AN EXPERIMENTAL ASSESSMENT OF THE EFFECT OF OVERALL GEARING ON THE ECONOMY OF A CAR

The subject of the present investigation was the effect of overall gearing on the fuel consumed by a typical family saloon car. There are several ways in which the overall gearing of a car can be raised without too much difficulty, the easiest being a change to tyres having a larger effective rolling radius. Such a change usually permits only a modest gain in overall gearing because of the limited range of tyre sections which can be accommodated within existing wheel-arches. A second, relatively-simple method involves a change in final-drive ratio, a modification which can be easily incorporated on the assembly line if the tooling for production is available. The third way in which the objective could be achieved is by the use of an overdrive. Generally an overdrive does not operate on all the normal gear ratios, but is used on the upper ones to give greater economy and reduced engine speeds whilst cruising. However, for the test car chosen, the output torque in first gear was within the transmission capability of the overdrive unit and therefore it was used as a device to give a completely different set of ratios and not strictly as an overdrive, thus extending the scope of the investigation into the effect of higher final-drive ratios. This report concerns the efficacy of these methods of reducing fuel consumption. /TRRL/

  • Corporate Authors:

    Ministry of State, England

    Department of Industry
    London,   England 
  • Authors:
    • Spencer, RRH
    • Dodd, A E
  • Publication Date: 1977

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 18 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00179190
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Monograph
  • Files: ITRD, TRIS
  • Created Date: Sep 27 1978 12:00AM