Abstract: A plurality of upstream main exhaust passages extend from cylinders of an engine. A downstream main exhaust passage is connected to the upstream main exhaust passages. A main catalytic converter is mounted in the downstream main exhaust passage. A plurality of upstream bypass exhaust passages extend from the upstream main exhaust passages. Each upstream bypass exhaust passage has a sectional area smaller than that of the corresponding upstream main exhaust passage. A downstream bypass exhaust passage is connected to the upstream bypass exhaust passages and has a downstream end connected to the downstream main exhaust passage at a position upstream of the main catalytic converter. An auxiliary catalytic converter is mounted in the downstream bypass exhaust passage. A gas flow switching device is provided which 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.

Abstract: An exhaust system of an internal combustion engine having at least one cylinder comprises a main exhaust passage connected to the cylinder; a main catalytic converter disposed in the main exhaust passage; a bypass exhaust passage that diverges from the main exhaust passage, the bypass exhaust passage having a gas flow resistance larger than that of the main exhaust passage and having a downstream end connected to the main exhaust passage at a position upstream of the main catalytic converter; an auxiliary catalytic converter disposed in the bypass exhaust passage; and a gas flow switching device that is capable of forcing exhaust gas from the cylinder of the engine to flow toward the bypass exhaust passage when assuming a given operation position.

Abstract: An exhaust system of an internal combustion engine having at least one cylinder comprises a main exhaust passage connected to the cylinder; a main catalytic converter disposed in the main exhaust passage; a bypass exhaust passage that diverges from the main exhaust passage, the bypass exhaust passage having a gas flow resistance larger than that of the main exhaust passage and having a downstream end connected to the main exhaust passage at a position upstream of the main catalytic converter; an auxiliary catalytic converter disposed in the bypass exhaust passage; and a gas flow switching device that is capable of forcing exhaust gas from the cylinder of the engine to flow toward the bypass exhaust passage when assuming a given operation position.

Abstract: A plurality of upstream main exhaust passages extend from cylinders of an engine. A downstream main exhaust passage is connected to the upstream main exhaust passages. A main catalytic converter is mounted in the downstream main exhaust passage. A plurality of upstream bypass exhaust passages extend from the upstream main exhaust passages. Each upstream bypass exhaust passage has a sectional area smaller than that of the corresponding upstream main exhaust passage. A downstream bypass exhaust passage is connected to the upstream bypass exhaust passages and has a downstream end connected to the downstream main exhaust passage at a position upstream of the main catalytic converter. An auxiliary catalytic converter is mounted in the downstream bypass exhaust passage. A gas flow switching device is provided which 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.