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Old 11-02-2009, 04:17 AM   #1
The Blue Pilot
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Default Turbo upgrade without the exhaust swap

My thoughts: putting a stock STI exhaust on my car + catted downpipe, catless uppipe, K&N intake (typhoon), then the fuel pump, injectors, and finally...the turbo.

Goal: car with an upgraded turbo + power while maintaining extremely close to stock dB levels.

How would a 16g/18g fare with the STI exhaust vs with a regular free turboback? I'm talking in terms of power, so a guesstimate of hp/tq differences would be nice..and I'm willing to run the maximum boost possible (with a good powerful tune).

Thoughts? Please don't suggest any aftermarket exhausts such as the borla hush or crap...since I'm asking specifically about the STI exhaust...thanks
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Old 11-02-2009, 04:35 AM   #2
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Enjoy your boost creep. No point in spending all that money just to be so stubborn as to restrict your car like that. The only part of the STI exhaust you should bother yourself with is the axleback. The rest, for all intents and purposes, is the same as what you have now.
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Old 11-02-2009, 01:12 PM   #3
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Quote:
Originally Posted by Byzantium View Post
Enjoy your boost creep. No point in spending all that money just to be so stubborn as to restrict your car like that. The only part of the STI exhaust you should bother yourself with is the axleback. The rest, for all intents and purposes, is the same as what you have now.
Well, that's what I was saying...STI axleback + aftermarket catted DP / aftermarket catless UP with for the upgrade. I'm really only doing it for the sound, nothing else. And just a really newbie/brain fart question....boost creep? Is that where boost slowly builds?

Basically, if the difference is only going to be ~20 whp with minimal affect on turbo lag (difference of) then it's worth it to me. If I'm going to be having stage 2 power with stage 4 spool...then nty
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Old 11-02-2009, 01:45 PM   #4
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So just to be clear, you are going to use the OEM STI cat-back, but an aftermarket 3" or so down-pipe with a high-flow cat?

If so, this can work pretty well. The biggest restriction in the exhaust is the down-pipe with the OEM cats in it. As long as you are replacing that, this setup should work pretty well, and be just slightly louder than stock.

It sounds like you are basically going the Turbo XS stealth rout, and lots of people have done that with good results.

Good luck with your project.

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Old 11-02-2009, 01:50 PM   #5
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Originally Posted by FlatironsTuning.com View Post
So just to be clear, you are going to use the OEM STI cat-back, but an aftermarket 3" or so down-pipe with a high-flow cat?

If so, this can work pretty well. The biggest restriction in the exhaust is the down-pipe with the OEM cats in it. As long as you are replacing that, this setup should work pretty well, and be just slightly louder than stock.

It sounds like you are basically going the Turbo XS stealth rout, and lots of people have done that with good results.

Good luck with your project.

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Thank you sir...but the turbo xs route? You mean turbo xs downpipe? (assuming it's one that mates perfectly with the STI OEM catback...)
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Old 11-02-2009, 01:58 PM   #6
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TurboXS makes a "stealthback" which is a complete replacement exh, until you get to the muffler section, you can retain the stock STI muffer.

This will get you more performance than using a normal downpipe and full STI catback, but the same sound and volume level.

Its the best option out there if you are looking to keep the stock muffler, stock look and stock sound.
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Old 11-02-2009, 02:07 PM   #7
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Originally Posted by Defiant Autospeed View Post
TurboXS makes a "stealthback" which is a complete replacement exh, until you get to the muffler section, you can retain the stock STI muffer.

This will get you more performance than using a normal downpipe and full STI catback, but the same sound and volume level.

Its the best option out there if you are looking to keep the stock muffler, stock look and stock sound.
Nice...thank you. Only reason I'm going with a catted DP is because the catless (invidia) downpipe I have now is making more than enough of a stench...and combined with my stock wrx axleback, the leak is making the stench even worse...
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Old 11-02-2009, 02:08 PM   #8
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More than likely you have a tune issue if your car stinks bad. IE you are too rich. Catless will smell a LITTLE more, but if its a LOT more, and especially if you get discoloration on the bumper, you have afr problems and are too rich.

unfortunately what makes this situation even worse, is that a lot of so called "professional" tuners (which in some cases means nothing more than they bought a laptop/cable and started charging people) leave their maps FAR too rich, to combat the detonation that is coming from their poorly mapped timing tables.
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Old 11-02-2009, 02:19 PM   #9
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You can get a 3" downpipe adapter that will help it mate up a flat flange DP to a stock catback section. If your DP has a taper to 2.5", then this won't be needed.

