The new Porsche wind tunnel was built in three years from 2011 and 2014. In the meantime, Porsche decided to build two reference cars, so as to be able to compare the pressure distribution on the vehicle surface, both on the road and in the wind tunnel.
The concept of having a reference car to compare results on the road and in the wind tunnel is not new. In the case of Porsche, the choice of the vehicles was guided by two requirements, i.e. to have a car shape typical of the Porsche family and to produce different blockage effects.
The cars were equipped with the best available instrumentation, which was carefully calibrated in order to insure accuracy and repeatability.
Multiple road tests and measurements in various state of the art wind tunnels, with different moving ground simulation systems and different geometries, were then carried out.
As a result of the post processing of these data, it has been possible to recognize interference effects in the various wind tunnels.
Porsche has then used these vehicles in the calibration phase of the new wind tunnel, so as to reach a flow quality, in terms of time-averaged values, that is as close as possible to conditions experienced on the road.
Furthermore, thanks to the interchangeable moving ground system in the new Porsche wind tunnel, the reference cars were able to show clearly, for the same wind tunnel interferences, the differences in the pressure distribution caused by the two different moving ground systems.
In addition, thanks to the high-quality 5 belt system, it was possible to measure the cD_vent (ventilation drag), necessary to improve the prediction of Fx in coast-down tests. A comparison between wind tunnel and coast-down results was carried out and will be shown.
