The power stroke of a four-cycle diesel engine ends when ____________.

The power stroke of a four-cycle diesel engine concludes when the exhaust valve opens. At this point, the combustion process has already generated the power needed to push the piston downward, allowing for the conversion of heat energy from fuel combustion into mechanical energy. The opening of the exhaust valve marks the beginning of the exhaust stroke, where the spent gases created during the power stroke can now exit the cylinder.

Understanding the sequence of events in a four-cycle engine is crucial. It involves four distinct strokes: intake, compression, power, and exhaust. The power stroke is where the energy is harnessed, and it naturally transitions into the exhaust cycle when the exhaust valve opens, facilitating the expulsion of gases. Therefore, recognizing that the end of the power stroke is marked by this opening helps solidify comprehension of the entire operation of the engine cycle.