What happens during the power stroke?

During the power stroke of a four-stroke engine cycle, the piston is forced down by the rapid expansion of gases produced by the combustion of the air/fuel mixture. This process occurs after the mixture has been compressed and ignited by the spark plug. The combustion generates a high-pressure, high-temperature gas that pushes the piston downward, converting the chemical energy of the fuel into mechanical energy, which ultimately drives the engine. This stroke is critical for the engine's power output, as it is the only moment in the cycle where work is done on the crankshaft, propelling the vehicle or operating machinery.

The other stages in the engine cycle, such as compression, exhaust, and intake, are important for the overall operation but do not contribute to the immediate power generation that occurs during the power stroke.