Thread: Dreadful drone
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Join Date: Jan 2003
Location: Burlington, Wisconsin
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Originally Posted by JFairman View Post
If the droning gradually increased over a few months or whatever I would check to see that the sound absorbtion packing hasn't gradually blown out of the muffler or melted.
If that happened, and it just recently happened to someone that lives near me with one of these mufflers and there's a post about it here the muffler would gradually become louder and if there is a droning at certain rpms than the pitch of the exhaust may be hitting the resonant frequency of the engine bay sheet metal, or possibly the floor pan and rear bulkhead firewall.
If sound absorbtion material has been removed from the floor or behind the back seats to lighten the car, that will just make it louder and more resonant at certain frequencies.

What do you use for sound absorbtion material in your mufflers?

Chopped fiberglass packing blows out of 4 cylinder glass pack mufflers in no time from the exhaust pulses so long strand fiberglass usually stays in place in those applications.
I've also heard of stainlees steel wool fibers being used. Not sure if I've heard of carbon fiber being used in muffler packing.

With being the owner of M&K I have had the luxery of trying all kinds of sounddeadening materials. Ironically I used chopped fiberglass on my prototype turbo conversion when I did that 6 years ago. It still had the fiberglass in it when I sold the kit last year at this time to another pelican. With other testing I found that fiberglass matting works well and the stainless wadding does work as well though the most effective is the longer strand material similar to home insulation. it holds up the best. now these examples are with straight through designs and if it were to melt out there is something real bad going on with the car those type of heats should be no where near a turbo charged engine. but that is just my experience with many different combonations and many many miles

914-6 2.4s GT tribute. manufacturer of 914-6, GT, Conversion parts
Old 12-30-2009, 05:23 AM
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