Referring to FIG .1 , an engine 1 is provided with a piston 2 , a fuel injector 3 , an intake valve 4 , an exhaust valve 5 , an ignition plug 6 , a combustion chamber pressure sensor 24 for sensing pressure in a combustion chamber , and a knocking sensor 25 . A intake pipe 18 is provided with an air flow sensor 7 , an air cleaner 8 and a intake pipe pressure sensor 23 for sensing pressure in the intake pipe 18 . An exhaust pipe 19 is provided with an air/fuel ratio sensor 9 , a catalytic unit 10 , and a catalyst temperature sensor 26 for sensing catalyst temperature , i.e. , the temperature of the catalytic