This article examines some of the principal factors that affect the efficiency of gasoline usage by the automobile. Since 1930 there has been an increase in the average engine compression ratio and engine operating efficiency. However, qverage vehicle fuel economy has shown a gradual decrease. This is explained by the fact that the internal combustion (ic) engine of today is designed for an operating mode that results in a degradation of thermal efficiency--engines that can supply 100 horsepower are being used, when most of today's driving situations require that the engine need supply much less than this. Also, the transmission in present vehicles attempts to match the variable engine speed to variable vehicle speed. Modern automatic transmissions are a compromise among performance, efficiency, and cost. The chemistry and hydrodynamics of flames also play a part in the efficiency of the ic engine, and there does not yet exist an acceptable theoretical model of turbulent flames or of the quench thickness of a turbulent flame impinging against a cold wall. The control of emissions of carbon monoxide, hydrocarbons, and nitrogen oxides is another factor which, with today's emission control procedures, is resulting in a loss of fuel economy. To increase fuel economy, attention is being focused on various new engines, such as the Stirling engine, the gas turbine engine, and the fuel cell. Also, new fuels are being tested. This article concludes that hydrocarbons are the most effective fuels, primarily because of storage considerations. Two general conclusions concerning the ic engine and the prospects for improving its efficiency are made. First, research and development should be directed toward improving the thermal efficiency of the Otto cycle ic engine, which presently has a 35 percent thermal efficiency. Second, research has shown that improvements in fuel economy are feasible, but engineering developments that can lead to a better fuel economy await the arrival of sufficient economic benefit to offset their initial cost.

  • Availability:
  • Corporate Authors:

    Massachusetts Institute of Technology

    Department of Civil Engineering, 77 Massachusetts Avenue
    Cambridge, MA  United States  02139
  • Authors:
    • Kummer, J T
  • Publication Date: 1975-2

Media Info

  • Features: Figures;
  • Pagination: p. 26-37
  • Serial:
    • Technology Review
    • Volume: 77
    • Issue Number: 4
    • Publisher: Massachusetts Institute of Technology
    • ISSN: 1099-274X

Subject/Index Terms

Filing Info

  • Accession Number: 00099738
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 30 1975 12:00AM