Four-stroke cycle operation in automobile engines is common nowadays. The four strokes in the operation of a four-stroke cycle petrol engine are suction stroke, compression stroke, power stroke and exhaust stoke. The inlet valve should keep open and exhaust valve closed during suction stroke. Downward movement of piston creates a partial vacuum inside the cylinder. This leads to sucking of the mixture of air and petrol into the cylinder. Both the inlet and exhaust valves are closed during the compression stroke. The compressed mixture gets vapourized and a spark is produced in the spark plug igniting the mixture during this stroke. Inlet and exhaust valves remain closed during power stroke. But the burning of gas forces exhaust valve to open. During the exhaust stroke, the inlet valve is closed and the exhaust valve is open. Here the burnt gas is pushed out of the cylinder which forces exhaust valve to close and inlet valve open.