Method and apparatus for controlling ignition timing in a multicylinder

Abstract

Engine parameters are detected to set a basic ignition timing, and this basic ignition timing is forcibly changed to effect feedback control in which engine output is detected for finding an optimum combination of ignition timings of the individual cylinders. Engine is operated with a plurality of different ignition timing combinations, where the number of the combinations equals the number of the cylinders added by one. The engine is further operated with one of the ignition timing combinations so that the engine is operated twice with an identical ignition timing combination. As a result engine output change caused by factors other than ignition timing change is detected. Thus, one of a plurality of ignition timing combinations, which gives the lowest engine speed is found and is replaced with a new ignition timing combination with which the engine produces higher output. The replacement is carried out selectively in accordance with the variation rate of the engine output data. An average value of various ignition timing combinations is used to renew the same. In this way the ignition timing combination is renewed succesively for finding the optimum ignition timing combination.