The 21 lb/h rating is Ford's spec at 40 psi differential across the injector (fuel rail pressure + -[manifold pressure in psi]). I.e. at -9 psi manifold pressure (19 inHg vacuum at idle) the rail pressure would be 31 psi--31 + -(-9) = 40 psi differential.
At 43.5 psi differential (the standard pressure for rating injectors) they are spec'd as 22 lb/h. Here is the formula for recalculating injector capacity as differential pressure changes:
So for the Bosch 22lb/h rating at 43.5 psi the GT pink injectors flow:
(40/43.5)^0.5 * 22 = 21.09 lb/h
At 36 psi with the vacuum line off (I assume at idle) the pressure "across" the injectors would be around 45 psi (36 psi in the rail, + -(-9 psi vacuum)). Meaning that under those conditions the 21 lb/h injectors (at 40 psi) have become;
(45/40)^0.5 * 21 = 22.2 lb/h injectors
Which is why your short term trim is at -10%. The PCM thinks they are 21 lb/h injectors (19 lb/h if your are running the stock tune, which I suspect you are), but they are behaving, due to the increased fuel pressure, as 22.3 lb/h units injecting too much fuel. The PCM has compensated for this by injecting -10% less fuel--just about the difference between 19 lb/h and 22 lb/h.
Are you running a custom tune? If so do your know what the low and high injector slopes are set to? IF it is the stock tune do you know the box code/catch word--it will be a 4 character code like XSH2, or MDE3 and should be on a label on the PCM.
If you can get the box code I can look up the tune (I have almost 6000 in my library) and see what the injector setting are. What year is your car, as you have the pink injectors I assume late 2002 to 2004.
Back to your original question, Bosch rates them to 100 psi, however that is mostly because that is the maximum working pressure for SAE 30R9 rated hose--the most commonly used OEM fuel line hose. I have run other Bosch injectors up to 135 psi.
Tell me more about your setup...
- 2003 GT, UPR X, FRPP 24lb/h, Magnaflow, PP 70mm TB & plenum, Delta Force tuned,
Steeda UDPs, Ralco flywheel, RAM HDX clutch, 3.73s, 262 rwHP/305 lb-ft.
New ride (7/1/2013) 1998 Mercedes SL500-5.0L 32V VVT 326/347 HP/tq