## How does combustion work in a car engine?
Combustion is the process of burning fuel to create energy. In a car engine, the fuel is gasoline, and the energy is used to power the pistons. The combustion process is divided into four stages: intake, compression, power, and exhaust.
### Intake
The intake stroke begins when the piston moves down the cylinder. This creates a vacuum in the cylinder, which draws air and fuel into the cylinder through the intake valve. The intake valve is then closed.
### Compression
The compression stroke begins when the piston moves back up the cylinder. This compresses the air and fuel mixture, which increases its temperature and pressure. The compression ratio of an engine is the ratio of the volume of the cylinder when the piston is at the bottom of its stroke to the volume of the cylinder when the piston is at the top of its stroke. A higher compression ratio means that the air and fuel mixture is compressed more, which increases the power output of the engine.
### Power
The power stroke begins when the spark plug ignites the air and fuel mixture. This causes the mixture to burn, which creates hot gases that expand rapidly. The expanding gases push the piston down the cylinder, which turns the crankshaft. The crankshaft is connected to the wheels of the car, so the power stroke is what actually propels the car forward.
### Exhaust
The exhaust stroke begins when the piston moves back up the cylinder. This forces the exhaust gases out of the cylinder through the exhaust valve. The exhaust valve is then closed, and the intake valve opens, starting the cycle again.
The combustion process is a continuous cycle that repeats itself as long as the engine is running. The speed at which the combustion cycle occurs is controlled by the engine’s speed.
