PURPOSE: To provide an apparatus comprising a main pipe and a branch pipe attached to the main pipe for defining a branch chamber in the manner that it can be communicated to the main pipe, which is capable of preventing degradation of the engine performance in its high-speed region, by providing at the connecting portion of the branch pipe a valve means which is closed when the engine speed has reached a predetermined value.
CONSTITUTION: An exhaust pipe 10A consists of a main pipe 11 and a branch pipe 12 attached to the main pipe 11 at the portion thereof located on the side of the vehicle body. The main pipe 11 is designed such that a high engine performance can be obtained in its high-speed region, while the branch pipe 12 is designed such that a high engine performance can be obtained in its low- and medium speed regions when the branch pipe 12 is attached to the main pipe 11. At the portion connecting a branch chamber R2 and a main pipe chamber R1 of the main pipe 11 to each other, there is provided a valve means 20 for establishing and interrupting communication between these two chambers R1 and R2. The valve means 20 is composed of a butterfly valve 22 which is driven by a solenoid 25. Here, the solenoid valve 25 operates to close the valve 22 by an engine-speed detecting mechanism consisting of a tachometer 31 and a relay 32 which supplies current to the solenoid 25 when the engine speed is higher than a predetermined speed.
TAKEUCHI KOUICHIROU
MURAMATSU TOKUJI
