Forty years ago, a panel of auto journalists picked the NSU Ro80 as European Car of the Year. Now mostly forgotten, the Ro80 was a German sedan with an aerodynamic shape that presaged the Audi 5000 and Ford Taurus of the 1980s. As important as its trend-setting styling, though, the Ro80 featured the first Wankel engine in a mass-produced car.

Potential game-changers in the auto industry have often ended up as blind alleys. Dinosaurs at least have birds as their living legacy, but innovative cars like the Tucker, Corvair and Citroen DS can be found only in the automotive fossil record. Carmakers have learned that it doesn’t always pay to innovate.

But for a brief time in the late 1960s and early 1970s, it looked as if real innovation was taking hold in the form of a new power plant that was lighter, smoother, simpler than a reciprocating piston engine and also capable of producing more power for its size. Companies from American Motors to Mercedes-Benz rushed to license Wankel engine technology.

Felix Wankel, an engineer at NSU, had been experimenting since 1954 with a simpler internal-combustion engine. His elegant design consisted of a rounded triangular “rotor” that spun in an oval combustion chamber. As the rotor moved in its eccentric orbit around a central shaft, the area of the three combustion chambers (one for each side of the triangle) contracted, creating compression and thus power.

But an obstacle to engine longevity emerged: It was hard to get a good seal on the combustion chambers where the rotor tips, or apexes, met the inside of the chamber.

Before the Ro80, there had been attempts at Wankel-powered cars — NSU’s own Wankel Spider and the Mazda Cosmo sports cars — but the Ro80 was the revolutionary engine’s first shot at the big time. If things had gone as planned, BMW wouldn’t be the only prestigious three-letter brand of German cars today.

Initial orders for the 1968 NSU Ro80 were brisk. Soon, however, NSU was dealing in damage control.

In late 1968, the German magazine Auto Motor und Sport reported that half of the 191 Ro80 owners it had surveyed said that engines had been replaced under warranty. In neglecting to test the cars in real-world stop-and-start driving conditions, NSU snatched defeat from the jaws of victory.

The culprit turned out to be bad bearings and ineffective rotor tip seals; the warranty claims that resulted nearly drove the company to bankruptcy. NSU eventually merged with Volkswagen.

However, in a protracted deal involving a cast of many — including Felix Wankel and, oddly, a group of Israeli bankers — several former NSU shareholders retained control of licensing rights to the engine. Still, it fell to the Japanese to perfect the power plant.

Early proponents

Toyo Kogyo, the parent company of Mazda, was one of about 18 NSU Wankel licensees. In the late 1960s, Mazda decided that its future lay in differentiating itself from Toyota and Nissan. It cast its lot with the Wankel, which the company called the rotary engine. The first rotary-powered Mazda to make an impact in the United States was the RX-2, introduced in 1970.

The RX-2 was a small coupe roughly the size of a Toyota Corolla, but with the pep of a small V-8. Enthusiasts gushed over the smooth and ample power.

C.J. Batten was the first design engineer that Ford hired for its Wankel development program in 1971. In a recent interview, Batten said that Ford began looking at the Wankel because its archrival, General Motors, “had one that was nearly production-ready” for its Chevrolet Monza coupe.

In an interview, Batten recalled evaluating a Mazda and being impressed. “The RX-2 with a little over 100 horsepower would run like a 200-horsepower Mustang,” he said. Batten reckons that the advantages in packaging and smoothness weren’t enough to overcome the reciprocating engine’s advantage of incumbency.

GM’s president, Ed Cole, was a proponent of the Wankel. In the early 1970s, GM showed several Wankel-powered mid- engine Corvette design studies that would have been world-class sports cars. Car magazines said the sleek midengine ’Vette was a sure bet for production. Cole also planned to use the Wankel in mainstream cars.

Batten recalls that as wishful thinking. He said the accountants who held the purse strings pointed out that Chevrolet could already sell every Corvette it could build. Why was a more advanced, more expensive car needed? The logic was hard to dispute, and the Corvette would soldier on until 1984 with its 1963-vintage platform.

Not much later, Cole retired and the Arab oil embargo underscored how thirsty the early Wankels were. GM’s Wankel program came to a sudden halt. Ford ended its development program.

What became of the Wankel?

The cancellation of GM’s Wankel even had a ripple effect on American Motors, which had engineered its futuristic, glassy Pacer to take a GM-built Wankel. Instead, AMC had to make do with a heavy cast-iron 6-cylinder.

The only automaker other than NSU and Mazda to market a Wankel-powered production car was Citroen, a company that celebrated eccentricity. But Mercedes-Benz expressed an interest, teasing enthusiasts in 1970 with the brilliant C111-II research car that had gullwing doors and a 370-horsepower four-rotor Wankel that could reach 180 miles an hour.

The 1974 Arab oil embargo hit Mazda hard. Its small RX-2 could barely manage 15 miles a gallon, about half as much as the comparably sized Corolla. The RX-3, a larger successor, added a wagon body style. But that car was bigger and heavier, and had even worse mileage.

Mazdas piled up at dealers and at the ports, so the company hedged its bets with piston-engine cars, while it improved the rotary’s cleanliness and efficiency. In 1978, it introduced the car that made the best use to date of the rotary’s distinctive qualities. The 1979 RX-7 was a milestone; at a time when sports cars were growing flabby, the RX-7 was light, nimble and basic with an engine so rev-happy that a buzzer had to be installed to let the driver know when the engine speed had reached the danger zone.

Mazda’s new strategy was to reserve the rotary for its specialty cars, while using piston engines in the rest of its line. Mazda’s rotary design reached its pinnacle with the Renesis engine introduced in the 2003 RX-8, the most powerful, efficient and cleanest naturally aspirated Wankel yet.

And because it is also well-suited to run on hydrogen, it may have a future beyond the odd four-door coupe that it currently lives in.

Early Wankel cars seldom appear for sale in the United States. The Ro80 is somewhat popular as a collectible in Britain, though many have been refitted with more reliable Mazda engines. Prices run around $15,000. A Wankel Spider recently sold on eBay for $17,000.

First-year Mazda RX-7s are bargains at $4,000 to $6,000. The 1967 Mazda Cosmo is the most collectible early Wankel car. In 2007, a seller at an auction in Australia turned down an $83,000 bid.