Patent ID: 7748213

Claim:
An exhaust system for an internal combustion engine comprising: a main exhaust passageway including a plurality of upstream main exhaust passageways in fluid communication with a respective one of a plurality of cylinders of the internal combustion engine and a downstream main exhaust passageway, with the upstream main exhaust passageways merging together to fluidly communicate with the downstream main exhaust passageway; a bypass exhaust passageway including a plurality of upstream bypass exhaust passageways in fluid communication with the upstream main exhaust passageways so as to bypass portions thereof between upstream junctions at which the upstream bypass exhaust passageways branch out of respective ones of the upstream main exhaust passageways and a downstream junction at which a downstream bypass exhaust passageway merges into the downstream main exhaust passageway, the upstream main exhaust passageways converging downstream of the upstream junctions; a bypass catalytic converter provided in the bypass exhaust passageway; a bypass control valve provided in the portions of the upstream main passageways and configured to open or close the portions of the upstream main passageways; an upstream air-fuel ratio sensor disposed upstream of the bypass catalytic converter to sense air-fuel ratio of an exhaust gas flowing into the bypass catalytic converter; a downstream air-fuel ratio sensor disposed downstream of the bypass catalytic converter to sense air-fuel ratio of the exhaust gas flowing out of the bypass catalytic converter.