Well, lots of people wonder how the FPR works... and how the nitrous pressure controller from the zex, nos or other dry kits work in conjuction with the FPR...

well, here is the info on how it works, and how the NPR can control the FPR to raise the fuel pressure when nitrous is flowing...


1. the FPR is a vacume activated vavle.
It is normally CLOSED. When the FPR valve is CLOSED, fuel pressure is HIGH because it does not allow any fuel to pass to the return line, therefore building up pressure in the fuel rail and the injectors squeeze out more fuel...

2. when the car is at IDLE, with the TB CLOSED, there is a HIGH amount of vacume in the intake manifold.. this vacume is ported to the FPR via a hose.. when the car is idling, the FPR IS OPEN, therefore, allowing fuel to pass through it into the return line, and the fuel pressure remains quite low because there is no demand for fuel.

3. when you hit the pedal all the way down (WOT) then the vacume in the intake manifold drops to ZERO then steadily rises slightly and steadily... when the vacume is ZERO, the FPR CLOSES, and therefore the fuel pressure rises to meet the demand of hard acceleration in a WOT condition.

4. When nitrous is activated, the device known as the Nitrous Pressure Regulator (NPR) which is housed inside the ZEX box, or attached in between the two nitrous solenoids on a NOS kit.. delivers PRESSURE TO THE FPR... therefore forcing it to CLOSE.. same thing that would happen if you were at WOT.. but, it forces it down HARD.. and keeps it closed as long as the nitrous is spraying...

This forces the fuel pressure to rise even higher than a normal WOT condition.. this almost DOUBLES the pressure to nearly 80 PSI or more...

that is how your dry kit adds the extra fuel required to keep your engine from blowing up.


well, i hope you all learned something.
if there are any errors with this explanation, please reply and clear it up for me.


regards to all !!!


STEVE.

 

Correct but the pressure doesn't go up to 80 psi. The stock fuel pump will clip out at 65 psi, the FPR will start bleading fuel back into the return line around 63 psi or so to keep the pressure down to stop the pump from clipping, the stock FPR would probably pop at 80 psi since it is a bladder not a valve. The recomendation to upgrade the fuel pump was made since the stock pump flows less fuel at hi psi, the resistance is just to great, a wet system does have the advantage here since it mixes the fuel with the nos seperate from the injectors and doesn't have the pressure problem with the stock pump BUT there is still a flow limit, you'll still need a stronger pump. Still below 75 shot a dry system is easier and just as safe if the precautions are done, above 75 shot I say wet system with a progressive controller.

 

thanks for clearing that up. smile.gif


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