guidelines for upgrading Fuel Injectors

Anyone know the guidelines for upgrading fuel injectors. I have the whipple 550 HP kit with 39 lbs injectors and was curious how high that could take me safely? I am shooting for the 550 range and my next upgrade is the clutch and one piece shaft drive. Any lessons learned on any of these 3 parts would be much appreciated.

I have 1700 miles on the new forged engine so all is well. My dad just installed one of those in garage-in ground storm cellars and I used it to change my oil. Worked like a charm.

There is alot to this. They have their rated flow 39 lbs in your case. Flow rate is rated at a certian psi drop across the injector. Yours as an example would be 39#/hr which is rated to deliver 39# of fuel at 42.5 PSI. The injector will flow 39#/hr as long as the pressure at the supply side, minus the pressure in the manifold is 42.5 psi. In ford systems the psi drop across the injectors is 39.5.

On a blown car your fuel psi must increase 1 psi per pound of boost. Lets say your going to run 14 psi boost, so for fords you should have under boost 39.5 psi + 14 psi boost = 53.5 psi that has be maintained to make the injector work like its rated.

To calculate injector hp ratings roughly you have to know BSFC (brake specific fuel consumption) and on a blown 4.6 liter it is 0.6 actual maybe slightly different but this is close. Take you 8 injectors times 39# = 312 #/hr of fuel divided by the BSFC of 0.6 = 520 hp flywheel. How ever all this changes when you change pumps install a boost a pump. The cobras i have seen with stock injectors 39 # have supported over 550 to the tire. You should be fine with the gt500 pumps and 39# injectors. I am running the ford gt pumps and 39# injectors. The duty cycle will have to be logged you dont want to be maxing the injector out all the time. If you wanted to be on the safe side a 42# or 60# injector will give you room to grow also the Mass air flow sensor maybe close to pegging depending on the sensor you have. My head hurts now

Good info

If you want to see how much room you have to grow with your 39s you can do some logs and see what your duty cycle is.