What occurs when the piston reaches the top of the cylinder?

When the piston reaches the top of the cylinder, this position is known as Top Dead Center (TDC). TDC is critical in engine operation as it represents the point at which the piston is at its highest position in the cylinder, thereby having the smallest volume in the combustion chamber. This position is significant because it marks the completion of the compression stroke and can also be the point where fuel is injected or ignition occurs, depending on the engine design.

In contrast, Bottom Dead Center (BDC) is the position where the piston is at its lowest point in the cylinder. The compression stroke refers to the phase during which the piston moves upward, compressing the air-fuel mixture, and the exhaust stroke is when the piston moves back up after combustion to expel exhaust gases. Therefore, while the other options refer to different aspects of engine cycles or piston positions, TDC specifically signifies the peak position of the piston in the cylinder.