E85 and what you need to know
Running E85 has become commonplace in the performance sport compact community as it is an affordable option for a high-octane fuel. In this article we are going to explain why E85 can make more power than pump gas and what is all needed to run it, and the benefits of Flex Fuel. E85 has a typical octane rating of around 100-110. That’s 7-17 more octane points than 93, 9-19 more points than 91 and one of the big reasons you can make more power with E85. Turbocharged Subaru engines, as well as other brands, are knock limited from the factory on 91/93 octane. So, increasing the octane allows us to run more ignition timing, higher boost levels and leaner AFR. The higher boost, advanced ignition timing, along with leaner AFR’s are what makes the car have more power when running E85. You also get the benefit of cooler charge air temps as ethanol absorbs heat better than the regular pump gas when it changes from liquid to vapor.
At minimum to run E85 you will need upgraded fuel injectors, upgraded fuel pump, and tune on the EJ engine 2002-2014 WRX, 04-current STI, 05-12 LGT/OBXT, and 04-13 FXT. On the FA engine (2015+ WRX) you will need an upgraded in-tank fuel pump and a tune. On Mitsubishi EVO VIII, IX, & X you will need upgraded fuel injectors and an upgraded fuel pump. On the 2013+ BRZ/FRS all you need is a tune.