View Full Version : Grrr....elusive exhaust noise
Ever since I installed Borla mufflers on my car, I've had an exhaust noise. All I did was have the muffler shop swap out the mufflers, nothing more. Now, when I roll to a stop, at about 17 mph, I hear a rubbing noise. And under certain conditions under light throttle in 2nd or 3rd gear, the exhaust system resonates very loudly. My MM sounds like a ricer!
The muffler shop cannot find anything rubbing. We've had the car on the lift for 2 hours banging on the exhaust system, and it's solid. I asked the manager if it could be something internal in the muffler, and he said no. This is driving me nuts. Anyone else run into this?
Raudermaster
06-07-2007, 02:59 PM
No, mine is sound as a pound, until I drop the hammer :D. Maybe it's your tips rattling? That used to happen on my old car Jon at stoplights and such.
fastblackmerc
06-07-2007, 03:23 PM
Rubbing noise? Look for any shiney spots next time you have your car on the lift.
Hotrauder
06-07-2007, 04:45 PM
Long shot but I had a Cat media break in half and the pieces were banging around in the muffler opening under low exhaust pressure situations. ??? Dennis
MENINBLK
06-07-2007, 04:54 PM
Did the muffler shop remove the weights from your exhaust ?
The weights act as resonance dampeners and that could be
what you are hearing.
fastblackmerc
06-07-2007, 06:30 PM
Did the muffler shop remove the weights from your exhaust ?
The weights act as resonance dampeners and that could be
what you are hearing.
I had Magnaflows installed on mine minus the weights and no weird noises.
sicilianmarquis
06-07-2007, 06:42 PM
i ws trying to figure out what the hell those weights were there for
snowbird
06-07-2007, 07:02 PM
Like someday else posted, could be a cat getting bad and partly broken inside. About rubbing noise, the only moving part in the area are the driving shaft and rear tires. Having one of the tube rubbing should be easy to spot ..
I had an ace mechanic friend of mine drive the car, and he said it was definitely exhaust. I took the OEM mufflers off and replaced them with Borlas. I didn't know anything about weights... should I have salvaged them and put them on the Borlas?
The sound is not a banging sound, it's a buzzing sound. Something is resonating in the exhaust system somewhere.
Herco23
06-07-2007, 07:34 PM
did you replace the stock tips with the deleted tips?
did you replace the stock tips with the deleted tips?
Nope, the exhaust system is untouched except for the mufflers.
Raudermaster
06-07-2007, 08:30 PM
I have a solution, get an aftermarket kit.
snowbird
06-08-2007, 02:56 AM
I had an ace mechanic friend of mine drive the car, and he said it was definitely exhaust. I took the OEM mufflers off and replaced them with Borlas. I didn't know anything about weights... should I have salvaged them and put them on the Borlas?
The sound is not a banging sound, it's a buzzing sound. Something is resonating in the exhaust system somewhere.
I would try to weld back the weight or find similar weight if not available as a try. Having the stock tail pipes in 2" sometimes induce vibration on idle with aftermarket mufflers that have 2½" inlet and outlet. Right now i'm redoing mine in 2½" SS area by area. When I did the tail pipes area, the vibration went away to my surprise.
Marauderjack
06-08-2007, 03:26 AM
I had a CV that I put duals on and the system rattled like it had a loose mufler clamp somewhere...added a second vibration damper and no more rattles!!:beer:
If you can salvage the OEM dampers just clamp them on with hose clamps and see what happens...If it works have them welded on!!:rolleyes:
Good Luck!!
Marauderjack:burnout:
Raudermaster
06-08-2007, 05:10 AM
Geez Jon, go back an question your "ace mechanic" about this. I'd be mad at him if I were you!
Krytin
06-08-2007, 09:36 AM
I had an ace mechanic friend of mine drive the car, and he said it was definitely exhaust. I took the OEM mufflers off and replaced them with Borlas. I didn't know anything about weights... should I have salvaged them and put them on the Borlas?
The sound is not a banging sound, it's a buzzing sound. Something is resonating in the exhaust system somewhere.
I did but the dampers back on my car - helped a little.
This is interesting. I put Glass packs on mine a few months ago - they are loud. The last few days I picked a high freq. "buzz" or "rattle" @ mid throttle in second and third gears. Not all the time and goes away when I change throttle position. I thought I broke the transmission but except for the noise it's working fine.
I'm going to start checking my exhaust - maybe a crack somewhere that is opening/closing?!
Keep posting until one of us figures this out!
The stock vibration dampers that were on the stock mufflers are long gone. Can the muffler shop duplicate those somehow? Any pics?
Drock96Marquis
06-08-2007, 04:50 PM
Check the heat shields on the cats, they will make an intermittent buzz/rattle when loose.
Worth a shot.
