The aim of this paper is to identify and investigate the effect of small changes in test conditions when quantifying fuel consumption. Twelve test set-up variables were identified and intentionally perturbed from a standard condition, including the effect of removing the power-assisted steering pump. Initially, a design-of-experiment (DoE) approach was adopted and the results showed that most of the tested parameters (namely, the battery state of charge, engine oil level, pedal busyness, speed error, road fan speed, vehicle alignment, tyre type, tyre pressure, and simulated vehicle mass) had significant effects on fuel consumption. Most of these effects were greater than the effect of typical technology changes assessed on chassis dynamometer facilities. For example, an increase of 8.7 % in fuel consumption was observed following a 90 minutes battery discharge from vehicle headlamps. Similarly, an increase of 5.5 % was observed when the rig was run 3 km/h faster over a drive cycle, and 2.6 % when using tyres deflated by 0.5 bar. Interestingly, the engine start temperature had no significant effect on fuel consumption. As a consequence, statistical tolerancing was used to suggest typical tolerances for test rig set-up variables. For example, it was recommended that the tyre pressure be controlled to within 0.1 bar, simulated vehicle mass to within 50 kg, roadspeed fan speed to within 20 % of the calibrated value, and the test rig speed to 0.3 km/h. Further investigations were conducted into the effect of battery discharge, coast-down time, and engine cooling. These highlighted the need for rigorous battery charge management as the battery voltage was found not to be an appropriate measure of the variation in the alternator loading. A better way of assessing excessive engine loading is to monitor the energy flow into the battery using current clamps. Coast-down time was found to be a good control measure for a number of set-up variables affecting the rolling resistance of the vehicle. Finally, the variations in the engine cooling were quantified using a cumulative engine temperature over a drive cycle. This was found to correlate well with fuel consumption. For each of these subsequent investigations, results were compared with the DoE predictions and found to agree well when considering the relatively low number of tests compared with the number of factors.


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    Title :

    Increasing accuracy and repeatability of fuel consumption measurement in chassis dynamometer testing


    Additional title:

    Steigerung der Genauigkeit und Reproduzierbarkeit von Kraftstoffverbrauchsmessungen auf Rollenprüfständen


    Contributors:
    Brace, C.J. (author) / Burke, R. (author) / Moffa, J. (author)


    Publication date :

    2009


    Size :

    15 Seiten, 13 Bilder, 6 Tabellen, 13 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English