Quote:
Originally Posted by jeffc31337
Is there any actual proof a 2.5" set produces any less HP than 3"? Lots of people think bigger is always better which isn't always true. It's basically a trade off for less pressure drop post turbo with a 3" vs. more exhaust gas velocity/thermal efficiency with a 2.5". Every engine needs to be evaluated independently to determine what's best and even that can be subjective. Sometimes you trade a tad more lag/loss of low end for a few HP up top with a bigger pipe. Some might like this trade off, some may not.
AR Designs - YOu had asked VK if they had data to back up there prototype testing. I would ask you if you could provide the same showing you evaluated a 2.5" design and it did not meet your expectations?
I have no bone to pick as I don't even have a x35, just an interested forum member.
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It has been proven a billion times over that no exhaust is the best exhaust on a turbo.
We just built 3" downpipes for the B5 Audi S4. Picked up over 30awhp with test pipes and over 20awhp with HFC secondaries over a set of gutted primary cat OEM downpipes. Going from HFCs to test pipes, we lost virtually no torque, and picked up around 10awhp. OEM downpipes are either 2.5 or 2.25in.