I just bought a fuel pressure gauge and it sits at 40 with just the key in the on position, roughly 38 with the engine running. So since my N2O setup is in my trunk I have no way to see my fuel pressure at WOT. Is it safe to assume my WOT fuel pressure is 47psi?
(BP=bottle pressure, FP=fuel pressure)

NX says run 41N 24F @ 1100 BP and 47 FP
My BP is 900ish so the calculator says run 41N 23F if the FP is 40-45, but run a 22F if FP is 46-47psi

I don't have a 23F so I just ran a 22F and boy that was a hell of a difference. Will the difference between a 22F and a 23F cause me problems?

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I'll assume a few things here - correct me if I'm wrong:

1. You are using a V6 stock fuel pump that to quote Archie "puts out a little over 40psi" (My LT1 also requires a 41-47psi pump.)
2. BP should ideally be 950-1000 psi.
3. You are using a wet NX kit.

You could watch the fuel pressure guage while moving the throttle by hand - my experience is that it is normal for the pressure to drop 5-7psi on EFI engines while the engine is running.

Leaning out the fuel jets would give you a noticeable increase in power but could also end in tears.
My suggestion is to check the plugs (all of them) for the proper colour (slight blueish).
Unless they are perfect switch back to the larger fuel jets.

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1986 Fiero2m8 (LT1 NX / 4T60 Roadster Build)
https://www.fiero.nl/forum/Forum2/HTML/071642.html

you are right the BP should be 1050psi but I have no bottle warmer. So I have to deal with 900psi and if I am going to keep it at the temp I will have to adjust my fuel accordingly, but I was wondering about the 22F or the 23F jet.

I was just checking the NX site - check this out

http://www.nitrousexpress.com/Instructions/gmjetting.pdf

Basically if your engine has a fuel pump that is 41-47 psi, count on 43.5 psi as your pressure.
At WOT with little vacuum you should have 42psi or more.

Fiero2m8

So is the difference between the 22 and 24 jet a need for alarm?

quote Originally posted by goatnipples2002: So is the difference between the 22 and 24 jet a need for alarm?

Anytime you lean a nitrous engine you should be concerned. The only way to know for sure is to put the car on a chassis dyno with a wideband O2 sensor.
I had a NX wet on a 88 Fiero and the dyno showed a AF ratio of 10 (very rich), I finally used a 41N 18F to get a 75hp shot, but this was confirmed by the wideband. I think it cost me $75 for the dyno runs.
Better to be safe than sorry.............Paul

^^^what he said^^^

I think that the calculator is usually slightly rich for stock engines for safety.
Until you can do some proper tuning, my advice would be to pick up the correct jet in your guide (23F)
and run that as your baseline.

Ryan

wanting to run 75 shot? just check your plugs, keep close eye on lean condition but i honestly dont think you will have much to worry about.

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<IMG src="http://i2.photobucket.com/albums/y6/JB1/DCP_0025s.jpg[/IMG]
[IMG]http://i2.photobucket.com/albums/y6/JB1/DCP_0036.jpg">

87 GT
series 1 3800sc (7.597 @88.53 1.579 60ft)
86 GT Archie F40 Style Body kit
SBC / 5sp

[This message has been edited by jb1 (edited 07-13-2006).]

Here is the calculator
http://www.dynotunenitrous.com/store/scripts/installation_instructions/jet_calculator/nitrousjetcalc.asp

It says run a 23F at 45psi or less and run a 22 for 46-47psi.

Thanks for the calculator - plus for you!

Ryan

If I put my car on jackstands and run through the gears while someone watches my FP gauge would that be accurate?

last year, I used 200mph tape to attached the guage to the back window and my passenger watched it while I was driving.

My FP gauge is in my trunk with my relay and solenoids. So my only option is to rev the motor. I was told that to check fuel pressure you do it with the key in the "on". Either way I reved my motor to see how high it would go but even reving to redline I got nothing above 40psi.

[This message has been edited by goatnipples2002 (edited 07-13-2006).]