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Doomed Dorito - 1986 Mazda RX7S Group S Prototype

Mazda - Doomed Dorito - 1986 Mazda RX7S Group S Prototype - Car History

Since 1982, the world of rallying had been all about a single letter: B. The Group B regulations freed up manufacturers to produce some of the most powerful and extreme designs ever seen on a world rally stage. With low homologation numbers (200 examples and 20 evolution models), it had become relatively easy for car companies to produce a fire-breathing rally special.

One of these companies was Japanese automaker Mazda. Like their compatriots Mitsubishi, they were a little late to the Group B game, as the RX7 GSL Rally had to wait until 1984 to make its debut. By then the advantages of four wheel drive systems had become painfully obvious, as pioneers Audi had already clocked in a constructor’s and a driver’s title, and Peugeot’s new machine was proving to be even faster.

Even the excellent Lancia Rally 037 was losing out, which meant the traditional production-based, rear wheel drive Mazda had little hope of succeeding. A single third place at the 1985 Acropolis Rally was all it could muster.

The Group B RX7 never stood a chance against its more advanced opposition.
The Group B RX7 never stood a chance against its more advanced opposition.

As the Group B RX7 was reaching its absolute peak, the FISA presented a way out for Mazda. Late in 1985 the governing body announced Group S, a formula intended to replace Group B. The ultimate goal of Group S was not to decrease speeds or limit power, but rather to expand on the formula and allow even more manufacturers to compete.

With Group S the FISA sought to bring down the cost of competing by shrinking down the homologation requirement to just ten cars, effectively creating a prototype class with even more design freedom than Group B had provided. The new regulations made it much easier and cost-effective to build a specialized rally weapon, as manufacturers no longer had to produce at least 200 road going models.

The new car had no real connection to Mazda's road car range.
The new car had no real connection to Mazda's road car range.

With the plans laid out, Mazda instructed its subsidiary, Mazda Rally Team Europe, to start design work on an all-new Group S prototype. MRTE was founded as private Mazda rally preparation business by West German driver Achim Warmbold in 1984, but was largely ignored by the Japanese company. By 1985 the Brussels-based team had gained full works support, and under Warmbold’s direction the RX7 GSL Rally finally scored its one and only podium.

The RX7S's chassis design was simple but effective.
The RX7S's chassis design was simple but effective.

As the incredibly low homologation numbers negated the need for a connection to any sort of road car, MRTE was able to start with a clean sheet of paper. This resulted in a steel spaceframe with a very loose connection to the contemporary FC3S- generation RX7. Naturally, this meant the car received one of Mazda’s trademark rotary engines.

In the older GSL model, this had been a naturally aspirated 2-rotor 13B engine, displacing the equivalent of 2.6L. The unit produced some 300 horsepower, but this was far from enough. Rival designs from Audi, Toyota, Peugeot, Lancia and MG-Rover all produced figures far above the 13B‘s capability. Seeking a cheap and easy solution for their prototype, MRTE turned to Mazda’s Group C program and lifted the 3-rotor, 2L 13G R3 engine from the 757 endurance racer.

The 757 provided proper motivation for the Group S project.
The 757 provided proper motivation for the Group S project.

The swap provided the Group S machine with 450 horsepower and 404 nm (298 lb ft) of torque right out of the box, and the potential to gain much more. Like all rotary designs, the 13G benefited from extremely compact dimensions, which allowed MRTE to fit it behind the front axle line to improve weight distribution. This made the RX7S one of the few Group S cars with a front-mid engine layout, as even Audi was in the process of converting to a rear-mid configuration.

The 3-rotor 13G engine was compact enough to be mounted in a favorable position.
The 3-rotor 13G engine was compact enough to be mounted in a favorable position.

The unusual location for the engine was justified by its diminutive size and weight, and the fact it made the design of a four wheel drive system much more simple. With the engine in the front the layout of the five-speed manual gearbox and its many differentials was much more straightforward.

