Passenger Vehicle Hill Coast-Down Math Model

Abstract

Our mission is a comparative evaluation of passenger vehicle hill-coast-down and vehicle EPA city-hwy (mpge) (mile per gallon equivalent) driving simulation test procedures. Based on h ill-coast-down distance-velocity vs time test data, respectively, a mathematical model was developed to estimate vehicle aerodynamic (Cd) drag coefficient. Hill-coast-down test data was obtained for: a Conventional bike, Olympic bike, 4dr Buick Park Avenue, 4dr Buick Lucerne, Ford Mercury Mountaineer SUV. Test data correlated with our predicted math model coast-down performance curves. We concluded, math model developed by this study was fundamental. Consequently, math model may be applied to a wide range of vehicles, e.g., Olympic bike and rider (84kg) to Ford SUV (2000kg). Further, the theoretical coast down math model equation coefficients were found to be easily derived given vehicle design parameters: test mass, tire and aerodynamic drag coefficients, vehicle flat plate frontal area, coast down hill gradient, and atmospheric temperature plus barometric pressure. Our mission includes an ongoing program to develop EPA city-hwy driving schedule mathematical models (to predict passenger vehicle ideal mpg at 100% overall (o/a) drive train to tire -road interface efficiency). However, scope of this report is limited and confined to development of the hill-coast-down mathematical model plus correlation with observed coast down test data. The EPA model is the subject of another report.