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      09-02-2009, 05:26 PM   #15
mixja
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Drives: 2011 E90 DCT Silverstone
Join Date: Jun 2008
Location: Beverly Hils, CA

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Quote:
Originally Posted by NavM3 View Post
Based on what I read, the power gains with 2ndary cat delete are minimal so the turner set up is an option since you are willing to cut the midpipe and weld it to the turner straight pipe. The better option is to go with High flow sport cats from Fabspped or Encore and weld it to the rest of the x-pipe. That way, you gain the most since the primary cats are the most restrictive part of the exhaust and keep the stock secondary cats and resonator to keep the noise levels down and won't be smelling or inhaling exhaust fumes.
With the Primary Cat delete, you still have the Secondary Cats in place, so I'm assuming fumes won't be an issue (also where I live we don't have emissions checks so that isn't an issue for me). So I don't really see the point of replacing the primary cats with high flow cats in my situation, if you are going to keep the secondary cats.

The only potential reason for replacing with high flow primary cats would be that having a straight through pipe might upset your backpressure balance too much causing the low RPM torque dip you see with full aftermarket systems - but I'm picking the remainder of the OEM system will keep a sufficient amount of backpressure to avoid this issue (and hopefully still be able to flow enough to maximise power at high RPMs)


Quote:
Originally Posted by NavM3 View Post
Another option, albeit more noisy, would be to get the high flow cats along with the resonated x-pipe. It will be noisier due to lack of secondary cats but I don't know how loud it is going to be. The advantage would be a little more power and no cutting of the stock midpipe.
Not really an option for me, want as close to stock as possible (just want performance gains )