Heres the deal, i have a 99' civic SI(B16A2) with a T3/T4 (.48,.54), i have bing *** IC from JohnnyRacecar.com and blah blah blah, right now for exhuast my downpipe is crush bent and its kinds small, i have test pipe so no car and stock cat back except for straight through big *** muffler, i just bought some 450cc injectors and the S-AFC and i was planning on running 8PSI dyno'd tuned, the question is is that the place that was going to dyno and tune the car is saying that my exhuast is too restrictive and that i need a new downpipe and cat back or i'll lose like 20 WHP, is this true? because i cant be havin this my friend just got his eclipse tuned and its running 259 WHP, i have to get close to that.

 

if you're running stock exhaust and a pee shooter downpipe thats going to definitely be restrictive.

 

well of course i realize that but the guy said im gonna be losing like 20-30 WHP, that sounds kinda crazy

 

yeah man, its all about good flow. that's why eminem is famous, he flows good.

 

yeah i realize that , but i was thinking of a loss of like 10WHP, not 30WHP, thats a big ------- difference.

 

i am confised, since when you oopen the exhaust flow, it flows out more and INCREASES horsepower, someone tell me if im wrong...

 

I'm a bit confused by that.
On a F/I vehicle you need a large exhaust. The less back pressure, the better. No restriction.....
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30 whp can be a true number, but it depends on how much your car's hp is depending on the boost. An upgrade on the downpipe for a Supra can increase close to 30hp (don't quote me, saw it on the magazine)