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Premium Member
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350 Posts
Discussion Starter · #1 ·
Currently I'm pro tuned for stageII using the Cobb catted DP making 281 whp, 310tq @ 91 with 17.5psi in California. I have a cat back (5zigen pro-race) which is 2.5 inches from the DP all the way to the muffler :( . Both the tuner and I know it was restrictive during the tune. California law enforcement isn't wild about grapefruit shooters so I'm looking at the Cobb cat back for both the stock look and 3 inch piping. Relatively speaking, if the boost stays reasonable due to the difference in back pressure, what kind of whp increase could I expect? 5 maybe 10?

Also, not wanting meth, larger turbo or FMIC, what else could net me a couple more horses? Inlet tube perhaps?

Thanks guys.
 

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Banned
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8,265 Posts
meh...Ive always been a firm believe that there is not a HUGE difference in WHP gain going from 2.5-3. Would it be noticeable? Not sure....

You could have been tuned at 19psi and would have made more hp....easily.

A catted DP is also restricting power! However I wouldnt mess around with catless in CA, no way, so I guess your stuck there.

If you want to keep a low profile look, get the maddad midpipe as I have, and mount it to the stock axelback, prodrive axelback, or even the genome.

It really keeps the sound done, and has a low profile look. I still plan on painting it black one day, just never got around to it yet.

Why dont you go buy an full 3" catback, and show us the difference. I would like to know there is a large difference. However my maddad midpipe is full 3" so about 2 feet of my setup is 2.5" and I really dont care at this point. Ive added the APS header, and my setup is EVEN QUIETER!
 

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The Hoff Fan Club, member #001
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10,384 Posts
you might see a 5whp difference if you swap to a 3'', but i doubt you would see much more than that. If down the road you upgrade to a new turbo, then i would def suggest going with 3'' piping all the way, but with the stock turbo its not that much of a big deal.
 

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Premium Member
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5,332 Posts
I agree with Caesar on the recommendation on the maddad intermediate pipe. The power that 3" will have over 2.5" is not that much, but It would be wise to extend the 3" piping as far back as the axle-back portion for the most benefit. There are many 2.5" axle-back's as Caesar mentioned.
 
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