Four-Stroke Engine

An engine operating on a cycle which is completed in four strokes, or two revolutions of the crankshaft.

The four strokes are:

Induction Stroke - The stroke where the fuel-air mixture is drawn into the cylinder.

Compression Stroke - The stroke of the internal Combustion Engine where the piston moves into the cylinder, compressing this fuel-air mixture to high density, pressure and temperature.

Ignition - An electric spark then ignites the mixture and converts it into extremely hot burned gas.

Working Stroke - The piston stroke during which the combustion gases exert a pressure on the moving piston.

Exhaust Stroke - The piston stroke during which the exhaust gases are expelled from the cylinder ready for the next induction stroke.

Historical Notes

1877 Four stroke internal combustion engine invented by Nikolaus Otto.

1890 First four-cylinder, four-stroke engine built by Wilhelm Maybach.