The exhaust dampeners are mounted on the H-pipe to cat down-pipe flanges, not on the mufflers. Your's are probably still there.
Krytin
06-09-2007, 09:40 AM
The stock vibration dampers that were on the stock mufflers are long gone. Can the muffler shop duplicate those somehow? Any pics?
No.
The OEM parts are actually a wieght encased in an elastic/rubber compound. They are engineered to vibrate/oscilate at a frequency to cancel an existing harmonic frequency. They are engineered for the factory exhaust system to eliminate inherent harmonics from the engine/exhaust.
I reinstalled mine on the glass packs after driving w/out them - I felt it took the edge off of the "drone" between 1800 - 2000 rpm.
They won't be the end all solution as any aftermarket exhaust is different than the OEM and can add/detract from the original harmonics that the OEM wieghts were designed to eliminate.
[quote=Krytin;502746]No.
The OEM parts are actually a wieght encased in an elastic/rubber compound. They are engineered to vibrate/oscilate at a frequency to cancel an existing harmonic frequency. They are engineered for the factory exhaust system to eliminate inherent harmonics from the engine/exhaust.
quote]
So, could they be making my vibration worse since they are not tuned to the Borla exhaust?
Krytin
06-10-2007, 01:48 PM
Theoretically, yes. Depending on how/where you mount them and the system you mount them to, it could make things worse! Without the design software, known harmonics and the actual specs on the damper, it is a bit of a crap shoot!
That said, part of the design that went into the dampers was the harmonics that the engine will create itself. If the aftermarket replacement exhaust components are of similar size/weight/placement, the dampers should provide at least some, if not considerable, relief.
wchain
06-11-2007, 09:19 AM
I had borlas on my DTR, no issues, but I did later discover, when the car got warm the tailpipe was expanding and then rubbing on the fuel tank! This only occurred after idling or a hard run, when the metal expanded a lot. I went back and the had to rebend pipe to make it right.
Yeah, I had that problem, too. But it's been taken care of, and I still have the buzzing.
Maybe this is a good excuse to get DR's Cobra system :)
Marauderjack
06-12-2007, 03:41 AM
If you can find a couple lead dive belt weights just clamp them on with SS hose clamps and see if it works??:cool: If so I have the OEM damper weights from my system that I'll let you have!!:beer: I would suggest just in front of the mufflers.....If successful I would weld the dampers on the inlet pipes or the mufflers themselves!!
Marauderjack:burnout:
Krytin
06-13-2007, 06:27 AM
If you can find a couple lead dive belt weights just clamp them on with SS hose clamps and see if it works??:cool: If so I have the OEM damper weights from my system that I'll let you have!!:beer: I would suggest just in front of the mufflers.....If successful I would weld the dampers on the inlet pipes or the mufflers themselves!!
Marauderjack:burnout:
If you are going to use the OEM dampers (I did and found them to be helpful), weld them to the front/outside corners of the mufflers.
Anyone have a photo of the OEM dampers? I don't see them on my car. Marauderjack, I may just take you up on your offer!
Krytin
06-14-2007, 10:15 AM
Anyone have a photo of the OEM dampers? I don't see them on my car. Marauderjack, I may just take you up on your offer!
My car is pretty low to the ground now, but if I can get my old fat a$$ under there, I'll get some pics of the glass packs w/the OEM dampers on them.
Marauderjack
06-14-2007, 02:27 PM
OEM Dampers.....
Marauderjack's been kind enough to send me his old ones. Can someone post of pic of how they are mounted?
Well, I had DR send me a tune file and I uploaded it last night. The idle is a little higher, and the trans shifts out at higher rpms than before. I took the car out and drove it, and the buzzing was almost gone. So today, I took the car to the muffler shop and had them tack the dampeners onto the Borlas, and that took care of what remaining buzzing I had left. It's totally gone now, and I'm a happy camper!
:banana:
and :beer: to Marauderjack
Marauderjack
06-23-2007, 03:46 AM
I'm glad they worked Jon!!:up:
Marauderjack:burnout:
Krytin
06-23-2007, 07:59 AM
Well, I had DR send me a tune file and I uploaded it last night. The idle is a little higher, and the trans shifts out at higher rpms than before. I took the car out and drove it, and the buzzing was almost gone. So today, I took the car to the muffler shop and had them tack the dampeners onto the Borlas, and that took care of what remaining buzzing I had left. It's totally gone now, and I'm a happy camper!
:banana:
and :beer: to Marauderjack
I glad that worked out!
I just found out yesterday what my intermitent "buzz' was - I had spun the left rear axle bearimg!
The oil seal let go yesterday and I dropped it at the dealership last night. Between the TSB for the soft axles ang the premium ESP this will be a waranty repair. Might be time for gears - Motive makes a 3.90 set for under $200.
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