Patent ID: 8051835

Claim:
An internal combustion engine including a supercharger capable of compressing intake air and feeding the compressed intake air into a combustion chamber, boost pressure detecting means for detecting the boost pressure, air/fuel ratio changing means for changing the air/fuel ratio, ignition timing changing means for changing the ignition timing, and control means for causing the ignition timing changing means to retard the ignition timing when the air/fuel ratio changing means changes the air/fuel ratio from a stoichiometric air/fuel ratio to a lean air/fuel ratio, wherein: when the control means changes the air/fuel ratio from the stoichiometric air/fuel ratio to the lean air/fuel ratio while retarding the ignition timing, the control means keeps the retard amount of the ignition timing at a constant value if the boost pressure detected by the boost pressure detecting means becomes equal to or higher than a target boost pressure that is set in advance depending on operating conditions of the engine.