Control system for internal combustion engine

A control system for an internal combustion engine which performs an engine output control so that an output of the engine coincides with a demand output by changing at least one of the intake air flow rate and an ignition timing of the engine. An output reduction control in which the engine output is reduced by changing at least one of the intake air flow rate and the ignition timing, is performed when the demand output decreases. A retard limit of the ignition timing is calculated according to an operating condition of the engine. A retard limit output, which is an output of the engine corresponding to a state where the ignition timing is retarded to the retard limit and the intake air flow rate is maintained at a value immediately before the demand output decreases, is calculated. A retard limit intake air flow rate is calculated when the demand output is less than the retard limit output. The retard limit intake air flow rate is an intake air flow rate at which the engine output is equal to the demand output under the condition where the ignition timing is retarded to the retard limit. The engine output is made to coincide with the demand output by retarding the ignition timing, when the demand output is equal to or greater than the retard limit output. When the demand output is less than the retard limit output, the ignition timing is retarded to the retard limit and the intake air flow rate is controlled so as to coincide with the retard limit intake air flow rate.