Internal combustion engine exhaust system

A muffler for an exhaust system of an internal combustion engine, the muffler comprising:

• a molded housing body open along one side and a cover removably attached to said housing body, said cover and said housing body together defining a hollow housing composed of a material resistant to corrosion by exhaust gas and to elevated temperatures;
• an inlet communicating with the interior of said housing and an outlet communicating with the interior of said housing;
• formations in the housing body defining between the inlet and the outlet a seat;
• a filter cartridge replaceably received in the seat of said housing and defining in the interior thereof an inlet compartment communicating with said inlet and an outlet compartment communicating with said outlet, said filter cartridge having a rigid thin shell and a permeable mass generally filling the shell and formed with passages communicating with said compartments at said sides for the acoustic damping of the exhaust gas, some of said passages opening only into one of the compartments and the other passages opening only into the other compartment;
• and
• means for securing said cover over the open side of said housing and thereby laterally closing said compartments with the cover and holding the cartridge in the seat to subdivide the inlet compartment from the outlet compartment with the cartridge so that flow between them is only possible through said passages and through the material in said cartridge.