Shift-time Limited Acceleration: Final Drive Ratios in Formula SAE

Even with relatively unrestrictive rules in the Formula SAE competition, established teams are fighting diminishing returns in vehicle mass and engine horsepower. The typical FSAE vehicle incorporates a six speed gearbox, yet reaches a (course-limited) top speed in competition of only about 110 kph. Selecting a final drive for this top speed would result in 5 gearshifts in less than 4 seconds. As a result, final drive ratio is very sensitive to shift delay time. Although vehicle mass, engine performance and traction still play a major role, a typical FSAE vehicle acceleration is significantly limited by the time it takes to complete a gearshift.