http://www.importimageracing.com/p/3...9-WRx-STi.html

For a short-term solution, a 3" flange WILL mate up to a 2.5" pipe w/ donut gasket. Just get some longer bolts and it'll hold. I did that with my 3" catback mated to the stock DP, at least until I get my 3" DP in.
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Old 11-02-2009, 02:26 PM   #10
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Quote:
Originally Posted by Defiant Autospeed View Post
More than likely you have a tune issue if your car stinks bad. IE you are too rich. Catless will smell a LITTLE more, but if its a LOT more, and especially if you get discoloration on the bumper, you have afr problems and are too rich.

unfortunately what makes this situation even worse, is that a lot of so called "professional" tuners (which in some cases means nothing more than they bought a laptop/cable and started charging people) leave their maps FAR too rich, to combat the detonation that is coming from their poorly mapped timing tables.
Unfortunately, I'm running the v.1 AP and I'm using their OTS stg. 2 map currently with my invidia downpipe/uppipe (everything else remains stock). Their maps are known to run rich...hence why that's probably the case...thanks for the explanation though, I had missed that. Although there is no discoloration of the bumper (or so I think, haven't checked lately)


Quote:
Originally Posted by 2point0 View Post
You can get a 3" downpipe adapter that will help it mate up a flat flange DP to a stock catback section. If your DP has a taper to 2.5", then this won't be needed.

http://www.importimageracing.com/p/3...9-WRx-STi.html

For a short-term solution, a 3" flange WILL mate up to a 2.5" pipe w/ donut gasket. Just get some longer bolts and it'll hold. I did that with my 3" catback mated to the stock DP, at least until I get my 3" DP in.
Thanks for the link + advice bud.
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Old 11-02-2009, 02:54 PM   #11
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Quote:
Originally Posted by Defiant Autospeed View Post
More than likely you have a tune issue if your car stinks bad. IE you are too rich. Catless will smell a LITTLE more, but if its a LOT more, and especially if you get discoloration on the bumper, you have afr problems and are too rich.

unfortunately what makes this situation even worse, is that a lot of so called "professional" tuners (which in some cases means nothing more than they bought a laptop/cable and started charging people) leave their maps FAR too rich, to combat the detonation that is coming from their poorly mapped timing tables.
This. I've been catless for longer than most people here have owned their cars, and until my current tune (which the tuner did a terrible job on) I've never had a smell.
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Old 11-02-2009, 03:44 PM   #12
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This. I've been catless for longer than most people here have owned their cars, and until my current tune (which the tuner did a terrible job on) I've never had a smell.
Even if you leave your car idling in some sort of closed space for a bit?
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Old 11-02-2009, 03:48 PM   #13
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Even if you leave your car idling in some sort of closed space for a bit?
I never parked my car in reverse in my garage. Parking garages, no.
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Old 11-03-2009, 04:27 AM   #14
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I never parked my car in reverse in my garage. Parking garages, no.
Excellent. All that talk about harming the environment...psh

This diverts me to another simple question: which turbo to run? A 16g variant (preferably evo3) or the TD05-18g? Which turbo could I run higher boost on? My overall end setup should look like this:

K&N typhoon intake
invidia catless uppipe
turboxs stealthback
sti axleback
xx turbo
walbro FP
injectors
damn good ass tune on the v.1 AP

What do you guys think?
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Old 11-03-2009, 10:11 AM   #15
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The Evo III 16G will give you a wider powerband, but the 18G will give you more power up top.

Also, the 16G will spool up a bit faster than the 18G.

You might also want to look into the FP HTA68.
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Old 11-03-2009, 12:05 PM   #16
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Quote:
Originally Posted by FlatironsTuning.com View Post
The Evo III 16G will give you a wider powerband, but the 18G will give you more power up top.

Also, the 16G will spool up a bit faster than the 18G.

You might also want to look into the FP HTA68.

On that subject, here is what I have found.

The EVOIII-16G is a miserable performer on a 2.5L motor. But is OMGAMAZING on the 2.0L motor.

The FPHTA68 is one of the most over rated turbos ever. But, its dirt cheap, and does work well on the 2.0L motor, so its hard to actually slam it.
On the 2.5L motor, again, miserable match. The housings choke the engine off badly. You cant get around small housings by using high tech machining on the compressor wheel. Its the same reason the small housing 18Gs dont work well on the 2.5L motor, but the large housing 18Gs work VERY well on that same motor. (conversely, the small housing 18G actually works better than the larger housing, on the 2.0L motor)


If they stuck the HTA68's compressor wheel into a TD06 compressor housing, retained the TD05 hot side, but went to an 8cm exh housing, I am betting it would be an AMAZING turbo on the 2.5L. But they dont, and the performance compared to a large housing 18G 8cm on the 2.5L, show this.
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