I think the right injector for the car is always the one that provides right around 80 - 85% duty cycle at WOT. This provides the best fuel atomization, mileage, emissions, and lines up correctly with the injection timing.
If you are truly building exactly 500 rwhp, let's work the math backwards. Considering a 15% loss for drivetrain losses, that's about 588 fwhp. Add in another 15 or 20 HP for accessory drive losses, and your talking a gross fwhp number of around 608.
That may be dead on, or just close, but we have to use some sort of calculations to take our best shot, so there it is. 608.
Now, the math is easy. Using the industry standard for injector size calculations, we get (@ .6 BSFC):
608 FWHP @ 80% duty cycle = 57.00 #/hr
608 FWHP @ 85% duty cycle = 53.65 #/hr
608 FWHP @ 90% duty cycle = 50.67 #/hr
Now remember, just because you only netted 500 rwhp doesn't mean that the block, crank, pistons, rods, bolts, combustion chamber, head gaskets, and fuel system didn't feel the 608 HP pinch. So if you don't want to push a stock 5.0 block to 600+, you might want to reconsider your RWHP goals.
If we were to bump that FWHP number down to 550, that's about 450 rwhp, and here's the math on that 550 FWHP requirement (@ .6 BSFC):
550 FWHP @ 80% duty cycle = 51.56 #/hr
550 FWHP @ 85% duty cycle = 48.53 #/hr
550 FWHP @ 90% duty cycle = 45.83 #/hr
The Lightning 42# injectors flow 43.01 #/hr @ 39.15 PSI, the standard Ford pressure. As you can see, all of the above scenarios require more fuel than that, so an upgrade is in order. We always want to use a Ford Racing injector, or a Siemens 60 or 80 #/hr injector (also sold as Ford Racing). Your choices are 42#, 47#, and 60# for EV1 and EV6 type injectors. The EV6 type is more desirable, as it is a much newer/superior design. The 47# would work in some of the above scenarios, but would require a connector adapter. But it appears the Siemens Deka 60 would be the best choice, and it comes in either type connector. Stock 5.0 connector is the Bosch/Minitimer.
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