 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.