title: The Effect of Compression Ratio, Fuel Octane Rating, and Ethanol Content on Spark-Ignition Engine Efficiency.
abstract: Light-duty vehicles (LDVs) in the United States and elsewhere are required to meet increasingly challenging regulations on fuel economy and greenhouse gas (GHG) emissions as well as criteria pollutant emissions. New vehicle trends to improve efficiency include higher compression ratio, downsizing, turbocharging, downspeeding, and hybridization, each involving greater operation of spark-ignited (SI) engines under higher-load, knock-limited conditions. Higher octane ratings for regular-grade gasoline (with greater knock resistance) are an enabler for these technologies. This literature review discusses both fuel and engine factors affecting knock resistance and their contribution to higher engine efficiency and lower tailpipe CO2 emissions. Increasing compression ratios for future SI engines would be the primary response to a significant increase in fuel octane ratings. Existing LDVs would see more advanced spark timing and more efficient combustion phasing. Higher ethanol content is one available option for increasing the octane ratings of gasoline and would provide additional engine efficiency benefits for part and full load operation. An empirical calculation method is provided that allows estimation of expected vehicle efficiency, volumetric fuel economy, and CO2 emission benefits for future LDVs through higher compression ratios for different assumptions on fuel properties and engine types. Accurate "tank-to-wheel" estimates of this type are necessary for "well-to-wheel" analyses of increased gasoline octane ratings in the context of light duty vehicle transportation.
authors.affiliation: Ford Motor Company, P.O. Box 2053, Dearborn, Michigan 48121, United States.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Leone
authors.affiliation: Ford Motor Company, P.O. Box 2053, Dearborn, Michigan 48121, United States.
authors.forename: James E
authors.initials: JE
authors.lastname: Anderson
authors.affiliation: General Motors Powertrain, 850 Glenwood, Pontiac, Michigan 48340, United States.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Davis
authors.affiliation: FCA US LLC, 800 Chrysler Drive, Auburn Hills, Michigan 48326, United States.
authors.forename: Asim
authors.initials: A
authors.lastname: Iqbal
authors.affiliation: FCA US LLC, 800 Chrysler Drive, Auburn Hills, Michigan 48326, United States.
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Reese
authors.affiliation: Ford Motor Company, P.O. Box 2053, Dearborn, Michigan 48121, United States.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Shelby
authors.affiliation: General Motors Powertrain, 850 Glenwood, Pontiac, Michigan 48340, United States.
authors.forename: William M
authors.initials: WM
authors.lastname: Studzinski
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis; D000431:Ethanol / Q000737:chemistry; D005742:Gasoline; D017752:Greenhouse Effect / Q000517:prevention & control; D018986:Motor Vehicles; D009795:Octanes; D014481:United States; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D005742:Gasoline; D009795:Octanes; D001335:Vehicle Emissions; D002245:Carbon Dioxide; D000431:Ethanol; C026728:octane