The polytropic volume method to detect engine events based on the measured cylinder pressure

► A novel approach to detect valve and combustion key events in internal combustion engines is presented. ► The measured in-cylinder pressure is used as an input. ► The method is based on the polytropic change of state during compression and expansion. ► A polytropic volume is calculated which can easily and intuitively be compared with the known real cylinder volume. ► Events are detected using wavelet transformation.