| 摘要 |
PURPOSE:To make it possible to prevent generation of torque variation, by performing ignition timing control when the desired air-fuel ratio at feedback control of air-fuel ratio is changed, according to the air-fuel ratio variation at this time. CONSTITUTION:When it is decided that present operating condition is in a thin air-fuel ratio control range, in a control unit 30, a spark advance correction value at thin air-fuel ratio control time, is referred according to real air-fuel ratio, calculated according to oxygen density in exhaust gas, which is detected by an oxygen sensor 20. After that, as air-fuel ratio becomes thinner through being advanced the control for the desired thin air-fuel ratio, the referred spark advance correction value is increased, the ignition timing is more advanced, and consequently, it is set at the engine demand ignition timing. Accordingly, if the operating condition has shifted from being under theoretical air-fuel ratio control to the thin air-fuel ratio control range, the ignition timing is not varied suddenly, and generation of torque variation at change of the desired air-fuel ratio, can be avoided.
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