PURPOSE: To avoid generation of pre-ignition by setting the ignition time correction quantity on the basis of a setting difference between the temperature inside of a combustion chamber, which is estimated on the basis of the operation condition of an engine, and a pre-ignition limit temperature, which is set on the basis of an alcohol concentration of the fuel.
CONSTITUTION: During the operation of an engine; in a ECU 41, the standard ignition time is set by a standard ignition time map on the basis of the intake air weight Ga per one stroke, which is obtained on the basis of the output from an intake air quantity sensor 28, and an alcohol concentration M, which is obtained on the basis of the output of an alcohol concentration sensor 26, as parameter. Next, plug temperature is estimated by a map on the basis of the output of an intake air temperature sensor 39 and the intake pipe pressure sensor 40 and the engine speed N as parameter. Furthermore, pre-ignition limit temperature is set by a pre-ignition limit temperature map on the basis of the alcohol concentration M as parameter. A temperature difference between the plug temperature and the pre-ignition limit temperature is computed, and the pre-ignition correction spark-delay quantity is set by a map on the basis of that temperature difference as parameter, and the standard ignition time is corrected to compute the ignition time.
SAITO YOICHI
KURIHARA MASARU
