 Although part of the IMSA GT Championship which was usually contested by Nissan's GTP ZX-Turbo, it was decided that the R90Cs were better suited for the Daytona endurance.Three R90CKs were entered in 1991 by NPTI under an invitational class for Group C cars.Although two failed to finish, the R90CK of Bob Earl, Derek Daly, Chip Robinson, and Geoff Brabham managed to finish first in class and in second place overall, although 18 laps behind the winning Joest Racing Porsche 962C.