Advice on exhaust

LegacyT · Post by **LegacyT** » Sun Mar 21, 2004 11:54 pm

Ok in the spring I plan on fabbing up a custom 3" turbo back. The only part I will buy is an ebay downpipe and a muffler of somesort. The thing is I want it to sound stock (stock is quite refined) or more refined than the stock sound. I don't want that cheap ass (in my opinion) boxer burble and rumble. I want a more porsche, bmw sound, a very refined sound. I'm looking for exhaust experts to help me out. What type of muffler to get, and what kind/how many resonators to put in.

Thanks,
Mark

THAWA · Post by **THAWA** » Sun Mar 21, 2004 11:59 pm

ciper said equal length headers would make it sound more like a v8 than a boxer.

ciper · Post by **ciper** » Mon Mar 22, 2004 4:35 am

Yeah, it sort of smooths out the lumps. Not completely, the twin scroll is also supposed to remove some of the boxer sound, though Ive only heard it in videos.

If you want it refined think about keeping a cat and using two mufflers. That is what Im doing.

Check this out http://bbs.legacycentral.org/viewtopic. ... 7&start=24
(Im thinking about using a different dp than mentioned)

jake15 · Post by **jake15** » Mon Mar 22, 2004 7:10 am

the twin scroll sounds almost like a completely different car. definitley smoother

LegacyT · Post by **LegacyT** » Sun Mar 28, 2004 11:59 am

Are the stock headers equal length? I love the way the car sounds stock, whats the best way to replicate it with a 3 inch turbo back? Ciper, you said more then one muffler? Do you mean a muffler and a resonator? Maybe two resonators? I don't want any cats.

Mark,

THAWA · Post by **THAWA** » Sun Mar 28, 2004 5:46 pm

The stock headers on turbo cars aren't equal length the driver side header is longer, on an NA car they are closer to equal but still I think the driver side is a lil longer. I believe ciper is running two mufflers in series to quiet it down.

Kelly · Post by **Kelly** » Wed Mar 31, 2004 6:17 am

IMO, nothing will ever sound like a Porsche, but a Porsche.

I run an equall length, (with open 3" stainless turbo back) and without the silencer in my muffler, it sounds like a big Honda on steroids. Not my favorite.

I think the sound your looking for is the Borla Stealth System for WRX. Its actually pretty quiet, but low pitched, and no rasp. It bolts together using slipjoints, and clamps, and it will need to modified for the Legacy.

Call Sean at Rallitek, I think they were pretty cheap.

BAC5.2 · Post by **BAC5.2** » Wed Mar 31, 2004 7:24 am

Any advantages to equal length vs. unequal length headers?

Anyone have clips of both? Boxer = awesome sounding.

THAWA · Post by **THAWA** » Wed Mar 31, 2004 7:40 am

I believe most equal length headers net at least 10 more hp

NICO · Post by **NICO** » Thu Apr 01, 2004 9:19 am

leave it the same, if u put a 3" pipe with no cats and 2 muffs or res it will still sound loud. i got a bmw and cuz got a porsche you will never get that german sound out of a subaru. think of all that extra weight you are adding plus u could blow up your turbo. make it sound like a rally car the way it sould sound.

NuwanD · Post by **NuwanD** » Thu Apr 01, 2004 3:59 pm

Equal length headers match the pulses on the exhaust allowing for a bit more low end torque, this also results in the turbo spoooling up faster than before... i've driven a ver8 with twinscroll and although the exhaust note is a bit different from a regular suby, the drone from the engine that gets into the cabin still sounds like a boxer... same with all the wrx's and turbo 2.5 motors i've driven, the exhaust is less lumpy but the boxer sound still finds its way into the cabin.

