well when I spray my car my fuel pressure only jumps to about 50~ psi
whereas it should be going to around 73psi if memory serves. my
question is how should I go about tracking down my problem?

my thoughts are it's either the nitrous pressure regulator, fuel pressure
regulator, fuel pump, or a vacuum leak.

problem is how do I check to see if the nitrous pressure reg or fuel
pressure reg are working properly? I don't believe it's the fuel pump
because I get 43psi WOT on the motor, 40~psi idle/cruising and isn't a
hard starter. what kind of vacuum should I look for on a cammed (more
specifically CC503) car on warm idle, etc?

 

I saw your post on fbody.com, and there it had the full mods list, including the fact that you are running an NOS dry kit, have quite a few mods, and are running 30# injectors. You also have to state how much you are spraying. No one can answer your question accurately without knowing all that info.

Pressure requirement is determined by fuel requirement. Fuel requirement depends on how many NA flywheel HP you are making, whether the PCM was correctly tuned for the 30# injectors, and what your shot represents as a percent of NA flywheel HP. That would be the ony way to approximate the new pressure required when you spray. The stock 5176 kit pushes the fuel pressure to about 80-85psi for the 125-shot, but that's based on a "stockish" HP engine, running stock injectors.

Have you run your NOS 5176 system before? Were you able to tune it correctly, using the optional "fuel jet" tuning setup? Do you have that option? Have you verified that there are no leaks between the blue nitrous pressure regulator and the fuel pressure regulator? If you have the optional fuel jet setup, is there a jet installed? Do you have the inline booster pump hooked up, and verified that it is operating correctly?

 

the car is currently jetted for a 75shot, I've had this system for a while but never had such a problem. I don't have the inline booster pump but neither do 2 of my friends who have the same kit without the booster pump and they've never had a lean issue. my friend who has the same kit, cc305 cam, 30# injectors is getting 80~ psi.

my car has been dyno tuned, but I hadn't run the kit in months so I figured maybe something is sticking from unuse over time. the car never had a lean issue on the dyno before I did the cam swap and let the kit sit for a while

what is the fuel jet setup? would that be the jet in the T fitting between the fpr and npr? as far as I know according to NOS jetting charts, the "fuel jet" never changes from 75 shot to 180 shot

 

The 5176 kit was initially not adjustable (and still isn't, if you read the NOS page).... it came with a single 0.067 jet for the nitrous, and sprayed ~140HP. Eventually, they came up with an optional kit to adjust the HP. That involved adding the fuel jet in the tee, and using various combinations of nitrous and fuel jets to adjust the shot. Smaller shot used a smaller nitrous jet and a larger fuel jet. The fuel jet was in the side of the "tee" that came from the engine vacuum source. In effect, by using a larger jet in that location, the system bled nitrous entering the "tee" off to the intake manifold, resulting in applying a lower pressure to the FPR, and hence provided a fuel flow that more closely matched the nitrous flow.... less nitrous and less fuel for smaller shots.

Even some NOS employess deny that there ever was such a kit, but I had one, and there are tables floating around on the internet that show the various combinations of fuel jets and nitrous jets to use for various shots.

Again.... how much pressure you need depends on how much NA HP you are making (since the NA tune is determining the pulse width of your 30# injectors), PLUS how big a shot you want to spray. Since you are only looking at a 75 shot on top of an engine that makes a bit more NA HP thatn a stock engine, its not likely that you need 80psi to get the required fuel flow.

Are you running a stock fuel pump? Since you aren't running the inline booster, your stock pump may not be capable of supplying the required total fuel flow when you spray. As you increase the flow, the pressure capability of the pump drops. That's why NOS put the inline pump in the 5176 kit.

The actual FPR may also affect how the system reacts to the nitrous pressure. I had one of the first 5176 kits, and NOS told me that it would work with my AFPR. It didn't. After actually driving to the NOS shop, and having my fuel system tested to insure the booster pumpp was working correctly, they told me to put my stock FPR back in. That solved the fuel problem.

 

I have a stock FPR and a Walbro 255 pump

any idea how I go about checking the fpr?

the 59 jet should still be in the T since when I bought the kit

thanks for the bits of knowledge fred I didn't know about alot of that