The Nissan R90C was a platform used for Group C racing cars built in 1990 by Nissan Motors for competition in World Sportscar Championship (WSC) based in Europe and the All Japan Sports Prototype Championship (JSPC). The cars based on the basic R90C platform would compete until 1993 before Nissan chose to withdraw from sports car racing, not returning until 1997. It won three JSPC championships and several significant endurance races during its career.
Development
Mechanically, the R90Cs shared much with their predecessor, the R89C. Most of the chassis construction was the same, as well as the mechanical layout. The Nissan VRH35Z 3.5 litre twin-turbo V8 that debuted in the R89C was successful and kept as part of the R90C's design. Although mechanically similar, the cars were nearly all new constructions. Chassis builder Lola Cars International termed the cars T90/10, succeeding the T89/10.
Unlike the R89C, Nissan felt the car was a compromise. This led Nissan to develop two different cars. Although Lola built the basic chassis, Nissan Motorsports Europe constructed the R90CK in its shops evolving the R89C design. At the same time, the R90CP was built at Nismo's headquarters in Japan in a lower downforce, high speed layout. This gave the two cars a noticeably different design.
R90CK
The R90CK was an evolution of the R89C's design, borrowing many stylistic elements. The front end of the car was low, with two deep channels on either side of a slanted nose leading to radiator inlets on the sides of the cockpit. Small slated inlets were placed on the leading edge of the car, partially feeding brake cooling ducts. The cockpit featured a longer raked windshield than the R89C, yet the areas around the cockpit remained nearly identical, including the sides of the car. At the rear, the rear wing was mounted high on exposed struts for better downforce.
The design and development of NPTI's R90CK was conducted in association with Ray Mallock Limited and the cars were prepared and run out of RML's workshop in 1990, before being shipped to the United States to take part in the 1991 24 Hours of Daytona.
R90CP
The R90CP ("P" referring to the Oppama Nissan plant where Nismo is based) had a low downforce design. The front of the car featured a higher nose, with the narrow channels eliminated and replaced with large ducts on the inside of the fender. The fenders themselves were also redesigned, with headlights placed vertically instead of the horizontal design on the R89C and R90CK. The cockpit of the R90CK was identical to its R90CP sibling, yet the sides of the bodywork were changed. Most notably, the rear-view mirrors were integrated into the bodywork on the fender, instead of small exposed mirrors on the side of the windshield. The turbo inlet was placed on the front edge of the rear fender, instead of on top of the engine cover on the R90CK. The rear wing was placed much lower on the car, with the rear wheel fender bodywork extending to connect with the rear wing endplates, similar to a style used on the Nissan GTP ZX-Turbo in North America.
Later versions
For 1991, Nissan officially withdrew from the World Sportscar Championship. Nismo continued competition in the All Japan Sports Prototype Championship, and decided to upgrade the R90CPs to better compete with Toyota and Mazda. The new cars, known as R91CP and R91VP, had slight modifications over the previous car. Most notably, the boxy turbo inlets placed on the rear fenders of the R90CP were made into smaller slits, while a large snorkel was added to the top of the engine cover to cool the rear brakes in place of the previous twin brake ducts. The cars were further modified for 1992 with an upgraded VRH35Z twin-turbo V8, while the cars were renamed R92CP.
Nissan ran the R90CKs at the 24 Hours of Daytona following their retirement from the World Sportscar Championship at the end of 1990. For the 1992 running of Daytona, the R90CK's VRH35Z engines were replaced with smaller 3.0L twin-turbo V8s. They were not as successful as the race-winning R91CP.
There were three additional unique R90Cs. One was a R89C upgraded to become a R90CP, originally used by Nissan in the JSPC before all cars were completed. Nova Engineering purchased chassis #07 from Lola and initiated their own upgrades to the chassis, calling the car a R91CK. The final modified car was a R90CP bought by Team Le Mans and modified into the R91VP. The cars featured minor aerodynamic differences from the other R90CKs and R90CPs.