Abstract: A device for determining the abnormal degree of deterioration of catalyst of a catalytic converter arranged in an internal combustion engine exhaust system is disclosed. The device comprises ability value grasping means for grasping an ability value in relation with a current purification ability of the catalyst and varying amount grasping means for grasping a varying amount of the ability value grasped by the ability value grasping means. It is determined that the degree of deterioration of the catalyst is abnormal when the varying amount grasped by the varying amount grasping means is smaller than a predetermined value.

Abstract: A device for determining the abnormal degree of deterioration of catalyst of a catalytic converter arranged in an internal combustion engine exhaust system is disclosed. The device comprises a purification ability grasping unit for grasping a current purification ability of the catalyst and a temperature sensor for grasping a current temperature of the catalyst. Therefore, a threshold of the purification ability which corresponds to the abnormal degree of deterioration of the catalyst is determined in accordance with the current temperature of the catalyst. An appraisal value is determined in accordance with a difference between the threshold and the current purification ability. It is determined that the degree of deterioration of the catalyst is abnormal when the integration value of the appraisal value exceeds a predetermined value.

Abstract: A device for determining the abnormal degree of deterioration of a catalyst of a catalytic converter arranged in an internal combustion engine exhaust system is disclosed. The device includes first and second air-fuel ratio sensors located upstream and downstream of the catalyst. The device determines a first purification ability based on readings of the sensors during a warmup stage of the catalyst, and a second purification ability after the warmup is completed. An overall purification ability of the catalyst is determined by combining the purification ability of the catalyst during warmup and the purification ability of the catalyst after warmup, where the weight of the purification ability during warmup is less than the purification ability after warmup in the overall purification ability. If the overall purification ability of the catalyst is less than a certain amount, then the device determines that the catalyst has deteriorated.

Abstract: A device for determining the excessive degree of deterioration of catalyst of a catalytic converter arranged in an internal combustion engine exhaust system is disclosed. The device comprises a purification ability determining unit for determining a current purification ability of the catalyst and a temperature sensor for determining a current temperature of the catalyst. Therefore, a threshold of the purification ability which corresponds to the excessive degree of deterioration of the catalyst is determined in accordance with the current temperature of the catalyst. An appraisal value is determined in accordance with a difference between the threshold and the current purification ability. It is determined that the degree of deterioration of the catalyst is excessive when the integration value of the appraisal value exceeds a predetermined value.

Abstract: A device for determining an abnormal degree of deterioration of catalyst of a catalytic converter, arranged in an internal combustion engine exhaust system, is disclosed. The device comprises a temperature sensor for measuring a temperature of the catalyst and an electronic control unit which assumes a temperature of the catalyst on the basis of the engine operating condition and calculates a ratio of a varying value of the measured temperature by the temperature sensor to a varying value of the assumed temperature and determines that the degree of deterioration of the catalyst is abnormal when the ratio is smaller than a predetermined value.

Abstract: An exhaust apparatus connected to a V-type internal combustion engine which is mounted in an engine compartment in a front part of a vehicle. The exhaust apparatus comprises a front exhaust manifold and a rear exhaust manifold connected to banks of the V-type engine respectively, an exhaust assembly connected to the exhaust manifolds and a catalytic converter interposed in the exhaust assembly. The wall thickness of the front exhaust manifold is made thinner than that of the rear exhaust manifold. By the thin front exhaust manifold, the heat capacity of the front exhaust path extending from the front exhaust manifold toward the catalytic converter is lessened, thereby suppressing the dropping of temperature of the exhaust gas flowing through the front exhaust path. As a result, the dropping of temperature of the exhaust gas reaching the catalytic converter is suppressed as a whole, and a catalyst in the catalytic converter is warmed up quickly to a required temperature.