Animation: Control of a four-stroke petrol engine

This animation illustrates the engine control processes of a four-stroke petrol engine. A cross-section of the valve design is shown. In the animation, the valves open and close in accordance with the control diagram.

Note on use

After starting the application, you can view the animation in full-screen mode. To do this, click on “View” and then on “Full screen”:

To exit full screen mode, press the Esc key.

Description of the animation

A timing diagram, also known as a camshaft diagram, shows the valve timing of an internal combustion engine as a function of the angle of the camshaft. The length of the respective phases depends directly on how the cams are aligned on the camshaft.

The ignition timing is shown in the timing diagram. The air-fuel mixture is ignited even before the piston reaches top dead centre. This is the point at which the piston is at the top of the cylinder.

The ignition point shifts depending on the engine speed. In the animation, the engine speed can be changed interactively, as happens when the accelerator pedal is pressed.

The cross-section of the four-stroke petrol engine can be zoomed in. The valve overlap then also becomes visible. Valve overlap means that both valves are open at the same time for a short time when expelling.

Valve overlap offers several advantages:

  • More efficient gas exchange: exhaust gases are expelled more efficiently. More fresh air enters the combustion chamber.
  • Improved cooling: The engine is cooled better thanks to the improved air exchange.

The duration and position of valve overlap varies from engine to engine and depends on the design features and performance targets. Careful optimisation of valve overlap can influence engine performance, fuel consumption and emission levels.

Overview and download

TitleControl of a four-stroke petrol engine
Target groupTeachers and lecturerse
PlatformsMicrosoft® Windows®
Apple® Macintosh®
FeaturesFull screen mode
lossless zoom
Large screens and projection screens supported
DownloadContact us


C. Hein, S. Rikowski

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