It's been a long time since I dabbled, but from memory the likes of E85 is good for fixed load use (eg. drag racing) but not great for variable load (track racing cars, motocross etc) because petrol has a wide range of evaporation points compared to the much narrower range of E85.
anonym29|7 months ago
It also lets the engine run cooler despite burning hotter precisely because of those evap characterisics.
That's not to say there are no downsides. It's less energy dense so you need larger injectors or a higher duty cycle, you get less mileage, it's extremely hygroscopic, it has different corrosive properties, and a different stoich ratio so most vehicles need some amount of modifications and tuning to properly utilize it.
But all in all, it's wildly economical alternative to traditional high performance fuel.