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HELP-3' exhaust in (with I/C) and car feels slower


Guest jjohart

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Guest jjohart

I had "Custom Tubes" of Woburn MA put on a NPR I/C and plumbing and a 3" exhaust all round (Magnaflow muffler), and I swear the car is moving slower up the pre boost rev scale, and once the boost catches, it seems to taper off quickly, so much that I see the needle for boost rock forwards towards 7psi and then slightly move back in the opposite direction!

From other people doing the 3" exhaust, I heard claims of how the 20bhp increase was felt immediately (I had stock Nissan exhaust before). There is zip, zero improvement as of yet, and I'm wondering if I should wait to give the car to my Z tech in NH in 10 days, or if there's something I should bring the car back to the tubes installer over. The exhaust sounds good (not quite as loud at WOT as I expected), and there's no weird smells or rattles. The only thing amiss is the installer used flexible hosing to tie in the BOV to the turbo, and I noticed it kinking at one point..I think getting that airway opened kind of helped a little, but I swear, the car is NOT even as fast as it was before. For 3 grand..what could be wrong, or is it me not getting the point that one doesn't "just plug everything on and expect it to come online all by itself"?

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Don't take this as rude, and please be sure that your fuel curve is stable before you proceed:

 

TURN UP YOUR BOOST.

 

7psi with an NPR intercooler? 7 is stock boost, with NO intercooler. Your lag feeling is probably due to having more IC piping to fill with air before you're technically making boost. I recommend turning up the boost to about 10psi to counteract the added piping, then let us know how it feels.

 

Remember, intercoolers add very little power by themselves. What they do is give your the overhead to run more boost, due to greatly reducing intake temps.

 

P.S. if your needle dips when it hits 7psi, you make have a small leak in your intake between the turbo and throttlebody. Pop the hood and rev the car by carefully pushing the linkage down on the TB, and see if you can find a leak. Careful, stuff gets hot quick.

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