Just wanting to know what some guys have there fuel pressures set at? Also I just bought a Fuel Pressure Safety Switch and its Adjustable. Anyone know how many turns or how to set it????

 

Do you have an adjustable fuel pressure regulator?
The hobbs switch should be set on the low side of what you would normally experience with the engine at wot. I would recommend 5-7 psi lower than what your pressure is now at wot. I recommend that the switch be hooked through your activation relay and not direct to the solinoids. The solinoids draw a fair amount of current during operation which can kill the hobbs contacts. If the cutoff setting is too high then the swich may cycle on and off rapidly as the fuel pressure recovers from deactivation. If you have an AFPR then start the car and let it idle. Note your fuel pressure. Take off the vacuum line to the regulator and note the rise in pressure. If your pressure rises 5-7 psi then hook the vacuum line back up and put an ohmmeter on the switch contacts. Remove the rubber plug and adjust the switch till you just have continuity at idle.
A little (3-4 psi) drop in fuel pressure during nitrous activation is normal for a stock fuel pump. I wouldn't be alarmed. The kits are calibrated rich - sometimes 20% rich, for safety.
I have seen hobbs switches thrown over 50 yards at the dragstrip because they failed to cooperate. No kidding.

 

I do have a TPIS Adjustable Fuel pressure Regulator. It is set at 46 psi right now with my LT4 Hotcam in it. I was just wanting to know cause I don't want my car to run really lean on the spray.

 

I didn't qualify why I asked if you had an AFPR. If your fuel pressure didn't increase 5-7 psi because of a high overlap cam then you would want to lower it by that amount to set the on/off point. I'm sorry for that. Depending on your nitrous system your fuel pressure may not need to be adjusted from where you have it now. Some systems spray onto the mass air meter, inject nitrous and fuel together and yet others boost fuel pressure with the nitrous pressure (dry kit) though I am unaware of any dry kits for the LT1, there may be some out there. Call the N2O company and get their recomendation.

 

I have this problem. How do I fix it? Everytime I hit the WOT switch I hear it rapidly cycling on and off. I have the Nitrous Works kit with the plate that goes behind the throttle body. Its a wet kit.

 

Set your cutoff pressure threshold lower. Drop the shutoff pressure 5 psi and see if it does the same thing. Its possible you may need a stronger fuel pump, depends on how much power you have the system set at.

 

Quote:
If the cutoff setting is too high then the swich may cycle on and off rapidly as the fuel pressure recovers from deactivation.


do you mean it makes a fast tickign noise?

if so mine does that, but also sends fuel into the intake causing it to bog.

i put a test light to it, and the instructions says to have the test light ON while touching the FPSS and turn the screw i think down, till the light shuts off, and that should be it....

is this correct? i have the NOS FPSS

 

Yes that is correct as long as you have the pressure temporaily set at the lowest setting you feel is safe. The nitrous shot will drop pressure the instant the fuel solinoid opens. Depending on your pump and regulator it may not recover, or only partially recover. This is why I recommend you give the system some pressure flexibility before it shuts off. As the systems are calibrated fairly rich there is some latitude. When pressure drops less fuel is being injected by the injectors as well leaning things some. You'll have to play with it.