During which stroke does the engine prepare to expel exhaust gases?

The exhaust stroke is the phase in the four-stroke engine cycle where the engine prepares to expel exhaust gases. During this stroke, the intake valve is closed, and the exhaust valve opens as the piston moves upward in the cylinder. This upward movement creates pressure that pushes the spent gases out of the combustion chamber and into the exhaust system.

Understanding this stroke's role is crucial because it ensures that the combustion chamber is cleared of exhaust fumes before the next intake of fresh air-fuel mixture, allowing for efficient engine operation. Proper functioning of the exhaust stroke is vital for performance, emissions control, and overall engine longevity.