Not stopping there, the team fitted an experimental four wheel steer system to improve the car’s agility in tight rally stages. Suspension-wise, the car featured double wishbone suspension supported by dual coilovers on all four corners to help negotiate harsh terrain at break-neck speed.

Contrary to most Group S designs, the RX7S was front-engined.
Contrary to most Group S designs, the RX7S was front-engined.

The car’s bodywork was made up of light reinforced plastics, and featured two giant clamshell-sections front and rear, which gave easy access to vital components like the engine and suspension systems. In an effort to keep the front end as light as possible, the radiator, oil cooler and transmission/differential coolers were moved to the rear of the car right behind the driver’s compartment.

A system of intakes integrated into the roof and C-pillars made sure these coolers received their much-needed supply of fresh air. Curiously, RX7S also inherited the unusual single centrally mounted windshield wiper arrangement from the 757 Group C prototype.

Unlike rival designs, the RX7S sported didn't sport any large wings.
Unlike rival designs, the RX7S sported didn't sport any large wings.

Apart from the massively wide wheel arches, the RX7S’s overall design was rather subdued. There were no large aerofoils and splitters to be seen, as the Mazda instead relied on a subtle ducktail spoiler which double as ventilation for the rear clamshell.

Additionally, a hood scoop was fitted to feed the hungry 3-rotor engine. The final version vaguely resembled Ford’s RS200 from the front, and bore a likeness to the Mk3 Escort from the rear, resulting in a very strange overall look. In all, the finished car weighed just 950 kg (1433 lbs).

The RX7S during a private test at Eurocircuit Valkenswaard, 1987.
The RX7S during a private test at Eurocircuit Valkenswaard, 1987.

In total secrecy, just two examples of the ground-breaking car were produced. MRTE conducted extensive testing to ensure the car would be ready for Group S’s 1988 debut, which included a trip to Eurocircuit Valkenswaard, a motocross and rally cross complex in the Dutch province of Noord Brabant.

Valkenswaard, 1987.
Valkenswaard, 1987.

Sadly the car was made obsolete after the cancellation of both Group B and Group S following the lethal accidents of Joaquim Santos at Rallye Portugal, and Henri Toivonen and Sergio Cresto at the Tour de Corse in 1986.

The tyrannical FISA-president Jean Marie Balestre cancelled the plans for Group S on the grounds of it being too dangerous, and moved to promote the lesser Group A to the pinnacle of world rallying. His brash decision made him fall foul of several teams working on Group S racers, and the mounting political pressure saw him go back on the ban in September 1987.

Mazda - Doomed Dorito - 1986 Mazda RX7S Group S Prototype - Car History

This time Balestre sought a compromise by restricting the use of large aerodynamic aids, limiting power to 300 horsepower, displacement to 1.2L (turbocharged) and 2.4L (naturally aspirated) and requiring a 1000 kg minimum weight to prevent the use of fragile and flammable materials.

The new plan was met with some approval, but the volatile Frenchman shifted his point of view again shortly after the announcement, and killed Group S for good. As a result the innovative Mazda RX7S never got a chance to shine even in restricted form, and its existence remained unknown until one surviving example made an appearance at the Nostalgic 2 Days autoshow 27 years later in the hands of a private Japanese collector.

Mazda - Doomed Dorito - 1986 Mazda RX7S Group S Prototype - Car History

The Mazda RX7S was the company’s highly advanced and ambitious attempt to finally reach the top in the world of rallying. After experiencing indifferent results with the traditional rear wheel drive car, Mazda saw the ideal opportunity to move into a higher level with the advent of Group S.

The Japanese firm grabbed this golden opportunity with both hands, and commissioned a next-generation rally monster from their friends in Belgium. Mazda Rally Team Europe duly delivered with a spectacular four wheel drive, four wheel steer 3-rotor machine, but the project was cut short by a succession of tragedies and political strife. With the incredible amounts of technology hidden under the humble grey plastic body, one can only wonder what the RX7S could have achieved.

Check out Rally Group B Shrine for more exciting Group B/Group S machinery.