MUFFLER OF INTERNAL COMBUSTION ENGINE

PURPOSE:To get high engine power at middle and low speed as well as at high speed by opening subpipe line having an additional muffling chamber in the case of partial opening through operating a directional control valve by means of a servo motor. CONSTITUTION:A main pipe 2 and a subpipe 3 are inserted into a muffler 1, while a third muffling chamber 5 is added to the subpipe 3. A directional control valve 7 is provided at a branch connection of the main pipe 2 and a front part of the subpipe 3, and is operated by using a servomotor which is controlled by engine speed and throttle valve opening. Consequently, in the range of partial throttle valve opening at middle and low speed, exhaust gas passes through the subpipe 3, and is discharged through a first muffling chamber 5 via the main pipe 2 which is opened at the time of high speed after passing through a second muffling chamber 5 which is communicated with a baffle pipe 6. It is thus possible to get high engine power even in partial throttle valve opening.