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Impreza SportsWagon 99 2.0
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I apologise in advance for a stupid question but can I ask, why couldn't you just bolt it right on? Whats the need for the adapter? Sorry for stupid question I'm new to exhausts and such.
 

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2001 2.5RS Coupe
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1,207 Posts
I apologise in advance for a stupid question but can I ask, why couldn't you just bolt it right on? Whats the need for the adapter? Sorry for stupid question I'm new to exhausts and such.
I had a GD (2002-2007) catback from my brother and when I tried to match it up with my GC, the part where it bolts in the catalytic converter on my GC (2.5RS Coupe) was not matching up, that's why the OP (original poster) mentioned you'd have to rotate the flange. If you try to rotate the whole catback assembly to match the catalytic converter flange, the bends won't line up with the undercarriage.

 

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Impreza SportsWagon 99 2.0
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I had a GD (2002-2007) catback from my brother and when I tried to match it up with my GC, the part where it bolts in the catalytic converter on my GC (2.5RS Coupe) was not matching up, that's why the OP (original poster) mentioned you'd have to rotate the flange. If you try to rotate the whole catback assembly to match the catalytic converter flange, the bends won't line up with the undercarriage.

Ahhhh right ! that makes alot more sense now, i though OP was just doing it for length so I didn't think it was necessary but I understand now. Im guessing this is like this for all catbacks? Thanks heaps!
 

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1993 Subaru Impreza 1.8L FWD
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19 Posts
Man I need one of these. I feel like an exhaust shop around me is going to charge a lot more than I want to pay
 

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2000 Subaru Impreza 2.5RS
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5 Posts
So I see all the time people wanting to run GD turbo exhausts and such on our GC/GM/RS's. Everyone tells them "yes, they will fit, however you will need to extend the midpipe and rotate a flange for it to fit." Everytime I read this, I think "why? then you can't re-sell it later?"

That brings me to this post, I'm sure a lot of you have figured this out and done it, but I would just like to put it out there for EVERYONE. Have an adapter made that will bolt up to your stock cat section AND the GD exhaust. That way down the road when you get tired of the catback or decide to go turbo, you don't wont have a problem selling or reusing your existing catback.

What are your guys' thoughts on this? Has anyone else done this besides me? Am I just over-thinking this a bit?

To illustrate this, my exhaust set up my adapter is twice as long as yours should be! use this as an illustration ONLY please.:
adapter

unchanged catback


measurements:
cat-adapter flange: 2.5"
piping: 2.5" stainless steel with taper to 3"
adapter-catback flange: 3"
I don't know too much about the flanges except that they are 2 bolt flanges (obviously). Next time I remove my exhaust, I can take actual measurements of the bolt holes if needed.
Ill also see if I can't measure how long the actual adapter is as well tomorrow.


reason why MY adapter is twice as long as any of yours should be, is the catback I am running is a 3 piece design which has the taper its own separate piece. I just removed this taper section, and extended my adapter.

Mods can feel free to move/edit this post if needed.
Would this concept also work for a GD axle-back on an 00' RS? I currently have a Stromung cat-back specific for the NA engine, but I've been wanting to make my car louder. I also read that the optimal pipe diameter for the NA engines is 2.25" so I am trying to keep my Stromung mid-pipe.
I have the opportunity to pick up a Crawford Performance Gymkhana axle-back (which has 3” piping) for dirt cheap and it is exactly what I was looking for in terms of loudness :) If i do pick up the axle-back, I am planning on making an adapter of 2.25” to 3” but from the end of the mid-pipe to the axle-back. Would this work?
 
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