Improved knock detection method for lean burn SI engines

The purpose of this study was to improve the accuracy of knock detection for lean burn SI engines. In this study, we conducted an experiment to observe autoignition in an engine cylinder using a borescope and a high-speed camera under an air excess ratio of 2.1. In addition, the resonance frequency of each vibration mode by knocking and the knock intensity were also calculated from the in-cylinder pressure history. Autoignition was optically observed in all cycles with a knock intensity of more than 20 kPa or more, and in some cycles with that of less than 20 kPa. We compared the vibration caused by combustion and it caused by autoignition. As a result, by distinguishing between the vibration caused by combustion and it caused by autoignition using window functions, a knocking cycle that could not be detected by the conventional index was detected.