Without custom code and additional hardware there is no real way to do TRUE flex fuel, the fuel trims will only go +25% and that is not enough adaptation for pump gas to e85. Furthermore, running lean and not having timing optimised is stupid. You will either have timing that's suited for pump gas and will not be taking advantage using ethanol or your timing would be too aggressive for pump gas. The easiest way would be just to use a mode switching routine, and switching between modes depending on the fuel you put in the tank. In order for a real mode switching you would need to use an ethanol sensor which uses a pwm output and not a linear 0-5v output. So your options would be to use a PWM to analog output ran to a reallocated i/o and some custom code to routinely check the content and adjust fueling and timing maps to suit. Alterintly you may be able to use the PWM input for the egt sensor thats used on some 1.8t software versions and avoid the pwm to analog adaptor. Regardless unless you can write custom code, you are a tad out of your wheelhouse, start by making an actual tune for one type of fuel first and optimise that. Keep it simple to start with, its not hard to switch between tunes or get another ecu to swap out. The other option is to use a dual chip riser and switch between calibrations with a toggle switch Picture attached
Oh okay, thank you for all those informations, it’s kinda interesting what we can do on a ECU. Before my injectors changes it was the default value + 20% on the KRKTE to do "flexfuel", someone told me to do that, it seemed to work (with LTFT, not going on -25 or +25). I guess it was just working but to really optimize it have to get hardware mods yup.
Anyway I have some issues I want to talk about, I’ll do it in the first post I made when I receive the cables to do the logs, it might be delivered on Monday or Tuesday.
Happy new year by the way
