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A dynamic vehicle simulation has been developed to predict straight-line acceleration of a traction limited, manual transmission vehicle that is capable of high rates of tire slip. The simulation incorporates an empirical non-linear curve which predicts tire friction as a function of tire slip. A vehicle is tested to compare and correlate simulated performance to actual performance, and the simulation is shown to be accurate. The model is then exercised to predict the impact of vehicle design on performance. All major systems of the vehicle are extensively studied, including vehicle weight, center of gravity location, aerodynamic drag coefficient, and drivetrain ratios, inertias, and efficiencies. These studies indicate that the most influential parameters on 0-60 MPH times (other than horsepower) are tire friction, rear weight bias, engine inertia, and total vehicle weight.

Typical vehicle dynamics simulations demand a trade-off between short computation times and accuracy. Many of the more simple models are based on the kinematic roll center and the more accurate models tend to be multi-body dynamics simulation programs. There is a need for a model that improves the accuracy of the kinematic roll center models while still maintaining short computation times. Such a model could be used track-side during races to guide race teams toward improved handling. The model presented in this paper removes many of the assumptions and limitations of the kinematic roll center model. The model accounts for three-dimensional forces present at the contact patch and predicts deflections of suspension components. The modeling approach is applied to a NASCAR Craftsman Truck to predict the effects of suspension design and tuning on steady-state understeer characteristics of the vehicle. Braking and acceleration forces can also be applied to the vehicle.

A dynamic simulation has been developed to predict the acceleration of a manual-transmission vehicle at wide-open throttle. A notable feature of the model is that tire slip is included, and the coefficient of friction varies with slip. This allows the simulation to start from zero vehicle speed and include the dynamics of gear shifting. The model was used in optimization studies for 3-speed, 4-speed, and 5-speed transmissions which indicated that fastest times, for the vehicle studied, are obtained when the mass center is as close to the drive axle as possible, and gear ratios are selected so that the engine speed brackets the horsepower peak. Also, optimal gear ratios deviate slightly from a geometric progression by closer spacing in higher gears and wider spacing in low gears, a common practice in gear box design.