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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.

Difficulty: Easy

Agree
Disagree
True except during brief overlap near TDC
Insufficient information

Correct Answer: Agree

Explanation:

Concept/Approach
In 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 Answer
Agree.

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