Patent ID: 7726119

Claim:
An exhaust system of a multi-cylinder type internal combustion engine, comprising: a plurality of upstream main exhaust passages connected to cylinders of the engine respectively; a downstream main exhaust passage that is connected to the upstream main exhaust passages; a main catalytic converter mounted in the downstream main exhaust passage; a plurality of upstream bypass exhaust passages; a downstream bypass exhaust passage that is connected to the upstream bypass exhaust passages, the downstream bypass exhaust passage having a downstream end connected to the downstream main exhaust passage at a position upstream of the main catalytic converter; an auxiliary catalytic converter mounted in the downstream bypass exhaust passage; and a gas flow switching device that is capable of forcing the exhaust gas from the cylinders of the engine to flow toward the upstream bypass exhaust passages when assuming a given operation position, in which the gas flow switching device comprises switch valves that are operatively mounted in the upstream main exhaust passages, respectively, and configured to close the upstream main exhaust passages when assuming given operation positions, respectively, wherein the plurality of upstream bypass exhaust passages respectively extend from the upstream main exhaust passages and wherein each upstream bypass exhaust passage has a sectional area smaller than that of the corresponding upstream main exhaust passage, and wherein a branched portion of each upstream main exhaust passage from which the upstream bypass exhaust passage extends is provided away from a rear end of the upstream main exhaust passage, and the switch valves are located at the rear ends of the upstream main exhaust passages.