This article explains why slower running of goods vehicle engines substantially reduces their fuel costs. The fuel consumption charts, published by every engine manufacturer, show that, at the upper end of the vehicle's speed range, the specific fuel consumption curve curls upwards in a 'scorpion tail'; this means that more fuel is used for each unit of motive power produced. If the rpm of the engine is reduced to a lower, more efficient figure, not only is the consumption per horse power much less, but also less horse power is used at greater torque, thus achieving a double saving. The best economies are obtained while using an engine around the middle of its speed range, on full or part-load running. A typical fuel consumption chart shows curves of constant fuel efficiency, over a range of engine speed and load, thus indicating clearly the best speed-load combinations. The article discusses possible ways of ensuring that drivers keep within the most effective rev limits. One approach is daf's visar monitoring system, which displays to the driver whether he should increase or decrease his revs. Road speed limiters are not entirely effective, as they do not limit engine speed. An increasing number of goods vehicle operators use engine-speed recording tachos, which can record drivers' performance and show where their behaviour costs extra money. Discussion of a numerical example shows that poor driving can lead to extra fuel costs per goods vehicle of order 3000 per year, with little benefit in return.

  • Corporate Authors:

    FF Publishing Limited

    97 Earls Court Road
    London,   England 
  • Authors:
    • KENNETT, P
  • Publication Date: 1989-5


  • English

Media Info

  • Pagination: p. 95,97,99
  • Serial:
    • TRUCK

Subject/Index Terms

Filing Info

  • Accession Number: 00498779
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Sep 30 1990 12:00AM