WLTP – On the increased importance of aerodynamics and impact on development procedures

For some years a new test procedure has been developed among the UN for the determination of pollutant and CO₂ emissions and fuel consumption, which should represent the average customer behaviour. Beside the EU various other countries are involved (e.g., India, Japan). The test procedure WLTP and the underlying driving cycle WLTC was developed with the help of worldwide accumulated driving data and covers driving situations from city up to highway traffic.Beside the driving cycle also the consideration of optional extra equipment for the CO₂ and consumption determination is a reason for the increasing work load on aerodynamics. Compared to today the influence of the aerodynamic drag on the whole consumption will increase with the introduction of WLTP. In addition, this generally increases the development and test expenditures of the OEMs – not only in aerodynamic development. Decisive for the future expenditure increase in the aerodynamics development due to the type approval procedure of all vehicle variations will be whether these are measured in coast-down tests like today, or whether suitable CO₂ determination methods will be used which enclose wind tunnel measurements and CFD.