Ignition timing control method for internal combustion engines

Claim 1

An ignition timing control method for an internal combustion engine having a catalytic exhaust emission purifier for scrubbing toxic exhaust gas components from exhaust gases emitted from the engine by means of a catalyst, wherein the timing at which a mixture in the engine is ignited is controlled on the basis of an ignition timing set in dependence upon operating parameters of the engine, the method comprising the steps of: sensing temperature of the engine after the engine is started; sensing a particular operating condition of the engine; sensing elapsed time from the moment the engine is started when the sensed engine temperature lies within a predetermined temperature range, within which said ignition timing can be retarded for activation of said catalyst without causing stalling of said engine, and at the same time the engine is in a condition other than said particular operating condition; setting a delay angle correction amount in dependence upon the sensed elapsed time, said delay angle correction amount being set ot lower values as the sensed elapsed time grows larger; correcting the ignition timing by the set delay angle correction amount; controlling the ignition timing in accordance with the optimum ignition timing so corrected; and terminating correction of the ignition timing immediately when said particular operating condition of the engine is sensed even if the ignition timing is being controlled in accordance with the optimum ignition timing so corrected.