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Discussion Starter · #1 ·
Which downpipes are only the front piece? I mean, which ones only replace the first Cat after the turbo. I want to leave 1 cat on so I'm thinking of doing this... Any thoughts? Thanks.

MK
 

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I was thinking about doing the same thing. Out of the 3 cats on the car, the 3rd one downstream probably affects performance the least. The best one I've seen so far that replaces the 2nd cat is the bosal twin dump model.
 

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im getting the bosal to do just that. The Stromung is also a "short" pipe. So is the scooby sport DP.

chris
 

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I am not positive but i think if you want to go with one cat i would leave the last one, removing the cat on the uppipe seems to be a very good starter mod. The cat between the exhaust port disrupts crucial flow to the turbine. I would think that quicker spool (getting air to the turbine) not max boost (max flow after system is at equilibrium) is the limiting factor, except for very high boost situations(over simplified).
Any good uppipe and downpipe will do, seems mfg market the third cat replacement pipe as a race pipe or at least turboXS does.
 

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TurboXS replaces the third cat with a high flow cat. They do offer a racing pipe as well though.

Scoobysport's exhaust peices all replace their factory couterparts. You can mix and match them at will. So you could get their down pipe and leave the third cat in. You could get their cat back and still have the third cat. You could buy their front center section and remove/replace the third cat as you see fit (track days, emission testing days :D ).
 

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RallyPerformance had them when I called.
 

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from what i've seen so far, 3" seems better on a turbo car to get it to go faster

even on my old integra gsr 3" helped a lot compared to stock (which was 2" i think, not 2.5") and the only other mod i had was an intake
 

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Depends on what you are aiming at, I heard that 2.5" are better for low end, and 3" is great for the top.

Perrin also released a dp with wastegate collecting pipe plus a high flow cat, looks like a pretty good piece.
 

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Discussion Starter · #12 ·
I have yet to see the one with the cat, but from seeing the other catless pipe, it looks pretty good.
 

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when i asked scott at suby specialties this same question today, he said go ahead and get 4 inches even if you dont care about sound. on a turbo car the bigger it is the more power you will get, backpressure isnt really needed
 

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1 quick question....

Which brands of 3 inch diameter downpipes will bolt right up to the Turbo XS test pipe back exhaust system? My friend's car has the huge 4 inch TXS downpipe on it, but he wants to change it to a 3 inch.

Any help will be appreciated. Thanks.
 

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New member/lurker reply:

Yah. Turbochargers are by themselves a huge restriction of the exhaust system. While to some extent, gigantic I.D. exhausts will actally diminish torque on n.a. cars due to decreased exhaust gas velocity/extraction, This isn't the case with tubocharged vehicles, our wrx's included.

Go BIG!!!

j.p.
 

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Thanks. That helps alot.
 
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