Optimizing Gear Ratio Selection for Lap Performance 2020-01-0543
The goal of this paper is to select the optimal gear ratios to determine the best overall lap time for a racing vehicle. Given a discrete set of individual gear ratio and final drive ratio options, the simulation chooses the set of gears and final drive that produce the minimum overall lap time. For example, one vehicle studied in this paper, an F2000 formula car, has 32 ratio choices for four forward gears and a final drive that has three different options. The simulation will iterate through the gear options to find the optimal gear selection for the best lap performance, accounting for various factors that could cause improper selection of gears. The simulation accounts for aerodynamic factors, gear shift time, rolling resistance and tire scrub. All values have been estimated from logged vehicle data, but experimental data can be easily used to help improve the vehicle model. Two vehicles were used in this simulation to compare the different types of racing and how that affects the gear selection. The first vehicle is the F2000 racecar, also called a Formula Continental. The F2000 car competes on a high-speed racetrack where aerodynamic loads will have a large effect. The second vehicle is a Formula SAE vehicle which competes on a relatively slow autocross track where traction will play a larger role and the aerodynamic effect will be lower. Because the Formula SAE car also has an event where lap performance and fuel efficiency are measured, the gear ratios are selected for solely lap performance and lap performance and fuel efficiency combined to see the comparison. The selection of the optimal gear stack should show where the optimal area to run the engine in the given RPM range.
Robert Frederick, Brandon Dixon
Univ. of Alabama, University of Alabama