I have an Ed Wright chip and he recommends stock Fuel pressure (which is 42psi for me..though I run 43psi now).

However, I was reading TPIS insider hints on the toilet today and it showed how a speed density 305 made the MOST power with 47psi. With my mods, what fp should I run?

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91 Formula
305 TPI 5speed
1LE/G92/WS6
Cold air ind. w/K&N, SLP airfoil, ported/polished plenum, March pulleys, TB coolant bypass,Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL, Holley 9mm wires, fastchip, Bosch O2sensor, SLP headers & catback,short shifter,3:73s w/Auburn posi,160* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

 

See my reply in "Fuel Pressure & Pulse Width" post on this board. It is very interesting how the fuel pressure and injector pulse width interacts. It is not constant or linear.

 

im running a quarter in the FPR, for a supposed 5psi boost. I should probably just get an AFPR and be done with it. I can tell you, however, that my car sure felt stronger with that and the ported plenum.



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91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

Built on Wednesday

 

Fuel pressure is another one of those things that is different with every car. Its like "what is the best cam, what is the best heads, what is the best exhaust?" etc, there is no right answer for everyone. You'll have to keep playing with your fuel pressure until you find the one that makes your car run the best.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

By modifying the Injector Flow Constant and the VE tables, fuel pressure is not an issue. You can make the engine run optimal for the fuel pressure you prefer.

So MrJ, you CAN leave your quarter in, and just look at the eprom. In fact, this is a better method as I am finding that just cranking up the fuel pressure may not be the best thing to do. Unless you have some serious mods requiring a lot more fuel, the average guy with a basically stock engine and a few bolt ons don't need extra fuel pressure. The GM eprom is overly rich by design.

 

Theformula,
When I had my 305, I read the same article as you did and turned my pressure up from 42psi stock to 47psi and my engine started back fireing! So I slowly turned it down, and found 44psi to be best for me.

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Convertible, L98, Mini-ram, ZZ9 cam, Comp Cams 1.52/1.6 steel roller rockers, Trick Flow 23* heads, K&N's with chopped airboxes, March underdive pulleys, Edelbrock ceramic coated TES, Flowmaster cat-back exhaust, Dynomax high flow converter, MAC subframe connectors, Accel box & coil, 3.23 rear gears, white face gagues, and NOS!
When I get back from Kosovo I will be installing these on-order items!

 

Backfiring? Now that is a weird one. I am trying to think of why this would occur.

 

Glenn, mine did the same thing. I would depress the clutch to shift and it would backfire. Or in neutral if I started reving up the engine it would backfire. This happned when the FP was from 48-50

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91 Formula
305 TPI 5speed
1LE/G92/WS6
Cold air ind. w/K&N, SLP airfoil, ported/polished plenum, March pulleys, TB coolant bypass,Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL, Holley 9mm wires, fastchip, Bosch O2sensor, SLP headers & catback,short shifter,3:73s w/Auburn posi,160* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

 

I have my fuel pressure set at 48 psi and get no backfiring from my car at all. My car runs stronger than before I put on the ported plenum and AFPR....so im guessing where my fuel pressure is set at is good for my car.

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88 IROC-Z 305 TPI 5 speed
Performance Resource Chip, Flowmaster American Thunder cat back exhaust, B&M Ripper shifter, MSD coil, TB bypass, TPIS MAT relocation kit , TPIS 170* t-stat, Richmond 3.73 gears, March Power & Amp pullies, Home made Ram Air, Steve Spohn SFC's, TPIS AFPR, Ported plenum by Daniel Burk, Gutted cat
Best et: 14.338
Best mph: 96.97
Best 60': 2.106
http://hometown.aol.com/famioso15/johnnyiroc.html

 

Hey Johnny, is your Performance Resource chip custom? How much was it? What temp do your fans come on?

Those are some pretty good times..

 

the formula...my PR chip is not a custom, and it cost me around 215 shipped to my home. With the PR chip the first fan turns on at 190 and shuts off at around 175. My time in my sig. is with bad wheelhop when I chirped second gear and without Steve Spohn SFC's, TPIS AFPR, Ported plenum by Daniel Burk, Gutted cat. With these mods and bfg drag radial I hope for a 13.9 in march, but I think I am also going to get steve spohns lower control arms and panhard bar. Later

 

Hey what kinda gains did you get wit the pulleys and AFPR? I have a TPiS AFPR iI havent had the time to put on yet and was wondering if there is any sort of noticable gain. TPiS claims you pull harder up around 5k. Is this true? That's what I'd like the most cause right now I am at 65 MPH when I shift outta 2nd and It would rule to be at 70.

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-Red '88 IROC 5 Speed 305 TPI w/3.08
-Dual Friction Centerforce Clutch
-Accel 300+ Racing Ignition
-Accel 300+ Pro Sleeve Plug Wires
-Accel U-Groove Plugs
-Flowmaster Force II 3 Chamber Cat Back Exhaust
-Hypertech Chip
-Hypertech Airfoil
-Removed, Then Re-installed (out of fear) MAF Screens
-Gutted Air Box
-Best E/T 14.686, 60' 2.205, 1/8th mile 9.461, 1/4 MPH 93.91
-Best 60' 2.17