Patent ID: 8468813

Claim:
A muffler for an internal combustion engine exhaust system, the muffler comprising: a housing having an outer shell and inlet and outlet headers enclosing opposite ends of the shell; a partition inside the housing dividing a housing interior into first and second chambers, the first chamber having sound absorbing material positioned therein, the partition having at least one aperture therethrough providing for fluid communication between the first and second chambers; a through pipe extending through the inlet and outlet headers and the partition and having a plurality of perforations enabling fluid communication between the through pipe and the first chamber; and a valve assembly having a planar valve flap positioned inside the through pipe for rotation with an axle pivotally coupled to the pipe, the valve flap being rotatable between a closed position and an open position whereat a plane of the valve flap is parallel to a longitudinal axis of the through pipe, wherein the valve is positioned downstream of the pipe perforations such that all of an exhaust gas flowing through the muffler passes through the valve regardless of the valve flap position.