in the manifold.

As we mentioned in above chapter, when a gas flow has a difference in density, then pressure wave is generated. Therefore, this difference is transmitted during the manifold with sound velocity. This is called the exhaust pulsation.

Just before the exhaust valve is closed, if it is possible that the density around the valve is lower than other portions, then it is accelerated that the remained gas in the chamber shall be took out as well as the fuel mixture shall be inhaled from the intake valve.

3. Component of the Exhaust Gas

The exhaust gas from engine and fuel system to atmosphere comprises of the burnt gas from the exhaust pipe, the blow by gas from the crank room, and the vapor gas from the fuel tank by the hot weather and hot temperature of the working engine. As these gases include harmful materials contaminating the atmosphere, a purification system should be equipped.

Especially, the exhaust gas is the most important gas.

If the fuel is combusted perfectly, then any harmful material is not included in the exhaust gases. The fuel, gasoline, consists of hydrocarbon, the compound of the carbon and the hydrogen. In the chamber, the fuel is changed into the carbon dioxide (CO₂) and water (H₂O) with making heat energy.

In actual chemical reaction, the hydrocarbon and the oxygen are not changed at a moment into the carbon gas and water vapor. This chemical reaction is very complicated. For example, the hydrocarbon would be divided into a small unstable material by the heat and reacts with the oxygen, or the results particles are reacting each other, and so on.

Among the gases generated during this complicated reaction, the carbon monoxide, hydrocarbon gas and the nitrogen oxide are the major harmful materials. The carbon monoxide (CO) is the unstable material having one carbon and one oxygen so that it can be easily changed into the carbon dioxide, the stable and harmless material, if additional oxygen and heat are supplied. If we breath the carbon monoxide, then it will catch the oxygen delivered by the hemoglobin in the blood to be carbon dioxide, more stable material. So, our body is lag of oxygen.

The hydrocarbon gas (Hm Cn : here m, n are integer number) is come from the fuel not combusted or the intermediated material during the chemical process of combustion. It is come from the blow by gas or the vaporized fuel from the fuel tank.

If this gas is revealed at the atmosphere, then it will react with the oxygen and hydrogen and change into the aldehyde, the harmful material having strong stimulus.

The nitrogen oxide (NOx) is come from the reaction between the nitrogen (78% of the air) and the oxygen in the air by the high temperature of 2000℃ in the chamber. As the nitrogen oxide is made by the difference mechanism with the carbon monoxide or hydrocarbon gas, it will be increased when the carbon monoxide and hydrocarbon are reduced by almost perfect combustion. When the combustion temperature is low, the nitrogen oxide will be less; however, the combustion efficiency will be worse. So, the nitrogen oxide shall be treated at the exhaust system.

4. Air-Fuel Ratio and Exhaust Composition

As the harmful material in the exhaust gas is the product from the combustion, one of chemical reactions, the amount of it is decided by the air-fuel ratio, e.g. the ratio between the amount of air and the gasoline, the combusting temperature and the gas flow status. When the air-fuel ratio is lower than theoretical value (Stoichiometric), that is rich fuel, the combustion is not completely performed, so that more hydrocarbon gas and carbon are made.

Contrarily, if the air-fuel ratio is higher than the theoretical value (Stoichiometric), that is lean fuel, then the gasoline shall be combusted completely. So, the amount of the carbon monoxide and the hydrocarbon gas will be less, however, the amount of the nitrogen oxide will be increase because the combustion temperature is high. Especially, when the temperature is over 2000℃, the nitrogen oxide will be abruptly increase. Even the nitrogen and the oxygen are not react in the room temperature, in the high temperature, they are changed into the nitrogen monoxide and then changed into nitrogen dioxide After exited from the exhaust system.

The amount of the nitrogen oxide will be maximized at about 16 air-fuel ratio higher than the theoretical ratio (14.7). With lower ratios than 16, the nitrogen oxide amount will be reduced because the combustion temperature is lowered. When the air-fuel ratio is over 18 with less fuel, the fuel can not combusted properly so that the hydrocarbon will be increased.

To reduce the harmful material, it is important how to decide the air-fuel ratio. In some cases, the air-fuel ratio can be controlled by inhaling the combusted gas into the mixtures; it is called the exhaust gas recirculation device (EGR).

The exhaust gas recirculation device is called as EGR as an abbreviation. It is the device for returning some amount of the exhaust gas back to the cylinder. Doing so, the actual amount of fuel is reduced and the combustion speed is slow, and then the maximum temperature of the combusting chamber will be lowered and the amount of the nitrogen oxide will be also reduced. But, if the amount of the re-circulated exhaust gas is too much, then the engine output and fuel efficiency will be worse, so it is important to control the amount of EGR.

In the carburetor system, the amount of the re-circulated exhaust gas is controlled by the reverse pressure of the intake manifold. In the ECM system, the amount will be determined in optimizing the vehicle status by the sensing and calculating with the temperature of mixture and cooling water, the vehicle speed, and the load.

5. Exhaust Purification System

Devices for reducing the harmful material from the exhaust gas are the exhaust oxidation device combusting the carbon monoxide and carbon and the 3way catalysts device treating the exhaust gas using oxidation and de-oxidation reaction by the three catalysts for carbon monoxide, hydrocarbon, and nitrogen oxide.

As the carbon monoxide and the hydrocarbon gas are come from the incomplete combustion of the hydrocarbon and oxygen, the oxidation device supply additional air to the exhaust port to make oxidation the incomplete combusted gas included in the exhaust gas. So it is called as the secondary air device. In some system, in the middle of the exhaust pipe, a oxidation catalyst coveter, the vessel including the oxidation catalyst may be equipped for converting the carbon monoxide and the hydrocarbon into the carbon dioxide and water, respectively.

The electronic control engine uses the 3way catalysts device, generally.

In the nitrogen oxidation, there are nitrogen monoxide consisting of one nitrogen and one oxygen, and nitrogen dioxide consisting of one more oxygen. If the oxygen is removed from the nitrogen oxidation, e.g. de-oxidation reaction, then it becomes nitrogen gas. If the acquired oxygen from de-oxidation reaction of the nitrogen oxidation is supplied to the carbon monoxide and hydrocarbon to oxide them, then the three harmful gases can be simultaneously purified.

From this idea, the chamical action is performed the de-oxidation reaction on the nitrogen oxide and the oxidation reaction on the carbon monoxide and the hydrocarbon by controlling air-fuel ratio to eliminate the oxygen in the combusted gas completely. The catalyst is the material accelerating certain chemical reaction. The catalyst used in this purification is called the 3way catalysts. There are the pellet type covering a film of platinum and rhodium on the particle alumina and the honey comb type.

As the theoretical air-fuel ratio, the ratio of complete combustion is 14.7. Because the 3way catalyst is not work properly when the oxygen is remained, it is necessary to maintain the air-fuel ratio with the theoretical value. To do so, an oxygen sensor is used for detecting the oxygen. If oxygen is detected in the exhaust gas, then the computer will calculate the amount of intake air and EGR gas to maintain the fuel ratio to the theoretical value.

6. Blow-by Gas Recirculation Device

The blow-by gas is the leaked gas to the crankcase through the end gap of piston ring at the combustion stroke. It includes vaporized engine oil, too. The old type engine or some racing engine exhausts this gas into the atmosphere. When you stand near the racing car, you can smell like some oil burning result from the blow-by gas.

The components of this gas are the flammable gas of 75∼80% and the combusted gas of 20∼25%. As they are the main causes of air pollution, the perfect combustion system by recirculation of this gas should be equipped by law. This device is called as the blow-by gas recirculation device or the positive crankcase ventilation, PCV in abbreviation.

In the 1ℓ of blow-by gas, 0.04∼0.05g of the strong acid moistures are included, so that the inside of the engine can be easily corroded and the engine oil can be easily oxdized. Therefore, it is important to treat the blow-by gas for maintenance the engine.

The blow-by gas amount will be increased as the pressure difference between the cylinder and the crankcase is large. The pressure inside the crankcase is not changed so much even the engine is running with high speed. So, when the engine speed and load is increased, the blow-by gas will be increased. The blow-by gas treating should be performed in two steps according to the engine load.

The blow-by gas recirculation device comprise of hoses, one is connected between the rocker cover and the surge tank, the other is connected between the rocker cover and the intake duct before throttle body for fresh air. Also there is an air passage between the crankcase and the rocker cover.

When the engine is working, the pressure in the intake manifold is always negative pressure so that the blow-by gas will be flow from the crankcase to the manifold.

The blow-by gas in the intake manifold is inhaled into the cylinder. The blow-by gas will be treated by these method.

ENGINE CHAPTER 4 Intake System

2012-09-19T05:00:00.000-07:00

Chapter 4.

Intake System

1. Enhance the Volume Efficiency

The pressure of the fuel mixture at the end of the intake stroke is lower than the ambient pressure because of the resistance against the flow of the air cleaner and duct.

And the temperature of the fuel mixture is high because that it contacts with the hot valve and cylinder wall when it is inhaled. As the density of the air becomes low when the pressure becomes lower or the temperature becomes higher.

The volumetric efficiency is used for indicating the intake ability of the mixture. As indicating the amount of the inhaled air in rate about the engine displacement, the volumetric efficiency is calculated from dividing the weight of the inhaled air by the weight of the air amount with the displacement at the same temperature and the same pressure. In another method for indicating the efficiency of the intake stroke, the charging efficiency can be used also. This is the volume efficiency when the temperature and the pressure is in the standard condition (25℃, 99kPa).

In order to enlarge the maximum output of the engine, this volume efficiency should be as high as possible. The method for enhancing the volume efficiency is like the followings.

⑴ The ambient air shall be inhaled into the manifold with not high temperature as possible. For the engine having the turbocharger, it should be equipped with the intercooler to prevent from increasing the temperature of the inhaled air.

⑵ Reduce the flow resistance of the inhaled gas by increasing the number of valves, and enlarging the size and the bending radius of the duct and manifold.

⑶ Enlarge the diameter of the valve and the height of the life, and balance the valve timing properly.

⑷ Choose a long intake manifold at the lower speed , and choose a short one at the higher speed to use the inertia and pulsation effect of the air.

⑸ Enlarge the intake gas pressure by installing the turbocharger.

Until now, we mentioned about the enhancing method for volume efficiency related to the intake stroke. It is important to exhaust perfectly the burnt gas at the exhaust stroke as possible in order to enhance the volume efficiency. It is possible to apply the (2) ~ (4) of above mentioned methods applied to the intake system except (1) and (5) to the exhaust system. For example, the “flow resistance of the inhaled gas” of (2) is took place with the “flow resistance of the exhausted gas”, and the “inertia energy of air” of (3) is took place with the “exhausting inertia”. Furthermore, the exhaust interference shall be minimized as possible. Additionally, a turbocharger shall increase the intake resistance.

By tuning up the engine, it can be effective for increasing output even it is very difficult to tune up the engine.

2. Intake Inertia Effect and Pulsation Effect

In order to inhaling air having high density to the engine, to use the inertia of the air flow is called the inertia effect, and to use the characteristics of the longitudinal wave such as sound wave according to the density of the air is called the pulsation effect. In the inertia effect, as the high density air is inhaled into the engine using a inertia energy of air. It is called as the inertia supercharging.

The air into the engine has the flow inertia as a gas and is a media for transmitting the pressure wave. The air flow in the intake manifold is periodically intercepted by the valve, so the manifold pressure has variations from the difference of pressures between high density portion and low density portion.

Valve open (Inhaled air)

Valve close (High density air at valve)

Valve open (Inhaled high density air)

Therefore, the intake inertia effect and the pulsation effect could be made. When this pressure variation affects to the intake stroke at the cycle generating the wave directly, it is called as the inertia effect. When the pressure variation is not reduced and then affects to the next cycle, it is called as the pulsation effect. However, it is not distinguished between them exactly. We, here, will call as the inertia effect when the air flow inertia is mainly governed and as the pulsation effect when the pressure wave is mainly governed.

As the first example, assume that the intake valve is closed during the fuel mixture is inhaled into the cylinder. As the fuel mixture has the flow inertia, the mixture flow in the intake manifold can not stop instantly just at the closing the valve, but pretends to flow continuously. Therefore, the air just before the valve will be pressed by inertia energy of intake air. Consequently, the air density at the port portion will be increased. At that time, if the valve is opened in time, then the air of high density can be inhaled into the cylinder. This is the inertia effect.

Valve close (High density air at valve)

Density of following air is low & pressure wave are reflected by surge tank

High density air by reflection of pressure wave is inhaled

When the air density near the port is increased, the density of the following air is low respectively. So, the boundary portion makes the pressure variations, that is, noise. This air density variation passes through the manifold with the speed of sound. It reflects to the end of the manifold, and then it returns to the port. When the high density air is back to the port, if the port is opened, then the high density air can be injected into the cylinder. This is the pulsation effect.

As these effects are combined, it is hard to separate from each other. However, in order to maximize the effect, it is prefer to make the pressure wave in the manifold to make high air density near the port when the valve is opened. To do so, the diameter and length the intake manifold and the shape of the intake port shall be controlled.

