This entry will introduce you to the process that occurred in internal combustion 4 stroke engine. There are 4 major processes that occurred in engine that are intake stroke, compression stroke, power stroke and exhaust stroke. So, let’s look at each of this process.

Intake
In the intake stroke, the piston will move downward and the air-fuel mixture will be forced to enter the combustion chamber through the intake poppet valve which is drawn open by the vacuum produced by the intake stroke. The exhaust valve is shut by the spring.

Compression
The piston will rise and both the poppet valves will be forced shut by the increased cylinder pressure. The air-fuel mixture will be compressed.

Power
In this stroke, the spark plug will fire and then the compressed air-fuel mixture will be ignited. The piston will then driven downward.

Exhaust
In this stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted gases out of the cylinder.

Sources:
1. http://www.keveney.com/otto.html
2. http://auto.howstuffworks.com/engine1.htm

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