I seem to be getting some confusing info from various forum postings and other internet sources about tuning for E85. First of all I’ve seen postings that state that the stoichiometric ratio of gas and E85 are the same; the stoichiometric ratio of any fuel is a lambda of 1, but E85 and gas occur at different AFRs. Stoichiometric ratio is described as the AFR at which the lowest gas byproducts are produced, for gas it is 14.7:1 and E85 is 9.87:1, even with the 30% oxygenation of E85, or 12.83:1, that still isn’t close to 14.7:1 of gas. So it seems to me that if you’re running in closed loop with a narrowband O2 sensor you’re going to be running about 13% lean; so from what I understand whatever your fuel trims are at before going into open-loop or PE is what will be added or subtracted to your commanded AFR. I’ve also seen postings that say an O2 sensor doesn’t care about what fuel you’re running just about how much oxygen is in the air, which is true; but a narrowband O2 for gas is set to switch on/off at an AFR of 14.7:1; some postings make it sound like a narrowband O2 will always be 14.7:1 at the stoichiometric of gas for any ethanol mixture. Maybe someone with some knowledge of tuning for E85 can clarify all of this?