For the 1991 season, Nissan upgraded their cars into the R91CPs, while some older cars were sold off to privateers.
 Nova Engineering upgraded their R90C to R91CK specification utilizing the Yatabe (Japan Automobile Research Institute—JARI) wind tunnel, while Team Le Mans bought an R90CP and modified it into their own R91VP.
 Keeping the same driver line-up as the previous season, the factory Nissan team proved the pace of the new R91CP by winning the opening round at Fuji, while the Nova Engineering entry took second, and Team Le Mans fourth.
 The second race at Fuji saw Nissan's main rival, Toyota, debut their new 91C-V, yet it would not be capable of fighting the R91CPs.
 Nissan took the top two positions with their factory cars, a lap ahead of the new 91C-V.
By the third race at Fuji however, Toyota was able to improve their new car and take their first overall victory of the season, leaving Nissan to settle for second place, ten seconds behind, while the second team car was taken out in an accident.
 The 1000 km Suzuka saw further problems for the team as the Nova Engineering entry actually took second place ahead of the factory entry in third, several laps behind.
 A similar event occurred at the next round, with Nova Engineering ahead of Nissan, yet all cars managed to finish on the same lap as the winning Toyota.

Nissan managed to overcome Toyota at the 1000 km Fuji, winning by a minute even though the other three Nissans in the field were unable to finish.
 However, newcomer Jaguar would manage to take victory at the final race of the year, leaving Toyota in second and Nissans in third and fourth, several laps behind the dominant Group C car.
 Even with its troubles, Nissan was able to overcome Toyota in the points championship, winning by three points.
 Kazuyoshi Hoshino and Toshio Suzuki won the drivers championship by a mere two points over Toyota's leading pair.
For the 1991 season, Nissan upgraded their cars into the R91CPs, while some older cars were sold off to privateers.  Nova Engineering upgraded their R90C to R91CK specification utilizing the Yatabe (Japan Automobile Research Institute—JARI) wind tunnel, while Team Le Mans bought an R90CP and modified it into their own R91VP.  Keeping the same driver line-up as the previous season, the factory Nissan team proved the pace of the new R91CP by winning the opening round at Fuji, while the Nova Engineering entry took second, and Team Le Mans fourth.  The second race at Fuji saw Nissan's main rival, Toyota, debut their new 91C-V, yet it would not be capable of fighting the R91CPs.  Nissan took the top two positions with their factory cars, a lap ahead of the new 91C-V.
By the third race at Fuji however, Toyota was able to improve their new car and take their first overall victory of the season, leaving Nissan to settle for second place, ten seconds behind, while the second team car was taken out in an accident.  The 1000 km Suzuka saw further problems for the team as the Nova Engineering entry actually took second place ahead of the factory entry in third, several laps behind.  A similar event occurred at the next round, with Nova Engineering ahead of Nissan, yet all cars managed to finish on the same lap as the winning Toyota.
Nissan managed to overcome Toyota at the 1000 km Fuji, winning by a minute even though the other three Nissans in the field were unable to finish.  However, newcomer Jaguar would manage to take victory at the final race of the year, leaving Toyota in second and Nissans in third and fourth, several laps behind the dominant Group C car.  Even with its troubles, Nissan was able to overcome Toyota in the points championship, winning by three points.  Kazuyoshi Hoshino and Toshio Suzuki won the drivers championship by a mere two points over Toyota's leading pair.
Nissan R90C