This is an interesting and useful experiment that I did for my turbo-buick but the same principles apply here. The attached chart can be use as a tool to predict what the maximum horsepower (roughly) that a given fuel system configuration can support, and if it doesn't support your target hp, what is the resultant fuel flow and pressure. On this chart are the characteristic flow-pressure curves of some typical fuel pumps along with that of the stock injectors. On this chart you'll find the Airtex E8289 (which is the aftermarket stock replacement for the SRT6 and others) at 13.5 volts, the stock Pierburg 7.22156.50.0 at 13.5v, the Walbro GSL392 (at 12 and 13.5 v) , the Bosch 044 at 13.5v, and the SL55 AMG Pierburg "800" 7.00228.51.0. These curves come from the pump manufacturer's data. Airtex only gave me 3 points so the curve looks like 2 lines. The Bosch 044 info is almost off the chart (literally) as is the big Pierburg. They are the lines that run from top left to bottom-mid right.
Also on here are the characteristics of the stock injectors, at various boost levels (14, 18, 22 psi) and duty cycles, (80, 90, 100%). They run from bottom left to upper right. These curves come from the single operating points (45.8 pph at 43.5 psi, etc). Any other operating point can be calculated by using the square root of the ratio of the new pressure over the old pressure times the old flow rate. For duty cycles other than 100%, a straight linear relation of the given operating point was assumed. Given that there are 6 injectors and that gas weighs exactly 6 lbs per gal makes the math come out easy.
Looking at the chart, if your particular flow rate and pressure (which will reside on a DC-psi injector curve) is to the left of the pump curves, you will have plenty of pump capacity and your fuel pressure will not drop off as rpms climb. If you try to operate at or near a particular pumps limit (to the right of a pump curve), your fuel pressure will fall to that of where the injector and pump curves cross.
Results: The stock fuel system (both the stock replacement E8289 and the stock Pierburg 7.22156.50.0) is adequate for about 42 gph or 500 fwhp. (10% safety factor is 450 fwhp). A Walbro 392 at 13.5 volts and stock injectors would be good for over 600 fwhp. A Bosch 044 can supply enough fuel for over 700 fwhp (but rail pressures would be so high a change to bigger injectors is recommended). The big Pierburg is not needed unless you're trying to make 800 fwhp. Discussion of it is here: https://www.crossfireforum.org/forum...ad.php?t=32034
Also it is easy to see that if you're lean and need more fuel, then increased pulsewidth or duty cycle is the way to go. By increasing fuel pressure, you increase fuel flow but you also increase rail pressure which the pump is fighting against. Pumps flow less at higher pressures. With increased injector PW (or DC), you deliver more fuel and the rail pressuer is held lower so the pump can deliver more fuel.

Assumptions: No flow losses from fuel lines, fittings, no voltage losses form wiring etc. Duty cycles scale linearly, ignoring pintle opening and closing times. I would guess 10% flowrate loss from lines, etc. 0.5 BSFC (gas)

Please feel free to provide comments, questions, etc.

 

The chart has been updated with more relevant pump data. The stock Pierburg 7.22156.50.0 (old number 7.21960.04) curve has been added. The Walbro in-tank 340 data has been replaced with the external GSL 392 curve, and the Pierburg 360 L/Hr "800" 7.00228.51.0 SL55 AMG pump curve has been added.

 

Chart has been updated with the addition of curves for 65 lb/hr (680 cc/min) injectors at 85% and 100% duty cycles, with 22 psi boost.

Chart has been updated with BSFC = .57, and got better correlation with dyno numbers that have been reported here on the forum.