Fuel Pressure...

banditmwp · 03-10-2008, 09:11 PM

I'd like to get some suggestions on where to start setting FP. My combo is listed below in sig..cam specs are as follows:

.512/.512
226*/230* duration
110* LSA

I am running a 75mm Maf tuned for 30# injectors and a 75mm throttle body. The AFM power pipe is the 3.5" fenderwell pipe.

It has been suggested I start at 36 psi (static) and drive it a week like that. Then, if I'm still getting the piggy condition, drop it back from there. It is currently so rich I left big black circles on the curb at my store today just from letting it idle a few minutes.

I am going to try to dyno after about 3-400 miles on the new setup. Hopefully I can get in this weekend.

What I am really trying to find out is if anyone has run a similar setup with 30's and what the FP wound up being...

04 Mach1 · 03-10-2008, 09:18 PM

Hey Preston whats yours sitting at?

Italian LX · 03-11-2008, 09:38 AM

Quote:

Originally Posted by banditmwp

It has been suggested I start at 36 psi (static) and drive it a week like that. Then, if I'm still getting the piggy condition, drop it back from there...

Dropping it below stock (39psi) is going to adversly effect your fuel spray pattern. It's already going to be crappy at low RPM's trying to run 30# injectors on a small combo like that.... then, when you drop down the fuel pressure, the gas is almost going to be dribbling out of the injector and not going to mix well.

Put it at 38psi and let the long-range fuel trims in the computer sort it out. If it's too far off to compensate, then you may want to start saving up for a tuner.

coupe · 03-11-2008, 11:36 AM

Yup. That factory tune can only do so much with all those bolt-ons feeding the engine all that extra air... Changing the fuel/timing load calculations will be more beneficial than fuel pressure to get a really accurate tuneup.

I've never seen much difference in changing fuel pressure +/- 5 psi from stock.

03-10-2008, 09:11 PM	#1
banditmwp Welcome to America! Join Date: Dec 2004 Location: in the 11's Posts: 4,501	Fuel Pressure... I'd like to get some suggestions on where to start setting FP. My combo is listed below in sig..cam specs are as follows: .512/.512 226/230 duration 110* LSA I am running a 75mm Maf tuned for 30# injectors and a 75mm throttle body. The AFM power pipe is the 3.5" fenderwell pipe. It has been suggested I start at 36 psi (static) and drive it a week like that. Then, if I'm still getting the piggy condition, drop it back from there. It is currently so rich I left big black circles on the curb at my store today just from letting it idle a few minutes. I am going to try to dyno after about 3-400 miles on the new setup. Hopefully I can get in this weekend. What I am really trying to find out is if anyone has run a similar setup with 30's and what the FP wound up being... __________________ 91 GT Convertible 2006 Nissan Titan LE Crew Cab 2014 Peterbilt 337/Marion 22' box Last edited by banditmwp; 03-10-2008 at 09:13 PM.

03-10-2008, 09:18 PM	#2
04 Mach1 Bet I red light B4U Join Date: Aug 2005 Location: ANNISTON, AL Posts: 975	Hey Preston whats yours sitting at? __________________ 89 gt 2.3 stroked holley head with n12n port high flow intake with great big fart can skunk 2 seat belts with kool glow water squirters and new light up shift knob basically everything from wal-mart art carr C4 10.53@127.3 w/ 1.53 60' 89 gt vert 347 eldebrock heads and intake AOD w/3000 stall unknown with 5spd went 12.7 on steet tires 04 Mach1 automatic flowmaster K+N drop in 13.9

03-11-2008, 11:36 AM	#4
coupe Super Moderator Join Date: Dec 2004 Posts: 6,313	Yup. That factory tune can only do so much with all those bolt-ons feeding the engine all that extra air... Changing the fuel/timing load calculations will be more beneficial than fuel pressure to get a really accurate tuneup. I've never seen much difference in changing fuel pressure +/- 5 psi from stock. __________________ " If you can't explain it simply, you don't understand it well enough. " - Albert Einstein