3. Variable Intake System

At low speed

At high speed

The air flow in the intake manifold is not uniformed but variable according to the engine speed. When the high density air flow reaches at the port, if, ideally, the intake speed is maximum just before the closing the valve, then the intake inertia effect will be maximized.

The air pulsation frequency is decided by the diameter and the length of the manifold. When the diameter is same, the frequency of the long length manifold is small. It is the same that the sound has the lower frequency when the distance between the hole and the mouth piece of the recorder is larger.

Generally, the length of the manifold is already decided, so if the engine is running with certain velocity, the intake inertia is effective. However, if it is rotating with variable speed, then the lower density air can reach at the port when the valve is opened so, the charging of air may be worst.

Consequently, the method for varying the length of manifold is developed according to the rpm of the engine. When the engine has high rpm in which the valve is frequently opened and closed within the same time interval, the short length manifold is chosen to make the cycle be short. Contrarily, when the rpm is low, the long manifold is chosen to make the cycle be long. So, it is possible to get the intake inertia effect in wide range of rpm. As being the variable intake system, it is called as the variable inertia charging system or the variable intake control system.

There are many types to control the length of the intake manifold. Mainly, the two types are used. The one type is that the separated two manifold groups are connected together. When the engine is high speed, the path is divided each other, and when the engine is low speed, the two manifold groups are linked each other to elongate the length of the total manifold.

The other is to attach a bypass at the manifold system in which the air pass through the bypass when the engine is low speed, and the path to the bypass is closed to reduce the length of manifold at the high speed.

In case of linking some manifolds, the resonances may be occurred between the manifolds. This comes from the pressure vibration having the same frequency in the separated manifold. In this case, the inertia charging effect can not be expected even at the high speed. This phenomenon can be inhibited by enlarging the volume of the intake collector connecting to the manifold. When the resonance is occurred, at the middle and low speed, the inertia supercharging effect becomes high so the charging efficiency will be increased. This is called as the resonance supercharging effect.

4. Intake System

The intake system takes the air to mix with the gasoline and inhales the mixtures into the cylinder. Generally, the intake system comprises the air cleaner filtering the dust in the inhaled air, the carburetor mixing the air and the gasoline, and the intake manifold (or inlet manifold) inhaling the mixture into the cylinder, at the head portion of the cylinder. Nowadays, the electrical controlled unit for fuel injecting to the intake manifold directly is widely used, so the design of the intake system is changed very much.

Carburetor intake system

MPI intake system

At first, the air inlet port which was near the cylinder head is moved to the front grill to intake the ambient air having lower temperature than the air around the engine room.

As being low temperature air, the air has high density, therefore, the much amount of oxygen will be contained into the inlet air. With the same volume of the inlet air, the lower temperature of the air is the more prefer. For example, in summer of 30℃ temperature, when the air conditioner is working at the low speed such as at the rush hour in the city, the temperature of the engine room could be over 80℃. In this case, by calculation, the amount of the oxygen in the air around engine room is 15% less than that of the ambient air.

The inlet air to the front grill is inhaled into the intake manifold through the long duct via the air cleaner, resonance chamber and throttle body.

In the carburetor system, the dish type air cleaner was look on the carburetor, but nowadays, the box type air cleaner is installed at one corner of engine room. The air cleaner not only cleans the air going into the cylinder but also reduces the noise from the intake operating. The air cleaner element should be maintained periodically.

The resonance chamber is a small box branched from the duct as the device for reducing the intake noise, and it is called as the regenerator chamber or the side branch. According to the opening and closing the intake valve, the vibration of the air inside the air cleaner box or the duct can make a large intake noise or hinder the intake operation. Using the resonance effect by installing a resonance device, this vibration will be terminated.

5. Throttle Valve and Manifold

Butterfly type, slide type throttle valve

To rise up the engine rpm, we press the accelerator pedal, and to lower down the rpm, we release the accelerator pedal. As the accelerator pedal is linked to the throttle valve by the wire and linkage, when the pedal is pressed the throttle valve will be opened to intake the air into the cylinder. That is, the carburetor or the electronic control system for fuel injection automatically checks the amount of the air to supply the amount of gasoline proper to the driving situation.

In the carburetor system, the throttle valve is equipped with the carburetor. In the electronic control system, it is installed at the middle of the throttle body (throttle chamber) separately installed in the intake system and being with the air flow sensor detecting the air flow amount and the throttle position sensor checking the status of the throttle valve opening.

In the throttle valve type, there are a butterfly valve in which disk plate having the shape of the butterfly wing is attached at the axis inside the pipe to control the air amount by rotating the axis, and a slide type in which an aluminum plate controls the amount the air without any hindrance at opening the throttle valve, especially for racing engine.

The air passing through the throttle body and the mixture mixed with gasoline at the carburetor are distributed into the cylinder by the intake manifold. The fuel injection is performed before distributing the air at the manifold, or at each cylinder as the mixture. The important thing is that the intake manifold should inhale the mixture into the cylinder as smoothly as possible, so that the manifold should have less bent portions and smooth inside faces.

The mixed gasoline in the carburetor is inhaled into the cylinder as the foggy state in the air. When the temperature is low such as just before starting the engine, this foggy particle of the fuel can attach to the manifold wall during being inhaled. Therefore, the mixture is leaned so the combustion is not enough. To solve this problem, using the heat from the exhaust manifold or from the cooling water for the engine, the intake manifold should be heated up.

The method for heating the intake system using the exhaust temperature is only used for the counter flow type engine in which both the intake and the exhaust manifolds are installed at the same side of the engine. The method for heating the intake system using the cooling water is accepted in the cross flow type engine in which the manifolds are installed at the opposite side of engine each other.

ENGINE PRINCIPAL CHAPTER 3 Cylinder Head

2012-09-19T04:56:00.002-07:00

ENGINE PRINCIPAL

Chapter 3.

Cylinder Head

1. Cylinder Head

The cylinder head is attached on the cylinder block with being inserting a gasket to prevent from leaking the combusted gas. The bottom of the cylinder head is also the roof of the combustion chamber. Therefore, the shape of the cylinder head is very complicated. The rectangular box shaped portion located upper position has the valve driving system inhalation the mixture of fuel to the engine and exhausting the combusted gas, and the ignition plug so that the shape and operation of this part can decide the engine performance such as the combustion of the mixture of fuel.

The structure of the cylinder head is various according to the type of engine. The most cylinder head has the common structure as this. At the upper part, there is the valve driving system in which the intake port inhaling the mixture of fuel into the combustion chamber and exhaust port taking out the combusted gas in the longitudinal direction. Inside the cylinder head, there is a water jacket circulating the cooling water from the cylinder block.

The combustion chamber is very important part to decide the engine performance. So the shape and the size are the important factors. If the combustion chamber is big, the time interval for combusting the mixture of fuel is long even the mixture can be compressed enough. So the bigger power can not be ensured. Therefore, it is prefer for the sized of the combustion chamber to be compact.

Additionally, the shape of the combustion chamber has less uneven surfaces as possible to enhance the combustion of the mixtures. If the shape of the combustion chamber is complicated, then the heat from the combustion shall be easily lost because the surface of the chamber is too large about the volume of it. So, the force pressing the piston shall be lowered.

The intake port is also important part because that the flow of the mixture is defined by the size and the shape of it. Considering just about the flow, the smoother inner surface is better for reducing the resistance against the flow and the straight shape of port is the better. However, the shape of the port is helpful for the inhaling mixture into the cylinder to be form the swirled flow in order to be combusted at the combustion stroke as well as possible.

The water jacket will absorb the remained heat after the combustion until finishing the exhaust stroke as fast as possible to prevent from increasing the temperature of the next inhalation mixtures. Especially, the around portions having the high possibility of increasing the temperature such as the exhaust valve and spark plug should be cooled mainly to prevent from making a trouble by the over heat.

At the cylinder head, there is bearing for supporting the valve driving system including the cam shaft. The bearing is lubricated and cooled by the engine oil.

2. Cam and Camshaft

The cam drives the valves operation opening and closing the intake port for inhaling the mixture of fuel into the combustion chamber and the exhaust port for taking out the combusted gas. For the OHC or DOHC engine, the cam is attached at the camshaft installed at the middle part of the cylinder head.

The camshaft has the cams with the same number of the valves for intake and exhaust which are arranged with angles according to the timing of the opening and closing. For the 4-cycle engine, the opening ratio of the intake and exhaust valves is one about the two revolutions of the crankshaft. Therefore, the camshaft revolves with the ratio of one turn about the two revolutions of the crankshaft.

The extrusion portion of the cam is called as the cam nose or the cam robe. The height is called cam lift. The “lift” means that the cams lift the valve so that the opening status is determined by the cam profile. The opening and closing timing of the valves are determinded by the operation angle, the angle from the start point to the end point of the nose.

When the valve is closed to the valve seat, it is preferred that the impact shall be little as possible, so that the cross sectional shape of the cam is the egg shape.

The valve is always applied a force in the closing direction by the valve spring. By pressing the spring with the cam nose, the valves will be opened. If the cam velocity becomes fast to enlarge the inertia force of the valve, the reciprocal movement of the valve is not balanced with the rotational movement of the cam. The engine speed generated by this limited speed of the valve opening and closing is the maximum speed of the engine. So the cam profile is very important.

The cam nose should be treated special surface treatment to ensure the strength for enduring from the frictions with the valve lift and rocker arm installed at the valve. To do so, the camshaft is made of cast iron and the cam nose should be treated with a cooling treatment such as the chilling method to strength the textures of the surface, when it is cast.

Small cam lift Big cam lift

There are two methods for supplying the lubricant oil to the cam journal supporting the cam nose and the camshaft, from outside and from inside. In the outside supplying method, the oil will be supplied from the journal. In the inside supplying method, the camshaft has a hole for supplying the lubricant oil from the middle portion of the journal. In addition, the camshaft is made by hollow tube type and the lubricant oil may be supplied through the hollow tube.

3. Driving the Camshaft

For the OHC engine, the crankshaft is located under the cylinder block and the camshaft is located on the cylinder head, so there should be a chain or belt for transforming the rotational movement of the crankshaft to the camshaft. As the driving for the intake and exhaust valves should be exactly timed with the rotation of the crankshaft, for some case such as racing car, a gear is used for transforming the rotational movement exactly.

In the chain system for transforming, the tooth wheel for the chain is called the sprocket. The one attached at the crankshaft is the crankshaft sprocket, and the other attached at the camshaft is the camshaft sprocket.

In the system in which the camshaft is driven by the chain, the ratio the teeth numbers between the crankshaft sprocket and the camshaft sprocket is 1:2. In order to maintain the tension of the chain, a chain tensioner is attached, and the chain guide prevents from shaking the chain during rotating.

If this method is applied to the DOHC engine, the sprocket shall have the large diameter according to the number of teeth ratio. Therefore, the gap of camshaft and gap of valves of intake and exhaust will be enlarged. Consequently, this method is not applied to the compact type engines. To solve this problem, an additional sprocket is inserted there between to transmit the rotational movement to the camshaft sprocket.

The timing belt type uses belt having toothed surface and pulley instead of the chain and the sprocket, respectively. In this type, the sprocket and pulley attached at the end of the camshaft have the timing mark indicating the opening and closing timing of the valve. So we use the term of “timing” to the name of the parts. The pulley attached at the crankshaft is the crankshaft timing pulley and the one attached at the camshaft is the camshaft timing pulley. As well as the chain type, in this type, there are direct reduction type and double reduction type.

Even though the OHC engine can accept the long chain to drive the camshaft, the belt driving method is mainly used. The reason is that the long chain can make mismatching the timing and big noises, and the chain system needs the lubricating equipment. However, the belt is made of fiber and rubber so it can be easily broken by the heat or oil. It is prefer that it should be exchanged at every 90,000km running.

4. Intake and Exhaust Valve

The cylinder head includes the intake port inhaling the mixture of fuel to the cylinder and the exhaust port taking out the burnt gas. The valves at the ports are the intake valve and the exhaust valve, respectively. According to the valve shape of mushroom, we call poppet valve.

The poppet valves consist of the valve head and the valve stem. The valve stem supports the valve guide and the valve spring. The valve is opened by the pressing operation of the cam nose, and closed by the elastic force of the valve spring.

The combustion temperature is over 2000℃, and the temperature of the burnt gas passing through the valve is over 1000℃. Therefore, the temperature of the exhaust valve is over 800℃ and that of the intake valve is over 300℃. So the material of the valve should be heat resistance steel.

The valve size is represented by the diameter of the head portion. The intake valve is larger than the exhaust valve. Representing by the area of the head portion, when the intake valve is 100, the exhaust valve is about 75∼85. This difference in their sizes is for balancing of the gas flow. The intake is performed by the decreased pressure resulting from the downing of the piston, on the other hand, the exhaust is performed by the high pressure resulting from the combustion. To balance the flow of the intake and exhaust, the intake valve size may be larger than exhaust valve.

The valve stem is designed, considering the flow, such as that of the intake valve is thinner as possible to reduce the flow resistance and that of the exhaust valve is thicker as possible to transmit the heat from the extrude portion to the stem. The heat is transferred through the path of the valve stem → the valve guide → the cylinder head → the cooling water. Some high performance engine uses the hollow stem securing sodium for enhancing the valve cooling.

