Prof. Hausberger (TU Graz) presented the work program of the Institute for Internal Combustion Engines and Thermodynamics (IVT) at the TU Graz. He started with a review of vehicle related data needed for the modelling approach. To this purpose he modelled the WHVC for a large variety of conventional HD vehicle categories. As a result, WHVC leads to similar engine loads as WHTC for all tested vehicles (see slide 8). Deviations against WHTC are rather low for criteria pollutants (NOx ± 6 %, PM ± 25 %) and fuel consumption (± 2.5 %) for conventional engines (see slide 9). Influence of vehicle mass and air drag, simulated within ± 15 %, on NOx and fuel consumption was also < 2.5 % (see slide 10).

In order to reduce testing burden, IVT is proposing a “WHTC-corresponding” power cycle at the wheel hub. This would allow a vehicle independent approach and an agreement of powerpack load between HILS and conventional engine tests. Negative driving power has to be adapted against WHTC to account for mechanical braking. This approach also allows to consider PTO and auxiliaries, which are not engaged in engine tests. But for this option, PTO and auxiliaries would have to be simulated in HILS. The approach replaces power demand simulated in the HILS simulator by WHTC power demand. Either Pengine or Pdrive would be possible, but Pdrive would be the better approach. The calculation of Pdrive is shown in slide 14. Best interface for this replacement seems to be the driver model via relation gas pedal position and desired power, as shown in slide 26 of working paper HDH-07-04. The resulting cycle work (kWh) would then be the total system work and not just engine work, but Δ SOC must remain neutral over the cycle.

Japan has some concerns, but agreed to consider the approach. The Japanese understanding and response is given in working paper HDH-07-10. It was agreed to resume discussion at the 9th HDH meeting upon further information by TU Graz and Japan.

As regards PTO operation, it was agreed to use the US data for the time being.

As regards the WHVC weighting factors, IVT is proposing to use the PHEM model of IVT to simulate representative real world cycles and the WHVC for different vehicle categories. Weighting factors for WHVC sub-cycles would then be elaborated, which give similar cycle parameters as the representative real world cycles per HDV category. An example is shown in slide 20. The modelling would start with the three WHVC subcycles (urban, rural, motorway). The proposed method was agreed by the group.