Forgive the FI newb question, but everyone seems to be contradicting each other reguarding exhaust diameter.

Say I threw on an SC kit on my 3.5 and ran very safe boost (base 7 psi), how bad would a 2.5" setup hurt power? I've seen conflicting dynos.

I currently have Cattman headers, hi flow cat and full 2.5" catback. Can anyone speculate the loss from 3.0" to 2.5"? I'm assuming a full 3.5 (heads, cams) boosting 7 psi with stock 3.0 timing would put down something in the neighboorhood of 350whp.

 

If you already have a full 2.5" header-back mandrel bent exhaust, I don't think you will see huge gains going from 2.5" to 3.0" for SCing. It's more beneficial if you're turbo: quicker spool, lower EGTs, higher max boost, more power.

Are you making your own SC mounting plate? AFAIK, the stillen one doesn't bolt on to the VQ35 timing chain cover.

 

I swapped the VQ35 using Tilley's method: 3.0 timing chain covers, sprockets, water pump, timing chain and original 3.0 wiring harness/ECU on the 3.5. So the SC kit can be installed EXACTLY as it would be installed on a regular VQ30DE.

 

do u think that the hp figures u guessed might be a tad high?

 

Maybe you're right, I don't know. I was guestimating based on what Z's and G's with SC kits put down at 7-ish psi.

 

Cheapest and best option in my opinion. Keep the setup you've got, add a cutout right after the headers.

 

Excellent. Someone else just suggested the same thing to me.

Do you think 350whp on 7 psi is unreasonable given stock ECU, headers, cutout and a custom short runner IM?

 

i think the stock ecu is whats gonna kill you the most

 

I don't know what the 350zs are putting out with SC because I don't bother to read posts about SC 350zs, but a little ricer math tells me it should be fairly close to that. Maybe like 330 or 340.

 

Why do you say that?

 

Please elaborate. I was planning on keeping the stock ECU because the 3.0 ECU timing is very conservative for a VQ35, and acts as already-retarded timing for a 3.5. I was also going to run 94 Octane all the time anyway. This should make for a pretty reliable motor IMO. The A/F is important as ever, but I was planning on leaving the stock timing and rev limiter alone...