| 摘要 |
PURPOSE:To prevent deterioration of control accuracy in the method of air-fuel ratio control where feedback control of exhaust sensor output is performed, by providing a reverse flow preventive device for preventing exhaust of the second cylinder group from reversely flowing because of pulsation of the first cylinder group. CONSTITUTION:Air-fuel ratio of a mixture to the first cylinder group 1b, 1c is feedback controlled to logical air-fuel ratio by output of an exhaust sensor 18, simultaneously air-fuel ratio to the second cylinder group 1a, 1d is indirectly feedback controlled in accordance with an operating condition to a preset value different from the first cylinder group, and overall air-fuel ratio is controlled to a different value from the logical air-fuel ratio. At this time, an exhaust reverse flow preventive device 21 is provided in an independent exhaust passage 3a of the first cylinder group to prevent exhaust of the second cylinder group from reversely flowing into the passage 3a and eliminate an effect to the exhaust sensor 18, and air-fuel ratio of a mixture to the first cylinder group is correctly controlled to the logical air-fuel ratio to improve control accuracy. |
