So, my y pipe has been on a month or so. and i get this wierd rattle when i rev it up really high, like 4k+ and let the speed drop to idle. it seems like the sound is coming from inside the cat. i have looked for anything that could be hitting the pipe, but have found nothing. i certainly would not call it bees in a can, and it only happens when i go to WOT, not when i gradually gain engine speed. there does not seem to be any loose or broken catalyst in the converter, so i have no idea what is rattling. i had a mechanic look under the car today. no exhaust leak, no loose bolts, nothing bangin on anything, only an odd sound from the cat.

it does not happen at constant engine speed (like bees in a can), only when engine speed drops. so, i am stumped.

 

bump

 

no one?

bueler...


bueler....


bueler.....

 

Miasma:

I have Cattman Y-pipe, Stillen B-pipe and RT cat and experiening something similar. After replacing stock Cat with RT the sound became particularly nasty, most in 1800-2000RPM range, and double that (3600-4000) to a lesser degree (as a harmonics, a gather).
The only way to pinpoint the culprit, IMHO, would be to replace your aftermarket components with stock ones, on by one.
the Cat is not a culprit by itself as much as together with Y-pipe (which doesn't have a resonator as you know - so some deterioration of sound is expected).
Eugene

 

i am gonna give this one more bump

i expected a deterioration in sound, just not a rattle. there is no loose catalyst, no leaks, nothin...

 

Check for small rocks or pebbles stuck on the heatshield...

My RT Cat's heatshield broke loose and started to rattle (it was virtually new at the time).

 

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i have no heatshield under the cat right now.