I'm going to be running a 50-60 shot to start and I'm wondering if currently I don't have a FP gauge, is there any point into hooking up the FPSS at this time?

If I end up liking the 50 shot, I'll add the rest of the necessities such as the FPR, FPSS, upgraded FP, and the FP gauge but at this time I'm wondering if I need to hook up the FPSS since I wont be able to tune it.

 

IF you don't have a fuel pressure gauge you can't tune the FPSS anyway because you have no idea where to set it.

However, if you could borrow a mechanical pressure gauge and use it to set the FPSS it would add some protection for you.

Jim

PS You can buy a mechanical gauge for less that 20 dollars. Just throwing in bypass jets (if your running NOS) and hoping is pure suicide and I would not suggest you try.

If you are running NX all that goes out the window you don't need a fuel pressure gauge, FPR or high pressure fuel pump (just high flow).

 

Is it suicide even if I'm running 50 shot? Or are you saying that if I'm running 50 shot and my factory fuel pump is pumping out more than enough pressure, I wouldnt know it and thus couldnt make the necessary changes.

Also are we talking about a mechanical gauge I can get at Autozone or something I need to order. If the mechanical gauge is somewhat easier to hook-up it would be something I would definitely look into so I wouldnt need to mount a gauge pod (something I'm trying to avoid).

 

First off are you running a dry system? IF so then I wouldn't run any shot without knowing what the fuel pressure is. What you have to realize is that the jet for the fuel pressure regulator does not give the same pressure boost for all cars. It could vary by 30 or 40 psi or more. When I ran my NOS system I got 90 psi with a .038 jet, some people cannot get down to 90 psi using the largest jet you can buy. So you are really taking a chance just putting in the jets NOS recommends and going with it, without checking the pressure to make sure. Some people have done that, me included and it worked ok, but now that I know a little more about it I wouldn't attempt it again.

Yes you can buy a cheap mech gauge from almost anwhere. Don't put it in the cabin just under the hood for checking the pressure when you are tuning. I put a 2' hose on mine an clip it under the wiper blade for checking when driving.

Jim

 

I understand now.

Yes NOS 5124 dry. How do you install one of these mechanical FP gauges? I think I have all of the nitrous install down except for the splice of the fuel rail from the fuel filter, etc.

Also, what if I was to install the FPSS but don't tune it. Will I still have added security or will it be completely useless?

 

I am not exactly sure of what the factory setting is, but I assume there is one. I have never read anything in the manual that indicated what it is. Using it will not do any damage the cut-off may be way below what you want it to be.

When you splice or tee into the fuel line from the filter, just add another T and connect the fuel pressure gauge. It connects very easily. If you are going to hook a hose to make it longer like I do and stick it under the wiper blade, just make sure to get high pressure fuel injection hose and put a clamp on either end, pretty simple.

Thats all I used last year for racing but I am getting a remote model this year and put it in a pod, but the other way works just as well.

Also get fuel hose clamps do not use those cheap worm drive ones with the slots cut in the clamps they can overtighten and cut your hose and are extremely dangerous. They have caused numerous fires.

 

jdmmax says that the NOS factory setting for the FPSS is 50 PSI. Does that change anything now as far as installing the FPSS but leaving it alone?

 

I would probably have it set for 5-10 psi below WOT setting. Thats another thing I don't like about the dry system you have to reset it every time you change your shot size.

I have mine set for 35 psi which is 8 psi below my WOT pressure on the wet system.

 

So wouldnt the higher the setting be the safer way? For instace if the stock pump at WOT was not putting out at least 50 PSI, the FPSS would activate.

 

Its not how high it is, its how much below the WOT setting that matters.

In a dry system that all depends on what shot you are running because each shot has a different fuel pressure setting.

In a wet system the fuel pressure is always stock at 43 psi at WOT.

What I am saying is for you it all depends on what shot you are running, a 50 shot is what 60 psi? If so then the 50 setting will be ok. However if you were running a 100 shot where the fuel pressure is 90 psi you would want to run the fpss much higher ie 80 psi.

 

Yeah 62 PSI. I think the part I'm unclear on is WHEN the FPSS kicks in, or what forces it to kick in. Like you said, if I were running 100 shot, I would need the FPSS to kick in at 80 PSI. Does that mean if the FP dropped under 80, the FPSS would kick in because the NOS jet needs at least 80 PSI for 100 shot?

I intend to run 50 shot to start, so with a 50 shot jet you are saying the stock fuel pump is capable of putting out 62 PSI at WOT but if it dipped below 50 PSI, the FPSS would kick in if I were to just install it and leave it at it's factory setting.

That said, it is still a good idea to have a FPSS because even though it's not probable that the stock fuel pump were to just die and not be able to put out 62 PSI, it COULD malfunction and then I would be in trouble.

P.S. In most cases when people are being tongue-and-cheek and say "BOOM!" when referring to nitrous, in most cases are they saying the engine will explode into pieces or there will just be detonation which can cause serious problems?

 

You pretty well have it. The FPSS is just a pressure switch that conducts electricity all the time when the proper pressure is applied. When the pressure drops below its setting it opens and cuts off the electricity to the nitrous solenoids. Pretty simple really, the hard part is setting it because you have to simulate losing fuel pressure and the only way to do that is to have the nitrous on to jack the fuel pressure up to its 65 psi or whatever and then slowly reduce it until the fpss cuts out and that is your setting.

Someone did have a FAQ on it but not sure where it is.