How a Four-Stroke Engine Works

Interactive cross-section of the Intake, Compression, Power, and Exhaust strokes

Intake Valve Air + Fuel In Exhaust Valve Exhaust Out Spark Plug Combustion Chamber Piston Connecting Rod Crankshaft 1. INTAKE STROKE
Crank Angle: 0° / 720° Cycle: Stroke 1 of 4
Engine Speed 60 RPM
1. Intake 0° – 180°

The intake valve opens and the piston moves down, drawing a cool mixture of air and fuel into the cylinder.

2. Compression 180° – 360°

Both valves close and the piston moves up, squeezing the air-fuel mixture into a tight, hot space.

3. Power 360° – 540°

The spark plug ignites the compressed mixture. Expanding hot gas forcefully pushes the piston down to turn the crankshaft.

4. Exhaust 540° – 720°

The exhaust valve opens and the piston moves back up, pushing the burned exhaust gases out of the cylinder.