Abstract: A muffler for an internal combustion engine exhaust system includes a housing having an inlet and outlet headers enclosing opposite ends of an outer shell. A partition divides a housing interior into first and second chambers, the first chamber having sound absorbing material positioned therein. The partition has an aperture allowing fluid communication between the first and second chambers. A through pipe extends through the inlet and outlet headers and the partition and has a plurality of perforations enabling fluid communication between the through pipe and the first chamber. A valve assembly has a valve flap positioned inside the through pipe for rotation with an axle pivotally coupled to the pipe between a closed position and an open position. 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.

Abstract: A muffler for an internal combustion engine exhaust system includes a housing having an inlet and outlet headers enclosing opposite ends of an outer shell. A partition divides a housing interior into first and second chambers, the first chamber having sound absorbing material positioned therein. The partition has an aperture allowing fluid communication between the first and second chambers. A through pipe extends through the inlet and outlet headers and the partition and has a plurality of perforations enabling fluid communication between the through pipe and the first chamber. A valve assembly has a valve flap positioned inside the through pipe for rotation with an axle pivotally coupled to the pipe between a closed position and an open position. 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.

Abstract: An exhaust gas muffler has a housing composed of upper and lower press-formed parts with two chambers and a gas passage means composed of upper and lower plates with three parallel press-formed troughs defining a tri-flow gas path wherein one of said chambers serves as a turn-around from the gas path and the other of said chambers receives said troughs and is acoustically connected to the gas path through perforations in the walls of the troughs.

Abstract: A retroverted flow type exhaust gas muffler has curved flow directing and guiding plates mounted on end headers to facilitate flow reversal.