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Accession Number DE2013-1083739
Title Preliminary Examination of Ethanol Fuel Effects on EPA's R-Factor for Vehicle Fuel Economy.
Publication Date Jun 2013
Media Count 27p
Personal Author B. H. West C. S. Sluder
Abstract This report describes a preliminary analysis of the fuel economy data from the catalyst durability study, to determine the proper value for the R factor which is called out in the Code of Federal Regulations (CFR) for computing vehicle fuel economy on the certification cycle. The fuel economy equation that is specified in CFR for gasoline-fuelled vehicles is based on a carbon mass balance (CMB) approach to determine the amount of fuel consumed during the test by measuring the carbon-bearing emissions that are produced; however, it also incorporates a scaling factor (R factor) based on the net heating value of the fuel and the sensitivity of fuel economy to changes in the heating value. The impact of the R factor is a fixed ratio in the resultant fuel economy that is dependent upon fuel properties other than those required for a typical CMB calculation. This equation was put in place in 1988 to correct for differences between certification fuels to address corporate average fuel economy (CAFE) credit issues associated with fuel property variations. The algorithm adjusts the calculated fuel economy to compute what would have been measured had the 1975 certification fuel been used for the test. The R factor was defined as the sensitivity of the fuel economy result to changes in fuel energy content. When R equals 1.0, the fuel economy change exactly tracks the energy density difference between the fuels. If R is less than 1.0, the fuel economy change is smaller than the change in energy density. The R factor was defined to be 0.6 based on tests using 1980s vehicles. Since that time, the Auto/Oil test program has established that the R factor for 1990s vehicles is higher (about 0.93).SC More recently EPA analyzed the EPAct/V2/E-89 dataset to compute the R factor, resulting in an average of 0.82 to 0.86.
Keywords Air pollution control
Ethanol fuels
Fuel consumption
Fuel economy
Scaling factors

Source Agency Technical Information Center Oak Ridge Tennessee
NTIS Subject Category 97K - Fuels
97B - Energy Use, Supply, & Demand
85H - Road Transportation
68A - Air Pollution & Control
Corporate Author Oak Ridge National Lab., TN.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1325
Contract Number DE-AC05-00OR22725

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