VEHICLE EFFICIENCY: ROAD VS DYNAMOMETER. TECHNICAL REPORT

A series of steady-state tests was run on a 1976 Mercury Montego on a twin-roll dynamometer at the Environmental Protection Agency (EPA) and on the Transportation Research Center test track in Ohio. These fuel consumption tests were the first to measure wheel torque and vehicle speed, which are sufficient to calculate the work done by the vehicle. This can then be divided by the fuel consumed to give a measure of vehicle efficiency. Calculations show that the vehicle produced an average of 3612 joules/cc. fuel used (J./cc.) on the road for a vehicle efficiency of 11.3%. On the dynamometer, however, the average efficiency was 5430 J./cc. or 17.0%. Compared to the dynamometer runs, the vehicle consumed 34% more fuel on the road for the same amount of work. The dynamometer data represent a linear relationship between fuel consumed and energy extracted. A statistical t-test demonstrated a 99% confidence that the dynamometer efficiency was greater than that on the road. The observed fuel consumption difference could be explained by a direct temperature effect on the engine: the road tests were conducted at from 52 to 67 degrees F vs. 71 to 76 degrees F for the dynamometer tests. If vehicle engine operated under much richer fuel-air conditions at the lower temperature, this might explain the difference.

  • Corporate Authors:

    Environmental Protection Agency

    Emission Control Technology Division, 2565 Plymounth Road
    Ann Arbor, MI  United States  48105
  • Authors:
    • Grugett, B
  • Publication Date: 1979

Media Info

  • Features: References;
  • Pagination: 12 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00386634
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: EPA-SDSB-79-29, HS-029 187
  • Files: HSL, USDOT
  • Created Date: Jun 28 1984 12:00AM