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      07-23-2008, 05:48 PM   #1
dchen2
Second Lieutenant
 
Drives: E90
Join Date: May 2008
Location: USA

Posts: 275
iTrader: (7)

Exhaust drone with borla and a auto?

I recently installed the less aggressive single muffler borla exhaust onto my 08 335xi coupe auto and now my car is droning really badly along with a metallic vibration that happens in a certain rev speed..

The exhaust sounds extremely bassy idling and strangely from ~1500-2100rpm is very loud in a low bass tone sort of way but above 2200rpm quiets down and though somewhat louder than my stocks the borla sounds fabulous.

The problem is that since my local highways speed limits are mostly 55, I cruise ~60-65 which is right around 1900-2000rpm and around those speeds the droning is so loud it almost drowns out my music. Also right around 1700-2000rpm there is a weird vibration sound that sounds like either my rear console or part of the exhaust in the rear is vibrating creating a harmonic/resonance which is quite annoying. I have a feel that weird resonance is the cause of the exhaust sound so horrible at below 2200rpms but can't figure out where its coming from.

I had the muffler shop check for possible exhaust leaks and if parts of the piping might be vibrating but at first couldn't figure anything out.

During the recent Madison E90 meet earlier this week I checked out a couple other peep's cars and one member who had a Remius quad exhaust with midpipe secondary cat deletes in a 6sp 335i coupe was not nearly as loud idling and he had no drone when cruising.

I am pretty unpleasantly surprised since I heard the single muffler borla was supposed to be virtually drone free due to the built in crossover.

Anyone know what the problem may be and any possible solutions?

I am at the point of just wanting to restore of car exhaust back to stock due to the nearly intolerable droning. Other than the droning and really loud 1500-2000rpm range I really love the sound of the borla though!

Last edited by dchen2; 07-24-2008 at 12:22 AM.
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