Fuel Flow at WOT

[Bocephus]

Does anyone know exactly what this is? By the description I would assume it's a measure of fuel volume, since it mentions @ STP. Not sure if STP stands for Standard Temperature and Pressure. The units listed imply mass however, 68 mm3 or mg doesnt make sense for fuel at WOT. I'm also curious if this might have to do with the HPOP displacement and lookup tables for ICP since it's a big factor in fine tuning the engine, but cannot find any reference to HPOP specs anywhere. Perhaps it's in liters actually?

[RandomEnthusiast]

Maximum allowed fuel flow I believe.

[Bocephus]

Yeah I agree, it's just odd that factory calls for between 68, then tapering down toward 60 at 5000 RPM, but the calibration easily pushes 78 mg at WOT. Also I can easily call for 100 mg at the same setting, but cannot seem to call for 108 mg no matter what Scalars or Functions I change. I think I'm misinterpreting the Function.

[LSxSwap0613]

Could you post up a log of mass fuel desired going over 100 please... no matter what limiter I change...it caps at 100 mg

[Bocephus]

I apologize for the late reply. Truck is currently parked installing a new turbo due to worn bearings. I'll see if I can find one of my old logs, but I can confirm without a doubt that I've been unable to command more than 100mg of fuel per stroke using HPTuners or SCT Advantage software. Considering the FICM calibration only runs up to 120mm^3, I'm unsure if it can scale higher than the FICM map limits. 100mg does command 125mm^3, and can confirm I loosely extended the FICM tables by extrapolating the last couple points at an ICP of 4000 psi, with no change.

[LSxSwap0613]

Good deal I am getting the same exact results. It is odd that no matter what is commanded ... 100 is the cap... now you have also used the SCT and it caps at 100 also?
I wonder how the higher power guys are commanding more than that I would think with bigger injectors and all that,... you would need to command more... course I may have a lot more learning to do. I did find tht bumping up the ICP pressures did next more volume mm3 by 2 or 3. I have looked at other tunes from sct and hp tuners and there are some commanding 150mg of fuel.... in the pedal map and under the limit function makes me wonder if maybe the processor cant process about 100mg and 124mm3 but it I actually getting it. I guess that would be a great thing for a dyno test and smoke output

I know that using the formula for fuel density and the multiplier for the temperature function 100mg will net 124mm3 give or take

[Bocephus]

That's because most tuners spoof ICP to a lower value, fooling the FICM to command a higher pulse width to *compensate*. The end result is more fuel than a calibrated sensor would command, but the PCM/FICM are really seeing less. The nicer way to do this is to increase the FICM Duration Tables now that we have them, to achieve a smoother, more refined fooling of the fueling. FICM will still be commanding only 125mm3 but the increase in duration in those cells will actually inject more fuel. Remapping the FICM also eliminates the light-switch-pedal compared to spoofing ICP. Chevy and Dodges have had access to their Duration Tables much longer than we have.

IMHO, it would still be awesome to have the ability to command up to 110mm3 or 120mm3, that way the calibration is simply more true. Estimating desired Air/Fuel and other relationships will be more precise. If factory injectors are approximately 135cc comparably, I believe that comes out to about 108mg per stroke.

Oh yes, and the SCT software hasn't pulled anything greater than 100mg either. But I know HPTuner has been able to work around hard RPM limiters in some Ford cars, and have also given us FICM tuning where others haven't. I believe they could work around this too.

[RandomEnthusiast]

AS far as my research has given is ficm pwm values can be adjusted and get roughly the total limited on the injector. But I have not had the ability to flash a ficm for more info and testing limits. 100mg may as you say be the limit of processing power. This an be offset by larger nozzles and bigger injectors. If you wish there is always the 10k resistor mod that will trick the pcm and ficm to see a lower voltage on the icp than is actually happening.

[LSxSwap0613]

Thank you Bocephus .. I have been banging my head with the fueling.. makes perfect sense being I have been sifting through all my data and still come up to the same answer...stops at 100mg and 124mm3.... I have heard of spoofing and didn't want to get into that like you said especially since we have access to the FICM

please explain to me the pedal map theory I have seen tunes again at 150 and some at 125. why not just leave in at 100 since we can get over than anyway

[poulioteri]

Thank you Bocephus .. I have been banging my head with the fueling.. makes perfect sense being I have been sifting through all my data and still come up to the same answer...stops at 100mg and 124mm3.... I have heard of spoofing and didn't want to get into that like you said especially since we have access to the FICM

please explain to me the pedal map theory I have seen tunes again at 150 and some at 125. why not just leave in at 100 since we can get over than anyway

Most times it's to create a faster "run up" or greater slope in the graph to hit that max sooner. Other times it's wishful thinking.