In an engine cycle, what is the purpose of the exhaust stroke?

The purpose of the exhaust stroke in an engine cycle is to expel combustion gases from the cylinder. During this phase, the engine’s piston moves upward after the power stroke, creating a pressure differential that allows the spent gases from the previous combustion process to exit the cylinder. This is crucial for maintaining engine efficiency and performance, as it clears out the exhaust gases that would otherwise remain in the cylinder and interfere with the next cycle.

When the exhaust valves open, the combustion gases flow out of the cylinder and into the exhaust system, making way for fresh air and fuel to enter during the intake stroke. This clearing of burnt gases is essential for optimal combustion in the subsequent cycle, ensuring that the engine can operate smoothly and efficiently. Without an effective exhaust stroke, the engine would struggle to generate power due to the build-up of residual gases.