The only reason to do a 50/50 mix before going full e85 is just to have a stepping stone so your fuel supply requirements dont change by ~30% all at once. Aside from that there's no reason you cant just consume or pump out all your current gas and fill with E85. In general E85 is going to be a lot more forgiving with AFRs while tuning as well. If you are REALLY worried about tune being off and getting some dangerous knock, you can consider putting an additive in for some extra octane when you are first tuning for the ethanol. I went with some boostane, which is pretty popular with S/C V8s and also on the BMW forums where i spend a decent amount of time (i daily a modded 335i, running E30). I decided to put in 8oz of boostane into my 3000gt when i went to basically full E85, which should have raised my octane by around 7 points based on how much gas i had in the tank. Once my tune was pretty good i literally turned my MBC all the way up and I'm getting around 16psi or so since i have stock wastegate springs. No knock and low 11s AFRs.Lol. Damn alright then!
I mean it only makes sense that e85 will help with my low fuel trim problem too I think.
I’m not sure if anyone has ran 50/50 with an arc 2. Generally you keep the mid knob at -7. Wonder if that’ll change with a 50/50 mix?
Note if you run this a lot your plugs will turn orange.