The portion of the port contacting with the valve face is called as the valve seat. If the cylinder head is casting iron, then the valve seat has double structure. If the cylinder head is made of aluminum alloy, then the seat is made of heat resistance steel.

The valve spring always press the valve to attach to the cam so that the valve spring is preferable to be soft to reduce the frictional resistance generated when the cam nose presses the valve. Additionally, in order to enlarge the amount of intake and exhaust gas, the valve may be enlarged and the lift of the cam may be extended as well as the valve spring may be softened to operate faster. Then, it may make the surging problem and it is hard to be balanced.

5. Valve Driving System

As the valve controls the gases for inhaling into and the taking out from the cylinder, its driving method can give an important affects on the engine performances. There are various type of valve driving system. It has been developed from the side valve type, OHV, OHC to the DOHC type.

Side valve type

In the side valve type, the camshaft installed near the camshaft presses the long valve system to open and close the valve. The combustion chamber is large and it has long time interval for combusting the mixture of fuel so that it can not make high output power. Nowadays this type is not used.

OHV (Over head valve) type

In the Over Head Valve (OHV) type, the valve like in the side valve type is attached on the cylinder to open and close the valve using a long rod, the push rod. The shape and structure is similar with that of engines used now to enhance the performance.

OHV (Over Head Camshaft) type

After that, the OHC (Over Head Camshaft) type is developed. As know from the name, the camshaft is located over the head, exactly to say, in the middle of the cylinder head. In the OHC type, there are two types, the one is the in-line type in which the intake valve and the exhaust valve are alternatively arrayed along the linear direction, and the other is the V-shaped arrange type in which the intake valve and the exhaust valve are faced each other in opposite side to form the V-shape. The later has more enhanced efficiencies and higher performance.

DOHC (Double Over Head Camshaft) type

Developing this V-shaped arrange type more and more, the DOHC (Double Over Head Camshaft) type, in which the intake valve and the exhaust valve are independently driven by the different camshaft, is mainly used nowadays for the high performance engine. As we see from the name, there are two camshafts so we call it as the twin cam system also. Additionally, in the V-type engine, it has two cylinder head so the camshaft shall be four.

Direct type Swing arm type Rocker arm type

The driving method for the intake and exhaust valves is divided into the direct type, in which the cam directly drives the valves, and the rocker arm type, in which the cam drives the valve using a lever. The rocker arm means the lever connecting the leverage point and the cam. Using the lever, it can drive the valve faster than the cam lift.

The direct type has less components and high strength. Using the oil pressure for the hydraulic tappet, the valve can trace the cam profile always.

6. Valve Timing

The valve timing is the time at the opening and closing the intake and exhaust valve. Each time indicating when the valve starts opening and when the valve finishes closing is represented by the rotational angle of the crankshaft about the highest point or the lowest point of the piston as the standard time.

As simply saying about the opening and closing the valves, the exhaust valve will open when the piston is at the lowest point. After taking out the gas, when the piston is at the highest point, the exhaust valve will be closed. At the same time, the intake valve will be opened to take in the mixture of fuel. When the piston is at the lowest point, the intake valve will be closed.

However, this is just concept for the operation of valves. The mixture of fuel and the used gas have mass so the flow of the mixture or gas is not completed at a moment but need some time intervals. Furthermore, the valves can not open and close at an instant moment, too. For example, the intake valve need some time interval to open fully, and the mixture is not inhaled at a moment into the cylinder but inhaled during some time interval by the inertia of flow.

Therefore, the intake valve shall open prior that the piston is reached at the highest point. When the piston starts to go down, then the valve is already little opened to take into the mixture of fuel into the cylinder. By that the intake open little early, the valve will be fully opened when the piston is reached at the lowest point, so that the mixture of fuel can be inhaled enough.

Intake valve timing

When the piston is passed the lowest point, the intake valve is not closed thoroughly. To do so, the mixture will be more inhaled into the cylinder by the inertia of the flow of the mixture.

At the end of the combustion stroke, the exhaust valve will be open just before the piston is reached at the lowest point(BDC).

Exhaust valve timing

It is for exhausting the combusted gas as fast as possible by the remained expansion force in the cylinder. In the same manner of the intake valve, even the piston is passed the highest point(TDC), the valve is still opened to exhaust the burnt gas fully using the inertial of exhausting flow.

According to these operating process of the valves, there is some period in which the intake valve and the exhaust valve are opened at the same time, because the exhaust valve is closed after passing through the highest point(TDC) and the intake valve is opened before reaching to the highest point(TDC). At this time, the vacuum inertia force generated from the exhausted gas can accelerate the inhalation of the fuel mixtures. This period is called the valve overlap.

7. Variable Valve Timing

Variable camshaft angle type

Being overlapped in the opening time of intake and exhaust valve, the enhanced intake efficiency of the mixtures is as high as the enhanced exhaust efficiency of the used gas, that is, the rotation of the engine. On the other hand, when the engine is in the rotating state with low speed such as the idling state, the engine efficiency may be lowered by the lowered gas flow.

Especially, for some high performance engine having large overlap, in the low speed, the intake valve will open with large amount of burnt gas so that the burnt gas will be adhered to the intake port. Therefore, the combustion will be unstable or incompletely combusted. In the 4-valve engine, if the valve overlap is too large, then the engine will be easily unstable at the idling state. So, the overlap time for the 4-valve engine shall be very short, or some cases have the zero overlap time, that is, the intake valve is opened according that the exhaust valve is closed.

Selective camshaft-lobe type

As we mentioned, the valve timing is different according to the rotation speed of the engine. That is, the intake valve should be opened with little lately at the lower rotation, and with little early at the higher rotation. So, an additional switch operated by oil pressure is installed at the intake cam sprocket in order that the camshaft can be rotated somewhat when the engine is rotating over certain RPM so that the cam presses the intake valve early. This is the variable valve timing system.

In the variable valve timing system, the cam shape is not changed, so the valve shall be also closed early when it is opened early. Early closing the valve, the amount of the inhaled mixture is reduced. Therefore, the choice of the valve timing is decided by not only the rotation speed of the engine but also the load of the engine.

Consequently, the cam system will include the two kinds of cams, the one for the low speed of the engine and the other for the high speed of the engine. For the low speed cam, the valve will be opened lately and closed early, and the lift will be small and then the inhaled mixture of fuel will be reduced so that the fuel efficiency can be enhanced. For the high speed cam, the valve will be opened early and closed lately and the lift will be large to inhaled more mixtures so that the engine output shall be enlarged. This system also called variable valve timing system but this system controls the valve lift also. It is more advanced system.

8. Malfunction of the Valve

The valve is opened by the cam but closed by the spring. Actually, the valve attached by the spring to the valve seat is opened with the pressing by the cam nose. At that time, the force rotating the camshaft is rather small as possible. So the soft spring is more proper. However, for some high performance engine having large size of valve or lift, the spring shall be harder and the balance of the spring strength is important factor.

Even not occurring in the normal driving situation, the hardness of the spring with the weight and the strength of the valve can make an abnormal operation such as the valve jump, the valve bounce or the valve surge, when the engine is rotating over the limitation rpm.

The valve jump is that the inertial force of the valve is too large so that the cam can not press the spring and then the valve is jumped up from the cam nose when the camshaft is rotating with high speed. The valve can return back to the original position but the other dynamic components including cam, rocker arm, valve lifter, etc are damaged by friction each other.

The valve bounce is that the valve face is not contacted to the valve seat (contacted portion with the valve) but bounced from the valve seat when the valve is closed by the spring. The dynamic components shall be damaged by this bouncing. As increasing the rotation of the engine, the bouncing is occurred over than limited rpm. This limited rpm is called as the crush speed or limit rpm of the engine.

The valve surge is the abnormal vibration of the spring. As the natural frequency of the spring is corresponding with to the elastic timing by the cam, the spring can make a high movement by the self-excited vibration. When the engine is rotated in force. If it is continued then the spring shall be broken.

These abnormal operations of valve can be easily made when the valve is heavy and the lift is large. When the most used engine was the 2-valve OHC engine, they were main problems in engine. After the 4-valve DOHC engine is mainly used, these problems are scarcely occurred. As the 2-valve system became to the 4-valve system, the valve area would be enlarged so the intake and exhaust flow would be smoother. Therefore, the lift has not to be enlarged. Furthermore, the valve is to be lightened so that the spring has not to be strengthened even if the rpm is increased.

9. Overrun and Red Zone

In the tachometer of the engine, there is certain rpm range colored in red called as the red zone. Some meter has the yellow zone just before the red zone.

The rpm at the beginning of the red zone is the maximum allowable rpm decided by the characteristics and endurance requirement of the dynamic components including valve and valve spring and the main system components including piston and connecting rod when the engine is operated with the maximum speed having the maximum output.

To operate the engine over the maximum allowable rpm is called as the overrun or over-revo meaing the revolution. The over-revo may occur when the shift is down to the lower speed gear at the driving with high speed. When the engine is in the idling state, if the rpm is increased in force, then the engine will be overrun state.

When the engine is overrun, the valve shall be abnormally operated such as the valve surge, jump or bounce. In this case, the valve and spring may be damaged or in some cases, the piston may be damaged by bumping with the head of the piston and the valve. In order to prevent bumping between the piston and valve, a recessed portion is made at the piston. However, if the piston is jumped up over the recessed portion, then the piston will be bumped to the valve.

If the average speed of piston movement is abnormally fasted by the overrun, the gap between the piston ring and the cylinder will be damaged and the oil film of the bearing at the piston pin and the crankshaft will be broken so that the temperature will be increased or some parts will be adhered by this heat. When the engine is operating with high speed, the combustion speed is also fast and the around temperature of the combustion chamber will be increased. So, these problems might be easily occurred, so it needs to be careful.

Additionally, by the overrun, the engine has the increased inertia force being results of the abnormal vibration. The parts shall be broken or cracked.

The maximum allowable rpm is set with 300~1300 rpm higher than the maximum output rpm. In some engine, in the red zone the fuel injection will be cut to prevent the rpm from increasing over the maximum rpm and to prevent from making problems by the overrun.

ENGINE PRICIPAL CHAPTER TWO Cylinder Block & Moving parts

2012-09-19T04:54:00.001-07:00

ENGINE PRICIPAL

Chapter 2.

Cylinder Block & Moving parts

1. Cylinder block

The cylinder block is the basic part of the engine. It is made of cast iron or aluminum. It comprises of the cylinder in which the piston shall be moving reciprocally, the water jacket for circulating the cooling water maintaining the temperature of the cylinder, and the crankshaft installed underneath.

The role of cylinder is for guiding the reciprocal movement of the piston accepting the force and high temperature from the combustion of the mixtures, for cooling the cylinder properly, and for supporting the crankshaft. As the basis of the engine, it should have enough strength for enduring the supporting the attached all parts of engine.

For these purposes, the cylinder is generally made of cast iron because that the iron is easy to be processed mechanically and has the characteristics of good resistance against the ware and corrosion.

Recently, instead of the cast iron, the aluminum alloy is more popular. The aluminum is lighter and transmitting the heat easier than steel so that it is deemed as the ideal material for engine. It is not easy to apply the aluminum to the engine because it has different heat expansion coefficient with the steel, the main material of other parts and it is complicated to design the engine structures, as well as it is more expansive than steel.

For the passenger’s car, the weight of the engine is about 10∼15% of the total weight of the car. The 15∼20% of the engine weight is come from the cylinder block. It is very important to be light maintaining the strength of it as possible. Therefore, the skeleton structure of the cylinder block has different thickness such that the thickness is thicker of the portion applied heavy force or having possibility of deformation and the thickness is thinner of the other portions. To design the cylinder block regarding these factors, the structure analysis is performed by the finite element method in which the engine is divided into triangular or rectangular cells and the each element is established in simultaneous equations to calculate by numerical analysis using computer.

In side of the block, there should be the water jacket for circulating the cooling water so it should be precisely manufactured for the complicate structure. To prevent from cracking at the bottle neck point of different thickness or to enhance the resistance against wear, it should be heat treated.

2. Cylinder Liner

The inside wall of the cylinder block is the frictional face with the piston with a lubricant oil there-between. Therefore, it satisfies the strict requirements that it endures at the high temperature and wear, that its changes of the dimension by the heat expansion coefficient shall be within the tolerance, and that it should not be adhesive with each other by the high temperature.

Generally, when the block material is the steel, this part is made by polishing the cast iron cylinder, so called as the linerless type. When the block material is the aluminum alloy, the inside wall of the cylinder having a cylinder liner made of cast ion for preventing the ware of the side wall. The liner is the thing which is attached the inside of the cylinder. The cylinder liner may be made with the cylinder block or separately and joined after that with the cylinder.

For the aluminum cylinder block, the cast iron is used. It is heavier than the aluminum alloy as well as it has the lower heat transmission ratio than the aluminum. Therefore, for the engine of racing car or high efficiencies, the special liner made of the silicon alloy based on the aluminum or having special treatment on the aluminum surfaces are utilized.

