Gm Global Technolgoy Operations, Inc.

Ramesh C Shah

John Eric Kreucher

Richard S McClaughry, Iii

Daniel W Wendland

The present invention includes an automotive exhaust system including a catalytic converter having a substrate of substantial surface area and having a catalyst composition carried thereon. The catalytic converter substrate is carried in a housing extending the length of the catalytic converter substrate and conforming to the outer surfaces of the substrate and/or any mounting material. A two-wall diffuser is connected by an outer wall to the converter housing at one end and to an exhaust pipe at the other. An inner wall is spaced a distance from the outer wall and defines a diffuser portion having an inlet cross-section area less than its outlet cross-section flow area. The inner wall also defines an abrupt expansion section which is provided between the end of the diffuser section and the end of the inner wall nearest the substrate. The inner wall ends in the region between the substrate and the converter housing and is free-floating and is not rigidly connected to the converter substrate or housing. Thus, the inner wall is free to move with thermal cycling associated with operation of the automobile combustion engine. The space provided between the inner wall and the outer wall of the diffuser provides a thermal insulating air barrier which limits the thermal expansion and contraction the outer wall experiences at its mechanical connections to the converter housing and exhaust pipe.

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Novi, MI, United States of America

Ramesh C Shah