Building a quiet exhaust for BT

[theskuh]

I am just starting my BT plans. Suspension is now done.

I want a nice quiet exhaust that still flows OK? I don't want to call attention to my car driving around the parking lot at work or have a overly obnoxious drone on the highway.

I was looking at the apr for B6's and that is 3" and supposedly not much louder than stock. I wouldn't mind more note when I am hard on the gas but I lived with loud exhausts before and I am pretty much over it.

Well the single glass pack and side outlet on my Chevy 350 was sweet.

So what are the parts (muffler, Pipe size, resonators) that I need to create a decent free flowing exhaust that won't rob too much HP.

I will probably weld it up myself for fun and learning.

[biketsai]

Three letters, APR!
I had a custom exhaust with two resonators and it was still louder than my resonated Apr.

[317ssayzarc]

You need to add a few letters my friend lol...

Milltek, there is no quieter system than a Milltek, regardless of make/model... Plus its 2.75" which is bigger than almost all the systems out there

[ricebeater]

neuspeed from 034 its only 750 and its not too bad. I dont know on a BT Im just saying for a KO3. It might be your best bet for a BT from the piping size stand point.

[theskuh]

I kinda want to build it custom. do you know what mufflers would work to aproximate an apr, millitek or 034?

[biketsai]

forgot about miltek. Custom will not be as quiet as apr or miltek so don't waste your money.

[aytheory]

keep the cat - my only advice

[317ssayzarc]

keep the cat - my only advice

why do you say that?

[theskuh]

Yeah going to do a race cat. I just want it in the ball park of the APR with available off the shelf mufflers. Am I missing something? will the performance suffer over the Apr with off the shelf stuff?

its all a matter of the mufflers right? I put restrictive mufflers on it it will be quiet. I don't and it will be loud. The rest is just pipe.

[theskuh]

I think he says keep the cat because without it The exhaust will be much louder. It acts as another resonator.

I have run with a hollowed cat before and it is louder than with the material in it.

[AudiRacerS4]

why do you say that?

the cat quiets the exhaust note on these cars a lot and it also eliminates the droning. to the OP if you are looking into going BT with a custom exhaust and want a performance gain it is going to be noticeably loud no matter what.

[tdn]

I recommend Milltek with a test pipe or high flow cat. Mine sounds perfect with a test pipe and I like my exhaust quiet also. It opens up nicely when I want, but nice and quiet (basically stock like with a deeper tone) during my daily routine.

You can get it pretty quiet going custom, but it will be noticeable.

[biketsai]

Ok, previously I had a 2.5" exhaust with stock downpipe. It had 2, 18" resonators, and a testpipe, and was way louder than the APR. The magnaflows even had an inlet of 2.25. So smaller diameter mufflers wont help at all.

Seriously, dont waste your time and money, just get a milltek or APR!!!

[theskuh]

Whats the secret of the militek or apr? Specially designed mufflers?

[biketsai]

Gotta understand that there is more to it than just the muffler. They use thicker metal with nice mandrel bends and tons of R&D.

[theskuh]

Gotta understand that there is more to it than just the muffler. They use thicker metal with nice mandrel bends and tons of R&D.

Right but you are ruining my excuse to buy a welder.

[andyrew]

I have a borla 2.25" exhaust behind my APR stage 3 and it has a 3" test pipe...

It is REALLY quiet for my tastes, but gets loud when you are deep in the boost/rpm's

2 borla resonated mufflers, about 18" long...




I'll go 2 3/4 or 3" later on, I'll put 2 maniflow mufflers in the system (or one cherrybomb and one magniflow), and a HF Cat (removable maybe) along with a cutout (or removable exhaust from cherrybomb on back) after the cat and cherrybomb.


When under no load, it should be fairly quiet.. under load it should wake up and be loudish.

[317ssayzarc]

the cat quiets the exhaust note on these cars a lot and it also eliminates the droning. to the OP if you are looking into going BT with a custom exhaust and want a performance gain it is going to be noticeably loud no matter what.

Well a BT with a cat is pointless imo, each to their own

[Poopie]

gutted s4 muffler and a resonator. Mines too quiet. i still have a cat on though

[biketsai]

Not trying to ruin your welding plans or anything, I just want you to get what's right for you the First time. I was like you a while ago and thought there couldn't be a difference, that's why I went custom.