These special liners are so expensive and hard to manufacture. Also, there are some tries to develop the linerless cylinder with aluminum alloy cylinder block. Even though the linerless cylinder is more expensive, the engine can be lighter and compacted so that it is mainly accepted to the high performance engines.

The gap between the cylinder liner and the piston is depended on the material. When the liner is the cast iron and the piston is the aluminum alloy, considering that the heat expansion ratio of the aluminum is almost twice than that of the steel so that the gap will be reduce at the high temperature of the engine, the gap shall be 30∼40 microns (0.03∼0.04mm) at the room temperature. If the liner and the piston are all the aluminum, then the gap shall be 10 microns because there is no difference of the heat expansion between them.

The around of the cylinder liner is formed as a shape of path for cooling water, the water jacket, to maintain the temperature of the engine to certain value by absorbing the heat energy come from the remained energy of the combustion.

3. Water Jacket

When casting the cylinder block, the cylinder is surrounded by the core made of sand to form vacant spaces. These spaces are the water jacket for circulating the cooling water to take down the temperature of the cylinder head and cylinder to the proper temperature for operating.

The water circulating inside the water jacket goes into the engine from the lower outlet port of the radiator cooling the heated water. The water flows from the lower part of the engine to the upper part of the engine. After cooling the cylinder head, the heated water is taken out from the engine and goes into the upper inlet port of the radiator. During circulating inside the water jacket, it is important to cool down the each cylinder equivalently. The design of the water jacket is focused on the flow method to spread the water smoothly over the all parts with smaller volume of the water as possible. The heated water is cooled in the radiator and then return to the water jacket again. In winter, the heated water selectively flow into the another radiator for heating the cabin.

Generally, the water jacket is surrounding the cylinder thoroughly. In order to reduce the path length along to the cylinder array, the water jacket is surrounding the out side of the cylinder so that the water does not flow into the adjacent space the cylinders. This type is called the Siamese type. Like the Siamese twins, some portions of the jacket surrounding the each cylinder are merged into one body. The conventional jacket is called the full jacket type.

For the engine having the liner, the type is divided into two kinds by whether the water is contacting with the liner or not. When the cylinder liner is surrounded by the wall of the cylinder block so that the outside of the liner can not contact with the cooling water, it is called the dry type liner. When the most portions of the liner contact with the cooling water directly, it is called the wet type liner.

The wet liner has better cooling efficiency. It should be sealed with an O-ring between the liner and block to prevent leaking the cooling water. In HMC, the most engines having the liner are equipped with the dry type liner because HMC have not any problem come from the heat adhesive of the engine yet and we worry about the leaking the cooing water.

4. Piston

The piston moving inside the cylinder reciprocally transmits the weight force of 3~4 tons (5 tons for diesel engine) according to the combustion of the fuel mixture gas having over temperature of 2000℃ at the combustion stroke to the connecting rod. The first thing to be considered in design of the piston is that the piston should be made of light materials to reduce the inertia force of the reciprocal movement. The next point is that its material should have the strength enough to endure the combustion force. And then, the material of the piston shall have the good heat-trance and not be distorted or deformed by the high temperature.

At first, the aluminum or aluminum alloy can be considered for lightening and strengthening. Then, for enhancing the heat resistance to prevent from changing in dimension, the heat treatment shall be performed.

The upper part of the piston is called as the piston head or the piston crown. It is very important part forming the combustion chamber between the cylinder head. To enhance the combustion efficiency by combusting the fuel mixture instantly, the shape of piston head prefer to be flat. To enhance the compression ratio, the middle portion may be upraised or there are some recessed positions, the valve recess, to take the intake and exhaust valves not to touch with the piston. The under portion of the piston is the piston skirt stabilizing the reciprocal movement of the piston. The some front portions of the skirt looks like being cut out because that the balance weight is passing these areas when the piston goes down.

There is a gap between the piston and the cylinder. This gap shall be sealed with the piston ring. When the piston is moving in reciprocal, some portions of the skirt may be touching the cylinder wall. To reduce this touch, the shape of the skirt shall be changed. The shorter length of the skirt has fewer noises from the friction with the piston and lighter weight. However, it is preferable for designing the skirt to be balanced with the size of the piston.

The piston is connected with the connecting rod by a piston pin. So, the most forces of combustion are applied to this pin. As the piston pin is the shape of hollow cylindrical structure, the larger of outer diameter, in a same weight, is the more strength against the bending force. However, when the diameter of the piston pin is enlarged, the piston pin boss shall be also enlarged. Therefore, the compression height, the length from the pin to the piston head, is also longed so the weight of the engine is heavier. So, the diameter should be designed by considering the balance with the piston size.

5. Piston Ring

The main roles of the piston ring, the wheel shaped steel surrounding the head part of the piston, are to prevent from leaking the gas by sealing between the piston and the cylinder, to prevent from remaining the lubricant oil in the combustion chamber by gathering the oil down from the cylinder wall and to prevent from transmitting the heat from the piston to the cylinder.

Generally, the piston ring comprises of three rings. The two rings near to the piston head are called the compression rings, and the one ring near to the skirt is the oil ring. The top ring of the compression rings is used for sealing the gas, the oil ring is used for removing the lubricant oil, and the second ring of the compression rings is used for helping the sealing and for controlling the thickness of the lubricant oil film.

Some piston comprises of the two rings, the compression ring and the oil ring. In this case, the roles of rings are somewhat loss, but the fuel efficiency can be enhanced by reducing the loss of force from the friction between the piston ring and cylinder wall. Some racing cars accept the two ring system for shortening the piston height to reduce the engine weight.

The compression ring is made of the spring steel by casting iron, and the surface should be heat treated to reduce the friction and to enhance the lubricant of the piston. To insert the ring into the grooved portion of the piston and to ensure the tensile force for compressing to the cylinder, one portion of the ring shall be opened. This open portion is called the end gap. The combusted gas is leaked out through this end gap a little. This blow-by gas is returned to the combustion chamber by the returning device not to leak out.

The grooved portion of piston for the compression ring has slightly lager then the width of the rings. When the piston is moving up and down, the rings are rotating to prevent the end gap of the three rings from being aligned each other. If the rings have not enough strength, the rings are fluttering within the grooves at the high speed of the engine so it can not seal the gas properly.

The cross section of the oil ring has the shape of reversed “C”. The gathered oils by the rings are returned to the inside of the piston through the hole located at the lower portion of the C-shaped ring. When the engine has high speed, the ring can not gather the oil only with the its tensile force, so an additional spring, the expander, shall be attached to enforce the compressing force of the ring to the cylinder.

6. Connecting Rod

The connecting rod is the rod for connecting the piston and the crankshaft. It transfers the reciprocal movement to the rotation movement. The connecting rod moves very complicatedly with swing movement about the piston pin and the linear movement up and down. So, there is a balance weight to control the inertia force generated by the complicating movements.

The contribution ratio of the connecting rod weight to the inertia force is about 2 to the one reciprocal movement. To lightening the load to the bearing and the vibration by reducing the inertia force, the connecting rod should be light as possible. However, it has enough strength to transmit the combustion force to the crankshaft.

The connecting rod is made of the special steel by casting or forging. The forging is preferably used for ensuring the strength. For the racing cars, the expensive but very light and strong material, titanium alloy, is used also.

The types of the rod can be divided into two types according to the cross sectional shape of the rod, I type and H type.

If the strength is same, then the I-type is lighter than H-type. Therefore, general cars accept the I-type rod. The H-type has stronger structure against the bending force to the direction of the pin axis.

As the Connecting rod is longer, the lateral vibration is smaller. The reason is that, considering the force applied to the piston at the rotation of the crank by divided into lateral direction and longitudinal direction, the longer connecting rod can reduce the ratio of the force to the lateral direction than the shorter connecting rod so that the vibration and friction also shall be reduced. However, if the connecting rod is so long, the engine weight is heavier so it is not preferable. Generally, the length from the center of the piston pin to the crank pin, is about twice than the length of the stroke.

The end portion of the connecting rod to the piston side is called as the small end, and the end portion to the crank pin side is called as the big end. The small end is connected to the piston with the piston pin, and the big end is attached to the crank pin by inserting a bearing.

7. Crankshaft

The crank means the 『bended handle』 as the transfer from the reciprocal movement to the rotational movement as have mentioned until now. At the early time of the vehicles history, the engine is started with the crank. After the electric motor was used for the starting the engine, until 1950s, Some cars had have a crank at the front of the engine for emergency device at the malfunction of the motor.

The crankshaft connects the cranks of each cylinder. The main shaft is called the crank journal and the attaching part to the big end of the connecting rod with the crank is called the crank pin. The other side, the attaching part to the small end of the connecting rod with the piston is called the piston pin. The connector connecting the crank journal and the crank pin is called the crank arm. The sector formed pendulum at the front of the crank arm is called the counter weight or the balancing weight.

The reason of the shape of the counter weight being spreading from the center (root) to the circumferential portion (outer portion) is that it can have larger inertial force when it rotates about the root part; even the counter weight has the same weight density.

In the reciprocal engine, the piston is press the crank journal with the connecting rod at every combustion stroke. The crankshaft affected by the complicated bending and distorting force. Therefore, the crank journal shall have strength enough to endure these forces so it is made of the casting or forging steel. For the high performance engine or the racing car engine, the forging steel is most used for ensuring the strength. For the commercial or general purpose vehicle, the casting steel is used because the forging process is more expensive. Even though the casting steel has less strength than forging steel, it is not so critical point because that it is possible to manufacture the counter weight precisely.

The counter weight balances the weights force between from the reciprocal movement of the piston and from the rotational movement of the crankshaft. Simply think, to balance the weight is to match the inertia forces from the piston and the counter weight as the ratio of 1:1. The counter weight should be small as possible within the requirement load range of the journal in order to reduce the weight of the crankshaft.

8. Crank Case

The crank case is the part covering from the cylinder of the cylinder block to the crankshaft.

In the crank case, there are some auxiliary devices such as the alternator (the alternative current generator), generating the electric power, the compressor of the air conditioner and the oil pump for the power steering. And the engine mount brackets installing the engine to the vehicle body are also attached to the crank case. As the crank case is one part of the cylinder block, it is always vibrated by the reciprocal movement of the piston and the rotational movement of the crankshaft. Therefore, the material of the crankshaft should satisfy the requirement of the resistant against the shocking force and vibration.

The types of the crank case are divided into two types according to the covering range over the crankshaft, the half skirt type and the deep skirt type. In the half skirt type, the front portion of the crank case is covering to the center of the crankshaft. In the deep skirt type, the crank case is covering over the bearing cap.

Because the half skirt type has the short length, it is possible for the block to make be light. However, the joint strength shall be weaker than the deep skirt type, because the joining area is small when the transmission is attached to the engine. It is easy to make some vibrations so that it is necessary to be assisted by supporters. Additionally, the space for attaching the auxiliary devices shall be smaller.

To secure the crankshaft to the cylinder block and to reinforce the strength of the block, a supporting device might be formed with the bearing of the crankshaft at the lower part of the crank case. According to the type of this supporting device, there are the ladder frame style and bearing beam style.

At the lower part of the cylinder block, an oil pan is attached also. This is for gathering the oil completing the lubricating and cooling role. It is made of a pressed steel sheet and attached by rubber packing like the head cover. The oil pan is easy to make a noise so that it is made of the vibration resistance steel plate. The vibration steel plate is manufactured by inserting a resin plate between the two steel plates to prevent from vibrating.

9. Journal Bearing

The bearing is for helping the smooth rotation of the rotating axis and supporting the rotation axis. There are various types of the bearing including the plain bearing supporting the axis with the flat and wide side, and the bearing supporting the axis and the around of the axis with balls or rollers. Generally, for the crankshaft of the engine, the plain bearing is more used.

The reason that the roller bearing type is not applied to the crankshaft is that the load can be concentrated at the contacting portions of the ball or roller in a point or linear type. In the plain bearing the load is applied on the lubricated side, the larger contacting area than the ball or roller bearing so that the plain bearing can support large force.

As the plain bearing is also called as a sliding bearing, the shaft is sliding on the bearing with the lubricant oil. Even if the surface of the solid metal body is applied the smoothing surface treatment precisely and carefully, it should have roughness somewhat. Therefore, when the two solid bodies are directly contacted, they should be worn.

The lubricant oil inserting between the plain bearing and the axis can make the rough surface of these two solid bodies to be smoothly. The two solid bodies are not contacted directly even they are so closed.

The thickness of the oil film, that is the gap with the bearing, is changed by the load or heat expansion. When it is so small, it may be adhered by friction heat, otherwise, when it is so big, it may make vibrations and noise.

The bearing is made by welding the bearing alloy having light weight and good fatigue resistance such as the copper or aluminum. On the surface, a special metal basis on the lead is coated. The bearing has the oil hole and oil groove for supply the lubricant oil to lubricate the contact portion between the connecting rod and the crank pin and between the crankshaft and the crank case.

The crank journal, the rotational axis of the crankshaft, is attached at the lower part of the cylinder block by the bearing cap with the plain bearing. For the serial engine, this bearing should be attached at the front side and rear side of the cylinder. If it is the 4-cylinder, it has 5 bearings and if it is the 6-cylinder, it has 7 bearings, that is, it called as 5-bearing and the 7-bearing, respectively. Certain old style engine of 4-cylinder might have 3-bearing structure. This type is not used because the crankshaft is easy to be bent and make vibrations.

