Valve positions during compression in a four-stroke petrol engine: evaluate the statement. Statement: “During the compression stroke the charge is compressed when both the inlet and exhaust valves are closed.” Choose whether the statement is correct.

Concept/ApproachIn the ideal four-stroke SI cycle, once the intake stroke ends, both valves close and the piston compresses the trapped charge. Although real engines may have a small valve overlap near TDC for breathing, the compression phase occurs with valves effectively closed.

Final AnswerAgree.