ABCD - An Improved Coast Down Test and Analysis Method

An improved coast down method that incorporates the input of data measured with an onboard anemometer into the governing equation of motion is used to evaluate models representing the aerodynamic and mechanical drag characteristics of a wide variety of vehicles. Results from the application of the improved technique are presented to demonstrate the repeatability and precision of the analyzed aerodynamic drag coefficients, to address the merits of different wind tunnel blockage correction methods, to illustrate the method's usefulness in the study of tractor-trailer and light truck-travel trailer aerodynamic drag, to evaluate the influence of floor blowing in wind tunnel studies of the effects of various changes to the underbody of an automobile, and to compare track and dynamometer determinations of the variation of mechanical drag with speed on a vehicle equipped with a four-speed automatic transmission.