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This paper has the objective to present the study of typical friction forces variation (noise) on a vehicle coastdown test @ 110 km/h, correlate with the drag force raised in wind tunnel and finally compared them to determine the sensitivity of Cd variation which can be detected on an “A to B” coastdown test procedure. As “A to B”, comparison test means testing the vehicle with a known aero Cd compare to another one, creating real technical parameters. For this study, we used real data from certification coastdowns tests for a same vehicle configuration in the most controlled possible conditions (all tests performed in CAPG track facilities) and real vehicle aerodynamic data raised from the wind tunnel.

Automakers are seeking more efficient and green vehicles projects in terms of fuel consumption and CO2 emissions. Several factors are directly related to the performance and one of the most important is the aerodynamics. Cars with smooth geometries and transitions are expected to have a better aerodynamic behavior compared with the ones with rough geometries. Regardless the vehicle geometry changes, another way to improve the aerodynamics is by adding new parts, in order to improve the drag coefficient of the car. Most of the time, these parts are added but the functionality is not well defined. The main objective of this work is to identify, explain the way it should work and some applications of additional aeroparts. Those parts could be assembled in a vehicle in order to improve the drag coefficient, have a better fuel economy and lower emissions rate.