Flex Fuel S550

[FastLifeS550]

Hello

I know this is an old topic but I'm new in this area. I have a 2020 Mustang GT auto transmission and I wanted to enable the flex fuel logic from the tune. I enabled it from the tune and I copied all of the flex fuel tables from flex fuel truck. The issue now is after filling the tank with E85 the car was too lean and the short fuel trims are about 35-40% lean. I thought maybe it was bad E85 and I switched to X85 just to make sure I have clean gas. I've been searching and reading if I should tune the car after using E85 or the flex fuel logic should correct everything for me. Should I dial the MAF after enabling the flex fuel?

Thank you everyone.

[LastPlace]

Your maf should be dialed in on e10 not E85

Let the flex logic do what it wants.

it’s not very accurate…

[FastLifeS550]

Thank you for taking time to respond.

I wasn't sure because everyone says the fuel trims should be close to 0% in both fuels in flex fuel logic, and I didn't see that especially on the idle, the car stalled multiple times and I think because it's too lean on Ethanol. Any advice or information about flex fuel logic to keep the car happy?

Thanks again

[LastPlace]

what did your fuel test at?

also post your tune file and stock read

[Plimmer]

If you’re going to run straight e85, I wouldn’t bother with flex, just make yourself an e85 tune with flex turned off.

[FastLifeS550]

what did your fuel test at?

also post your tune file and stock read

I didn't test it, it was pure VPX85.

[17GT]

Didn't see the inferred ethanol vs stoich table populated so I added it to your tune. Also when you change the volume of the fuel in the tank by more than 10% it will recalculate the inferred ethanol content over the course of a few minutes of driving so drive easy immediately after refilling the tank or changing the tune over.

[LastPlace]

Didn't see the inferred ethanol vs stoich table populated so I added it to your tune. Also when you change the volume of the fuel in the tank by more than 10% it will recalculate the inferred ethanol content over the course of a few minutes of driving so drive easy immediately after refilling the tank or changing the tune over.

Do not use what 17GT posted.

Classic example of bad info on this forum.

Screenshot (46).png

[17GT]

You are right tried to paste over the correct numbers and somehow it didn't save in the row access here is the right data....Screenshot 2021-08-25 113338.png