Flex Fuel Tune Question / pros cons

[Cory S]

You can see because when you let off, the ARF pegs to 20 and the car will either learn back down from that or pause learning.

Only if DFCO is enabled in the tune. Many calibrators shut off DFCO when running Ethanol calibrations. I personally request all my tune files have DFCO disabled.

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[engineermike]

I found letting it idle for a long period of time at the start gets the E content up faster than driving. You can see because when you let off, the ARF pegs to 20 and the car will either learn back down from that or pause learning. Its best to let it idle the E content up, then when its in the 60ish range E, then I do light driving trying not to coast. I have HOURS AND HOURS of testing with the flex tunes and a mountain of logs and all I can tell you from experience it its very flawed. My car even with e90 tested, wont seem to learn up past 77. No matter what I do. I found a GATE gas station that consistently has E85-90 tested by me and a few others, and no matter how long I let it learn or what I do it seems to cap around 77. This is why I think the static E tunes are best. My car even on the pure E85 I can get, seems to be happiest around 10.20afr. Then for wot, .85 lambda.

Resurrecting old thread here...been playing around with it and noticed the standard "min learned A/F ratio" in the stock Ford F-150 file is 10.26/1. For whatever reason, Ford decided that it doesn't need to learn beyond that stoichiometry. If you do the math, it turns out that 10.26/1 stoichiometry equates to 77.5% ethanol. So, if the tuner is using Ford's min AFR then it can't possibly learn higher than 77.5%, which is my guess as to why you're seeing what you are. It would be very easy to change that min to 9.8 or 9.0 if you want to learn to 85 or even 100%.