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Old 08-02-2006, 12:15 PM   #1
dak125
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Lightbulb 2006 WRX. Stage 2 + stock exhaust. Anything wrong with my reasoning?

I searched and I read all pertaining FAQ's. There were two threads somewhat applicable to my situation but both dealt with the 2.0.

What I'm looking for is the performance of AP Stage 2 but with the sound of the stock exhaust. Right now the car has a Borla catback which I don't intend to keep. So here's what I'm looking at, I just want to make sure this is feasible:

-Stock uppipe, there is no cat in '06 uppipe's so I can leave that alone.
-Gut the stock downpipe (what are the chances of finding a gutted stock dp? )
-Gut the third converter section.
-Leave the midpipe alone.
-Leave the stock catback alone.

Any reason why this wouldn't work? Would this be unsafe for the car? I understand I may not get as large a performance increase like I would with a 3" TBE but I don't want this car to be obnoxiously loud.

Any comments and help would be greatly appreciated. Thanks!
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Old 08-02-2006, 12:47 PM   #2
captain spaulding
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Do you have emissions in illinios? I'd personally leave the stock cats alone, and just get an aftermarket dp, when it's time for an inspection a new dp/cat from subaru is going to cost you an arm and a leg. otherwise you should be ok, it might be alittle bit choked up with the stock exhaust..
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Old 08-02-2006, 12:49 PM   #3
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Quote:
Originally Posted by captain spaulding
Do you have emissions in illinios? I'd personally leave the stock cats alone, and just get an aftermarket dp, when it's time for an inspection a new dp/cat from subaru is going to cost you an arm and a leg. otherwise you should be ok, it might be alittle bit choked up with the stock exhaust..
For vehicles newer than 2001 (I think) all they do is scan the computer for codes. With the AP, that should remove any codes being thrown.

I would look into an aftermarket DP but I didn't want to "mickey mouse" the install and have a DP that's a larger diameter than the rest of the exhaust. I'm not sure if this would be an issue or not though.
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Old 08-02-2006, 01:23 PM   #4
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Why not get a TurboXS Stealthback and use your OEM axleback? Next best would be to mate that with a Prodrive axleback as it's the quiet king for exhausts. If the Stealthback is too much, consider cheaper alternatives like Mad Daddy, Stromung, or Crucial Racing to make your own "Stealthback". Gutting the OEM components and using Stage 2 is a recipe for low boost and not even close to full Stage 2 response.
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Old 08-02-2006, 01:34 PM   #5
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Quote:
Originally Posted by Unabomber
Why not get a TurboXS Stealthback and use your OEM axleback? Next best would be to mate that with a Prodrive axleback as it's the quiet king for exhausts. If the Stealthback is too much, consider cheaper alternatives like Mad Daddy, Stromung, or Crucial Racing to make your own "Stealthback". Gutting the OEM components and using Stage 2 is a recipe for low boost and not even close to full Stage 2 response.
Myself and pretty much everyone else who's run gutted pipes would disagree.

On the stock turbo, you'd be hard pressed to feel a difference between a gutted DP and an aftermarket one. The power levels are just so low. I know i'm not alone in that first hand experience.

And as far as saving you stock pipes for future emissions...a used DP would cost $25 on here...no big deal.

So 90% of the performance for ZERO dollars sounds like a DARN good deal to me...and many others who have, at one point or another, run guted pipes...

Go for it...you will NOT be let down!
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Old 08-02-2006, 01:35 PM   #6
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Quote:
Originally Posted by captain spaulding
when it's time for an inspection a new dp/cat from subaru is going to cost you an arm and a leg.
First, in the majoroty of states, you don't need cats to pass emissions with OBDII. Secondly, he can buy a used DP on here for PEANUTS.
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Old 08-02-2006, 01:37 PM   #7
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Don't even buy it pre-gutted. Gutting the DP is too easy to spend $$$ on.
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Old 08-02-2006, 01:49 PM   #8
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Thanks for the responses. I just want to confirm, a DP from '02-'05 would work just fine for my '06?
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Old 08-02-2006, 01:52 PM   #9
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Old 08-02-2006, 01:52 PM   #10
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Personally, if I were in your shoes, I'd rather just spend the money and get a used DP. The stocker - catless or not - still blocks the wastegate valve. Something like the PDE downpipe also has the built-in fix for the O2 sensor. From what I've read, you leave some power on the table by keeping the stock pipes behind the DP. You'll be at like Stage 1.75, as some like to say. A used DP and nice flowing quiet CBE will yield you the best results, methinks.

