Method for detecting the working stroke of a single-cylinder four-cycle engine

The method determines position and angular speed of the crankshaft. The period from the upper dead center to a set rotary angle of the crankshaft, or lower dead center, is measured, and the measured periods of two subsequent rotation of the crankshaft are measured. The combustion stroke takes place during the crankshaft rotation with the shorter period. Measuring of the periods is filtered, and a different filter time constant is used during starting and during normal engine operation.