| 摘要 |
PURPOSE:To prevent the unstable combustion, etc. in low speed operation and improve the combustion efficiency by discharging the exhaust supplied from a front side cylinder into a bypass exhaust passage when the throttle opening degree is small, while discharging the exhaust supplied from all the cylinders into a main exhaust passage, when the throttle opening degree is large. CONSTITUTION:In the low speed operation with the small throttle opening degree, the branched part inlet 12a of a main exhaust passage 12 is closed by the valve plate 17 of a selector valve 16. The exhaust supplied from the first cylinder flows into a bypass exhaust passage 13, and the exhaust supplied from the second and third cylinders is discharged into the main exhaust passage 12, and all the exhaust is discharged from an exhaust tube 15. Accordingly, each exhaust efficiency of all the cylinders is improved, and the scavenging in the low speed operation is carried out smoothly, and the unstable combustion state is improved. While, in the high speed operation with the large throttle opening degree, the branched part inlet 13a of the bypass exhaust passage 13 is closed by the valve plate 17 of the selector valve 16. Each exhaust of all the cylinders is discharged, passing through only the main exhaust passage 12. Accordingly, the operation with the superior fuel consumption rate can be carried out by the supercharge effect due to the exhaust pulse. |
