Borla Resonator and Resonance

[emmvette]

My car has the Borla exhaust system which was installed by LPE in 1997. At the same time LPE installed custom fabricated headers. Cats were removed this past year.

The car is fine for spirited driving, but with a 2+ hour drive results in a headache from drone. When I tap on the resonator; it sounds like an empty tin can. Is this normal, or is there some baffling missing or burned out?

Does anybody know if the Borla resonator had baffling or if it was just slotted pipes on the interior? I'm wondering if mine is "worn out" or needs to be replaced to cut down on the drone at highway cruising speeds.

Let me know of any thoughts. Borla doesn't make the resonator anymore and I don't see any replacements with the same pipe centerlines. Any thoughts on this?

[Gunny]

On my '90 I've run both the 2.5 Borla and the larger Borla Challenger with & without headers and with & without cats. Some drone was always there regardless of the setup and, like you, bothered me only on trips. My solution was to drop to 5th unless I could get above 2K rpm in 6th. I experimented with a temporary solution by blocking off one tip on each muffler and this did eliminate the drone. I never did figure out how to install a flapper in one of the tips on each side as many have done with other setups. My ultimate solution was to install a stock LT4 system behind the SW headers and install QTP electric cutouts at the entrance side of each muffler. The result - no drone with cutouts closed or even partially open; with the cutouts totally open I'm running an open exhaust w/headers (the LT4 resonator is not restrictive at all) - the sound is awesome and there is plenty of drone, but open cutouts are not for interstate cruising anyway.

Good luck on finding a solution - Borlas are great sounding but there is always some drone at certain RPMs.

[WARP TEN]

Originally Posted by Gunny

On my '90 I've run both the 2.5 Borla and the larger Borla Challenger with & without headers and with & without cats. Some drone was always there regardless of the setup and, like you, bothered me only on trips. My solution was to drop to 5th unless I could get above 2K rpm in 6th. I experimented with a temporary solution by blocking off one tip on each muffler and this did eliminate the drone. I never did figure out how to install a flapper in one of the tips on each side as many have done with other setups. My ultimate solution was to install a stock LT4 system behind the SW headers and install QTP electric cutouts at the entrance side of each muffler. The result - no drone with cutouts closed or even partially open; with the cutouts totally open I'm running an open exhaust w/headers (the LT4 resonator is not restrictive at all) - the sound is awesome and there is plenty of drone, but open cutouts are not for interstate cruising anyway.

Good luck on finding a solution - Borlas are great sounding but there is always some drone at certain RPMs.

I did the same thing as George on my '95--no cats, full '95 stock cat back with cutouts in front of the rear mufflers. No drone with the cutouts closed; can't tell with them open. The Corsa system also has no drone. The early Borlas, Power Effects, Desert Development and others had a lot of drone because none but the stock and Corsa systems had the requisite Helmholtz resonators to attenuate the two frequencies that cause the drone at 1800 and 3400 rpms. Not familiar with current systems. After years with loud exhausts (mostly corsas but others too) I was happy to have the no-drone stock system with the option to go full open exhaust with the cutouts.--Bob

[DRM500RUBYZR-1]

Originally Posted by WARP TEN

I did the same thing as George on my '95--no cats, full '95 stock cat back with cutouts in front of the rear mufflers. No drone with the cutouts closed; can't tell with them open. The Corsa system also has no drone. The early Borlas, Power Effects, Desert Development and others had a lot of drone because none but the stock and Corsa systems had the requisite Helmholtz resonators to attenuate the two frequencies that cause the drone at 1800 and 3400 rpms. Not familiar with current systems. After years with loud exhausts (mostly corsas but others too) I was happy to have the no-drone stock system with the option to go full open exhaust with the cutouts.--Bob

Bob,
You have made one of the best systems available.
Great job!
You are also spot on regarding the effectiveness of the Helmholtz technology.
I believe Billy Boat ( B&B ) uses that same technology in their Fusion Exhaust Systems, which also incorporates the special " Warp Ten Technology " of the Dual Modes.
Marty

[WARP TEN]

Originally Posted by DRM500RUBYZR-1

Bob,
You have made one of the best systems available.
Great job!
You are also spot on regarding the effectiveness of the Helmholtz technology.
I believe Billy Boat ( B&B ) uses that same technology in their Fusion Exhaust Systems, which also incorporates the special " Warp Ten Technology " of the Dual Modes.
Marty

Thanks Marty--I did like it. There are quite a few days when I wish I hadn't sold the '95. Oh well. The Z06 is a lot of fun....Bob

[RussMcB]

IIRC, the Borla resonator is pretty restrictive, so maybe replace it with something that might be better for drone and kill two birds?

[emmvette]

Thanks for some of the suggestions. Does anybody know if the Borla resonator is supposed to have any baffling inside or is it just a metal can?
What I'm trying to figure out is if my Borla resonator is toast (baffling burn out) or was is just fabricated metal and is probably the same as it's always been.

[GOLDCYLON]

Originally Posted by emmvette

Thanks for some of the suggestions. Does anybody know if the Borla resonator is supposed to have any baffling inside or is it just a metal can?
What I'm trying to figure out is if my Borla resonator is toast (baffling burn out) or was is just fabricated metal and is probably the same as it's always been.

It did have very little baffling but the system was always loud reguardless if it was just installed New or had been on the car a long time. Resonance was always a problem with the Borla system. It does not have substrate honeycomb ceramic like the cats have or a material internally that breaks down over time. So your options are somewhat limited unless you want to replace the whole system. I have a used Corsa 2.5 inch resonator only if you want to try and graft that into your system. PM me if interested