If the exhaust valve of a four-stroke cycle engine is closed and the intake valve is just closed, what stroke is the piston on?

Prepare for the FAA Reciprocating Powerplant Test. Utilize flashcards and multiple-choice questions, each with explanations and hints. Enhance your knowledge and ace your exam!

When the exhaust valve is closed and the intake valve is just closed in a four-stroke cycle engine, the piston is on the compression stroke. During this phase, the piston is moving upwards in the cylinder, compressing the fuel-air mixture that was drawn in during the intake stroke.

As the piston moves up, the closed intake and exhaust valves create a sealed environment, allowing the compression of the mixture. This compression is critical because it raises the temperature and pressure of the mixture, making it more susceptible to ignition when the spark plug fires. The timing of the valves is essential; if the intake valve is closing, it indicates that the intake stroke has just concluded, and the engine is now transitioning into the compression phase.

The power stroke, which involves combustion and expansion of gas to push the piston down, would not occur until after the compression stroke has been completed. The intake stroke and exhaust stroke phases are identified by the positions of the respective valves being open or closed, but at the point when both the exhaust valve is closed and the intake valve is just closed, it is unequivocally within the compression stroke.

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