Catalytic exhaust muffler for motorcycles

Abstract

Elongated, small diameter muffler assembly especially adapted for use on motorcycles has perforated tube and bulkhead portions at its entrance end for damping and diffusing the entering exhaust gas pulses to reduce their energy and to protect a ceramic catalytic element mounted within the muffler housing. Perforated tube and bulkhead portions at the exit end provide sound abatement and are sized to accomodate the increased volume of gases resulting from the heating provided by the catalyst element. The catalyst element is supported at each end in a manner which permits a sliding longitudinal movement relative to the housing by means of perforated tubes which are rigidly attached to the muffler housing at their outer ends only, while being free to thermally expand axially inwardly toward the catalytic element at a rate independent of the thermal growth of the muffler housing. The configuration of the exhaust gas flow path and the lengths of the inner metal elements and the ceramic catalyst element located inside the housing are selected to insure that the ceramic catalyst element is firmly restrained against vibratory movement in an axial direction as the outer housing expands at a higher expansion rate than the ceramic element during high temperature operation.