Effect of Ambient Conditions on the Measured Top Speed of a Winston Cup Car

The measurement of the top speed of a racecar on a test track is commonly used in the aerodynamic development of the car and as a verification of wind tunnel results. The speed differences resulting from typical drag and lift changes will be small, requiring precise (i.e. repeatable) speed measurement. Unfortunately, changing environmental conditions over one or several days of trials will make these results unreliable at the required level of accuracy. This paper discusses the errors encountered in top speed testing and suggests methods to improve accuracy.