To prevent unstableness of an amount of learning of knocking due to the change in engine cooling water temperature by an engine cooling mechanism, and further prevent occurrence of knocking and reduction in engine output resulting from the unstableness.
By controlling a flow rate control valve 21 on the basis of the engine operating condition, an electronic control means 40 regulates the temperature of cooling water passing through a cooling passage 14. The electronic control means 40 carries out averaging of the temperature of the cooling water detected by a water temperature sensor 52. The cooling water temperature for controlling which is delayed to respond to the cooling water temperature is computed as a parameter having a relation with the temperature of a wall surface of a combustion chamber. The electronic control means 40 amends the knocking occurrence marginal ignition timing on the basis of the cooling water temperature for controlling.
HIROWATARI SEIJI
TAKAGI NOBORU
Makoto Onda
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