
As our cars are mostly 4 Strokes or Otto cycle engine, we will be looking at one cylinder to see how the process works.
The four strokes involved are Intake, Compression, Power and Exhaust.
1) Intake
The four strokes involved are Intake, Compression, Power and Exhaust.
1) Intake
The piston starts at the top moving downwards as the intake valve open and takes in a cylinder full of air and gasoline mixture.
When the piston reaches the end of the downwards stroke, the intake valve closes. Trapping the air and gasoline mixture.
2) Compression
When the piston reaches the end of the downwards stroke, the intake valve closes. Trapping the air and gasoline mixture.
2) Compression
The piston moves back up compressing the air and gasoline mixture. The amount of the mixture compression is based on hte compression of the engine. The compression ratio of average engine is in the range of 8:1 to 10:1.
Example for 10:1. When the piston reaches the end of the upwards stroke, the air and gasoline mixture is compressed to about one tenth of its original volume.
3) Power
While the piston reaches the end of the upwards stroke, the spark plug emits a spark to ignite the air and gasoline mixture. The combustion pushes the piston downwards with great force which will turn the crankshaft to provide power to propel the car.
Combustion will occur by each piston at a different time which are determined by the engine order.
4) Exhaust
Once the piston is at the bottom of its stroke, the exhaust valve opens to allow the combusted exhaust gas to expell to the exhaust system. As the gas is pressured, it will expelled with a violent force.
The piston will moves upward to push all the exhaust gas out before closing the exhaust valve in preparation for the next cycle.