Practical Considerations for an E85-Fueled Vehicle Conversion

An original equipment gasoline-fueled 1999 Chevrolet Silverado pickup with a 5.3-liter, V8 engine was converted to operate on E85 (85% denatured ethanol and 15% gasoline). The simplest conversion of a gasoline-fueled vehicle to E85 requires modification to the fuel system, including use of components that are compatible with ethanol and fuel injectors that provide sufficient E85 for the stock engine control module (ECM) to effectively control engine operation. To retain the stock ECM, higher flow rate fuel injectors that provide approximately 40% more E85 than gasoline are required. With no engine modifications and similar engine control strategies, performance predictions show an approximate 7% torque and power increase for E85 over gasoline. The increase is primarily due to the specific energy differences between E85 and gasoline, although there should be a slight charge cooling benefit for E85 as a result of its higher heat of vaporization. Actual performance measurements result in an average increase in torque and power for E85 of ∼2.5%, although the measurements show a difference in equivalence ratio at WOT (∼1.11 for gasoline and ∼1.02 for E85). Based on miles per actual gallon of fuel, fuel economy predictions and constant speed on-road measurements result in a penalty for E85 of ∼24% when compared to gasoline. FTP city and highway tests yield fuel economy penalties for E85 of ∼32% and ∼31%, respectively, which agree with the Auto/Oil result of ∼29%.