Abstract: An ignition timing control apparatus for an internal combustion engine includes an electronic control unit configured to i) perform determination as to whether knocking has occurred in the engine; ii) update a first learning value and a second learning value such that the ignition timing is retarded when determining that knocking has occurred; and iii) derive, as a required ignition timing, a timing obtained by retarding a base ignition timing based on the first and second learning values. The electronic control unit is configured to update the second learning value within a range in which an update amount of the second learning value within a prescribed period set in advance does not exceed a prescribed amount, when updating the second learning value.

Abstract: An engine includes a variable valve mechanism capable of holding a valve timing of an intake valve in an intermediate phase when the engine is started. An ECU calculates a degree of deposit adhesion in a combustion chamber, and calculates a deposit correction amount that is a retard correction amount for an ignition timing set in accordance with the calculated degree of the deposit adhesion. The ECU calculates a first correction amount that is a first adaptive value for the retard correction amount for the ignition timing in a reference phase of the valve timing and a second correction amount that is a second adaptive value for the retard correction amount for the ignition timing in an adaptation phase of the valve timing. The deposit correction amount is set based on the first correction amount and the second correction amount.