The Flex Box offered by Flex Fuel is a fuel conversion kit that allows automotive engines initially designed to run exclusively on gasoline to use ethanol instead. Some gasoline is still required in the fuel mixture, and the company recommends E85, a fuel consisting of 85 percent ethanol and 15 percent gasoline. Modified engines are also compatible with E50, E20, E15, E10 and traditional gasoline. The conversion is certified by the EPA, and may qualify drivers for government rebates.
The fuel conversion kit has three primary components: a sensor that determines how much alcohol is in the fuel, a processor that determines how much additional fuel is needed, and an injector to distribute additional fuel. Ethanol engines are slightly less efficient than gas-only motors, and gas-only engines are not calibrated to sense the resulting need for additional fuel. The conversion kit's racing-grade processor determines the amount of additional fuel needed, taking fuel mix and driving conditions into consideration, and distributes it through the fuel injector located in front of the throttle plate.
The Flex Box is only available for certain vehicles, including Ford, Lincoln, Dodge and Chrysler models. Compatible engine sizes include 5.7L Hemi motors, 4.6L, 4.6L V-8 and 5.4L. As of 2015, more recent models are not compatible with the product. A full listing of supported years and makes is available at FlexFuelUS.com.
Customers save on their gas bills despite reduced efficiency by taking advantage of ethanol's lower cost compared to gasoline by about 72 cents per gallon. Flex Fuel offers a chart on its website detailing how long it takes to recoup the $975 installation cost through fuel savings, controlling for factors such as annual distance driven and a State of Illinois rebate. The time ranges from six months to nearly six years.