Abstract: A stamp formed muffler includes a first plate, a second plate and at least one sheet. A second plate and the sheet are secured in face-to-face relationship with the first plate and define a plurality of tubes and an internal chamber. External shells are secured around the internal plates to enclose the tubes and the internal chamber. The external shell may be formed to engage the internal chamber such that the internal chamber divides the external shell into upstream and downstream chambers.

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 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.