Exhaust silencer apparatus for internal combustion engine

Abstract

A tuned pipe exhaust for a two cycle internal combustion engine for snowmobiles and the like includes a conically shaped converging megaphone section terminating in a small end tube. An absorptive spiral muffler unit is co-axially secured to the end tube and includes an inner radial end wall extending radially from the end tube. The muffler unit attenuates high frequency exhaust noise. The space between such end wall and the upstream conical wall of the tuned pipe is enclosed with a tubular resonator wall to define a resonator cavity with coupling opening in the end tube. The cavity and throat opening defines a Helmholtz resonator which attenuates low frequency exhaust noise. The combination of a low frequency reactive section and a high frequency absorptive section creates an effective balanced silencer operating over the normal frequency spectrum of such engines.