Serious HP Horsepower Performance released a chassis dyno video today of their E85 tuned Hellcat Challenger making 753 RWHP, which, by traditional measures, is an astonishing 886 hp at the crank — 81 hp and 70 lb-ft more than their standard 93 octane tune. (Estimates of SAE horsepower are by rule of thumb.)

https://www.youtube.com/watch?v=eYjA8h8s5Mo

E85, or gasoline with 85% ethanol, can, with proper tuning, generate much more power than 93-octane premium  gasoline, albeit with about a 70% increase in fuel volume.  Along with the fuel change, they added an additional fuel pump that adds pressure and volume to the system, upgraded injectors (larger capacity and E85 capable), upgraded driveshaft, and the HP Tuners 2.25 software.

Power is limited by transmission shifting; if HP Tuners is able to provide transmission-computer support, horsepower levels should rise and quarter-mile times should fall.  Some are already predicting thousand-horsepower Hellcats. (Increasing the power of the engine is likely to reduce its life, and most likely the life of surrounding systems, and is almost certain to void the entire powertrain warranty.)