The Mazda Cosmo Sport 110S Story

The Impossible Engine

In the late 1950s, the Wankel rotary engine was supposed to be the future of the internal combustion engine. Invented by Felix Wankel and developed by NSU in Germany, the rotary promised a revolution: fewer moving parts, smoother operation, higher power-to-weight ratio, and a compact design that would transform automotive engineering. Dozens of manufacturers licensed the technology, General Motors, Mercedes-Benz, Citroen, Rolls-Royce, Toyota, Nissan, and a small, relatively obscure Japanese company called Toyo Kogyo, which the world would later know as Mazda.

Most of those licensees gave up. The rotary engine had a fatal flaw that no one could solve: the apex seals. These small strips of metal ride on the tips of the triangular rotor, sealing the combustion chamber against the epitrochoid housing. In theory, they work like piston rings. In practice, they wore out with terrifying speed. NSU’s own Wankel-powered Spider and Ro 80 were plagued by engine failures, owners were replacing engines at 30,000 km. The industry consensus by the mid-1960s was that the Wankel rotary was an elegant concept that could not be made reliable enough for production.

Mazda disagreed.

Kenichi Yamamoto and the 47 Engineers

The man who saved the rotary engine was Kenichi Yamamoto, a Mazda engineer who was assigned to lead the company’s rotary development programme in 1963. Yamamoto assembled a team of 47 engineers, a number that became legendary within Mazda, and set them to work solving the apex seal problem. The team worked with an intensity that bordered on obsession, testing hundreds of seal materials, dozens of housing coatings, and countless geometric variations.

The breakthrough came through a combination of innovations. Mazda developed a cross-hollow apex seal design that allowed the seal to maintain contact with the housing across a wider range of temperatures and pressures. They experimented with carbon-impregnated aluminium seals, then moved to cast iron and eventually to chrome-plated steel. They developed a housing surface treatment, a sprayed composite coating, that reduced friction and wear. And they designed an oil metering system that injected precise quantities of lubricant directly into the combustion chamber.

None of these innovations alone solved the problem. Together, they transformed the rotary from an unreliable curiosity into a viable production engine. Yamamoto’s team had achieved what NSU, with its head start and European engineering resources, could not.

The Cosmo Sport, Birth of a Legend

Mazda chose to debut their rotary engine in a car that matched its revolutionary nature. The Cosmo Sport, named for the Space Age that was captivating the world in the mid-1960s, was a purpose-built sports car, not a rotary engine dropped into an existing model. Its design was striking: a long bonnet, a low roofline, a sweeping fastback profile, and a cockpit that looked like it belonged in a science fiction film. The dashboard featured a prominent tachometer, aviation-inspired switchgear, and a design language that communicated modernity and ambition.

The car was first shown to the public at the 1964 Tokyo Motor Show as a prototype. Development continued for three years, Mazda was determined to launch a car that worked, not a car that merely existed. During this period, the engineering team subjected the 10A engine to extensive endurance testing, including a gruelling 84-hour continuous run at the Miyoshi Proving Ground in Hiroshima prefecture.

Production began on 30 May 1967 at Mazda’s Hiroshima factory. The first Cosmo Sport, chassis number L10A-10001, rolled off the line and into history. Mazda had beaten NSU’s Ro 80 to production, the Ro 80 wouldn’t launch until October 1967, making the Cosmo Sport the world’s first twin-rotor production car.

Series I, The L10A (1967-1968)

The initial production Cosmo Sport, designated L10A, was a handbuilt low-volume sports car. Just 343 were produced. The car was powered by the Type 10A engine, a 982cc twin-rotor producing 110 horsepower at 7,000 rpm and 130 Nm of torque at 3,500 rpm. These were remarkable numbers for a sub-litre engine in 1967.

The L10A had a wheelbase of 2,200 mm, weighed just 940 kg, and featured a distinctive split rear window. The body was constructed from hand-finished steel panels, and the level of craftsmanship reflected the car’s status as Mazda’s flagship. The transmission was a four-speed manual, and the suspension combined wishbones at the front with a De Dion tube rear, a sophisticated arrangement more commonly found on racing cars.

Performance was respectable: 0-400 metres in 16.3 seconds, with a top speed of 185 km/h. More importantly, the engine was smooth, willing to rev, and, crucially, reliable. The Cosmo Sport was not just a technology demonstrator. It was a real car that real people could drive without fear of catastrophic engine failure.