10. Flywheel

The flywheel is equipped to the transmission side of the crankshaft to maintain the smooth rotation using inertia force and to reduce the irregularity of the rotational force. The crankshaft is rotated twice per one of the combustion. At the other strokes, the reversed directional force shall be needed for the compression, the intake and exhaust. If there is no the flywheel, then the rotational force of the crankshaft shall be reduced at these strokes. Therefore, when the intervals of the each combustion stroke are long like in the idling state, the engine may be stopped.

Around the flywheel, a ring gear is attached to rotate the crankshaft by being teethed with the pinion gear. The clutch disk can attach to the flat side of the flywheel by the spring to transmit the driving force to the transmission.

The magnitude of the torque is calculated by multiple the magnitude of the force to the distance between the center of the axis to the point at which the force is applied. The magnitude of the force is proportional to the inertia mass so that if the fly wheel is heavy and the outer diameter is large, or if the outer portion is heavy, then the force of the flywheel might be large.

In general engine, the half of the total inertia mass is distributed at the flywheel. Therefore, when the rotation of the engine is low or when the engine is in the idling state, the inertia mass of the flywheel should be large to rotate the engine regularly. However, with the large inertia mass of the flywheel, the rotation of the engine can not be changed easily. It is hard to increase the engine rotation by pressing the accelerator, or to take the engine brake by releasing the accelerator. That is, the engine response will be worse. So, the fuel efficiency shall be worst too.

Some engines use the 30% of the torque generated from the engine to increase the rotation of engine itself when the accelerating is performed with the lower speed shift. The size and the weight of the flywheel are decided by the purpose of the vehicles. For example, the engine for the racing car uses small size one, and that of the family car uses large size one. For the general purpose, the flywheel is made of the cast iron, and for the special purpose such as the racing car, it is made by cutting the steel material having high strength.

11. Balance shaft, Balancer for the secondary inertial force

The piston, the Connecting rod and the crank make inertia force according to the reciprocal and rotational movement. For this reason, if the one-cylinder engine has not the counter weight for balancing between the inertial force and the weight of the piston, the connecting rod and the crank, then the engine may be severely vibrated by the unbalancing.

For the serial 4-cylinder engine, the four pistons are connected to the crankshaft with being paired the first, forth and the second , third, in facing each other. When the crankshaft is rotating, the inertial forces are offset so that the counter weight might be not needed.

In actual movement structure of the piston-crank system of the 4-cylinder engine, the inertia force shall not be offset. This is come form the structure in which the piston in reciprocal movement is connected to the crank in rotational movement with the connecting rod. For example, in the half rotation of the crankshaft when the piston moves from the highest point (TDC, Top Dead Center) to the lowest point (BDC, Bottom Dead Center), the piston has the maximum speed at the near of the highest point of the stroke rather than at the middle of the stroke. The rotation of the crank is regular so that the inertia force of the crank of each cylinder (the first inertia force) is easily offset. However, the inertial force of the piston is not. For example, the upper inertia force generated when the first and forth pistons are moving from the highest point to the lowest point is larger than the lower inertia force generated when the second and third pistons are moving from the lowest point to the highest point.

By representing these relationship on the graph with the inertia force at the vertical axis and the rotation angle of the crankshaft at the horizontal axis, when the upper inertia force of the first and fourth pistons is maximum value, the lower inertia force of the second and third pistons is minimum value, and vice versa after the crankshaft with 180°. From this relationship, we know that the inertia force is generated with the ratio of 2 times per one rotation of the crankshaft. This inertia force is called as the secondary inertia force. It is easy to be generated when the engine is in the idling state.

The four-cylinder engine is equipped in the small passenger car generally. For the convenience of the passengers, a balance shaft having the half circle shape in the cross sectional view shall be attached at the both side of the engine to reduce the vibration from the secondary inertia force. This balance shaftt is designed to rotate with two times of speed in reverse direction against the crankshaft. The additional inertia force generated from the balance shaft will offset the vibration from the secondary inertia force.

ENGINE PRINCIPLES

2012-09-19T04:49:00.002-07:00

Engine Principles

Chapter 1.

What is the engine?

1. What is the engine?

This book introduces about the automobile engine especially the gasoline engine.

However, it is very complecate to define about the engine, so called, what the engine is. In general concept, the engine is 『the devices driving something by changing the energy in the natural source such as fire, wind or electric material to the mechanical energy continuously』. There are many types of the engine and they are driven in different ways.

Therefore, we can define the gasoline engine, as a kind of combustion device in other word, the 『device changing the heat acquired by combusting the gasoline to the mechanical force for driving the vehicles』.

How is the heat energy changed into the mechanical energy? For example, the bottle or pot. As they are heated, the covers move with a noise.

The heat acquired from the gas or electric energy boils the water so as to make the water vapor pushing up the cover of the bottle or pot.

There is an important thing. The moving force is not come from the heat energy, but the hot air or vapor by the heat works.

That is, the media is need for changing the energy form. This media is the working fluid in the technical terminology. The working fluid for the gasoline engine is the air in-taken with the gasoline into the engine and then combusted and exhausted.

The procedure for transmitting the fuel to the mechanical energy in the vehicle engine will be explained in the following sections.

In this process, the working fluid is the air. If there is no working fluid, the energy transformation shall not be performed.

In contrary, think about the transforming the mechanical energy to the heat energy. In the vehicle, the brake is the represented example. The principle is the friction heat coming from the rubbing or striking the two materials. We can warm our hands by rubbing each other, that is, the moving force(rubbing) can easily transform to the heat energy(warming hands). At this time, there is no working fluid. The force is changed into heat directly.

However, when the heat energy is transformed into the mechanical energy, there must be a working fluid. Being the media for the transforming the energy, there should be a lot of loss of energy, at any case. Therefore, how much energy of the heat can be transformed into the mechanical energy, the efficiency, is an important factor in the engine.

2. Kinds of engine

There are many kinds of the engines.

The engines can be classified by the number of cylinder, the array style of the cylinder or the equipped method at the vehicle, and so on.

As you know, the engine makes the driving force by the reciprocal movement of the piston in the cylinder so that the power is decided by the number of the cylinder.

Therefore, the engine is mainly classified by the number of the cylinder. The commercial vehicles are classified into the 2, 3, 4, 5, 6, 8, and 12 cylinders. More displacement volume has the more cylinders.

According to the array of the cylinder, there are three types including the In-line type with serial arraying of the cylinder, the V type with V-shaped arraying of the cylinder and the opposed type in which the cylinders are arrayed facing each other.

According to the engine installation type, there are two types; the one is the lengthwise type and the breadthwise type. When the engines are arrayed in length direction of the vehicle is called as the lengthwise type, when the engines are arrayed in width direction of the vehicle is called as the breadthwise type.

Lengthwise type Breadthwise type

For example, the FR type car having the engine at front and driving the rear wheels has the lengthwise type engine. The reason is that the propeller shaftt transmitting the driving force to the rear wheels shall be run underneath the floor. In the case of FF type car, the most small car, having the engine at front and driving the front wheels, the engine is breadthwise type because that the rotation axis of the engine and the driving axis rotating the wheels should be are parallel. However, when the FF type car has the 6-cylinder engine, if the serial engine is installed in width direction, then the width of the car is too wide. Therefore, in that case, the engine rather is the V-type. In this manner, considered with the displacement volume and vehicle type, the engine array type and the installation type are selected for the best combination in design.

3. Engine layout

FF : Front Engine Front Drive

FR : Front Engine Rear Drive

MR : Midship Engine Rear Drive

RR : Rear Engine Rear Drive

It is possible to assume that the engine will be installed at the front of the car. However, the all vehicles do not have their engine at front side. In 1770, the origin of the car, the engine of the steam car of Cugnot was located at the front ends of the body. In 1885, the first car equipped the gasoline engine, the engine of the Daimler’s car is located at the under the seat and the front of the rear wheel axis.

In the history, many researches had been performed to find the best condition where the engine was installed. In 1891, the FR (front engine rear drive) car was in France. The FR type is that the engine was installed at the front side and the rear wheels were driven. After that, this type would be the set as the standard layout of the engine. Until now, the most large passenger cars and the sports cars accept this type.

The typical characteristics of the FR type car is that the cabin space is located to rear side, the steering is controlling the front wheels and the driving is contributed to the rear wheels so that the operation and weight load are evenly divided to the front side and rear side and the movement performance and passenger convenience are balanced as well as the vibration and noise are less than other types.

In the layout of the relatively small public car, there had been two big developments for about hundred years. The first one is the Volkswagen in 1936 having the engine at the rear side for driving the rear wheel. After the World War II, this type was leading the worldwide design of the mainstream the passenger car of rear engine and rear drive (RR) type. The second one is the Mini of England in 1959. The Mini accepted the front engine and front drive (FF) type having the breadthwise type engine at front side for driving the front wheels. Nowadays, this type is applied to the small cars as well as the middle sized sedans.

The FF type car has the engine and driving devices at the front side so that it should not applied to the car of which weight is concentrated to the front side. The defect of this type is that it is not easy to steer the car. However, it has the relatively large space of indoor and trunk, and the safety is better than other types. Therefore, it is the best design for the layout of the utility cars.

The midship engine and rear drive (MR) type is focused on the performance rather than the convenience of the passenger so that it is mainly applied to the sports cars. When the main parts of the engine are located at front side than the rear wheel type, it is called the midship type. When the main parts are located at rear side, it is called the rear engine type.

4. Expansive Force and Inertia Force

Almost of the commercial gasoline engines for the vehicles are the Recipro-engines except for the rotary engine of which working principle is different. The word “Recipro” comes from the “Reciprocating”. The reciprocation is the mechanical movement of go and back so that the Recipro-engine is the device transforming the reciprocal movement to the rotational movement using the crank which is the device having the prominence and depression shape.

The cross sectional view of the Recipro-engine shows that there is a piston reciprocal moving in the cylinder at the upper side and there is a crankshaft at the lower side and the piston and the crankshaft are connected by the connecting rod.

The gasoline engine uses the air as the media of working fluid for transforming the heat energy to the mechanical energy. The air is mixed with the mist of gasoline in the cylinder. When the mixture of air and gasoline are compressed using the piston and combusted, then the expansive gas will press the piston. The expansive force pressing the piston shall drive the car.

At this time, except for the expansive force, there is an inertia force which we are considering. This force is somewhat strange because it is not generated intentionally; however, this force is followed in the moving part of the engine naturally. Therefore, it can affect to the performance of engine or is the source of the vibration or noise.

Considering the reciprocal movement of the piston, the piston starts moving from the halt state at the highest position of the stroke, has the maximum speed at the middle of the stroke, After that, the speed is reduced and stops to the lowest position of the stroke, and then goes back to the highest position again. During performing these movements, the inertia forces shall be generated when the speed of movements are changed. For example, from the highest position of the piston to the middle of the stroke, there is an ascending inertia force. After that there is a descending inertia force from the middle of the stroke to the lowest position of the piston.

When this inertia force is resonated with the other inertia forces from the other pistons, there may be vibrations or noises.

5. Reciprocal Engine

The Recipro-Engines are classified into two types, the 2-cycle type and the 4-cycle type. After developed by Daimler of Germany in 1883, the 4-cycle type which had been completed its standard system until 1900 is the mainly used in the most of vehicles.

The principle of the reciprocal engine is that the mixture of the air and the gasoline are injected into the cylinder, the mixture is combusted using the electric spark to explode, the combustion force drives the piston in reciprocal movement, and the reciprocal movement is changed to the rotational movement by the crankshaft.

The operation of the 4-cycle engine is like that. When the piston is at the highest position, the intake valve is opened. Being down the piston, the mixtures of fuel gas is injected into the cylinder and then the intake valve is closed [Intake Stroke]. Next, the piston will go to upward to compress the mixtures of gas [Compression Stroke]. Then, the compressed mixtures of gas will be burnt by an electrical ignition [Combustion Stroke]. The burnt gas having the high pressure and temperature will press the piston downward. At this time, the exhaust valve shall be open to take out the burnt gas [Exhaust Stroke]. These strokes are repeated.

Among these 4 strokes, only at the combustion stroke, the engine makes the power for work. Therefore, there are needed the additional forces, for intake and exhausting the gas at the intake and exhaust stroke, and for compressing the mixture at the compression stroke. To do so, a flywheel is installed to the crankshaft to make these additional forces using the inertia force to ensure the continuous rotational movement.

The 2-cycle engine comprises of the two strokes. The operation of this engine comprises the four components such as the intake, the compression, the combustion, and the exhaust as the 4-cycle engine.

Compression and Expansion

Exhaust and Intake

However, before and After the piston is located at the highest position, the compression and combustion operations are performed, and before and After the piston is located at the lowest position, the exhaust and intake operation at the same time. So, through the two strokes, the one cycle of engine operation is completed. The 4-cycle engine performs the combustion stroke at one time per two cycles of the crankshaft, but, the 2-cycle engine performs the combustion stroke at every cycle of crankshaft. Therefore, the 2-cycle has higher efficiency.

