What happens during the intake and compression strokes of four stroke engines?

During an engine's intake stroke, the piston moves down, creating a vacuum that draws air (or air-fuel mixture in gasoline engines) into the cylinder through an open valve (the intake valve).

Intake stroke:

- The piston moves down in the cylinder, increasing the volume

- The intake valve opens

- Air (or air-fuel mixture) is drawn into the cylinder

Compression stroke:

- The piston moves up in the cylinder, reducing the volume

- The intake valve closes then compression begins

- The air (or air-fuel mixture) is compressed, raising its pressure and temperature.

This helps prepare the mixture for ignition in the next stroke, the combustion stroke.