Why are you trying to do this?

E-85 is 15% gasoline, and 85% ethanol

20% nitro fuel is 20% nitromethane, and 74% methanol (the other 6% is lubricant, and that number changes with the type and brand of fuel)

So if you're going for some sort of green fuel you're on the wrong track.

You could get a 1/5 scale car to run E-85, but at that point you might as well run 100% ethanol.