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Old 02-02-2012, 09:54 AM   #1
be0tch
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Join Date: Jul 2004
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2005 WRX STi
FP HTA Green Turbo

Default 05 STi Stage 2 - downpipe only or stealthback?

Hello sagacious NASIOC members.

I have read some threads to the effect that installation of an aftermarket downpipe (like nvidia's catless downpipe) will allow running Cobb AP Stage 2 with significant gains over Stage 1 and nearly the same gains as going stealthback.

I don't want to go full turboback exhaust. Would you recommend going downpipe Stage 2?

Is it worth getting TurboXS's Stealthback and doing that instead? I want to keep the STi's axleback for stock appearance.
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Old 02-02-2012, 11:21 AM   #2
be0tch
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Thanks mods for moving this thread - there are quite a few forums and I wasn't sure where to put it. Now that you mention it, it does seem like an accessport forum post
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Old 02-02-2012, 12:27 PM   #3
Cobb Tuning
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Quote:
Originally Posted by be0tch View Post
Hello sagacious NASIOC members.

I have read some threads to the effect that installation of an aftermarket downpipe (like nvidia's catless downpipe) will allow running Cobb AP Stage 2 with significant gains over Stage 1 and nearly the same gains as going stealthback.

I don't want to go full turboback exhaust. Would you recommend going downpipe Stage 2?

Is it worth getting TurboXS's Stealthback and doing that instead? I want to keep the STi's axleback for stock appearance.
You can run an aftermarket downpipe with the stock catback with our stage 2 maps, just that there will be some performance decrease compared to a full turbo-back. If you do go with a full-turboback, we recommend a catted downpipe (catless can sometimes result in boost creep).

Bill
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Old 02-02-2012, 12:46 PM   #4
be0tch
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Join Date: Jul 2004
Chapter/Region: Tri-State
Location: Brooklyn, NY
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2005 WRX STi
FP HTA Green Turbo

Default

Thanks Bill.

So what you're saying is that it is ok to run a catless downpipe with the stock catted midpipe and catted axleback (at reduced performance gain obviously) but if I were to go to an aftermarket "free-flowing cat" midpipe that it would be safest to use a catted downpipe to prevent boost creep?

My apologies for all the questions, I'm trying to figure this all out before committing to any new parts.
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Old 02-02-2012, 01:06 PM   #5
Cobb Tuning
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Originally Posted by be0tch View Post
Thanks Bill.

So what you're saying is that it is ok to run a catless downpipe with the stock catted midpipe and catted axleback (at reduced performance gain obviously) but if I were to go to an aftermarket "free-flowing cat" midpipe that it would be safest to use a catted downpipe to prevent boost creep?

My apologies for all the questions, I'm trying to figure this all out before committing to any new parts.
If you go with a shorty downpipe, you could retain the stock midpipe section with a cat (or a high-flow cat aftermarket midpipe) and that should be good enough to avoid boost creep in most cases even with an aftermarket catback. That is essentially the same thing as a full-length downpipe with hi-flow cat, just that it is in two pieces instead of one.

So, bottom line, if you have a cat in there somewhere, you should be fine.

Bill
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Old 02-02-2012, 01:10 PM   #6
be0tch
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Quote:
Originally Posted by Cobb Tuning
So, bottom line, if you have a cat in there somewhere, you should be fine.



Great. Thanks for your prompt responses and excellent product. Stage 1 has already been blowing me away compared to stock.
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Old 02-02-2012, 02:10 PM   #7
Migraine777
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This is some of the exact information I've been looking for for my new Sti. Trying to set up my timeline of what to upgrade first and how the individual mappings will result in different performance. I called Cobb today and had a long conversation with one of the tech guys about customizing the mappings and was very impressed with their knowledge. Look forward to more info from you in the future!

-Pat
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