-Mike
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Old 08-02-2006, 01:53 PM   #11
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The entire downpipe will work (both cats). The length of the 3rd cat pipe changed for 2006 (don't know why), but the overall length remained the same.
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Old 08-02-2006, 01:54 PM   #12
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FEEL and see on a dyno are two different things. With Cobb's AccessPORT it is VERY SPECIFIC on what it needs. Now if the original poster goes out and guts a downpipe and then only sees 13PSI and puts down 190 WHP on a dyno....who will he blame. Butt dynos are notoriously false. If you have dyno proof like the gutted OEM uppipe vs aftermarket uppipe dyno data in my Uppipe FAQ, I'll shut up. Until then.....gutten downpipes are for non-emissions friendly states or hardcore DIY types.
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Old 08-02-2006, 01:55 PM   #13
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with an AP you can still pass OBD emission testing and have no cats. AT least thats what I find from reading/searching here. The AP clears the CAT codes and with a mechanical CEL fix makes the ecu read cat readiness status.
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Old 08-02-2006, 01:58 PM   #14
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Quote:
Originally Posted by Unabomber
FEEL and see on a dyno are two different things. With Cobb's AccessPORT it is VERY SPECIFIC on what it needs. Now if the original poster goes out and guts a downpipe and then only sees 13PSI and puts down 190 WHP on a dyno....who will he blame. Butt dynos are notoriously false. If you have dyno proof like the gutted OEM uppipe vs aftermarket uppipe dyno data in my Uppipe FAQ, I'll shut up. Until then.....gutten downpipes are for non-emissions friendly states or hardcore DIY types.
Will I just need an adapter to go from an aftermarket DP to the rest of my stock exhaust? Whether I use a stock DP or an aftermarket really isn't an issue to me. I'm just not looking for a loud exhaust and I figure why spend $XXX amount of dollars when I can more or less get the same thing for next to nothing?

I plan on attending P&L's dyno day in a couple of weeks for a baseline. I'll also discuss this with them while there. But if anyone around Chicago has some form of DP lemme know .
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Old 08-02-2006, 01:59 PM   #15
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Quote:
Originally Posted by Unabomber
FEEL and see on a dyno are two different things. With Cobb's AccessPORT it is VERY SPECIFIC on what it needs. Now if the original poster goes out and guts a downpipe and then only sees 13PSI and puts down 190 WHP on a dyno....who will he blame. Butt dynos are notoriously false. If you have dyno proof like the gutted OEM uppipe vs aftermarket uppipe dyno data in my Uppipe FAQ, I'll shut up. Until then.....gutten downpipes are for non-emissions friendly states or hardcore DIY types.
I said he wouldn't be seeing the full potential...

If you called cobb and asked them if an HKS (flat plate) DP would work, I'd bet they'd say yes it would. I HAVE asked them about a gutted DP and they also said it was fine to run...you just wouldn't get 100% of the power.

Like I said...90% of the power...for free....he's not going to complain.

From running one myself, as well as the opinions of EVERYONE else who's run one...the difference isn't distinguishable...if you are goign for dyno bragging rights, then this obviously wouldn't be for him.

I put down 217 whp on a gutted stock exhaust and 16 PSI back in late 2002. Stock WRX's were at about 170 whp. Didn't have the mid range without EM, but the DP was not choking the engine in the slightest.

And anyones butt dyno can CERTAINLY feel a 30 whp difference. He won' be putting down 190 whp instead of 220...no way...no how.

Do you have any basis for your opinion on the power loss??? Any personal experience? If a flat plate HKS is good for 220 whp on the stock turbo...theres no way a gutted stocker isn't good for 210+...

