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Old 09-21-2005, 02:22 PM   #1
Larsony
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Member#: 35273
Join Date: Apr 2003
Chapter/Region: MWSOC
Location: Southwest MI
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2005 Saab 9-2x Aero
Stage 2

Default 3 inch downpipe with 2.5 inch catback?

I know this probably isn't the ideal setup, but can it be done? Yes, I have read the Unibomber's exhaust FAQ's.

I am planning on running Cobb stage 2.

Thanks in advance for responses, and please keep the "Search N00B" to a minimum.
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Old 09-21-2005, 03:45 PM   #2
specialev
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07 SV650

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Yup, I am doing it right now. With the ERZ DP and a factory catback, on Stage 2 maps, my car is more powerful than ever. However, three inch pipe will certainly only improve things for either you or me.
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Old 09-21-2005, 03:48 PM   #3
Larsony
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Stage 2

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So did you have to use a special kind of adapter for the setup, or weld together, etc.?
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Old 09-21-2005, 03:55 PM   #4
isis
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Quote:
Originally Posted by Larsony
I know this probably isn't the ideal setup, but can it be done? Yes, I have read the Unibomber's exhaust FAQ's.

I am planning on running Cobb stage 2.

Thanks in advance for responses, and please keep the "Search N00B" to a minimum.
Cobb says that the factory catback will be fine with an aftermarket downpipe. If the downpipe says it will mate to any aftermarket catback (many of them taper in at the end so you can use the donut gasket) and the catback says it will mate to the factory downpipe, then you shouldn't need an adapter.
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Old 09-21-2005, 03:56 PM   #5
AdmiralWRX
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It's going to depend on the type of downpipe you get. I know that the MadDad downpipe (which I have) has the option of two different types of exit flanges: a factory style donut gasket exit flange (for mating up with your factory catback) or a 3 inch crush gasket flange (for mating up with a 3 inch aftermarket catback).

I'm not sure if that means you have to purchase a new 3rd cat eliminator pipe section (with a new exit flange type) when you decide to change your catback. I'm pretty sure it does.

At least it give you a little flexibility while saving up for a new catback.
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Old 09-21-2005, 04:00 PM   #6
specialev
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The ERZ is designed for a flat gasket-type flange interface, the OEM uses a donut. I was able to seal the two dissimilar parts together by simply maneuvering the donut betwixt the two and tightening the crap out of it. I am sure I ruined the donut, but I am not worried about it; my new CBE is in the mail by now, hopefully.
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Old 09-21-2005, 04:26 PM   #7
Larsony
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Stage 2

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Quote:
Originally Posted by specialev
The ERZ is designed for a flat gasket-type flange interface, the OEM uses a donut. I was able to seal the two dissimilar parts together by simply maneuvering the donut betwixt the two and tightening the crap out of it. I am sure I ruined the donut, but I am not worried about it; my new CBE is in the mail by now, hopefully.

So no problems with leaking then?
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Old 09-21-2005, 10:54 PM   #8
BoostinEJ20
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what are u planning on getting or do u have that is 2.5"? why not just buy full 3"?
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Old 09-21-2005, 11:15 PM   #9
specialev
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Quote:
Originally Posted by Larsony
So no problems with leaking then?
I had problems when I initially fitted it, but that leak lasted all of five minutes. I removed the fasteners and reversed the donut seal so it fit into the ERZ better, then applied suitable amounts of torque so as to make it seal. It only took one try, and the leak was eliminated.
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Old 09-21-2005, 11:24 PM   #10
Larsony
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Stage 2

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Quote:
Originally Posted by BoostinEJ20
what are u planning on getting or do u have that is 2.5"? why not just buy full 3"?
Because I may first want to put on a downpipe, flash to stage 2, then put on a catback when the funds allow.
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Old 09-22-2005, 02:47 AM   #11
electricpork
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<--- 3" Stromung DWG DP, Daddys 3CE taper pipe, 2.5" cat back. Keeps original donut gasket. Works great.
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Old 09-22-2005, 11:57 AM   #12
Larsony
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2005 Saab 9-2x Aero
Stage 2

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Quote:
Originally Posted by electricpork
<--- 3" Stromung DWG DP, Daddys 3CE taper pipe, 2.5" cat back. Keeps original donut gasket. Works great.

Nice!! Thanks for the info
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Old 09-22-2005, 02:38 PM   #13
kx02wr
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this is what i want as well. Power without attracting everyone's attention especially PoPo. I'm goin either stromung or sti 2.5 out the back.
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Old 09-22-2005, 09:07 PM   #14
WRX03
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FYI: The donut gasket is pretty $$ from the dealer. I replaced a leaking one recently.
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