USAF-Vette

I've made some LTFTs adjustments to my car using my predator. Question though...

Do WOT throttle runs in between adjustments give inaccurate LTFT data? I'm using DSlog Redux, and I'm wondering if I'm throwing my numbers off by doing WOT runs. I decreased injector slope and now it's telling me to add +4. Temperature was a bit different though...10-15*F.

Thanks,

Rick

06MonteSS

ltft's are not used at WOT, unless they are positive... yes your ltft's should be 0 or slightly negative when you go WOT, so that no additional fueling gets added on top of the WOT fueling table.. the fuel trims are used for part-throttle, to dynamically adjust the fueling in order to keep the AFR at stoich 14.7...

and when doing WOT-only data logs, don't worry about what the ltft adjustment tells you in that app...

and when adjusting the slope for part-throttle fueling, and installing the tune, you need to put on at least about 100-150 miles so that the fuel trims, idle, etc get relearned by the ecm and settle in before you do another steady driving log to check them...

but when doing WOT data logs, don't worry about the ltft info in that app, since your driving conditions were not for steady driving...

and keep in mind, that app does not take into account the intake air temp when recommending adjustments... it just shoots for a 0 to -2.xxx average fuel trim no matter what... which shouldn't be the case... if your intake air temp is only 30* out, then your average fuel trims should actually be a little positive, because then once the temps warm up, your intake air temp will be higher/hotter, and you will go more negative on fuel trims which means you'll be running too rich...

really need to go through data logs manually and take into account the intake air temp so that you can base your adjustment off of that info as well... also, best bet is to get a custom tune done for it so that the MAF sensor table can be scaled instead of adjusting the fuel injector slope...

and then just leave it, because average fuel trims that are in the positive range during colder temps is normal, afterall, that's their purpose, to dynamically adjust the fueling in order to keep the fueling at the stoich value during part-throttle operations...

USAF-Vette

I think this might be the problem...changing temperatures throwing my numbers off. Is there any document out there that I can use to learn the temperature/fueling relationship a bit better?

Thanks,

Rick