Scavenging

Additionally, it has no intake and exhaust valves so that it has simple structure and low cost. However, this merit can be a defect.

The exhaust gas is exhausted by the entering new mixtures of gas when the piston is located at the lowest position. Therefore, some new mixtures will be mixed the combusted gas and unburned gases will be exhausted. It makes the air pollutions and the large fuel consumptions.

6. Exhaust & Intake Stroke

This content will explain about the engine on focusing the 4-cycle gasoline engine, the most used type.

To understand the 4 strokes, the intake, the compression, the combustion, and the exhaust, it is helpful to refer the figures, the indicator diagram (P-V diagram), showing the process of the engine operations.

It looks somewhat complicated, but it is easy to understand just following the figures.

The indicator diagram is the graph consisting of the horizontal axis representing the pressure of the chamber and the vertical axis representing the volume of the chamber. At the left ends of the graph, C and F, the piston is located at the highest position of the cylinder, and at the right ends of the graph, G and H, the piston is located at the lowest position of the cylinder.

By comparing the lines of the graph to the 4 strokes, the line of A-B is the intake stroke, the line of B-C is the compression stroke, the line of C-D is the combustion stroke and the line of D-E is the exhaust stroke.

In act, the cycle of the strokes is starting from the intake stroke. To understand the engine operation, it is easy to start from the exhaust stroke. To inhale more air as possible, the engine uses also the force from the exhausted gas outgoing to the outside of the engine through the exhaust port.

The exhaust stroke is for pushing the combusted gas to outside of the chamber by moving the piston from the lowest position to the highest position with being opened exhaust valve. In principle, it is think that the exhaust valve will be opened when the piston is reaching at the lowest position.

Exhaust stroke

However, actually, the exhaust valve prefers to be opened before the piston reaches to the lowest position, that is, at the position of D in the drawing. Remaining the pressing force of the burent gas, the exhausting the used gas is more effective by opening the exhaust valve in advance. After that, the piston will push out the remained used gas thoroughly to finish the exhaust stroke.

At the intake stroke, the intake valve is opened, and the piston goes down from the highest position to the lowest position so that the mixtures of fuel gas and the air are inhaled into the cylinder from the intake port. At that time, the intake valve shall be opened just before the piston reaches the highest position, that is, the E in the drawing. Doing so, the intake operation is enhanced somewhat because of the exhausting force of the used gas will pull the intake gases.

Intake stroke

With the same manner, the intake valve shall be closed when the piston is at the B. Doing so, more mixtures of gas shall be inhaled into the cylinder by the inertia force of the intake gas. To inhale air into the engine is performed by the difference of air pressure. When the piston goes down, the air pressure in the cylinder is lower than that of the outside of the cylinder, so that the air around the intake valve shall be inhaled to the cylinder. The opening timing of the valve is different from the stroke position is to use this force to inhale more air as possible

7. Compression and Combustion Stroke

At the compression stroke, the mixtures of gas are compressed by the piston, so that the pressure is increased and the temperature is high by adiabatic compression. Therefore, the gasoline is vaporized by the compressive heat of the air, ready to be combusted. The injected gasoline in the cylinder like the misty with the air is vaporized to be gas state by the heat from the adiabatic compression. Then it is ready to be combusted easily. This space for combustion is called the combustion chamber.

The reason of that it is hard to start the engine in winter is that it is hard for the gasoline to be vaporized. To solve this problem, one method is to mix more gasoline with the air. Another problem is that; when the gasoline is vaporized, the ambient heat is used to the vaporization, so the temperature of the chamber is lowered somewhat. It may decrease the fuel efficiency of the engine. To prevent from lowering the fuel efficiency, the amount of the gasoline is reduced. However, to do so, the temperature of the chamber is so high that the combustion may be performed prior to the ignition, so called the abnormal combustion.

The most important fact from the intake stroke to the compression stroke is the flow of the mixtures of the gasoline and the air. It is not proper that the flow is too strong to be ignited. The little particles of gasoline should be mixed with air to be the mixtures. Therefore, many manufacturers research and develop the shape of the intake port and flow pattern of the mixtures so that the strength and the pattern of the mixture flow are maintained until the combustion stroke for the best efficiency of the engine.

Compression stroke

As processing the compression stroke, the piston reaches the highest position. When the piston is at the C of the drawing, the ignition will be performed by the electric spark generated from the spark plug. The timing to make the spark is very important. The mixture is not fully combusted at the ignition time, but the combustion is started from the ignition. It is needed some time interval between the time of the ignition and the time to be maximum pressure of the chamber.

Combustion stroke

The ignition timing is determined by considering that the combustion shall be completed between the highest position and the almost half position of the combustion chamber. Additionally, this combustion speed is proportion to the rotational speed of the engine so that the ignition timing should be adjusted with the engine speed.

Beginning the combustion, the vaporized mixtures are combusted in a short time so that the pressure and the temperature are increased. At this time the expanded gas by the combustion shall press the piston. This pressing force should be stronger as possible. The time period of combustion is preferable to be short to strength the force. If the time period for combustion is longer, then the combustion force is not leading the pressing the piston but following the piston. Therefore, the engine efficient is worst. The combustion time period is affected by flow of the mixtures defined by the size and shape of the combustion chamber and the component of the mixture and so on.

8. Engine structure

The gasoline engine is a complicated machine having comprising of parts. Look into how the engine is structured.

The engine is similar with the 3 floors building. The first floor is the crank case including the crankshaft transforming the reciprocal movement to the rotational movement. The second floor is the cylinder block including the cylinder of which a piston is moving with reciprocal movement. The third layer is the cylinder head.

In this structure, the moving parts of the first layer and the second layer are called as the main moving part. It includes the piston, the crankshaft and the connecting rod.

In the third layer, there are the valves controlling the intake and exhaust of the mixtures gas and the used gas and the camshaft operating the valves. These are called the cylinder head system.

On the cylinder head, there are intake manifold sending the gasoline and the air to the cylinder and the exhaust manifold taking out the burnt gas. These are called the intake-exhaust system. The manifold consists the “many” and the “fold”, that is, many materials are combined. In actual, they are many branched pipes distributing the air and gasoline to each cylinder or merging the exhausted gases in one place.

There is the fuel system including the fuel pump taking the gasoline from the fuel tank and the carburetor or fuel injector to make a air fuel mixture.

There is the lubrication system including the oil pump supplying the oil for reducing the frictions and the oil filter for filtering the oil.

Also there is the cooling system including the radiator and water pump for maintaining the temperature of the engine properly.

To drive the engine, the electric power is needed. There are electric devices including igniting spark plug, the alternator generating the electric power and the start motor supplying the initial movement to the engine.

Additionally, there are the auxiliaries such as the oil pump for the power steering the air-con compressor and so on.

9. Diesel Engine

The diesel engine has similar shape and structure with those of the gasoline engine. The different point is the ignition method. The gasoline engine ignites the mixture of fuel with the electric spark. Contrary, in diesel engine, the fuel is injected into the compressed air having the high temperature. When the air is compressed, the temperature of compressed air is increased. The gasoline engine compresses the mixture of fuel gas up to 1/10 of the initial volume.

The diesel engine compresses the air about 1/20 of the initial volume to increase the temperature of the air over 600℃, and injects the fuel compressed with over 100 atm at the injection pump during 1/1000∼2/1000 seconds. The output shall be controlled by the amount of injected mixtures of fuel and air for the gasoline engine. On the other hand, the output of the diesel engine can be controlled by the amount of the injected fuel without controlling the air (the fixed amount of the air).

To combust the fuel perfectly by increasing the temperature of the air, the compression ratio shall be increased. However, doing so, the expansion power will be increased also. Therefore, the engine should be stronger to endure the increased force. Additionally, the high quality of fuel injecting pump may be needed. Then the engine is heavier and the cost is expensive. So diesel engine is not proper to apply to the passenger’s car.

In the diesel engine, because almost constant amount of the air about the volume of the cylinder is inhaled, the load applying to the engine is relatively light. When the fuel amount is small at the low speed, the fuel shall be almost perfectly combusted. However, with the full load, the diesel engine needs more amount of fuel so that the air amount is respectively small. Therefore, it may exhaust a lot of black smoke.

In the gasoline engine, the ignition is performed by the electric spark to the mixture so the combustion time period is very short. However, in the diesel engine, the fuel diesel is sprayed into the compressed air, so it needs some time period to be vaporized. Therefore, the maximum speed of engine is limited relatively lower and the output shall be lower than the gasoline engine.

Compared with the gasoline engine, the expansion force and the inertia force of the moving part are bigger so it makes bigger noise and more vibration. It has merits of easy maintenance resulted from not having the delicate parts such as the ignition system and of good fuel efficiency so that it is used for commercial or business purpose rather than passenger’s car.

10. Internal Combustion & Motor

The force of the 4-cycle gasoline engine, as one of the internal combustion, is changed according to the RPM (Revolutions Per Minute) of the engine compared by the electric motor or the steam engine. So, it is impossible to drive with the lower revolutions than certain RPM value. Therefore, the clutch and the transmission should be equipped when the gasoline engine is used for vehicles.

For the 4-cycle engine, using the four strokes, it makes moving force by combusting the mixture of fuel and air in the cylinder. It is very different with the electric motor used in electric vehicles which can start just by applying the electric power. If the mixtures are not supplied into the cylinder at idle condition, the engine can not continue to run. In order that the engine should be operating continuously when the vehicle is stopped, the device for connecting or disconnecting the moving force of the engine to the wheels such as clutch should be equipped.

In general, the vehicles needs larger power when it is started or accelerated, but when it is driven in constant speed, it does not need larger power. For the motor, it outputs larger force when it rotates with lower RPM, and when the RPM is increased, the output will be lower. Therefore, the electric motor can be applied to the engine of the vehicles without any transmitting device.

However, for the gasoline engine, the power is determined according to the RPM of the engine. The range of the RPM is limited within certain ranges. For example, the RPM of the gasoline engine is about 700∼7000 revolutions per minute, and the RPM for getting the maximum power (torque) is about 4000 revolutions. Therefore, when the vehicles are running with various speeds, it is necessary to control the speed and power of the vehicle by inserting a transmission between the engine and the wheels.

At simple sight, the motor may be the best engine for the vehicles. The important thing is the fuel, the source of power. The gasoline is easy to store during operating the engine, but it is hard for the motor to store the electric power effectively.

To develop the electric vehicles, it is essential to develop the batteries having the high efficiency for charging and maintaining the rechargeable batteries in equivalent state. Many companies are trying developing the method for maintaining the rechargeable batteries. Even though the basic performance has been developed in field test, the manufacturing cost is very high. However there are being suggested some patents and technologies for utilizing.

11. Lean Burn Engine

The exhaust purification system using the 3way catalysts has the characteristics of maintaining the actual air-fuel ratio to the ideal valve to perform the oxidation and reduction of the harmful compounds simultaneously. To do so, the purification of the exhausted gas will be limited, and the fuel amount used for the engine is decided by the engine driving status. Therefore, the engine shall not be developed no more to get higher driving force with less amount of the fuel.

The lean burn system is developed for enhancing the fuel efficiency with the good purification of exhaust gas. To enhance the fuel efficiency is most important point for future. The lean burn engine is one of the most attracted public attention technologies.

With the high A/F ratio by reducing the gasoline in the mixture, how are the three major harmful materials, carbon monoxide, hydrogen carbon, and nitrogen oxide. The oxygen is more plentiful than fuel, so the amount of carbon monoxide will be less or the most carbon monoxide will be changed into carbon dioxide, harmless gas. The hydro carbon will also be completely combusted and changed into carbon dioxide and water. Now we will concern only the last one, nitrogen oxide.

If the A/F ratio is higher, then the temperature will be increase by the plentiful of the oxygen and the amount of the nitrogen oxide will be increased. At about 16 of A/F ratio, the nitrogen oxide will be maximized. If the A/F ratio is higher than 16, then the combustion temperature will be down so the torque is also down. If the A/F ratio is higher and higher, the combustion is not stable, and torque is very unstable, finally combustion will not be performed.

A manufacturer focused on the torque variations according to the lean burn. By adapting the combustion pressure sensor detecting the combustion pressure in the cylinder, the engine is operated with the A/F ratio just before the torque variation is occurred. Therefore, they can make next generation lean burn engine having the low fuel consumption and the less amount of nitrogen oxide. In that system, the lean burn is performed at the condition in which the driving is not hindered by the low torque at low load. When the vehicle in accelerating or high load, the combustion is performed with the theoretical A/F ratio and the exhaust gas is purified by 3way catalyst. Many manufacturers continue to research for enhancing the fuel consumption by focusing on the intake system and combustion chamber with 16∼20 of A/F ratio. Many new engines satisfying this combustion requirement and having less exhaust gas problem are shown more and more.

