Sooooo I will start off with saying I have never tried tuning a car on flex fuel with a flex fuel sensor. When I have tuned in the past, it was very straight forward to tune for 1 fuel type. I searched the web for a few days now, and I can't seem to find what I am looking for. There are a ton of threads on spark advance adjustments in relation to flex fuel, but I can't seem to find anything on supplemental fueling.
My STFTs (LTFTs are disabled) were almost spot-on before installing the sensor and activating flex fuel in the tune as the car [09 G8 GT; e38] tuned on the "normal" 93 pump gas (e10). Yesterday evening on my way to work I decided to put a little bit of E85 (probably more like e70), which brought the content to high 3X% then settled in the high 2X%. I noticed the STFTs had increased to ~5-6% while cruising and 20%+ at part throttle acceleration while remaining in CL where they are normally right at 0%.
This might sound st00pid, but is there a table to supplement CL fueling for various alcohol contents, or is my only option to jack with the AFR table to force fueling? I am not sure if the latter even works... I reckon I might try when I leave work in a couple of hours. I was really hopeful that the injectors fueling would account for the alcohol content.
Sorry for the long post! I've attached the tune below for reference.
345s_and_E_V1.2.hpt
Edit: Does transient fueling need adjusting to account for fueling differences? The fuel mass evaporation and gain doesn't seem to logically make sense since it is all still reaching the cylinder in some form or another.