RC Engineering

Ok..the above is from a website called RC Engineering. They deal with injectors and fuel systems. Lots of good info on that page.
The equation is how to fugure what flow rate an injector will have with a change in fuel pressure. lets run through the changes and then Ill try to explain it a lil more.

Ok first we know you have 19 lb/hr injectors. But you also have to know what your fuel pressure is to make sense of that. I believe yours is 42 psi as set by Ford from the factory. So the actual rating of your injectors is 19 lbs/hr at 42 psi.

Now if you were to change the fuel pressure...it would also change the flow rating of your injector. So lets run it through the equation.

sqaure of new pressure(75 psi)/old pressure(42psi)=1.336xold flow rate(19lb/hr) = new flow rate(25.4 lb/hr)

So if you set the nitrous kit up the way the instructions say to and spike your fuel pressure up to 75 psi using the FPR your 19 lb/hr injectors now become 25.4 lb injectors.

now go to the website to see how much HP 25.4 lb injectors can deliver. Probably around 400 crank hp.

To understand why an injector can flow more fuel at higher pressure you need to understand what an injector is. Basically an orifice with a needle that opens and closes to stop or start the flow of fuel...nothing more. It does not push fuel or regulate fuel in any other way except the amount of time that the injector stays open or closed. So naturally if the pressure behind a closed injector is 42 psi and the injector opens for 1 second it will flow a specific amount of fuel. Now jack the pressure behind that injector up to 75 psi and open it for that same 1 second...obviously it will flow more fuel through that injector in the same 1 second. Get it?

How the nitrous kit spikes the fuel pressure is just mechanical means. Each brand dry kit has various methods that all spike the pressure at the FPR only when nitrous is activated. During normal driving you are always back at the normal 42 psi.