Inferred Flex Fuel Tuning Trims?

[Speedy!]

Subject is a 2016 Hellcat. Dual pump drop in fuel system and ID1000 injectors. Flex Fuel tuned. Car calculates ethanol content to within less than 10% of actual as measured with the beaker.

While commanded lambda seems to be spot on, as the weather has cooled the fuel trims are going VERY positive. I noticed it after throwing a P2097 code.

I started logging and at part throttle inputs trims are +12-15% at WOT they're +20%.

Is that expected on a FF tune, or is there some variable I need to adjust?

[Hemituna]

Something is not right in your FF tune.

[Speedy!]

Thanks, good to know it's not normal. Time to start digging.

[Matt1231]

I?ve had this same thing happen when cold weather came.tune would be rich/lean for no reason. We ended up making inj PW adjustments as it?s just a guess when you tune in the summer it takes a lot of logging an time to get temps an fuel content at different environments. An factor in fuel pump efficiency at 120 temperature fuel compared to 30.

[Speedy!]

Well, for inferred flex fuel tuning it shouldn't require any injector adjustments assuming the trims are right on 93, which mine are. The flex fuel algorithms are supposed to handle the rest as ethanol content changes. There are several flex fuel tables that are temperature based, so I'm hoping one of those will be the silver bullet.

These adjustments should be true for standard pump gasoline as well since there are temp based tables for gasoline too.

[Hemituna]

I have mine updating the E content as soon as trims are over 5% (used to use 2.5% but then will update all the time unnecessarily).
If your trims are truly correct on 93, you just need to mess with the FF settings to get it solid on E.
Mine rarely run trims more than 2-3% these days and E percentage calculated is super close to actual measured.
But if you are having issues, at least have it chase it with E % changes...You will know you have it right when trims are good and E % no longer moves around.

[Speedy!]

Thanks. Mine was doing great until the temps got cool, then this really odd positive fuel trim thing. 10% at part throttle inputs and 20% at WOT. Ethanol calcs are very close typically, over the summer spot on, but with these positive fuel trims it is impacting the calcs now. Mine are set to update at 6% variance, however there is a type of timer that after some time it will make a decision and lock in then the trims will just be what they be.

I'll get it sorted.