The L10A was sold exclusively in Japan. Prices were high, ¥1,480,000, roughly equivalent to a Jaguar E-Type in the Japanese market, and production was limited. Mazda was not trying to make money on the Cosmo Sport. They were proving a point.

Series II, The L10B (1968-1972)

In late 1968, Mazda revised the Cosmo Sport with a longer wheelbase (2,350 mm), a more conventional single-piece rear window, a five-speed manual gearbox, and a revised 10A engine producing 128 horsepower. The Series II car was slightly larger and more refined than the L10A, with improved interior appointments and better luggage space.

The L10B was produced in larger numbers, approximately 833 units, but was still a low-volume, hand-assembled car. It remained exclusive to the Japanese domestic market.

The Series II improvements addressed some of the L10A’s limitations. The five-speed gearbox gave better highway cruising, the longer wheelbase improved stability, and the additional 18 horsepower made the car genuinely quick for its era. The L10B could reach 200 km/h, serious speed in the late 1960s.

The Cosmo Sport in Competition

Mazda entered the Cosmo Sport in the 1968 Marathon de la Route at the Nurburgring, an 84-hour endurance race on the full Nordschleife circuit. Two Cosmo Sports were entered, competing against established European GT cars. One car retired with mechanical issues, but the second car finished fourth overall, completing the gruelling event and demonstrating the 10A engine’s durability under the most demanding conditions imaginable.

This result was transformative for Mazda’s reputation in Europe and gave the company confidence to pursue a full-scale motorsport programme with rotary-powered cars. The Marathon de la Route result led directly to the development of the Mazda R100, the RX-2, and the RX-3, the car that would conquer Bathurst.

The Australian Connection

The Cosmo Sport was never officially sold in Australia. However, the car’s significance in Australian rotary culture is immense, because it is the origin point of everything that followed. When Australians celebrate the RX-3’s 1972 Bathurst victory, or queue at Rotary Reloaded events, or debate the merits of 12A versus 13B at a meet, they are celebrating a lineage that began with the Cosmo Sport and the 47 engineers who refused to give up on the Wankel engine.

A tiny number of Cosmo Sports have been imported to Australia over the decades, perhaps fewer than a dozen. Each one is a known car within the Australian rotary community. They appear occasionally at concours events and major rotary gatherings, where they are treated with the reverence they deserve.

Engineering Legacy

The Cosmo Sport’s engineering influenced every rotary Mazda that followed. The 10A engine’s architecture, twin rotor, peripheral ports, eccentric shaft, became the template for the 12A (enlarged displacement, wider apex seals, improved materials) and the 13B (the most successful rotary engine ever produced). The oil metering system, the cooling requirements, the sealing technology, all were refined from the Cosmo Sport’s foundations.

More broadly, the Cosmo Sport proved that a small Japanese manufacturer could innovate at the highest level. Mazda’s commitment to the rotary engine, despite the scepticism of the global automotive industry, defined the company’s identity for the next five decades. The “never stop challenging” ethos that Mazda still promotes today traces directly back to Kenichi Yamamoto’s team and their refusal to accept that the rotary engine could not work.

Production Numbers

Series	Years	Units Produced
L10A (Series I)	1967-1968	343
L10B (Series II)	1968-1972	833
Total	1967-1972	1,176

End of Production

The Cosmo Sport ceased production in 1972, replaced in Mazda’s sports car lineup by the RX-2 and eventually the RX-3. But the car’s purpose had been served, brilliantly. The Cosmo Sport proved the rotary engine, established Mazda’s engineering credibility, and launched a dynasty of rotary-powered cars that would span four decades and win on racetracks around the world.

Kenichi Yamamoto would eventually become president of Mazda, and the 47 engineers who worked on the rotary programme are remembered as pioneers within the company’s history. The Cosmo Sport itself has become one of the most collectible Japanese cars ever produced, a symbol of ambition, persistence, and the conviction that a better solution is always possible.

In Australia, every RX-3 that screams down the straight at Bathurst, every FD RX-7 that idles at a Saturday morning meet, and every 13B that spits flames on overrun owes its existence to a small, beautiful sports car from Hiroshima and the 47 engineers who made it possible.