1992 Mazda RX-792P

To compete at the highest levels of motorsport competition, it takes experience, a competitive edge, and skill. Mazda enjoyed a very successful and impressive season in 1991, with an outright win at LeMans and the IMSA GTO Championship in North America. It had also learned a lot from running the MX-6 in the GTU class and enjoyed much success with that program. With these accomplishments, the team made the decision to contest the more-competitive Grand Touring Prototype (GTP) class for 1992, where it would race against Nissan, Toyota, Porsche, and Jaguar.

Such a bold and daring move required a new racing car. Engine rules changes by the FIA forced Mazda to abandon their R26B 4-rotor in the World Sportscar Championship, however, IMSA rules continued to allow the use of rotaries. This led Mazda to bring the R26B to North America. The engine was modified to better suit the shorter races and circuits.

Crawford Composites was tasked with constructing the tub, with the assistance of Fabcar. The end result was a car that shared little with its predecessor, the 787B, due to the differences in the racing program. The tub was constructed from carbon fiber. Lee Dykstra, of Jaguar Group 44 fame, headed the design team tasked with creating the bodywork. Randy Wittine was given the primary responsibility for the development of the exterior design. Instructions were given to incorporate style elements of the third-generation RX-7 road-going car, which was soon to be released. This was a difficult task, but several small design cues were able to be incorporated. The end result was an enclosed coupe that had sweeping lines and a large exposed vent flowing out from the front wheel well.

The front suspension setup was comprised of double wishbones and push-rod actuated springs and dampers. In the rear, the setup was a little more complicated as it shared the same space as the ground-effect tunnels. Trying to avoid the ground-effect tunnels altogether proved to be an impossible task. In the end, many of the suspension components were able to be mounted above the tunnel, but a good solution could not be found for the lower wishbones and driveshaft and were mounted in the tunnel.

Mounted mid-ship longitudinally as a stressed part of the chassis was the LeMans winning four-rotor 'R26B' engine. This was the same powerplant found in the 1991 IMSA GTO-winning RX-7. The engine featured four variable intake trumpets and was fitted with an electronic fuel injection system. The engine was paired with a March five-speed gearbox and braking was controlled by cross-drilled ventilated disc brakes at all four corners.

Mazda's new GTP competitor was named the PX-792P. One example was completed in time for the Miami Grand Prix at Homestead. As would be expected, there were significant unforeseen problems. The most immediate was with the exhaust system. When the fumes exited the system, they were tremendously hot and caused deterioration to the carbon-fibre tub, and eventually, the car caught on fire. The next race the car contested, it failed to qualify due to its exhaust system producing over 108 dB, the maximum allowed.

These issues were resolved for the car's third race - Road Atlanta. The team had fitted a resonator to combat the noise. To reduce heat, the muffler was coated on the inside and cooling was improved.

At Road Atlanta, the first car was joined by a second RX-792P. The Mazda RX-792P qualified 9th and would finish 15th. Finishing the race was a satisfying accomplishment, but it was hardly the success envisioned by the team. Further work was needed to help it keep pace with the twin-turbocharged NPi Nissans and Toyotas.

One of the next improvements to the Mazda was a twin-tier rear wing used to increase downforce. Though a smaller improvement, it did help the team score a 3rd and 4th place finish at Lime Rock and a very impressive 2nd place at Watkins Glen. These would prove to be highlights for the RX-792P, as much of the remaining season was met with disappointment, mostly due to mechanical problems and accidents.

1992 had been a disappointing season, even with the occasional podium finishes. Mazda North America decided to soldier on, continuing work in preparation for the 1993 season. A third tub was created and built to accept a smaller three-rotor engine. This was built for a customer who intended to compete in the IMSA Lights category. Sadly, Mazda Japan ceased the rotary racing program at the close of 1993 and by then, nearly every racing series had banned the powerplant.

Mazda had proven to have the skill and experience to compete in the highly competitive and well-contested GTP category, and they even opted to use an unconventional powerplant. Where they fell short was in the development of the car. They had proven that they could compete, scoring impressive finishes at Lime Rock and Watkins Glen. With more time, development, and a larger budget (they were operating at a fraction of what other teams had), the car may have been a serious contender.

by Daniel Vaughan | May 2011