Abstract: A muffler is provided with a pair of plates formed to define an array of tubes therebetween. At least one external shell is secured to at least one of the plates to surround selected portions of the tubes. The shell is formed to define a plurality of chambers separated from one another by a baffle crease. The baffle crease is parallel to and abutting a selected tube of the muffler to simplify the draw of metal material in the vicinity of the baffle crease and to thereby save metal. The baffle crease is of substantially uniform depth along a major portion of its length and is free of pockets that could conceivably retain corrosive fluids.

Abstract: A stamp formed muffler comprising a pair of internal plates and a pair of external shells is provided. The internal plates are stamp formed to define first and second spaced apart arrays of tubes and a single intermediate tube therebetween. Tubes in one array may have perforations or apertures to permit expansion of exhaust gases, while the other array may define at least one tuning tube. The tubes are disposed on the internal plates such that at at least one location thereon a straight line extending entirely across said internal plates will intersect only the one intermediate tube. The external shells are stamp formed to define a plurality of chambers which cooperate with the tubes in the internal plates. The chambers are separated from one another by a crease disposed to align with the intermediate tube. The crease is characterized by a single outwardly convex portion to engage the single bulb. As a result, the crease is not provided with recesses that conceivably could retain corrosive materials.

Abstract: A muffler is provided with a pair of internal plates stamp formed to define an array of tubes therebetween. An external shell, which may be stamp formed, surrounds and encloses at least selected portions of the internal plates. The array of tubes stamp formed in the internal plates includes at least two tuning tubes. One tuning tube terminates at a tuning aperture in one of the two internal plates, while the other tuning tube terminates at an aperture stamp formed in the other of the two internal plates. Thus, one tuning tube will communicate with a low frequency resonating chamber on one side of the pair of internal plates, while the other tuning tube will communicate with a low frequency resonating chamber on the opposite side of the assembled internal plates.