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I've been following this forum for quite some time now and finally got my STi around Christmas. I've been wondering if the exhaust bypass that Quick Time Performance (quicktimeperformance.com) sells would actually help diminsh the backpressure in the exhaust system. In addition, you could switch back from open to close with a switch, restoring your "stock" exhaust flow. However, even if the butterfly valve is closed, wouldn't it still affect the flow of the exhaust system by creating turbulence? Or is the length of the exhaust system after the Y-pipe long enough for the gases to get fully-developed? What do you guys think?
 

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with the bypass pipe and the qtec,you are completely bypassing the exhaust system.so there would be zero backpressure.and yes there would be more turbulence.but it would be worth it for convenience if you go drag racing.
 

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on another note, I was looking into this and was wondering if you think i could get away with it in SCCA stock class auto-x. I know its not technically "legal", but as it would add no performance when closed, and would be easy to tell when it's open, I might get away with it. Thoughts?

EDIT: nevermind, its catless.
 

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Actually, I believe if you install a QTEC bypass and leave it closed, it will reduce your performance by virtue of creating extra turbulence in the exhaust flow.
 
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