Old stainless silencer making loud musical echoing sound - Fix?

Akagi

Akagi

Akagi

Caporegime
Joined
29 Jul 2011
Posts
37,181
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In acme's chair.
Helloooo

Thought I may as well ask here...

E30 has a stainless Scorpion centre exhaust on it, its quite old and has been bashed about a few times.

It makes a really annoying/loud echoing sound, a bit like someone blowing over the top of a glass bottle, which is louder at certain RPM's.

If you apply pressure to the bottom of the silencer, it almost completely stops the noise.

I tried lashing it to something so that any vibration is taken out of it/damped, but there isn't anywhere really to lash it to, and its a bit of a hillbilly fix.

Any ideas before I either - Start hitting it with a mallet, or, cut it open, try to figure out whats going on and weld it back up, or, stick it on eBay.

Danké :)
 
Vita said:
Baffle gone inside? Only thing I can think of if it's not caught on anything.
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I thought that but it goes when I apply pressure to the bottom, thought if it was the baffle it would still make the noise. I dunno... :p

I could always gut it, would make it louder, but will probably make it droney and awful.
 
Take box off and shake it. Thatll tell you There's not damage to the bottom of it is there?
 
Vita said:
Take box off and shake it. Thatll tell you There's not damage to the bottom of it is there?
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Yes theres damage to the bottom of it. Used to be on a ******** air-ride E30. :p

Was cheap but in hindsight, I should probably have tried it before I sold my original one to my pal.

3e7mHLo.jpg


Will probably take it off tomorrow. Not sure I'll be able to separate it from the backbox for optimal shaking though.
 
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So is that where you're holding it for it to stop making the weird noise? Or is it further along?
 
If I apply pressure in the middle for example, it stops making the noise. Best position to apply pressure is probably dead middle, or slightly off middle, towards the scorpion logo.
 
The fact that the noise goes away with slight pressure would suggest to me that the resonation is coming from interaction between the exhaust and something else. There's no way a bit of pressure on the outside of the box is changing what's happening inside it, unless it's made of tracing paper.
 
No its just the exhaust. i think its cos it stops it vibrating when I touch it in a specific way.
 
Acme said:
it stops it vibrating when I touch it in a specific way.
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Ooh err missus!

If you are certain that it's not fouling anything else then whip the box off and shake it as suggested. If there is no rattling in the box then **** knows.
 
Broken exhaust hanger somewhere further up or down the system, allowing it a bit of freedom at certain frequencies?
 
the mid box rubber hanger is missing but if i hold it by the hanger it makes no difference.
 
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