SIX STROKE ENGINE

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SIX STROKE ENGINE

The six-stroke engine is a type of internal combustion engine based on the four-stroke engine, but with additional complexity intended to make it more efficient and reduce emissions. Two types of six-stroke engine have been developed since the 1990s:

In the first approach, the engine captures the heat lost from the four-stroke Otto cycle or Diesel cycle and uses it to power an additional power and exhaust stroke of the piston in the same cylinder. Designs use either steam or air as the working fluid for the additional power stroke.^[1] The pistons in this type of six-stroke engine go up and down three times for each injection of fuel. There are two power strokes: one with fuel, the other with steam or air. The currently notable designs in this class are the Crower six-stroke engine, invented by Bruce Crower of the U.S. ; the Bajulaz engine by the Bajulaz S.A. company of Switzerland; and the Velozeta Six-stroke engine built by the College of Engineering, at Trivandrum in India.

The second approach to the six-stroke engine uses a second opposed piston in each cylinder that moves at half the cyclical rate of the main piston, thus giving six piston movements per cycle. Functionally, the second piston replaces the valve mechanism of a conventional engine but also increases the compression ratio. The currently notable designs in this class include two designs developed independently: the Beare Head engine, invented by Australian Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann.

Engine types

Griffin six-stroke engine

In 1883, the Bath-based engineer Samuel Griffin was an established maker of steam and gas engines. He wished to produce an internal combustion engine, but without paying the licensing costs of the Otto patents. His solution was to develop a 'Patent slide valve' and a single-acting six-stroke engine using it.

By 1886, Scottish steam locomotive maker Dick, Kerr & Co. saw a future in large oil engines and licensed the Griffin patents. These were double acting, tandem engines and sold under the name "Kilmarnock".^[2] A major market for the Griffin engine was in electricity generation, where they developed a reputation for happily running light for long periods, then suddenly being able to take up a large demand for power. Their large heavy construction didn't suit them to mobile use, but they were capable of burning heavier and cheaper grades of oil.

The key principle of the "Griffin Simplex" was a heated exhaust-jacketed external vapouriser, into which the fuel was sprayed. The temperature was held around 550 °F (288 °C), sufficient to physically vapourise the oil but not to break it down chemically. This fractional distillation supported the use of heavy oil fuels, the unusable tars and asphalts separating out in the vapouriser.

Hot bulb ignition was used, which Griffin termed the 'Catathermic Igniter' , a small isolated cavity connected to the combustion chamber. The spray injector had an adjustable inner nozzle for the air supply, surrounded by an annular casing for the oil, both oil and air entering at 20 lbs sq in. pressure, and being regulated by a governor.^[3][4]

Griffin went out of business in 1923.

Only two known examples of a Griffin six-stroke engine survive. One is in the Anson engine museum. The other was built in 1885 and for some years was in the Birmingham Museum of Science and Technology, but in 2007 it returned to Bath and the Museum of Bath at Work.^[5]

Bajulaz six-stroke engine

The Bajulaz six-stroke engine is similar to a regular combustion engine in design. There are however modifications to the cylinder head, with two supplementary fixed capacity chambers: a combustion chamber and an air preheating chamber above each cylinder. The combustion chamber receives a charge of heated air from the cylinder; the injection of fuel begins an isochoric burn which increases thethermal efficiency compared to a burn in the cylinder. The high pressure achieved is then released into the cylinder to work the power or expansion stroke. Meanwhile a second chamber which blankets the combustion chamber, has its air content heated to a high degree by heat passing through the cylinder wall. This heated and pressurized air is then used to power an additional stroke of the piston.

The claimed advantages of the engine include reduction in fuel consumption by at least 40%, two expansion strokes in six strokes, multi-fuel usage capability, and a dramatic reduction in pollution.^[6]

The Bajulaz Six-Stroke Engine was invented in 1989 by the Bajulaz S A company, based in Geneva, Switzerland; it has U.S. Patent 4,809,511 and U.S. Patent 4,513,568.

The Bajulaz six-stroke engine features:

§ Reduction in fuel consumption by at least 40%

§ Two expansion (work) strokes in six strokes

§ Multifuel, including liquefied petroleum gas

§ Dramatic reduction in air pollution

§ Costs comparable to those of a four-stroke engine

Velozeta six-stroke engine

In a Velozeta engine, during the exhaust stroke, fresh air is injected into the cylinder, which expands by heat and therefore forces the piston down for an additional stroke. The valve overlaps have been removed and the two additional strokes using air injection provide for better gas scavenging. The engine seems to show 40% reduction in fuel consumption and dramatic reduction in air pollution.^[7] Itsspecific power is not much less than that of a four-stroke Gasoline engine.^[7] The engine can run on a variety of fuels, ranging fromGasoline and diesel to LPG. An altered engine shows a 65% reduction in carbon monoxide pollution when compared with the four stroke engine from which it was developed.^[7]

The engine was developed in 2005 by a team of mechanical engineering students Aaron Joseph George, Arun K Nair, Boby Sebastian, Krishnaraj U of the College of Engineering, Trivandrum.

NIYKADO Six Stroke Engine

This Engine was designed, developed and patented by Chanayil Cleetus Anil owner of NIYKADO Motors, Kochi during the year 2012. He holds the Indian patent number IN252642 which was granted to him by IPIndia on 25th May 2012. The engine has already undergone a preliminary round of full-throttle tests at the Automotive Research Association of India (ARAI), Pune.

This is the only engine that is categorized under fully working prototype.^{[citation needed]}The first prototype was developed in 2004 which used only two valves. The second prototype was improved design from the first prototype which used four valves in 2007.

Crower six-stroke engine

In a six-stroke engine prototyped in the U.S. by Bruce Crower, water is injected into the cylinder after the exhaust stroke, and is instantly turned to steam, which expands and forces the piston down for an additional power stroke. Thus, waste heat that most engines require an air or water cooling system to discharge is captured and put to use driving the piston.^[8] Crower estimated that his design would reduce fuel consumption by 40% by generating the same power output at a lower RPM. The weight associated with a cooling system could be eliminated, but that would be balanced by a need for a water tank in addition to the normal fuel tank.

The Crower six-stroke engine was an experimental design that attracted media attention in 2006 because of an interview given by 75 year old American inventor has applied for a patent on his design. ([1]) That patent application was subsequently abandoned.^[9]Leonard Dyer invented the first six-stroke internal combustion water injection engine in 1915, which is very similar to Crower's design. A dozen more similar patents have been issued since.

Dyer's six-stroke engine features:

§ No cooling system required

§ Improves a typical engine’s fuel consumption

§ Requires a supply of pure water to act as the medium for the second power stroke.

§ Extracts the additional power from the expansion of steam.

Beare Head

The term "Six Stroke" was coined by the inventor of the Beare Head, Malcolm Beare. The technology combines a four stroke engine bottom end with an opposed piston in the cylinder head working at half the cyclical rate of the bottom piston. Functionally, the second piston replaces the valve mechanism of a conventional engine. first use of "sixstroke" 1994

M4+2

The M4+2 engine working cycle animation

The M4+2 engines have much in common with the Beare Head engines, combining two opposed pistons in the same cylinder. One piston working at half the cyclical rate of the other. But while the main function of the second piston in a Beare Head engine is to replace the valve mechanism of a conventional four stroke engine, the M4+2 take the principle one step further.The double pistons combustion engine's work is based on the co-operation of both modules. The air load change takes place in two-stroke engine. The piston of four-stroke engine is exchange aiding system which improves air load change. It works as a system of valves. The cylinder is filled with air or with air-fuel mixture. Filling process takes place at overpressure by the slide inlet system. The exhaust gases are removed as in the classical two-stroke engine (by exhaust's windows in cylinder). The fuel is supplied into the cylinder by fuel injection system. The ignition is realized by two spark plugs. The effective power output of the double pistons engine is transferred by two crankshafts. The characteristic feature of this engine is an opportunity of continuous change of cubic capacity and compression rate during engine work by changing the piston's location. The mathematical models (mechanical and thermodynamical) were meant for double pistons engines which enable to draw up new theoretical thermodynamic cycle for internal combustion double pistons engine.

The working principle of the engine is explained in the Two- and four-stroke engines article.

]Piston charger engine

In this engine, similar in design to the Beare head, a "piston charger" replaces the valve system. The piston charger charges the main cylinder and simultaneously regulates the inlet and the outlet aperture leading to no loss of air and fuel in the exhaust.^[10] In the main cylinder, combustion takes place every turn as in a two-stroke engine and lubrication as in a four-stroke engine. Fuel injection can take place in the piston charger, in the gas transfer channel or in the combustion chamber. It is also possible to charge two working cylinders with one piston charger. The combination of compact design for the combustion chamber together with no loss of air and fuel is claimed to give the engine more torque, more power and better fuel consumption. The benefit of fewer moving parts and design is claimed to lead to lower manufacturing costs. Good for hybrid technology and stationary engines. The engine is claimed to be suited to alternative fuels since there is no corrosion or deposits left on valves. The six strokes are: aspiration, precompression, gas transfer, compression, ignition and ejection. This is an invention of Helmut Kottmann from Germany, working 25 years at MAHLE GmbH piston and cylinder construction.

Related U.S. patents

§ 1217788 Internal combustion and steam engine Feb 27, 1917. Hugo F. Liedtke seems to be one of the first to contemplate alternating between internal combustion and steam injection into the combustion chamber.

§ 1339176 Internal combustion engine May 4, 1920. Leonard H. Dyer invented the first 6-stroke internal combustion/water-injection engine in 1915.

§ 3964263 Six cycle combustion and fluid vaporization engine Jun 22, 1976

§ 4143518 Internal combustion and steam engine Mar 13, 1979

§ 4301655 Combination internal combustion and steam engine Nov 24, 1981

§ 4433548 Combination internal combustion and steam engine Feb 28, 1984

§ 4489558 Compound internal combustion engine and method for its use Dec 25, 1984

§ 4489560 Compound internal combustion engine and method for its use Dec 25, 1984

§ 4736715 Engine with a six-stroke cycle, variable compression ratio, and constant stroke Apr 12, 1988

§ 4917054 Six-stroke internal combustion engine Apr 17, 1990

§ 4924823 Six-stroke internal combustion engine May 15, 1990

§ 6253745 Multiple stroke engine having fuel and vapor charges Jul 3, 2001

§ 6311651 Computer-controlled six-stroke internal combustion engine and its method of operation Nov 6, 2001

§ 6571749 Computer-controlled six-stroke cycle internal combustion engine and its method of operation Jun 3, 2003

§ 7021272 Computer controlled multi-stroke cycle power generating assembly and method of operation Apr 4, 2006

Related Indian Patents

§ IN patent|252642|252642 Six Stroke Engine May 25, 2012

[References

§ Bajulaz Six-Stroke Engine Accessed June 2007

§ Bajulaz Animation Accessed June 2007

§ Lyons, Pete (February 23, 2006). "Inside Bruce Crower’s Six-Stroke Engine". AutoWeek. Retrieved 2007-06-22.sixstroke.com

INTERNAL COMBUSTION ENGINE

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Internal Combustion

The principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a potato 500 feet. In this case, the energy is translated into potato motion. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine!

Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated in Figure 1. They are:

Intake stroke
Compression stroke
Combustion stroke
Exhaust stroke

Figure 1

You can see in the figure that a device called a piston replaces the potato in the potato cannon. The piston is connected to the crankshaft by a connecting rod. As the crankshaft revolves, it has the effect of "resetting the cannon." Here's what happens as the engine goes through its cycle:

The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. (Part 1 of the figure)
Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. (Part 2 of the figure)
When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. (Part 3 of the figure)
Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. (Part 4 of the figure)

Now the engine is ready for the next cycle, so it intakes another charge of air and gas.

Notice that the motion that comes out of an internal combustion engine is rotational, while the motion produced by a potato cannon is linear (straight line). In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft. The rotational motion is nice because we plan to turn (rotate) the car's wheels with it anyway.

Now let's look at all the parts that work together to make this happen, starting with the cylinders.

Figure 2. Inline - The cylinders are arranged in a line in a single bank.

Basic Engine Parts

The core of the engine is the cylinder, with the piston moving up and down inside the cylinder. The engine described above has one cylinder. That is typical of most lawn mowers, but mostcars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine, the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures.

Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing cost and shape characteristics. These advantages and disadvantages make them more suitable for certain vehicles.

Figure 3. V - The cylinders are arranged in two banks set at an angle to one another.

Figure 4. Flat - The cylinders are arranged in two banks on opposite sides of the engine.

Let's look at some key engine parts in more detail.

Spark plug

The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.

Valves

The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.

Piston

A piston is a cylindrical piece of metal that moves up and down inside the cylinder.

Piston rings

Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.
They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly.

Connecting rod

The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

Crankshaft

The crankshaft turns the piston's up and down motion into circular motion just like a crank on a jack-in-the-box does.

Sump

The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).

Next, we'll learn what can go wrong with engines.

Engine Problems

So you go out one morning and your engine will turn over but it won't start... What could be wrong? Now that you know how an engine works, you can understand the basic things that can keep an engine from running. Three fundamental things can happen: a bad fuel mix, lack of compressionor lack of spark. Beyond that, thousands of minor things can create problems, but these are the "big three." Based on the simple engine we have been discussing, here is a quick rundown on how these problems affect your engine:

Bad fuel mix - A bad fuel mix can occur in several ways:

You are out of gas, so the engine is getting air but no fuel.
The air intake might be clogged, so there is fuel but not enough air.
The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly.
There might be an impurity in the fuel (like water in your gas tank) that makes the fuel not burn.

