ok... some advice on how to "fake" it.

get some silicon tubing (the kind that is heat proof" about 12" long this is to allow the exhost to cool a bit before dumping it into the "silencer"

next take a metal tube I would say about 1/2" diameter about the length of a coffee can and drill 1/8-1/4 holes in it .. this is to disperse the exhast into the "chamber"

take a coffee can and mount the tube in the center with epoxy/jb weld/whatever so that its in the center. with the "intake" on the open end. cut the plastic cover to fit over the open end and punch 1/4" holes in it for exhast.

now we need to fill it with something to "break up" the sound waves.

cotton is good but will get saturated quick and need to be replaced...

Rocks (about 1/2" - 2" in daimeter should work.

play around with stuff and see what works best.

I made a (bad) quick scetch of what im talking about.

this should work but i make no promises