Transforming fuel into motion, one stroke at a time.
An internal combustion engine is a heat engine where the combustion of a fuel occurs with an oxidizer (usually air) in a confined space called a combustion chamber. This combustion generates high-temperature, high-pressure gases, which directly apply force to a component of the engine, such as a piston, to move it over a distance, thereby generating mechanical energy. This is the fundamental principle behind how most cars, motorcycles, and many other machines move.
Before exploring the engine's cycle, let's identify its main parts. Hover over the labels to highlight the components in the diagram.
Most modern gasoline engines operate on a four-stroke cycle, meaning the piston completes four distinct movements (strokes) for each power-generating combustion event.
Click "Next Stroke" to advance through the four stages of the engine cycle.
The piston moves downwards, creating a vacuum. The intake valve opens, allowing a mixture of fuel and air to be drawn into the cylinder. The exhaust valve remains closed.
This flowchart summarizes the sequence of events in a four-stroke internal combustion engine.