[AudiRacerS4]

Well a BT with a cat is pointless imo, each to their own

haha i know that i'm just saying it quiets the exhaust. I woul dnever run a cat with a BT...hell i didnt run a cat on my K03 or K04 either

[AudiRacerS4]

Ok, previously I had a 2.5" exhaust with stock downpipe. It had 2, 18" resonators, and a testpipe, and was way louder than the APR. The magnaflows even had an inlet of 2.25. So smaller diameter mufflers wont help at all.

Seriously, dont waste your time and money, just get a milltek or APR!!!

yeah but custom is less than half the price of a milltek or APR exhaust. I paid $350 for a full turbo back exhaust.

[Poopie]

the muffler makes a huge difference. steal a stock s4 muffler and gut it. A 3in exhaust and its really not much louder then stock.

[Nebone]

I have a GHL 2.5" Turbo Back w/ HFC and I thought it was not that loud until I heard a Borla yesterday with a TP. GHL is much louder than the Borla. I'd love to have a Miltek or APR for stealth now. The Miltek is 2.75" and purrs while driving then opens up when stepped on it. The GHL does sound impressive and the popping makes up for the noise.

[Poopie]

my borla was very loud when I had it on my elim. No cat and BT really changed the tone.

[biketsai]

my borla was very loud when I had it on my elim. No cat and BT really changed the tone.

For sure, BT makes it soooo deeep. Its rediculous how drastically the tone changes.

[Nebone]

K03 is a pea-shooter muffler.

[sixfiveoh]

I have APR but with the resonator removed.

Much better

[NK2007]

My exhaust is custom, full 3" turbo back, with a race (hi flow) cat and 2 mufflers. one of them is a magnaflow and the other i am not sure if it is a second magnaflow or a different company.

I love the sound! Its quiet at normal driving, a little louder than stock, but at wot it has a very nice tone. Not raspy or ricer sounding at all.

[ShawFM]

I have a GHL 2.5" Turbo Back w/ HFC and I thought it was not that loud until I heard a Borla yesterday with a TP. GHL is much louder than the Borla. I'd love to have a Miltek or APR for stealth now. The Miltek is 2.75" and purrs while driving then opens up when stepped on it. The GHL does sound impressive and the popping makes up for the noise.

I love my Milltek too. That is the best one I have owned. Nicer than the Stebro, Scorpion or B&B Triflow (I believe they now make APR's). The fit was perfect, the sound is great, the clamps they shipped out with it sucked. They have since been replaced. But the exhaust was well worth the extra $$

[UN-PIMP-Z-A4]

i Recommend Milltek With A Test Pipe Or High Flow Cat. Mine Sounds Perfect With A Test Pipe And I Like My Exhaust Quiet Also. It Opens Up Nicely When I Want, But Nice And Quiet (basically Stock Like With A Deeper Tone) During My Daily Routine.

You Can Get It Pretty Quiet Going Custom, But It Will Be Noticeable.

I Have A Shotgun Testpipe With My Milltek Exhaust And Its Quiet...

[firstars]

make sure you get two mufflers in there. NOT one muffler and a resonator. Without a second muffler esp. with a test pipe the sound will be too loud for daily driving. trust me.

[onemoremile]

The reason that exhausts like the Milltek are quiet is tuning. We worked with Faurecia on a few projects and learned a lot. Cars have a few resonant frequencies. So do exhausts. So do sunroofs. Tune the port to the wrong size and flow and you get a nasty resonance. Close your windows, open your sunroof all the way, and go for a drive - you'll find a resonant frequency. This is an example of what happens inside a ported subwoofer enclosure below the port tuning frequency. Drop the back windows an inch and the resonance goes away. It doesn't take much to effect rather large tuning changes.

The oems tune the exhausts to whatever they want them through fancy math and trial and error. The aftermarkets do the same and it is often the same people doing the actual work. Changing the size of a can (cat chamber, muffler chamber, piping) changes it's frequency. By controlling all the variables they can do some crazy things like giving signature sounds to the Pontiac Grand Prix and Nissan/Infinity line. They got the same signature sound in the FX35 and 45 even though the engines are very different. It just took some tuning.

http://www.faurecia.com/pages/about_...ic_package.asp

Unrelated but worth checking out:
http://premium-attitude.faurecia.com/