| 摘要 |
PURPOSE:To avoid a wasteful replacement of a catalyst, by providing a first catalyst layer of a large quantity of the catalyst in an exhaust passage for always working cylinders and a second catalyst layer of a small quantity of the catalyst in an exhaut passage for not always working cylinders to equalize the lives of both the catalyst layers. CONSTITUTION:A cylinder number control circuit 14 receives a negative pressure signal S3 from a negative pressure sensor 15 and a water temperature signal S4 from a water temperature sensor 16 so that the circuit acts to cut off injection pulses Pb, Pc to put a second and a third cylinders 2b, 2c at rest when the load on the engine is not higher than a prescribed level and its temperature is not lower than a prescribed level. An exhaust passage 4a for always working cylinders 2a, 2d communicates with a first catalyst layer 17a provided in a converter 17 and made of a large quantity of a catalyst. An exhaust passage 4b for the not always working cylinders 2b, 2c communicates with a second catalyst layer 17b provided in the converter 17 and made of a small quantity of the catalyst. |
