how to quiet down 3 inch exhaust

turboswede wrote: Make sure the exhaust exits past the rear bumper or at least exits in a pair of turn downs. A lot of noise and resonance is worsened by exhaust that exits under the car. The Dynomax Super Turbos aren't the greatest chambered mufflers for killing noise. I'd look at bigger mufflers of similar configuration that can fit in place of the super turbos. Walker and Magnaflow are both good alternative brands. Spintech is another that I've not heard much about, but they look interesting. The only issue with glasspacks are that the fiberglass packing burns up over time and they get louder and louder. Stainless steel packed mufflers last a little longer, but aren't cheap.

FYI, Dynomax is Walker's performance brand.

There was a hot rod test a few years back about hp vs noise reduction. It was startling how BAD GLASSPACKS WERE. They lost hp and sounded terrible and loud. If you're interested, I will dig it up for you tonight and I can scan it or send it to you. It was really quite helpful and well done.

Car Chemistry makes some inserts that have baffles some wrapped in fiberglass that can be inserted into the header or perhaps a short section of pipe just after the header. You can find some info here:

http://www.carchemistry.com/shop/index.php?l=product_list&c=3

Don't know if it work for you or not.

I just looked up the TTI sheet for the exhaust system. You should have the #17793 Super Turbos in your kit. That's the 16" muffler shell.

If you go with the 17769, that's a 20" shell, 27" overall length. You'll need to modify the mid pipes to fit the longer shells to keep the over the axle pipes where they are now.

And yes adding sound deadener under the back seat bottom and behind the back seat back helps.

If it's just resonance that's bad, one of their new VT lines might work, but I don't know anybody that's used them yet.

I used a straight through Dynomax Ultraflow on a 2.5" exhaust and it was significantly more quiet than a friend's chambered Dynomax Superturbo muffler.

Wasn't there a GRM article on at least some of this not too long ago?

I didnt even read this thread because i already knew the answer:

Replace every straight section of pipe with glasspacks. Luckily glasspacks are cheap and come in every length imaginable.

ok now im reading

There was a hot rod test a few years back about hp vs noise reduction. It was startling how BAD GLASSPACKS WERE. They lost hp and sounded terrible and loud. If you're interested, I will dig it up for you tonight and I can scan it or send it to you. It was really quite helpful and well done.

If someone lost power with glasspacks then they bought louvered ones that also possibly dropped down in ID instead of straight through perforated core ones. Those will not lose any power.

Stainless steel packed mufflers last a little longer, but aren't cheap.

I would think they'd last a LOT longer. But then, ive never burned out a cheap glasspack in years so i dont have any personal experience with glasspacks going bad. I do have both fiberglass and SS mesh packed mufflers.

One thing about glasspacks, imo they will not quiet the noise down much at higher loads. Which is something i like about them.

Vigo wrote: ok now im reading

There was a hot rod test a few years back about hp vs noise reduction. It was startling how BAD GLASSPACKS WERE. They lost hp and sounded terrible and loud. If you're interested, I will dig it up for you tonight and I can scan it or send it to you. It was really quite helpful and well done.

If someone lost power with glasspacks then they bought louvered ones that also possibly dropped down in ID instead of straight through perforated core ones. Those will not lose any power.

Stainless steel packed mufflers last a little longer, but aren't cheap.

I would think they'd last a LOT longer. But then, ive never burned out a cheap glasspack in years so i dont have any personal experience with glasspacks going bad. I do have both fiberglass and SS mesh packed mufflers. One thing about glasspacks, imo they will not quiet the noise down much at higher loads. Which is something i like about them.

Except they sound TERRIBLE at high speeds. Not just good and loud.

the car IS sound deadened extensively. 2 layers of dynamat on EVERY surface from the underside of the roof to the floorpan. 1 layer of 3/4 foil backed just over that, with another layer of just attached to the carpet. also undercoated, and have polyfill filling the back seats. the trunk is not finished with my closeout panels yet, so only the dynamat back there for now,

i think ill definately be looking at the longer mufflers, rob, and maybe some resonators as well.

the noise is only tolerable from idle to about 2000 rpm. after that, its loud. no droning, but some lower frequewncy resonance at cruise RPM.

thanks for all the suggestions so far guiys. please, keep them coming.

Turndown?

Get mufflers with much longer cases. Magnaflow seems like a great brand. I'm also curious about Bosal straight rounds since they mostly end up on Japanese cars but they could be useful. Turndowns are a great idea as well.

My personal experience with glasspacks was a pair on true dual 2" pipes on my Capri. Sounded really nice and pretty quiet for about two weeks. Then they started to get louder, and more fart-like, and after a while it was almost like they weren't there anymore. Would avoid in the future.

Vigo wrote:

There was a hot rod test a few years back about hp vs noise reduction. It was startling how BAD GLASSPACKS WERE. They lost hp and sounded terrible and loud. If you're interested, I will dig it up for you tonight and I can scan it or send it to you. It was really quite helpful and well done.

If someone lost power with glasspacks then they bought louvered ones that also possibly dropped down in ID instead of straight through perforated core ones. Those will not lose any power.

+1

I ran into something similar with the 3" exhaust on my rotary powered Jensenator, only the noise is excessive outside the car even with a Dynomax, which is so far about the best of the reasonably priced turbo mufflers. I took a page from the old enduro rider's noise abatement handbook and built a quickly removeable exhaust tip which points the exhaust straight down and has a short piece of rectangular tubing welded to the opening. I started with a single opening which quiets the noise a BUNCH but is pretty restrictive, I'm going to add a second opening and see how that does.

Gearheadotaku wrote: Had Super Turbo's 2 1/2" on my C4 and they were terrible. Whole car buzzed and resonated. Replaced with plain 'ol glasspacks and was much, much better. Later dropped the big bucks on a Corsa system and totally loved it.

This. The Super Turbos are just loud. Regular Dynomaxes are quieter.

Where does the exhaust exit? If it's under the car, that won't help....

Spintech's larger mufflers are also very quiet, but have great flow...

I can't believe no one has said "Flowmasters". They sound teh sex on mufftangs.

Maybe Flowmasters work on boinger motors but on Dorito powerplants they make your ears bleed.