Patent ID: 7775322

Claim:
A muffler for an internal combustion engine exhaust system, the muffler comprising: a housing having an outer shell and input and output headers enclosing opposite ends of the shell; at least one partition inside the housing dividing a housing interior into first and second chambers, at least one of the chambers having sound absorbing material positioned therein, the at least one partition having at least one aperture therethrough providing for fluid communication between the first and second chambers; a through pipe extending through the input and output headers and the at least one partition and having a plurality of perforations enabling fluid communication between the through pipe and the first chamber; and a valve assembly having a substantially planar valve flap positioned inside the through pipe for rotation about an axle pivotally coupled to the pipe between a fully closed position wherein a first peripheral portion of the valve flap is in contact with an inner surface of the through pipe and a fully open position wherein a plane of the valve flap is substantially parallel to a longitudinal axis of the through pipe and a second peripheral portion of the substantially planar valve flap is in contact with an inner surface of the through pipe.