Last edited by REX8; 08-02-2006 at 02:10 PM.
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Old 08-02-2006, 02:11 PM   #16
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There aren't a lot of dyno's out there with gutted pipes...but there are some 1/4 slips floating around...
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Old 08-02-2006, 02:16 PM   #17
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Dyno #'s aren't relevent to me. This car won't ever see a drag strip so "meh".

Do I have to gut the 3rd converter section too?

The search begins for a DP, stock or aftermarket .
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Old 08-02-2006, 02:23 PM   #18
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Quote:
Originally Posted by dak125
Dyno #'s aren't relevent to me. This car won't ever see a drag strip so "meh".

Do I have to gut the 3rd converter section too?

The search begins for a DP, stock or aftermarket .
A lot of people don't gut the 3rd cat. It just helps with the smell at a minimal power loss.

If you're short on cash...the gutted DP is a great way to get to "stage II" power levels. If you later find a deal on a DP, go for it.

- Stealthback user
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Old 08-02-2006, 02:31 PM   #19
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I'm running gutted OEM UP, aftermarket downpipe and aftermarket intermid pipe, prodrive ovaltip, but left my stock third cat and reflashed stage 2. Much more power than before... and 5 gear isn't useless! (hooray torque increase)
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Old 08-02-2006, 02:32 PM   #20
dak125
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Quote:
Originally Posted by REX8
A lot of people don't gut the 3rd cat. It just helps with the smell at a minimal power loss.

If you're short on cash...the gutted DP is a great way to get to "stage II" power levels. If you later find a deal on a DP, go for it.

- Stealthback user
Thanks for all the info everyone.

Now Chicagoans sell me your DP and '06 AP!
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Old 08-02-2006, 02:52 PM   #21
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Quote:
Originally Posted by dak125
Will I just need an adapter to go from an aftermarket DP to the rest of my stock exhaust? Whether I use a stock DP or an aftermarket really isn't an issue to me. I'm just not looking for a loud exhaust and I figure why spend $XXX amount of dollars when I can more or less get the same thing for next to nothing?

I plan on attending P&L's dyno day in a couple of weeks for a baseline. I'll also discuss this with them while there. But if anyone around Chicago has some form of DP lemme know .
Many of the aftermarket DP's mate right up to the stock catback. What you need to look for is one that uses the stock donut gasket. Cobb's pipe would work and Daddy's also sells a DP that mates up to the donut.

One thing I would look into with a catless flat plate design on an 06 would be boost creep. I have heard that many people were having issues with this on the 2.5 and restricting the wastegate can't help that.
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Old 08-02-2006, 03:12 PM   #22
dak125
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Quote:
Originally Posted by brettm
Many of the aftermarket DP's mate right up to the stock catback. What you need to look for is one that uses the stock donut gasket. Cobb's pipe would work and Daddy's also sells a DP that mates up to the donut.

One thing I would look into with a catless flat plate design on an 06 would be boost creep. I have heard that many people were having issues with this on the 2.5 and restricting the wastegate can't help that.
What would you do to avoid the situation with boost creep? Thanks.
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Old 08-02-2006, 03:26 PM   #23
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Quote:
Originally Posted by dak125
What would you do to avoid the situation with boost creep? Thanks.
Well I don't have that problem cause I only have the 2.0. IIRC some of the methods to help with that are EM, porting the wastegate, keeping a cat in the system (even a high flow cat), and divorced waste gate downpipe. I haven't really researched it though so I don't know which works best. My advice would be to do a search in the 2.5L forum.
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Old 08-02-2006, 03:39 PM   #24
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Quote:
Originally Posted by brettm
Well I don't have that problem cause I only have the 2.0. IIRC some of the methods to help with that are EM, porting the wastegate, keeping a cat in the system (even a high flow cat), and divorced waste gate downpipe. I haven't really researched it though so I don't know which works best. My advice would be to do a search in the 2.5L forum.
Thanks for the info. Do you think the third cat would deter the issue?
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Old 08-02-2006, 10:08 PM   #25
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Let her take a deep breath....stock won't do that.
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