fuel preasure and RPM's

leathal injection · 09-05-2004, 04:19 PM

alright , my cars feeling alil slugish, only during normal driving around , when i go WOT she screams screams though ! so im gonna drop the fuel preasure a couple psi see what happens, its at 35 (Vacume ON) rightn now, im gonna bring it down to 32 see happens.

ok my question ! my cars rmps is alil jumpy cause of my cam but nothing serious 900 , 1000, 1100, then back down to 900, and so fourth. i notice my fuel preasure gauge jumps around with as the RPM"s jump around , WHAT RPM DO I WANT TO BE WHEN IM CHECKING MY FUEL PREASURE ?

and what do u guys think about 32psi with 24lbs injectors, w/255lph pump ? im also runnin afr 185's w/gt40- intake

1989GT · 09-05-2004, 06:46 PM

Well you should be setting your fuel pressure with the vaccum line off. That way it doens't matter what rpm your at...then you can play with the fuel pressure until you get it where you want it. Also your fuel pressure should change with the rpms.

leathal injection · 09-05-2004, 09:37 PM

yo thanks alot !

what kinda fuel preasure should i be running w/vacume off ?

thanks !

tmoss · 09-06-2004, 10:20 AM

Factory setting is 39psi vacuum off. Many cars make better power with a little lower FP.

88fivepointoh · 09-06-2004, 03:58 PM

With the vacuum off, anywhere from 38-45psi... every car is differnet and every car likes the FP in a different spot depending on mods.. I run mine at 42psi with 24's.. play around and road test it and use the dyno you sit on for the results.

09-05-2004, 04:19 PM	#1
leathal injection Registered Member Join Date: Mar 2004 Location: Long Island Posts: 58	fuel preasure and RPM's alright , my cars feeling alil slugish, only during normal driving around , when i go WOT she screams screams though ! so im gonna drop the fuel preasure a couple psi see what happens, its at 35 (Vacume ON) rightn now, im gonna bring it down to 32 see happens. ok my question ! my cars rmps is alil jumpy cause of my cam but nothing serious 900 , 1000, 1100, then back down to 900, and so fourth. i notice my fuel preasure gauge jumps around with as the RPM"s jump around , WHAT RPM DO I WANT TO BE WHEN IM CHECKING MY FUEL PREASURE ? and what do u guys think about 32psi with 24lbs injectors, w/255lph pump ? im also runnin afr 185's w/gt40- intake __________________ 1990 Mustang GT Engine- 308 (bored .40 over) Probe Forged pistons (10.5:1), Scat forged crank and rods, w/Main Girdle, AFR 185 heads, GT-40 intake, CSI electric water pump. AC delete kit, No smog pump, Manual rack and pinion steering. Ignition- MSD 6AL, MSD Blaster coil, MSD hellicore wires. Drive Train- Tremic 3550, Alum. Drive shaft, 3:73 gears, Stock carrier and axels. 26X11.5 M/T Et streets. Power adder- 175 shot of laughing gas. Best ET 11.5 @120mph on squeeze, 12.4 @109mph on muscle (on gt40 heads) on the 185 heads ... ??? tba

09-05-2004, 06:46 PM	#2
1989GT Registered Member Join Date: Apr 1999 Location: Cincinnati,OH Posts: 1,511	Well you should be setting your fuel pressure with the vaccum line off. That way it doens't matter what rpm your at...then you can play with the fuel pressure until you get it where you want it. Also your fuel pressure should change with the rpms. __________________ 89GT,Pro-Bullet 306, H/C/I and a bunch of other stuff. Sold 00GT, Vortech S-Trim, Steeda Boost Pipe, C&L intake, Mac off-road H-pipe, Flowmasters, B&M Ripper shifter, Eibach Sportline springs, Koni Struts/shocks, MM full length subframe connectors, Cobra brakes, 3.73's. My Car Domain Page

09-05-2004, 09:37 PM	#3
leathal injection Registered Member Join Date: Mar 2004 Location: Long Island Posts: 58	yo thanks alot ! what kinda fuel preasure should i be running w/vacume off ? thanks ! __________________ 1990 Mustang GT Engine- 308 (bored .40 over) Probe Forged pistons (10.5:1), Scat forged crank and rods, w/Main Girdle, AFR 185 heads, GT-40 intake, CSI electric water pump. AC delete kit, No smog pump, Manual rack and pinion steering. Ignition- MSD 6AL, MSD Blaster coil, MSD hellicore wires. Drive Train- Tremic 3550, Alum. Drive shaft, 3:73 gears, Stock carrier and axels. 26X11.5 M/T Et streets. Power adder- 175 shot of laughing gas. Best ET 11.5 @120mph on squeeze, 12.4 @109mph on muscle (on gt40 heads) on the 185 heads ... ??? tba

09-06-2004, 10:20 AM	#4
tmoss Registered Member Join Date: Mar 2003 Location: Saint Louis, MO Posts: 634	Factory setting is 39psi vacuum off. Many cars make better power with a little lower FP. __________________ Tom (Torque) Moss 88Gt 5spd Vert, FLowmaster Catbacks, stock cam advanced 4° @ 108.5° ICL, NMRA prepped GT40P heads 1.85/1.55 valves and 1.7 rockers, MAC P headers Jet-Hot coated, 97 Exlporer intake (ported lower), TB and injectors. 277RWHP/330RWTQ (SAE). http://www.fastlanecars.com/

09-06-2004, 03:58 PM	#5
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	With the vacuum off, anywhere from 38-45psi... every car is differnet and every car likes the FP in a different spot depending on mods.. I run mine at 42psi with 24's.. play around and road test it and use the dyno you sit on for the results.