... How a 4 stoke petrol engine work?

well this is random :D part of my college work :p

Task 1

a) Briefly describe the operating cycle of a 4 stroke petrol engine


1. The induction stroke is where the space above the piston ( the combustion chamber) it filled with a mixture of air and petrol, which comes through the inlet valve when it opens. The exhaust valve is shut. ( fig 1.1)

2. The compression stroke is where the piston goes up and compresses the mixture of air and fuel. This increases the pressure of the mixture in the combustion chamber. Both the inlet and the exhaust valve are closed. (fig 1.2)

3. The Power stroke is where an electric spark from the spark plug, which is mounted on the side of the engine block and goes into the combustion chamber, ignites the air and fuel mixture which pushes the piston down causing the crank to turn and producing power to the vehicle. (fig 1.3)

4. The Exhaust stroke is where the piston comes up and pushes the remaining gasses out through the exhaust valve, that just opened. The inlet valve is closed to stop exhaust gasses getting out into the inlet manifold and to stop a fuel mixture entering the cylinder. (fig 1.4)