METHOD OF CONTROLLING SPARK-IGNITION ENGINE, AND SPARK-IGNITION ENGINE

PROBLEM TO BE SOLVED: To properly and reliably suppress preignition by selectively taking effective measures depending on the character of the preignition.SOLUTION: In the case where the preignition as a phenomenon of too-early self-ignition of an air-fuel mixture is detected and where it is determined that an engine rotation speed Ne is less than a predetermined value Nex, first preignition avoidance control including control for decreasing an effective compression ratio by using a variable mechanism (15) is performed. On the other hand, in the case where the preignition is detected and where it is determined that the engine rotation speed Ne is the predetermined value Nex or above, second preignition avoidance control including control for decreasing the amount of combustion heat in a cylinder by changing a mode of fuel injection from an injector 18 is performed.