Duty Cycle with 55s


Nov 5, 2002
Well, I have just got my car up and running after installing the WB with powerlogger and alky, along with Eric's 6.1 chip for alky. I made some runs to try to log some data. My DC is around 93% with 23lbs of boost. This is with a A/F ratio of 10.8. I want to run 25 lbs of boost however I'm wondering if I have enough injector to run 25 lbs. My fuel pressure is set on 45 with the line off. I'm getting the 1 psi of pressure per 1 psi of boost rise. Do you guys think that the DC is too high and that I need bigger injectors? The car is really pulling hard, I can't wait to run it through the lights.:cool:
if pump is keeping up (1:1 says it is right now ) ...its time for injector upgrade
keep in mind that if you are on a single walbro 255lph that after you reach 55lb/hr per injector you dont have much pump left and it would be a wise move to step to a larger pump or go double pumper
Could be other factors than the injectors causing that high DC?

Fuel pump output due to old/faulty pump and not enough voltage to run it at capacity could be an issue, and also it is running very rich at WOT.

I would lean it out to 11.2 and log that run, then raise base fuel pressure ~5#'s and see what that data will give you for DC.
Forgot to mention that I have Red's double pumper, I thought that it was in my signature, sorry. Both pumps are on a separate hot wire kit. I have a hood mounted FP gauge it doesn't drop off one bit. Thanks guys!
are you firing on all cylinders
if you are ..
at 3700lb fuel calcs put you at 615hp ...enough for 10.60@128mph , not impossible on your combo
93% is getting close to no safety margin. Although 10.8 is kinda rich. With your DP, you can always run more base fuel pressure, may have to re-tune idle and part throttle but more bfp will bring down WOT duty cycle.
I could probably lean out the idle with my translator, idk. I might just get some 80s so I can have more of a safety margin. Do you guys think that I would still be safe at a 11.2 A/F? I forgot to mention that I do have the power plate, if that matters.
Go with some 80's. Coming from a reputable tuner down my way, you dont want injectors to be above 80% dc.