N20civicB18

I just sent my GSR block out to get sleeved, So I am going to work on the exhaust while that takes place. now I have a Black Widow body kit and I do plan on keeping it, Black widow kits have duel exhaust outlets. I bought 2 3" inlet cans for it but Im not sure what size tubing to use until the split. I was originaly planning 3" but I was reading some threads on here saying that would be good for 300-400whp, and that 3.5 would be good for about 500whp and 4" would be 600+whp. I want to minamize spool time, so obvious a 4" would be better for me but then It would be extreamly hard to use with my body kit. Now since I wil be going to 2 3" eventually I could run 3.5 or 4" over the axle then split to 2 3" For splitting options I am very limited do to the room though I was thinking I could just get a exhaust cut out (with the bolt flange) and run one the cutout side to the other can and go down from 4" to 3" right after the cutout but then that would act as a big restriction I would think even though it is 4" then down to dual 3". OR Flowmaster makes Y collectors but they are made for going from dual 3" to single 4" so I dont know how the flow would be running it the opposite way of how it was designed to run But the problem with this is that it is pretty long so it might be a tight fit or not fit at all. I know if I go 4" to dual 3" anyway as long as I step down after the split I shouldnt really be conserned about loosing a little bit of flow.

I am building my motor with buck02's specs as a guidline as he made some amazing numbers a while back (519whp at like 14 psi or something low) anyways I would probbaly use a little smaller exhaust turbine to help increase spool time but I am waiting to buy the turbo until after I do more research and after I finish putting this block together. I do have the Full Race header that they say will work with 4" downpipe

Anyways what do you guys reccomend besides getting rid of the body kit and/or running a single can?

N20civicB18

I just found this on a F-body site....
Single 2.50 inch exhaust would give 31% decrease in flow vs a single 3 inch system.
Single 2.75 inch exhaust would give 16% decrease in flow vs a single 3 inch system.
Dual 2.00 inch exhaust would give about 11% decrease in flow vs a single 3 inch system.
Single 3.00 inch system - BASELINE
Dual 2.25 inch exhaust would give about 12% increase in flow vs a single 3 inch system.
Single 3.5 inch exhaust would give 36% increase in flow vs a single 3 inch system.
Dual 2.50 inch exhaust would give about 39% increase in flow vs a single 3 inch system.
Dual 2.75 inch exhaust would give about 68% increase in flow vs a single 3 inch system.
Single 4.00 inch exhaust would give 78% increase in flow vs a single 3 inch system.
Dual 3.00 inch exhaust would give 100% increase in flow vs a single 3 inch system.

Just thought it was interesting...