Determination of the amplitude of the friction forces variation inherent to a coastdown test (typical noise amplitude), comparing it with the aerodynamic drag force and raise the sensitive of the coastdown test to the variation of the vehicle coefficient of drag (Cd)

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.