The conventional aspirating muffler, as used in conjunction with an internal combustion engine, includes a venturi through which exhaust gases are discharged, and the throat of the venturi communicates with an air inlet tube which is connected to a pre-cleaner of the engine so that the air is drawn from the precleaner to the throat of the venturi.
Spark arrestors are frequently used in conjunction with mufflers, and the conventional spark arrestor includes a structure which will swirl the exhaust gases so that the solid particles will be thrown outward by centrifugal force and collected in a collection chamber.
Combined spark arrestors and aspirating mufflers have also been marketed, and in the combination unit the exhaust gases initially pass through the spark arrestor section, and after removal of the solid particles, the exhaust gases flow through a plug-type muffler section. The plug-type muffler, as used in the past, includes a solid baffle disposed across an inner tube which is spaced inwardly of the housing, and the solid baffle deflects the exhaust gases outwardly through perforations into the chamber between the inner tube and the housing, and the flow is then redirected via perforations back into the inner tube on the opposite side of the baffle. To accommodate the plug-type construction, the dimensions of the outer body or housing must necessarily be increased and the resulting size not only adds substantial cost to the unit, but when mounted vertically on a tractor, results in an increased obstruction to visibility.