During scavenging, what term describes the period when both intake and exhaust valves are open?

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Multiple Choice

During scavenging, what term describes the period when both intake and exhaust valves are open?

Valve overlap is the interval when both the intake and exhaust valves are open at the same time, typically around the transition between the exhaust and intake strokes near top dead center. With both valves open, the flow of exhaust gases and the incoming fresh air–fuel mixture interact, helping push out spent gas and pull in a fresh charge. This overlap is what makes scavenging effective, using the motion and pressure of the gases to improve cylinder filling. The exact duration depends on cam timing and engine speed—more overlap can help at higher RPMs but can also raise pumping losses and emissions if too large.

Valve overlap is the interval when both the intake and exhaust valves are open at the same time, typically around the transition between the exhaust and intake strokes near top dead center. With both valves open, the flow of exhaust gases and the incoming fresh air–fuel mixture interact, helping push out spent gas and pull in a fresh charge. This overlap is what makes scavenging effective, using the motion and pressure of the gases to improve cylinder filling. The exact duration depends on cam timing and engine speed—more overlap can help at higher RPMs but can also raise pumping losses and emissions if too large.

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