Flex Fuel Tuning

[Higgs Boson]

When you guys are tuning Flex Fuel vehicles are you:

1) Disabling Flex Fuel with the drop down menu in the General tab?

2) changing the Stoich table to a consistent value?

3) Neither or a combo or???

Any special procedures above and beyond normal for FF?

[LSxpwrdZ]

If it's got the sensor then I leave it on. Commanded AFR will wonder around due to a change in the fuels stoich value. However the stoich ratio of your wideband isn't changing with the fuel so it will cause error readings to be off using units of AFR... Commanded Lambda will not! This is why I tune in unit's of Lambda instead of AFR.

[Higgs Boson]

If it does not have a sensor do you change the stoich table? Does the stoich table do anything in that case? Which vehicles have a sensor? I am mainly tuning trucks, 08 - 12...

[DSteck]

I recently did a Procharged Taho that was flex fuel and didn't have a master enable/disable for flex fuel (at least not that I saw). I changed the entire stoich AFR table to the same value and called it a day. The owner said he didn't want "that flex fuel BS" anyway. Lol.

[Higgs Boson]

What did you change it to? 14.68 across or 14.2?? Same situation here, no one uses E85, just E10.

Does the ECM use this table to correct trims and always have low error? How can you get a MAF curve in line if it is varying stoich all the time????

I disable to tune then re-enable but if that is pointless with only one fuel available, I can leave it disabled....

Advice there?

[DSteck]

If it has a real sensor, you just log in lambda and adjust accordingly. It is very simple.

I set it all to 14.68.

[Higgs Boson]

is there some sort of list of vehicles with real sensors? thanks.

[LSxpwrdZ]

To properly do it right you should measure the alcohol content of the fuel you are using and then set the stoich across the board based on the alcohol content. Then once you have your airflow tables calibrated reset the stoich slope to stock and let the narrowband algorithm calculate it like stock from there. If it's got flex fuel I try to keep it enabled due to the change in fuel types from summer to winter and pump to pump. Just another variable that seems to help take care of keeping fueling as close as intended.