I'll be making my own 3" turbo-back this summer as well...
- divorced downpipe
- 1 aftermarket cat (hi-flow)
- 1 muffler (straight through... but the type that does an "S" path in the muffler)

I love the rally car sound

JasonGrahn · Post by **JasonGrahn** » Thu Apr 01, 2004 5:52 pm

Porsche exhaust manifolds are a crazy thing. Take a look here: http://www.911pcar.com/images_old/90%20 ... ifolds.JPG

You want a porsche sound, get a porsche.

Being blunt; people who want power but no sound don't have their priorities straight in my opinion. Think about it this way, to make power, your engine basically needs to get rid of exhaust gasses quicker, right? If you decide to slap a bunch of resonators and mufflers on the car, sure it'll be quieter, but you won't have the power potential.

Case in point: I know a dude who has a 1G DSM AWD Turbo. Decides that he doesn't want the sound, but wants the power. Gets the great idea to install a few resonators that have the same inner diameter as his 2.75" exhaust. well, sure, the inner diameters are nice, but it still doesn't work right. His exhaust has more resonator sections in it then actual exhaust pipe; but damnit, his car sure sounds quiet!

Then he put on a 3" turboback exhaust, just for fun, and it wasn't THAT much louder at both idle and WOT then his butcher'd one. But it sure did produce more power! His QM time dropped by .3 seconds.

ciper · Post by **ciper** » Thu Apr 01, 2004 8:06 pm

How would a straight through Muffler of equal inner diameter as the rest of the exhaust piping reduce power over normal chunk of pipe?

vrg3 · Post by **vrg3** » Thu Apr 01, 2004 8:35 pm

The straight-through muffler still provides some restriction... You have to cause turbulence to quiet it down. The perforated lining interferes with flow somewhat.

ciper · Post by **ciper** » Thu Apr 01, 2004 8:40 pm

You have to cause turbulence to quiet it down? Thats not how I understood it. I thought the vibration reflected back and forth down the pipe until exiting, the straight through muffler lets this vibration enter the insulation while the air flows straight through?

JasonGrahn · Post by **JasonGrahn** » Thu Apr 01, 2004 8:45 pm

http://auto.howstuffworks.com/muffler.htm may have some good basic information.

ciper · Post by **ciper** » Thu Apr 01, 2004 8:51 pm

Okay Ive read that and now I feel even stronger that the straigh through muffler shouldnt reduce power. It acts as a restricted expansion chamber letting a small amount of pressure be delayed into the stream, which cancels some of the sound.

JasonGrahn · Post by **JasonGrahn** » Thu Apr 01, 2004 8:58 pm

If you've ever looked inside of a straight-thru muffer, you'll see what look like little bumps or teeny baffles inside. These create the vibration you refer to. But vibration cannot be created without friction, correct? Friction slows stuff down right? having your exhaust pulse slowed would be a restriction, would it not?

You are correct in that the vibration of the exhaust between chambers quiets the note of the exhaust, but this cannot be created without a restriction placed in the path of flow.

I'm not sure if i'm being crazy redundant or if that's some wacko circular logic, but somehow it makes sense to me. Can someone fill in the blanks of wat i just said? I know i missed something in there.

ciper · Post by **ciper** » Thu Apr 01, 2004 9:25 pm

The straight through mufflers I looked through didnt have bumps. It had a pipe with as many holes drilled in it as possible that was surrounded by insulation. Not enough turbulance to matter.

evolutionmovement · Post by **evolutionmovement** » Thu Apr 01, 2004 9:40 pm

Sounds like a glasspack.

Steve

LegacyT · Post by **LegacyT** » Fri Apr 02, 2004 1:47 am

JasonGrahn - I want my new exhaust to sound nice and refined like stock. I think the stock legacy turbo exhaust sounds amazing, well mine anyways. Thats what I'm asking about, how to build an free flowing exhaust that sounds stock. Like I said I don't want the shitty (IMHO) boxer burbble and rumble, I'll leave that for the impreza's. And apparently resonators don't add any restriction, so i don't mind throwing in as many as needed.

Mark,

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Advice on exhaust

Advice on exhaust