PURPOSE: To operate an engine always at the best fuel consumption rate, by a method wherein an amount of the air in a bypass is changed, at least by two different air-fuel ratio, and the air-fuel ratio is controlled in accordance with the change of an engine speed in the operating condition of an engine at the time.
CONSTITUTION: The outputs detected by a turning angle sensor 2 which is integrated with a distributor, the amount of air sensor 6, an intake pipe pressure sensor 9 and a throttle sensor 10 sensing the respective opening of a throttle valve 4, and given to an arithmetic circuit 14, which puts out control signals to an injection valve 15. Besides, a pneumatic electromagnetic valve 13 located in the middle of bypassed feeding pipes 11 and 12 is controlled by an arithmetic circuit 14, at least, by two air-fuel ratio which are near the target air-fuel ratio and are different to each other. From the engine speed signal, a torque signal, and the like, detected at a plurality of working point of engine operation at some different air-fuel ratio, the target air- fuel ratio is judged, whether it is in the rich side or in the lean side, in comparison with the detected value and the best ratio of air-fuel consumption, and the air-fuel ratio is corrected by the judged result.
OOMORI NORIO
NINOMIYA MASAKAZU
