Patent attributes
In an exhaust system, a first oxygen sensor is attached to an exhaust pipe connected to a standard cylinder in which the amount of injected fuel is the closest to the average of the amounts of fuel injected in a plurality of cylinders. A controller calculates the air-fuel ratio of the standard cylinder based on the value detected by the first oxygen sensor. Then, based on the difference between the calculated air-fuel ratio of the standard cylinder and a predetermined target air-fuel ratio, the amount of correction to the amount of fuel injected in the standard cylinder is determined such that the air-fuel ratio of the standard cylinder is equal to the target air-fuel ratio. Furthermore, based on the amount of correction to the amount of fuel injected in the standard cylinder, the amounts of correction of the other cylinders are determined.
