# E85 as race fuel? **URL:** \ **Category:** PittSpeed Automotive\ **Created:** [January 20, 2007, 8:42am UTC](https://forums.speedlife.net/t/e85-as-race-fuel/187529 "2007-01-20T08:42:16Z")\ **Posts on this page:** 1\ **Showing post:** 31
**Author:** ![sunhawk08](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@sunhawk08](https://forums.speedlife.net/u/sunhawk08)\ **Post date:** [January 29, 2007, 12:09am UTC](https://forums.speedlife.net/t/e85-as-race-fuel/187529/31 "2007-01-29T00:09:23Z")
> [@19's are gone.](https://forums.speedlife.net/t/19s-are-gone/27590/4): > > my 2 pennies. it takes 1.5 gallons of e85 to do the same that 1 gallon of regular gas does. common sense tells me that e-85 will cost more $ than normal gas. source is popular mechanics mag… dunno exact motnh., it is laying at the garage. > > however, being e85 has a motor rating of 100, it is ideal for gearheads. as we all know motor rating\>all. thats a pretty damn good rating for gas that is cheaper than normal pump gas. however, it dont hold a candle to true race gas. > > yet here is what i dont understand. on flex fuel cars–how do they decifer what gas is in the car? as duty cycle, egt, cht, flame properties, etc will greatly differ from the two fuels as they have an entirely different properties. how the hell does the ecu klnow what fuel is in it? Well its actually pretty simple to explain. Since the stoichiometric point for ehtanol is 9:1 instead of 14.7:1 as for gasoline, the air fuel mixture has to be changed for the % of ethanol present in the gas tank. In order to distinguish which gas is being used they added a composition sensor. So basically the sensor tells the computer what the stoichiometric pressure is and the sensor relays the message to the computer differentiating which fuel is being used.At that point the computer adjusts to the parimeters of the fuel and compensates. --- _[View the full topic](https://forums.speedlife.net/t/e85-as-race-fuel/187529)._