def not worth on NA unless you had some sort of flex fuel option. starting params, decel, everything is different, so you need completely separate maps for various concentrations of ethanol.

if you dont drain your tank all the way before you swap fuels, it will run like junk. thats the biggest drawback. unless you can always stick to 1 fuel, its not worth the hassle

 

Uprev does have really nice map switching so the params are not an issue...leftover fuel should be fairly easy for the ECU to handle in closed loop... but I can see avoiding WOT during the 'transition' fill up.

 

Without monitoring leftover fuel or mixture i.e. 2 gallons e85 in bottom full tank of 93; generally you can get away with driving it like normal and monitoring AFR's but i would generally tell people to run it as dry as possible and run through one tank without drag racing everywhere before going crazy.. Its not like a few gallons of either/or will make that huge of a difference.

Then again i knew someone who would fill up 2/3 93 1/3 e85 and ran a slightly richer tune and was fine.. its really all about playing around with it and being comfortable with tuning yourself. e85 is not something i would suggest for someone who has to take it to a shop to get a re-tune.

 

Most of the gas stations around here use 10% ethanol anyways... that's almost 2 gallons of ethanol per fill up; it doesn't do much to the AFR. But what do I know.

 

that is basically correct, as long as you can real time monitor your fine. Every car with a tune should have a wideband they cost like 170 bucks now.