What occurs during the intake stroke of a four-stroke engine?

During the intake stroke of a four-stroke engine, the piston moves down in the cylinder, creating a vacuum that allows the intake valve to open. This action facilitates the drawing in of the air-fuel mixture from the intake manifold into the combustion chamber. The process is critical for preparing the engine for combustion, as the correct amount of air and fuel must enter the cylinder to ensure efficient performance during the subsequent compression, power, and exhaust strokes.

This stage is essential because it sets the foundation for the entire combustion cycle. The correct timing and sealing of the intake valve are crucial to ensure that an optimal amount of the air-fuel mixture enters the cylinder for proper combustion. Understanding this mechanism is fundamental for anyone studying reciprocating engines, as it directly affects engine efficiency and performance.