| 摘要 |
PROBLEM TO BE SOLVED: To prevent engine performance from being lowered when an engine speed is in a high speed area, and to reduce booming noise when it is in a low speed area. SOLUTION: This automobile exhaust system 10 is equipped with an exhaust pipe 11, a bypass pipe 12 formed so as to have a smaller diameter than the exhaust pipe 11, and a switching valve 13 provided between a branch point J11 and a confluence J12 of the bypass pipe 12 in the exhaust pipe 11. The switching valve 13 closes the exhaust pipe 11 if an engine speed is less than a designated speed. At this time, exhaust gas receives a resistance when passing through the bypass pipe 12, and thereby, booming noise is reduced. On the other hand, the switching valve 13 opens the exhaust pipe 11 if the engine speed is not less than the designated speed. At this time, the exhaust gas does not receive that much resistance, since the exhaust pipe 11 has a larger diameter than the bypass pipe 12. Therefore, there is no chance that engine performance is lowered.
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