Working of an engine?

In a view to improve my knowledge, can anyone pls let me know about the working of an engine, (both petrol & diesel). Pls explain in a simple way, as i am a layman in this field.

Well, in general all internal combustion engines (i.e., those found in cars) do the following;

• Intake - take in air
• Mix - mix the fuel with air
• Inject - introduce the air-fuel mix into the cylinder (NOTE: in common technical usage this is referred to as "intake". However I have made a deviation here due to the context).
• Compress - compress the air-fuel mixture inside the cylinder
• Combust - ignite the air-fuel mixture. This causes the compressed mixture to expand pushing the cylinder's piston thereby providing the force to move the engine's crankshaft (i.e., output shaft). This is also the "power stroke".
• Exhaust - after the combusion residual gases are removed

In a 4-stroke engine the above cycle (excluding intake & mix - that is done outside the engine's cylinders) is completed in 4 stages (per revolution of the crank) while in a 2-stroke engine it is completed in 2 stages (per crank revolution). It can be seen that in the 4-stroke engine, the power stroke exists for only a fourth of the crank revolution while in a 2-stroke it lasts for half of the crank's rotation - this means that theoretically an ideal 2-stroke engine can deliver twice the power per crank revolution as compared to an ideal 4-stroke engine, both engines being of the same dimensions, weight & no. of cylinders. Practically 4-stroke engines are popular since they have less emissions. 2-stroke engines require the engine oil to be mixed with the fuel causing greater burnt oil in the exhaust (i,e more pollution) while 4-stroke engines don't need the oil to be mixed into the fuel. Oil is needed in order to lubricate the engine's cylinder and other parts.

Thanks for the description. I had lil knowledge about the 4 stroke engine. But i need to know about throttle and throttle valve. What does it actually means?

To add to the above - it is slightly incorrect to say that only internal combustion engines do the above. All engines do the above - only the way they do it is different. for example even an aeroplane jet engine does the same things - except that in this case all the stages are taking place continuously and simultaneously (in different regions of the engine). In the internal coumbustion engine all the stages occur at the same place - inside the cylinder (hence the term "internal") but in discrete steps.

Hope this post has not caused or added any more confusion than the previous post

Throttle refers to the accelerator. Technically it refers to how much air is being sucked in (or the physical mechanism that controls it). Throttle valve is simply a butterfly valve located in the air intake manifold - whose position (i.e. open/closed/more or less open) is controlled by the accelerator pedal (via a cable).

Does MPFI or ECM got anything to do with this procedure?

And what happens in Drive by Wire technology?

MPFI or ECM does not have anything to do directly with intake, mixing, etc. - most older cars did not use either technologies. However these are improvements to car design. MPFI was a big leap over SPFI and addition of ECU made it even better.

Drive-by-wire basically means that the driver's actions are not directly transmitted to the car (or used to control the car) but sensed by an electronic system. This system then actuates the related part or parts to control the car.

Note: MPFI stands for multi-point fuel injection - basically there are injectors located over every cylinder which open and close in unison with the fuel intake valve.

SPFI stands for single-point fuel injection - this term is merely used to differentiate such engines from MPFI. Before MPFI there were only intake valves opening from the intake manifold into the cylinders.

Mods: Please correct me if I am wrong here...

check this out,

http://www.youtube.com/watch?v=FfTX88Sv4I8

Fly by wire technology is becoming outdated. Fly by light is novel successor.

That means throttle controls only intake of air.

throttle controls the injection into the combustion chanber. So the more you use the throttle, the faster you go and vice versa

Does that mean throttle is the device through which air passes into the combustion chamber, and throttle valve is a device which controls the flow of the air.