With the increased interest in the use of ethanol as an alternative fuel to gasoline, Original Equipment Manufacturers (OEMs) have responded by adapting their current range of vehicles to be able to run on gasoline/ethanol blends. Flex fuel vehicles are defined are defined as those that are capable of running gasoline up to 100% ethanol. Other than changes to materials compatibility, to enable the required durability targets to be met when running on ethanol, very little in the way of changes are performed to take advantage of the properties of ethanol. Calibration changes are typically limited to changes in fueling requirements and ignition timing.
The physical and chemical properties of ethanol/gasoline blends offer a mixture of advantages and disadvantages. Lower energy density in the form of lower heating value reduces vehicle range whilst higher octane ratings make these excellent fuels for boosted operation.
Further enhancements can be made to flex fuel vehicles that better exploit the properties of ethanol by modifications to both the base engine and calibration. This paper describes an investigation into the potential benefits of an enhanced calibration strategy. Through the use of such strategies, it is possible to improve efficiency when running on ethanol. Design of experiments (DoE) methods have been used to investigate the behavior of a turbocharged direct injected spark-ignited engine on various blends of ethanol ranging from non-oxygenated gasoline (E0) to 85% ethanol (E85).
Enhanced wide-open throttle performance can also be realized when ethanol is combined with boosting and direct injection. Behavioral differences between gasoline and ethanol have been studied and the trade offs identified.
