Inside the Engine
The four strokes, step by step, in a petrol or a diesel engine.
Play
Step through the strokes
Step a piston through the four strokes, intake, compression, power and exhaust, and watch the valves, the spark and the crankshaft. Switch between petrol and diesel to see what changes. Then try Which Stroke? and test yourself.
Inside the Engine is our own code and drawing (simplified, not to scale). Every stroke description is one of the sourced facts on this site; the source shows with each one.