I just got done talking to Jim at TPIS,regarding fuel pressure.He said with the stock ecu programming,the more air that flows, the richer the mixture.he recommmened to lower the fuel pressure to high 30's (38-39) and work my way up,to where the engine runs the best.it seems like most Fbody owners are running way to rich.has anyone had to adjust the fuel pressure lower than stock(42psi)to get good results ,with minimum mods?.

91GTA-ported plenum,cold air induction,3" dynomax catback.afpr

 

Finally, someone at TPIS is admitting that their "claims" of higher fuel pressure = more power is BS.

But he is absolutely correct. The stock GM eprom is overly rich by design. Unfortunately, lowering fuel pressure introduces other problems like a poor spray pattern. I believe the optimum setup is to increase your fuel pressure while altering the eprom to give you a shorter pulse width.

When I first got into eprom burning, I was amazed how overly rich my engine was running. I lowered my fuel pressure as low as I could go and I still was rich..that is why I got into eprom burning.

I found around 46 psi with about 15-20% less fuel works optimally on a basically stock L98.

[This message has been edited by Glenn91L98GTA (edited March 30, 2001).]

 

Well every engine will require an different amount of fuel for best results, but remeber the computer ads fuel to added airflow, so if you are sucking more air thought the MAF you will get more fuel from the computer. Eith minimal mods I would say don't touch the fuel pressure. TPIS did a test on a 350 with many go fast parts like a cam and intake. Though if you have a ported plenum, runners and base you might want to bump pressure a point or two, its somethin you have to test out and try at different levels. I would say unless you are running 19# injectors on a 350, like I am, you will not need more that 44psi at anytime unles you are supercharged or running NOS. I have mine at 46PSI to get more fuel to compensate for the added airflow that my engine sucks in. The computer will not complete compensate for the 350 with the 305 program.



------------------
FOR SALE!!!!!!!!!!!!!!!
86 Trans Am 355 TPI Rebuilt 700R4 with Corvette servo, modified valve body, and a B&M Torque Converter (2000 rpm stall w/ lock up), 87 350 block bored .30 with new crank. Reworked 305 heads with 3-angle valve job. Added in the rebuild was an SLP TPI cam, BBK 58mm Throttle Body,MSD 6A, Hypertech Power Coil,MSD Wires, 1.5 Crane roller tipped rocker arms, SLP Intake Runners and Port matching in upper intake including fully ported plenum, TPIS adjustable fuel pressure regulator @ 46psi, Hooker shorty style headers w/ Thermotech heat wrapping, Custom 3” exhaust with Flowmaster muffler and chrome quad tips, Hypertech Thermomaster Computer chip, K&N open element cone filter on modified MAF per TPIS specs, removal of A/C hardware and added a 1LE firewall cover installed. Also there has been a PST front suspension kit with Hotchkis strut tower brace added.
Stereo has 2 Clairion Pro Audio dash plates, 2 Sony 6X9s, 2 Kicker 12's in a custom Carpeted box with a custom amp rack Holding 3 MTX 280 Amps, and a MTX electronic Crossover all wired with EFX cable.
Asking $4200 with all extra Parts that are needed to fix most apearance flaws. ie Complete hatch and wing from a 91 GTA
http://geocities.com/feltsb/kyle.html
Kills:
95 Talon TSI, 96 Probe GT, 91 T/A L98, 89 RS, 86 Mustang GT, 88 Mustang LX 5.0, 92 Thunderbird V8. couple or ricers that I think were Civics or Preludes not sure what year, 95 Celica GT-S, 94 Chevy 1/2 ton 350, one of those NASCAR F150's

The Third Gen Will Never be Forgotten