Lack of compression - If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons:

Your piston rings are worn (allowing air/fuel to leak past the piston during compression).
The intake or exhaust valves are not sealing properly, again allowing a leak during compression.
There is a hole in the cylinder.

The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.

Lack of spark - The spark might be nonexistent or weak for a number of reasons:

If your spark plug or the wire leading to it is worn out, the spark will be weak.
If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark.
If the spark occurs either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will not ignite at the right time, and this can cause all sorts of problems.

Many other things can go wrong. For example:

If the battery is dead, you cannot turn over the engine to start it.
If the bearings that allow the crankshaft to turn freely are worn out, the crankshaft cannot turn so the engine cannot run.
If the valves do not open and close at the right time or at all, air cannot get in and exhaust cannot get out, so the engine cannot run.
If someone sticks a potato up your tailpipe, exhaust cannot exit the cylinder so the engine will not run.
If you run out of oil, the piston cannot move up and down freely in the cylinder, and the engine will seize.

In a properly running engine, all of these factors are within tolerance.

As you can see, an engine has a number of systems that help it do its job of converting fuel into motion. We'll look at the different subsystems used in engines in the next few sections.

Engine Valve Train and Ignition Systems

Most engine subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine. Let's look at all of the different subsystems used in modern engines, beginning with the valve train.

Figure 5. The camshaft

The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called acamshaft. The camshaft has lobes on it that move the valves up and down, as shown inFigure 5.

Most modern engines have what are calledoverhead cams. This means that the camshaft is located above the valves, as you see in Figure 5. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams." SeeHow Camshafts Work for details.

Figure 6. The ignition system

The ignition system (Figure 6) produces a high-voltage electrical charge and transmits it to the spark plugs via ignition wires. The charge first flows to a distributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylinders) coming out of it. These ignition wires send the charge to each spark plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. This approach provides maximum smoothness. See How Automobile Ignition Systems Work for more details.

We'll look at how your car's engine starts, cools and circulates air in the next section.

Diagram of a cooling system showing how all the plumbing is connected

Engine Cooling, Air-intake and Starting Systems

The cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled instead (You can tell an air-cooled engine by the fins adorning the outside of each cylinder to help dissipate heat.). Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance. See How Car Cooling Systems Work for details.

So now you know how and why your engine stays cool. But why is air circulation so important? Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is called boost. A turbocharger uses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. A supercharger is attached directly to the engine to spin the compressor.

Photo courtesy Garrett

See How Turbochargers Work for details.

Increasing your engine's performance is great, but what exactly happens when you turn the key to start it? Thestarting system consists of an electric starter motor and a starter solenoid. When you turn the ignition key, the starter motor spins the engine a few revolutions so that the combustion process can start. It takes a powerful motor to spin a cold engine. The starter motor must overcome:

All of the internal friction caused by the piston rings
The compression pressure of any cylinder(s) that happens to be in the compression stroke
The energy needed to open and close valves with the camshaft
All of the "other" things directly attached to the engine, like the water pump, oil pump, alternator, etc.

Because so much energy is needed and because a car uses a 12-volt electrical system, hundreds of amps of electricity must flow into the starter motor. The starter solenoid is essentially a large electronic switch that can handle that much current. When you turn the ignition key, it activates the solenoid to power the motor.

Next, we'll look at the engine subsystems that maintain what goes in (oil and fuel) and what comes out (exhaust and emissions).

The exhaust system of a Porsche 911.

THOMAS LOHNES/AFP/Getty Images

Engine Lubrication, Fuel, Exhaust and Electrical System

When it comes to day-to-day car maintenance, your first concern is probably the amount of gas in your car. How does the gas that you put in power the cylinders? The engine's fuel system pumps gas from the gas tank and mixes it with air so that the proper air/fuel mixture can flow into the cylinders. Fuel is delivered in three common ways: carburetion, port fuel injection and direct fuel injection.

In carburetion, a device called acarburetor mixes gas into air as the air flows into the engine.
In a fuel-injected engine, the right amount of fuel is injected individually into each cylinder either right above the intake valve (port fuel injection) or directly into the cylinder (direct fuel injection).

See How Fuel Injection Systems Work for more details.

Oil also plays an important part. The lubrication system makes sure that every moving part in the engine gets oil so that it can move easily. The two main parts needing oil are the pistons (so they can slide easily in their cylinders) and any bearings that allow things like the crankshaft and camshafts to rotate freely. In most cars, oil is sucked out of the oil pan by the oil pump, run through the oil filter to remove any grit, and then squirted under high pressure onto bearings and the cylinder walls. The oil then trickles down into the sump, where it is collected again and the cycle repeats.

Now that you know about some of the stuff that you put in your car, let's look at some of the stuff that comes out of it. The exhaust system includes the exhaust pipe and the muffler. Without a muffler, what you would hear is the sound of thousands of small explosions coming out your tailpipe. A muffler dampens the sound. The exhaust system also includes a catalytic converter. See How Catalytic Converters Work for details.

The emission control system in modern cars consists of a catalytic converter, a collection of sensors and actuators, and a computer to monitor and adjust everything. For example, the catalytic converter uses a catalyst and oxygen to burn off any unused fuel and certain other chemicals in the exhaust. An oxygen sensor in the exhaust stream makes sure there is enough oxygen available for the catalyst to work and adjusts things if necessary.

Besides gas, what else powers your car? The electrical system consists of a battery and an alternator. The alternator is connected to the engine by a belt and generates electricity to recharge the battery. Thebattery makes 12-volt power available to everything in the car needing electricity (the ignition system, radio, headlights, windshield wipers, power windows and seats, computers, etc.) through the vehicle's wiring.

Now that you know all about the main engine subsystems, let's look at ways that you can boost engine performance.

The turbocharger system of the Nissan GT-R.

FABRICE COFFRINI/AFP/Getty Images

Producing More Engine Power

Using all of this information, you can begin to see that there are lots of different ways to make an engine perform better. Car manufacturers are constantly playing with all of the following variables to make an engine more powerful and/or more fuel efficient.

Increase displacement - More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger or by adding more cylinders. Twelve cylinders seems to be the practical limit.

Increase the compression ratio - Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (before the spark plug ignites it). Higher-octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high-octane gasoline -- their engines are using higher compression ratios to get more power.

Stuff more into each cylinder - If you can cram more air (and therefore fuel) into a cylinder of a given size, you can get more power from the cylinder (in the same way that you would by increasing the size of the cylinder). Turbochargers and superchargers pressurize the incoming air to effectively cram more air into a cylinder. See How Turbochargers Work for details.

Cool the incoming air - Compressing air raises its temperature. However, you would like to have the coolest air possible in the cylinder because the hotter the air is, the less it will expand when combustion takes place. Therefore, many turbocharged and supercharged cars have an intercooler. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder. SeeHow Car Cooling Systems Work for details.

Let air come in more easily - As a piston moves down in the intake stroke, air resistance can rob power from the engine. Air resistance can be lessened dramatically by putting two intake valves in each cylinder. Some newer cars are also using polished intake manifolds to eliminate air resistance there. Bigger air filters can also improve air flow.

Let exhaust exit more easily - If air resistance makes it hard for exhaust to exit a cylinder, it robs the engine of power. Air resistance can be lessened by adding a second exhaust valve to each cylinder (a car with two intake and two exhaust valves has four valves per cylinder, which improves performance -- when you hear a car ad tell you the car has four cylinders and 16 valves, what the ad is saying is that the engine has four valves per cylinder). If the exhaust pipe is too small or the muffler has a lot of air resistance, this can cause back-pressure, which has the same effect. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system. When you hear that a car has "dual exhaust," the goal is to improve the flow of exhaust by having two exhaust pipes instead of one.

Make everything lighter - Lightweight parts help the engine perform better. Each time a piston changes direction, it uses up energy to stop the travel in one direction and start it in another. The lighter the piston, the less energy it takes.

Inject the fuel - Fuel injection allows very precise metering of fuel to each cylinder. This improves performance and fuel economy. See How Fuel Injection Systems Work for details.

In the next sections, we'll answer some common engine-related questions submitted by readers.

Two-stroke Engine

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Two-stroke Engines Working

The Two-stroke Cycle

The following animation shows a two-stroke engine in action. You can compare this animation to the animations in the car engine and diesel engine articles to see the differences. The biggest difference to notice when comparing figures is that the spark-plug fires once every revolution in a two-stroke engine.

This figure shows a typical cross flow design. You can see that two-stroke engines are ingenious little devices that overlap operations in order to reduce the part count.

2012-04-27T05:02:00.000-07:00

BASIC ENGINE TERMINOLOGY

1. TDC

This refers to the position of the crankshaft when the piston is in its topmost position. ie, the position closest to the cylinder head

2. BDC
This refers to the position of the crankshaft when the piston is in its lowest position ie, the position farthest to the cylinder head
3. BORE
Diameter of the engine Cylinder

4. STROKE
Distance travelled by the piston From TDC to BDC
5. Clearance Volume
The volume of cylinder (including the combustion chamber) above the piston when it is in the TDC position is reffered to as the Clearance Volume
6. Piston Displacememt
This is the volume by the piston in moving from TDC to BDC. This is also called swept volume. If 'd' is the cylinder bore and 's' the stroke, the piston displacement, Vs is given by
Vs = 3.14*d*d*s
7. Engine Capacity
This is the total swept volume of all cylinder. 'n' is the total no of cylinder , Vs is the piston displacement . Then engine CC
Vd = Vs*n
8. Compression Ratio
9. Mean Effective Pressure
10. Power
11. Indicated power
12. Brake Power
13.Engine Torque

AUTOMOBILE

2012-04-26T05:06:00.000-07:00

AUTOMOBILE HISTORY
The first practical automobile with a petrol engine was built by Karl Benz in 1885 in Mannheim, Germany. Benz was granted a patent for his automobile on 29 January 1886, and began the first production of automobiles in 1888, after Bertha Benz, his wife, had proved with the first long-distance trip in August 1888 (104 km (65 mi) from Mannheim to Pforzheim and back) that the horseless coach was absolutely suitable for daily use. Since 2008 a Bertha Benz Memorial Route commemorates this event.

Soon after, in 1889, Gottlieb Daimler and Wilhelm Maybach in Stuttgart designed a vehicle from scratch to be an automobile, rather than ahorse-drawn carriage fitted with an engine. They also are usually credited as inventors of the first motorcycle, the Daimler Reitwagen, in 1885, but Italy's Enrico Bernardi, of the University of Padua, in 1882, patented a 0.024 horsepower (17.9 W) 122 cc (7.4 cu in) one-cylinder petrol motor, fitting it into his son's tricycle, making it at least a candidate for the first automobile, and first motorcycle.^[1]^:p.26 Bernardi enlarged the tricycle in 1892 to carry two adults.^[1]^:p.26

Until 2005, the U.S.A. led the world in total automobile production. In 1929 before the Great Depression, the world had 32,028,500 automobiles in use, and the US automobile industry produced over 90% of them. At that time the U.S. had one car per 4.87 persons.^[2] In 2006, Japan narrowly passed the U.S. in production and held this rank until 2009, when China took the top spot with 13.8 million units. By producing 18.3 million units in 2010, China produced nearly twice the number of second place Japan (9.6 million units), with the U.S. in third place with 7.8 million units.^[3]

AUTOMOBILE

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Mahindra Quanto

ENGINE Chapter 12. Performance, Fuel consumption, Noise, Vibration

ENGINE Chapter 11 Combustion and Combustion Chamber

ENGINE Chapter 10 Ignition System

ENGINE Chapter 9 Fuel System

ENGINE Chapter 8 Cooling System

ENGINE Chapter 7. Lubrication System

ENGINE PRINCIPLES Chapter 6. Charger

ENGINE PRINCPLES Chapter 5. Exhaust System

ENGINE PRINCPLES

ENGINE CHAPTER 4 Intake System

ENGINE PRINCIPAL CHAPTER 3 Cylinder Head

ENGINE PRICIPAL CHAPTER TWO Cylinder Block & Moving parts

ENGINE PRICIPAL

ENGINE PRINCIPLES

SIX STROKE ENGINE

Engine types

Griffin six-stroke engine

Bajulaz six-stroke engine

Velozeta six-stroke engine

NIYKADO Six Stroke Engine

Crower six-stroke engine

Beare Head

M4+2

]Piston charger engine

Related U.S. patents

Related Indian Patents

[References

INTERNAL COMBUSTION ENGINE

Internal Combustion

Basic Engine Parts

Spark plug

Valves

Piston

Piston rings

Connecting rod

Crankshaft

Sump

Engine Problems

Engine Valve Train and Ignition Systems

Engine Cooling, Air-intake and Starting Systems

Engine Lubrication, Fuel, Exhaust and Electrical System

Producing More Engine Power

HORSEPOWER

Two-stroke Engine

Two-stroke Engines Working

The Two-stroke Cycle

AUTOMOBILE