| 摘要 |
<p>PURPOSE:To prevent detection of deterioration in a catalytic device from being made inaccurate due to displacement of a phase of change in air-fuel ratio between cylinder groups, in the case of individually feedback-controlling air-fuel ratio of a mixture classified by each cylinder group. CONSTITUTION:In a V-engine 1, air-fuel ratio of a left bank 1a is feedback- controlled based on an output of an air-fuel ratio sensor 19 arranged in an exhaust passage 6a of the left bank, and air-fuel ratio of a right bank 1b is feedback-controlled based on the air-fuel ratio sensor 19 of an exhaust passage 6b of the right bank. A catalytic device 9 is arranged in a manifold exhaust passage 6c, and a concentration sensor 20 for detecting an oxygen concentration component in exhaust gas is arranged in further the downstream of the catalytic device. In the case of intending to detect deterioration of the catalytic device 9 by the concentration sensor 20, only one air-fuel ratio sensor 19 is used to collectively feedback-control air-fuel ratio of both the banks and to detect a phase of change of air-fuel ratio in an equal phase between both banks, and the deterioration is decided only in this condition.</p> |
