Importance

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Abstract

An engine has a plurality of the cylinders. The cylinders are divided into a first cylinder group and a second cylinder group, and each cylinder group is connected, via a corresponding branch exhaust passage, to a common interconnecting exhaust passage. In the interconnecting exhaust passage, an exhaust gas purifying catalyst is arranged. The air-fuel ratio of the exhaust gas of the first cylinder group is made lean to feed oxygen to the exhaust gas purifying catalyst, and the air-fuel ratio of the second cylinder group is made rich to feed fuel for heating to the exhaust gas purifying catalyst, so that the oxygen and the fuel for heating react with each other to heat the exhaust gas purifying catalyst to reactivate the exhaust gas purifying catalyst when the reactivation of the exhaust gas purifying catalyst is must be performed. In each branch exhaust passage, a start catalyst is arranged.

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First Claim