What does the term 'stroke' refer to in an engine?

The term 'stroke' in an engine specifically refers to the distance the piston travels from the top dead center (TDC) to the bottom dead center (BDC) within its cylinder. This distance is crucial because it plays a significant role in determining the engine's displacement, which is the total volume of air/fuel mixture that the engine can draw in and expel during operation.

The stroke length, combined with the diameter of the cylinder (known as bore), helps to define the engine's overall capacity and can influence its power output and efficiency. A longer stroke generally implies a larger displacement, which can lead to increased torque at lower RPMs, while a shorter stroke may enhance high-RPM performance by allowing quicker piston movement. Understanding stroke is vital for engineers and technicians when analyzing engine performance and designing modifications or repairs.