Ignition timing control system for internal combustion engine

Abstract

An ignition timing control system for vehicle internal combustion engines which retards the ignition timing during acceleration so as to reduce power shock caused by drive shaft vibration generated when the body of a vehicle with a high-powered engine is not able to keep up with the sudden change in engine output torque and so as to avoid the combustion knock that is apt occur during acceleration. In order to compensate for the monifold pressure lag when an acceleration state is detected, the engine load is monitored as to whether it reaches a reference level within prescribed a period, and only after it is confirmed that the engine output torque has actually begun to increase within the prescribed period, the ignition timing retard is commenced. The retarded ignition timing is maintained for another period when the engine load is above a second reference level and then returned in the advance direction at a first slow rate. On the other hand, if the engine load is below the second reference level, the retarded ignition timing is immediately advanced at a second rate which is greater than the first rate.