What does top dead center (TDC) refer to in a four-stroke engine?

Top dead center (TDC) refers to the position of the piston at the highest point in the cylinder during its stroke. In a four-stroke engine, this point is significant because it indicates the position where the piston has completed its upward movement after the compression stroke and is ready for the combustion process to occur.

At TDC, the volume of the combustion chamber is at its minimum, and the air-fuel mixture is compressed to its highest density, which is critical for efficient combustion. Understanding TDC is essential for timing the ignition system properly, as it ensures that the spark plug ignites the compressed mixture at the optimal moment for power generation.

In context, this understanding is fundamental when working with engine timing and performance, as it relates to the operational cycles of the engine, making it vital information for anyone studying small engine technology.