Automotive exhaust system

DETAILED DESCRIPTION In accordance with one aspect of the present invention, an exhaust system for exhausting gases from an internal combustion engine having an exhaust manifold on a vehicle is provided.
The system includes a uniform diameter pipe extending from the engine exhaust manifold to an opening to the atmosphere.
The pipe carries the exhaust gases within from the engine to the atmosphere.
A plurality of porous filters are positioned within the pipe along its length to muffle the noise of the exhaust.
The porous filters are formed of at least one section of expanded metal.
Each section is folded at preselected positions along its length to form individual filters between the folds with each filter spaced a predetermined distance from the filters formed by a common fold.
In accordance with another aspect of the present invention, the predetermined distance between filters is varied along the pipe to enhance the muffling of a range of sonic frequencies.
The exhaust system can also include at least one section along the length of the pipe without filters to form a mixing chamber in which the separated portions of the shock wave cancel one another.
The filters can have a rectangular (including square) cross section, forming four arcuate channels between the filters and inner wall of the pipe which assist in dissipating the shock waves.
The filters can have an elliptical (including circular) cross section between the folds to permit the filters to contact the inner wall of the pipe substantially about its inner circumference.
The element can be twisted in a spiral shape to form the filters with the edges of the elements contacting the inner surface of the pipe.
In accordance with yet another aspect of the present invention, the porous material can be selected from the group comprising metal, ceramics or high temperature plastics.
The openings in the porous material can be of varied dimensions to enhance muffling of a range of sonic frequencies and can include airfoil sections to enhance muffling