DreamerGT

I just noticed the stang has pink injectors and the vic has orange injectors I know the orange are 19lbs but what are the pinks rated at?

cliffyk

21 lb/h, Ford seems to have started installing them (maybe) in the 2001-1/2 model year--my '03 GT has them...

DreamerGT

oh ok, is there a reason why they made the change?

cliffyk

The 19lb/h injectors were borderline inadequate, requiring that they be pushed to 90% duty cycle to support the 260HP crank HP (at the 40 psi pressure Ford runs).

The 21lb/h can do this at 80% duty cycle.

Rule of thumb for n/a is:

Max HP = [lb/h] * [duty cycle] / 0.5 * [# of cylinders]

lb/h is generally spec'd at 43 psi, so for Ford's 40 psi you need to multiply the lb/h by 0.964 to get the effective flow rate.

[19 * 0.964] * 0.9 / 0.5 * 8 = 263 HP

[21 * 0.964] * 0.8 / 0.5 * 8 = 259 HP

Hangwire

Awesome info.....my 03 GT has the pink ones too.

According to this math the 36LB injectors sold with the 99-04 KB 2v kit are good for aprox 500 HP. However....i'm assuming with the BAP the fuel PSI will be different. How do I adjust this formula to that setup?

Eagle2000GT

Hangwire, I get 444 bhp using the 80% duty cycle formula for 36 lb injectors. 500 bhp is with the 90% duty cycle. My 42 lb injectors are 518 bhp at 80%. That would be approximately 440 rwhp. It looks like I'll have to change injectors if I get a forged rotating assembly.

I don't think the BAP changes fuel pressure, it just allows more fuel flow.

Hangwire

Correct, I came up with 500 @ 90% duty cycle.

And....doesn't more fuel flow mean that under heavier throttle you need more PSI to move the appropriate amount of fuel?

Eagle2000GT

I don't think so. We still have a variable fuel pressure system that's controlled by the computer keeping the fuel pressure at an adjusted 40 psi by varying the voltage at the pump. I believe the BAP just makes the fuel pump more efficient so that it can provide more fuel when the computer asks for it. It doesn't build more pressure because the fuel is being used by the injectors as fast as it is being pumped.

I don't have a BAP and my SVT focus pump (255 liters per hour) is quite sufficient for my 42 lbs. injectors.

P.S. Even if we were talking "raw" fuel pressure, unlike my ProCharger your KB builds its boost early and then bleds off the excess. I don't know for sure but your "raw" fuel pressure will probably reach its maximum psi around 2000 rpm at WOT.

Hangwire

From my understanding your car stock does not have the capability to take the fuel pump's voltage to its limit. Based on this....all a BAP does it jump the voltage up above the like 8 or 9 volts that your car can put it to now. Its capable of and can operate in voltages almost twice that if I have read/remembered right.

I know for a fact that my 2003 GT auto's fuel pump duty cycle is only at 42% on a WOT pull. Though this has nothing to do with voltage or supercharger applications.....my engine just cant breathe enough air to need all that fuel.

cliffyk

The 0.5 component of the n/a formulae I presented above is the BSFC (Brake Specific Fuel Consumption) for n/a engines. For forced induction you need to use a BSFC of 0.6 or a bit higher depending on boost levels (0.6 for 5-8 psi, 0.65 for 8-10 psi, and 0.7 or maybe more for 10-12 psi+).

Because the density of the compressed air is higher (I.e. more O2) you need a proportionally higher amount of fuel.

The correction for fuel pressure is the SqrRt([new pressure]/[old pressure]) * [old rate]:



For the 21lb/h (at 43.5 psi, the standard pressure for injector ratings) running at 40 psi this becomes: