Why are my fuel trims so damn inconsistent?

[dleach1407]

Makes sense. The rails get really hot. The tank isnt hot at all. I think there is a patch for 80s at higher pressure so ill probably just do that then check fuel trims. If not, ill be looking up the math to change my injector data.

[dleach1407]

Doesn't look like there is a patch for different pressure so looks like I'm doing some math. How much pressure? 4 bar?

[efloth]

I've been having great results with the 80s at 3.6 bar, though I'm not sure if my numbers are relevant to you since I am on speed density. Anyhow, Let me know if you want my offset data.

[dleach1407]

So i think I'm gonna just go to 4 bar. Just want to verify what i read. I am going from 39.5psi to 58psi which is 18.5 psi change. Would i set the scalar percentage to 1, then multiply the high slope, low slope and break point by 1.185? What about the voltage offset? Do i change the scalar percentage back after the changes or leave it at 1. The write up says it affects voltage offsets too but doesn't specifically mention breakpoint or voltage when it comes to changes.

[decipha]

you plug in the actual data from the manufacturee

[dleach1407]

I talked about multiple things and i asked more than one question. Can you please elaborate? Also, I am unaware of any injector data for the LU80 @ 4 bar.

[decipha]

I answered all of it in one simple reply.

No you don't mess with the scaling percentage. You simply plug in the correct injector data.

Anytime you change the injector data you have to compare to your previous file to copy over all the SP** values as they will be changed anytime you change the injector data.

[dleach1407]

I answered all of it in one simple reply.

Im not trying to argue or be a pain but your simple reply didnt contain enough information for me figure out what you were talking about which is why i had to ask again. I also do not see any manufacturer provided data for any pressure other than 39.15, there is no data in the injector reference for any other pressure than 30/40psi for my injectors. I also searched online last night for a few hours looking for it and didnt find it. So i guess im back to my original question. Do I multiply the low slope, high slope, breakpoint and voltage data by 1.185 to get the info? If not, which of the 4 items need to be multiplied?

[91GTman]

From what I read, you would multiply just the slopes by the 1.185 you mentioned and leave the scalar at 1. Would be worth saving as a test tune and seeing how it does.

I read this under the writeup "Fuel - Understanding Fuel Need and Tuning"

Fuel Pressure
"Changing the fuel pressure will change the all injector data, the slopes, breakpoint and voltage Offset for ballpark quick adjustment, I compensate 1% per psi, so if you up the pressure from 40 to 60, I would start by multiplying the slopes by 1.20 if I drop the pressure from 40 to 20, i would multiply the slopes by 0.80, if i went from 40 to 45 the i would multiply by 1.05 not exact, but good enough to begin dialing in the injectors for the new pressure. If you have published manufacturer data for your injectors then obviously use the actual data for the pressure your running."

[dleach1407]

Thats what I read. That says it will affect slopes, breakpoint and voltage but as you have shown, there is no information regarding what to do with the voltage or breakpoint changes.