BMW Z4 E85 Backgrounder on Flexible Fuel Vehicles PDF Manual

What is a Flexible Fuel Vehicle?
As currently offered to consumers by several automakers, flexible fuel vehicles (FFVs) are designed to operate on any mixture of gasoline and ethanol – with ethanol concentrations of up to 85% by volume (E85).* There is one major difference between an FFV and a conventional gasoline-fueled vehicle – the FFV detects the ethanol/gasoline ratio and makes appropriate adjustments to the engine’ ignition timing and air/fuel mixture ratios to account for the ethanol and optimize performance and maintain emissions control. The vehicle must be equipped with an air/fuel ratio map capable of handling the adjustments necessary for optimized performance on both gasoline and E85. Components of the fuel delivery systems on FFVs are also modified and upgraded to be resistant to the corrosive effects of alcohol in the fuel.

Availability and consumer purchase cost of FFVs
FFVs were first introduced in 1993 with a flexible fuel version of the Ford Taurus.† Other auto manufacturers soon followed in the mid-1990s with the production of FFV versions of several popular light truck and van models as well as passenger cars. The federal government and state governments, along with businesses in the alternative fuel industry, are required to purchase alternative-fueled vehicles by the Energy Policy Act
of 1992. In addition, under the Clean Air Act Amendments of 1990, municipal fleets can use alternative fuel vehicles to mitigate air quality problems. Blends of 85% ethanol with 15% gasoline (E85), and 95% ethanol with 5% gasoline (E95) are currently considered alternative fuels by the US Department of Energy.

The Alternative Motor Fuels Act of 1988 provides Corporate Average Fuel Economy (CAFÉ) incentives to the auto industry for producing vehicles capable of operating on alcohol or natural gas fuels either exclusively or in conjunction with gasoline or diesel fuel. The Energy Policy Act of 2005 extends the availability of these CAFÉ credits through 2010 and authorizes NHTSA to consider extending the incentives through 2014.‡ This opportunity to earn CAFÉ credits is likely the reason for the expanded offering of (particularly pickups, vans and sport utility) FFVs in recent years. (1)§

Ford, Daimler Chrysler, General Motors and Nissan currently offer model year 2006 vehicles for sale in the US which include the flexible fuel capability as standard equipment. Examples include the Ford Taurus, Ford F-150 pickup, GM Silverado, Chevy Tahoe, Chevrolet Impala and Dodge Ram pickup. (2, 24) Thirty-Four of the 520 models reported in the DOE/EPA Model Year 2006 Fuel Economy Guide are FFVs. (24) According to statements made by the manufacturers the FFVs are being made available at “little to no additional cost to the consumer.” (1, 19) Aside from Daimler Chrysler, General Motors and Ford have been the most aggressive in promoting the availability of FFVs nationwide. (3, 4, 5) Ford and Daimler Chrysler recently announced that they would not certify model year 2006 FFVs for California, and cited compliance concerns with respect to the stricter California LEV II evaporative emissions regulations which are currently being phased in. This has also precluded sales of Ford and DaimlerChrysler FFVs in those northeastern states which have adopted California emissions standards. (6, 7) Estimates of the total number of FFVs currently in operation vary from 4 to 5 million. (7, 21) This is equivalent to about 2-3 percent of the total fleet of cars, light trucks, SUVs and
vans on the road today.

Physical Properties of E85 and Comparison with Gasoline
The properties of E85 are governed by ASTM specifications which are shown in Appendix B.** These specifications were issued in 1999 and may be considered somewhat dated. For instance, they clearly do not reflect the EPA Tier 2/Gasoline Sulfur regulations which require refiners to meet a 30 ppm average gasoline sulfur limit starting in 2006. The ASTM specification for E85 allows for up to 300 ppm sulfur in the mixture. This high level could degrade the performance of catalytic converters that must be on the FFV to meet emission standards. Pure ethanol differs from conventional gasoline in that it has a constant boiling point temperature, higher octane, lower energy density, and requires more heat for aporization. (See Appendix C.) (8, 13) Blends containing 85% ethanol by volume have a higher octane value than regular gasoline, but because of the lower energy density of ethanol, an E85 blend contains only about 69 – 74% of the energy of regular gasoline on a Btu/gallon basis. This means that a 35% increase in the capacity of the fuel handling infrastructure (delivery tanks and carriers) would be needed for E85 systems to enable the same level of mobility (total vehicle miles of travel) as that provided by the current gasoline distribution system.

Neither the ASTM standards nor EPA regulations require deposit control additives to protect the intake valves and fuel injectors of vehicles operated on E85. The engines on FFVs operate like those on gasoline vehicles, but there is little published information available on their deposit formation tendencies. Evaluations of the need for deposit control additives in E85 (and their effectiveness) have not been completed. Much like gasoline, the volatility of E85 must be adjusted seasonally and by geographic region to assure adequate cold start and drive away performance. This is done by increasing bot the volatility and the amount of gasoline (typically from 15% to 30% by volume) in blends sold during colder months. Pure ethanol has broader flammability limits than gasoline and burns with lower flame luminosity. When blended with hydrocarbon fuels, the vapor space flammability limits of ethanol approach those of gasoline and luminosity is increased. (13) With a stoichiometric air-to-fuel ratio of 10 (compared to 14.7 for regular gasoline), E85 needs more fuel per pound of air for optimum combustion; therefore E85 can not be used in conventional vehicles which are designed for no more than E10.

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