E85 ethanol is used in engines modified to accept higher concentrations of ethanol such 'Flex Fuel Vehicles'. They are designed to run on any mixture of gasoline or ethanol with up to 85% ethanol by volume. There are a few major differences between 'FFVs' and non-FFVs. One is the elimination of bare magnesium, aluminum, and rubber parts in the fuel system as the ethanol can corrode these types of matterials.
Another is that fuel pumps must be capable of operating with electrically conductive ethanol instead of non-conducting dielectric gasoline fuel. Fuel injection control systems have a wider range of pulse widths to inject approximately 34% more fuel. Stainless steel fuel lines, sometimes lined with plastic or nylon, and stainless-steel fuel tanks in place of terne fuel tanks are used. In some cases, 'FFVs' use acid-neutralizing motor oil. For vehicles with in-tank-mounted fuel pumps, additional differences to prevent arcing, as well as flame arrestors positioned in the tank's fill pipe, are also sometimes used.
The power increase is mainly due to a *20% reduction in combustion temperature from the ethanol content and increased fluid injection (+34%) causing the inlet, valves and pistons to be cooled during opperation. This also means that more igition timing and boost pressure can be added to gain even more power from the engine.
Straight Tuned E85:
Some race cars like V8 supercars and even street cars are tuned ONLY on E85 with no fuel or timing trims for lower or zero ethanol content. Fine for those vehicle using a consistant and repeated blends of 'barrel' E85 fuel from manufactures such as ELF, HI-TECH OILS, and CHEATER but when inderviduals are filling up at a local petrol station designed for vehicles with Flex Fuel and begin tuning, issues can arrise.
One concern is an inconsistant level of ethanal from station to station, some as low as 75% ethanol in Australia, and another concern is that most E85 sold at a Petrol Station is mixed with 91RON uleaded fuel where as all 'barrel' E85 that we know of is mixed with 98RON unleaded which is another reason the cost is greater but means a higher octane rating and a higher threashold to detonation.