NXJeremy

The FPSS is not just to protect against a fuel pump failure. It's purpose it to protect the motor from going too lean from not getting enough fuel during the operation of the nitrous system. A lack of fuel can be caused by debris in the line, a fuel pump failure, or the biggest reason I have seen, people trying to run to much hp with an inadequate fuel system. Guys want to make big numbers so they modify the motor to the point where it is borderline with the fuel system they have, and then they add nitrous to the mix and the fuel system simply cannot support everything. In which case the FPSS is a very good thing to have.

I think the general recommendation is that it is a good idea to run one. That doesn't make it an absolute, or make someone wrong for not running one. However, there is a good reason that people like Dave, Robert, and others use the FPSS when ever possible.

critter

iTrader: (9)

See, there you go again. It is pretty hard to take anyone serious who makes statements like that.

1ScrudeDude

At what HP is the stock fuel pump good to? Mine's a 98 LS1 in case that matters...

critter

iTrader: (9)

Aha! Real information!

That makes sense. Since I have intentionally built an adequate fuel system (including a new pump) , it would not be as critical for me.
That is what I supspected and was trying to get at. It seems to me that the important FPSS would be after the solenoid since the probability of a solenoid plugging or failing is greater than fuel pump failure. If you use a standard on/off setup you can wire the system to only honor the FPSS when the system is active. But I am at a loss as to how you make that work with a proportional controller, which I think is a very good thing and would not run nitrous without.

NXJeremy

If I remember correctly the F-body's is good to ~500rwhp and the vette's are good to ~550-600rwhp. Robert correct me if I am wrong.

1ScrudeDude

Thanks Jeremy.

Hey, where's Dave been y'all? Haven't seen him on here recently, usually he camps in here

Robert56

iTrader: (2)

That's basically about right. The main problem for most of us (myself in past included) we don't know where our fuel systems are really at. Many do not run a press gauge. A fpss is cheaper than a gauge set-up. We can over tax a system and not know it. Or your fuel filter may clog up on you, or partialy, and comprimize fuel system on the spray.
Robert

NXJeremy

Critter- From what you posted, I think you already know this, but you can't run a FPSS after the solenoid if you are using a progressive controller.

Robert56

iTrader: (2)

Man, your a trip.
Robert

NXJeremy

Thanks Robert. I agree that, for most, it is tough to know when you've reached the point of the fuel system not keeping up with the power you are trying to make. A FPSS is just cheap insurance for any fuel delivery problems (other than a solenoid failure).

critter

iTrader: (9)

Well, I was just speculating based on the priciples involved, but you have just confirmed my suspicion. Thanks very much.
OK! Instead of a pressure switch, you use a pressure transducer. Then, since the micro knows when it is picking the solenoid, it can shut down if no pressure builds. That will work.

BTW, speaking of pressure switches ... this goes a long way back, to a 426 Dodge wedge. My friend had shimmed the oil pump relief spring (trying to keep the bottom end together) until it blew the oil filter about the time he grabbed second. He put a pressure switch in the system to kill the ignition if the oil pressure dropped below 50 PSI. Oh, and he backed off on the shims a bit

cantdrv65

iTrader: (3)

Disagree again. At the consensus 35psi trip that is recommended by the "experts" here it likely wont help in any event other than catastrophic fuel pump failure.... I couldnt bite the tongue on that one.

Disclaimer: Read Jeremys sig

jimmyblue

iTrader: (11)

"Those who think they have not time for bodily exercise
will sooner or later have to find time for illness".

- Edward Stanley, Earl of Derby

NXJeremy

I just re-read this entire thread and didn't see a single "expert" recommend that it be set at 35psi. The NX FPSS is pre-set at 35psi, that's all. I personally would tweak the cutoff psi of the FPSS to best suit the car that it's on....I couldn't help myself cantdrv65

goatnipples2002

Anybody have some insight on running 2 FPPSs. 1 before the noid and 1 after?

NHRATA01

iTrader: (10)

Problem is if you run one after the noid, I don't think the system will ever fire. The pressure switch will only see pressure if the fuel noid opens. So you'll never have that initial pressure in the line that would allow the FPSS after the noid to complete the circuit.

goatnipples2002

Thanks dude.

N2RACINGLS1's

iTrader: (2)

I just read this entire thread. No one talked about how you correctly adjust a FPSS. Let me start off by saying I want to use my FPSS!!!

I posted before on my 5177 dry kit with problems on the FPSS. Before this year the system worked perfect for three years then stopped working. I could get it to work at home in the driveway but not at the race track then three weeks ago I was told to adjust the FPSS. I adjusted the FPSS a half turn counter clockwise and the system worked but sputter a little. I than adjusted another half turn counter clockwise and the NOS system worked perfect.

I go back to the track yesterday with 900 PSI and the system worked perfect on the first NOS pass then started to sputter on the second pass.

I am only using a 75 HP on a 98 stock motor with stock injectors. I have installed a 2002 plastic tank though. The car ran 7.72 at 87.71 MPH NA and than 7.32 at 91.87 MPH on the NOS.

Any thoughts?

99Silverado5.3

iTrader: (7)

fpss=cheap insurance

Robert56

iTrader: (2)

You would have to use a low pressure switch because of being open ended. Stick a gauge on the out side of the noid and measure pressure, then adjust your low sw a little lower on opening. I don't know of anyone doing this, but it has been talked about before.
Robert