System for controlling an ignition timing in an internal combustion

Abstract

A system and method for controlling an ignition timing in an internal combustion engine which controls the ignition timing by correcting the ignition timing by a retardation angle for avoiding the occurrence of the knocking when the level of knocking exceeds a predetermined angle and/or by correcting the ignition timing (MBT control) by a correction value on the basis of an crank angle at which the combustion chamber pressure has reached its maximum. When the engine is not in a transient operating state, the system stores the correction value of the ignition timing during knocking avoidance control or during MBT control as a learning value corresponding to the engine operating condition and calculates the actual ignition timing on the basis of the learning value and basic ignition timing determined by the engine operating condition. When the engine is in the transient operating state, the MBT control is not carried out. Therefore, such an undesirable state occurs that the correction value of the ignition timing is varied to a large degree when the engine operating state is changed, thus torque variation results, and inaccurate ignition timing control is not carried out. In addition, since the history of retardation angle correction by means of the past knocking avoidance control reflects the present calculation of ignition timing angle value, a preventive control of the occurrence of knocking is achieved. Consequently, a driving range in which the MBT control becomes effective is extended so that the engine output power can be improved.