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The four strokes in four simple steps - accessible
Let’s get to grips with how a conventional port fuel injection four-stroke petrol engine works.
- The inlet valve opens as the piston is about to descend, sucking in the mixture of fuel and air.
- With both valves now closed, the piston rises upwards, squeezing the mix of fuel and air.
- Just before the piston reaches the top, the fuel and air mix is ignited by the spark plug.
- The exhaust valve opens and the piston rises back to the top, expelling the burnt gases.