Effect of Air Fuel Ratio on Knocking in Spark Ignition Engines

Abstract

Effect of equivalence ratio on knocking in homogeneous spark ignition engines was investigated by using a single cylinder engine. Knocking was evaluated by an index of the degree of constant volume, which showed how close to the ideal Otto cycle the tested cycle was. Petrol but also n-butane, iso-octane and toluene were tested. The maximum tendency to knock around the stoichiometric mixture was confirmed on the condition of the same manifold pressure. However, further experimental work indicated that the maximum tendency to knock shifted from the stoichiometric mixture to the lean mixture if the charge fuel was constant.