GTS, Borla, and Drone

Solid Red 98

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I was out driving my GTS over the weekend and while in the usual drone rpms, I drove over a grated drawbridge and the intensity went way down. I guess it interferes with the sound bouncing back up to the car off the ground. That got me to thinking of ways to diminish cabin drone without messing with the sweetness of the exhaust note. I moved my head way forward in the cabin and got a similar drone reducing effect. Has anyone tried some minor or major acoustical mods that have reduced GTS drone? How about a cargo cover? The rear fascia is as resonant as a sub-woofer. Perhaps a bit of sound proofing in that area would help. Any unreported solutions out there?
 

BOTTLEFED

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maybe dynamat the lower trunk area

I have the same problem, so I just drive faster ;)

and yes, the rear fascia is hollow and echos the sound inside
I can't think of any way to fix it though
maybe fill it with insulation foam lol!
 

ViperTony

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I can't think of any way to fix it though
maybe fill it with insulation foam lol!

At one point I was seriously contemplating buying several cans of "Great Stuff" spray foam and filling in those cavities over the rear wheel wells. The problem is I wouldn't be able to store my soft top due to the loss of the precious cargo space. I ended up switching to a Belanger exhaust and drive faster. :)
 
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Solid Red 98

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I was thinking about getting a cargo cover and putting egg carton foam on the back side of it in hopes of knocking it down a bit, but I figured it couldn't be that easy. I love the Borla, but I find myself saying, "what?" all the time :omg:
 

Brake Dust

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I have my car cover in the rear of the GTS. It cuts the sound way down .
Roe cats 3" random tec. :usa:
 

Dom426h

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I dont like keeping the cover in my trunk because it takes up to much space. I can see how filling in the trunk area with it would keep sound waves from bouncing around back there...

I'll try the EggCrate Foam idea and report back:2tu:

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ViperGTS

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That issue has been discussed numerous times here...:bdh:... get a Corsa 3" cat back for your GTS and the drone is gone!
 

agentf1

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That issue has been discussed numerous times here...:bdh:... get a Corsa 3" cat back for your GTS and the drone is gone!

Exactly. I can't believe the Borla sounds any better than the Corsa's do to make you want to deal with the drone. I LOVE MY 3" CORSA's.
 

sdaddy

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I had a crossover pipe welded in just in front of the rear mufflers. Did not eliminate 100% of the drone, but it eliminated a lot. Sounds the same as it did before at idle and under hard acceleration, but less drone when cruising. $100 at a good exhaust shop.
 

NorthernSnake

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Any chance that switching to a side exit exhaust layout would reduce cockpit noise while maintaining extior volume? I think side exit look wicked and wouldnt mind switching to lower cabin volume.
 

REDBLACK

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I had a crossover pipe welded in just in front of the rear mufflers. Did not eliminate 100% of the drone, but it eliminated a lot. Sounds the same as it did before at idle and under hard acceleration, but less drone when cruising. $100 at a good exhaust shop.

I added a 3" Magnaflow X-pipe in the rear and the drone is gone.:D
 

Vman455

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I went on quite the sound-deadening adventure earlier this year. Did the whole car with a layer of Damplifier Pro from Second Skin, then a layer of closed-cell acoustic foam, and finally a layer of mass-loaded vinyl. The bottom of the hatch area got two layers of Damplifier Pro, and I already had a Corsa catback (stock headers and cats). Still sounds good outside, but it's significantly quieter in.
 

Camfab

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One word...........Corsa

What's the point of having a 3" exhaust if your going to choke it down to 2 1/4" with a "Venturi Tube".
 
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AndrewDoe

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According to the Toyota and Audi guys, it hasn't impacted their HP, but does kille the drone. The piece is very short so the flow should not be significantly restricted.

It goes after the stock flange at the beginning to the muffler pipe.

For $30 it's worth the test.....
 
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Solid Red 98

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According to the Toyota and Audi guys, it hasn't impacted their HP, but does kille the drone. The piece is very short so the flow should not be significantly restricted.

It goes after the stock flange at the beginning to the muffler pipe.

For $30 it's worth the test.....

This looks like something to try. Perhaps a cheap fix for once.
I have stock headers, so a short restriction of the same diameter shouldn't make any difference in performance.
 

97GTS

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Any chance that switching to a side exit exhaust layout would reduce cockpit noise while maintaining extior volume? I think side exit look wicked and wouldnt mind switching to lower cabin volume.


If anything it would be LOUDER. Nowhere to put any sound deadening between the exhaust and your ears. Except maybe in the doors?


Ron
 

AHudson777

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Hmmm, I'm gonna give it a try, seems like deadening the hatch area of the cabin might do the trick. I've been wanting a cargo cover too.

The 'storing the car cover in the rear' got me thinking about ways to quiet the car down a bit. Then this...

I went on quite the sound-deadening adventure earlier this year. Did the whole car with a layer of Damplifier Pro from Second Skin, then a layer of closed-cell acoustic foam, and finally a layer of mass-loaded vinyl. The bottom of the hatch area got two layers of Damplifier Pro, and I already had a Corsa catback (stock headers and cats). Still sounds good outside, but it's significantly quieter in.

That was an 'over the top' application, and I'd love to hear how nicely you dampened the unwanted noise, so I did a compromise.

I took out the felt liner under the spare and all that. Put Dynamat on the entire area; all under the spare, across the floor, into the side wells. Then I 3M glued the closed-cell acoustic foam on the underside of the felt liner, which also goes side-to-side.

While in this area, my woofers in the back were determined to be junk (all the foam deteriorated) so I replaced those.

Anyway, reassembled the area, tucked everything in tightly and wonder-of-wonders the 'bad' noises are subdued mightily. The exhaust still makes its wonderful pitch (metal high flow cats from JonB)but the booming noise under the glass is now gone.

And I can actually listen to the stereo now (I had no idea how bad my old speakers were!) if I choose that very rare option.

I do NOT have pics (yes, I should be fired) but suffice to say, this is a '2' on a scale of '10' in difficulty, only requiring a careful blade and some contorting to reach the side wells. Gettting to sniff the 3M trim adhesive is just a side benefit.

I am super pleased with the result.
 

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