What does the piston stroke refer to?

The piston stroke specifically refers to the distance the piston moves within the cylinder from its uppermost point (top dead center) to its lowermost point (bottom dead center). This distance is crucial in defining the engine's displacement and efficiency, as it directly influences the volume of air and fuel mixture that the engine can intake and exhaust during its combustion cycle.

Understanding the piston stroke is essential for various calculations in engine performance, such as determining the engine's power output and the overall capacity of the engine. The other options focus on different aspects of engine operation. For instance, the total time taken for a full engine cycle relates to cycle duration rather than movement. The speed of the engine deals with rotational velocity, and torque pertains to the rotational force produced by the engine, which is independent of the piston's linear movement. Therefore, the definition of the piston stroke is accurately captured by the distance the piston travels between its limits.