I thought I would call GMPP to find out what they do. This is what I was told;
E10=13.81 AFR
E20+11.21 AFR

I took notes all they way down the line and cannot read my writing for the rest, Sorry! Also for their flex fuel vehicles they use a Composition sensor to determine the amount of alcohol in the fuel. And the computer does the rest. SSpdDmon was right when he said we might as well have a PID for the various types of ethanol fuel for the WBO2 sensors (ie his post)
It is important to make the correct adjustments. Another point was that one needs to be careful as to the fuel that you might mix (not knowingly or intentional), in other words from Gas to E*.* and Gas, as some Gas does not have the correct ingredients to mix them. So if I went to get gas in Portland and I have a 1/4 tank of E10 i need to be careful. I dont really know what I can do about that but the difference between E10 (13.81 AFR) and regular gas (14.7 AFR) is more than a little. So you still do need to know the AFR in order to get the right EQ and or LAMBDA. Once you know the correct AFR of the fuel in your tank, you can then tune with what ever you prefer. I wonder if there is a simple sensor we could buy to check the % of ethanol that we put in our tanks?
98 tigershark