4stroke

4 strokes of a petrol 4 stroke engine

A stroke refers to the full travel of the piston from Top Dead Center to Bottom Dead Center

The crankshaft completes its cycle with two revolutions of the crankshaft

Stroke 1- down

            Intake

            Piston travels down the cylinder bore and the intake valve is open. The low atmospheric pressure draws in the air/fuel mixture

Stroke 2- up

            Compression

            Both valves are close and the piston travels up the cylinder bore to TDC, compressing the air/fuel mixture

Stroke 3- down

            Combustion

            When the piston is close to TDC the spark from a spark plug ignites the compressed air/fuel mixture, the resulting explosion forces the piston down the cylinder bore. Creating the power for the other pistons attached to the crankshaft to rotate.

Stroke 4- up

            Exhaust

            The exhaust valve opens and the piston travels from BDC to TDC pushing out the exhaust gas, clearing the chamber so the process can start again