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Jun 23, 2023

Here's What Happened To GM's Experimental Wankel Rotary Corvette

In 1973, Chevrolet unveiled a pair of mid-engined, Wankel-powered Corvettes at the Paris Motor Show. Here it's their story. Chevrolet was determined to push the sports car boundaries with the third

In 1973, Chevrolet unveiled a pair of mid-engined, Wankel-powered Corvettes at the Paris Motor Show. Here it's their story.

Chevrolet was determined to push the sports car boundaries with the third generation of the Corvette, and Zora Arkus-Duntov tried to convince the automaker that a mid-engine solution was the best. Unfortunately, while the brilliant engineer didn't live to see his dream become a reality, he tried and made a few concept cars that featured a mid-ship engine solution. For that, he had to accept the compromise of not installing a V8 powerplant.

The idea of installing a Wankel engine under a Chevy hood was started by Ed Cole, GM's general manager, between 1967 and late 1974. He was a big fan of this rotary system promoted by NSU. This German automaker produced the Prinz between 1957 and 1973, a car that represents the start of a triangular rebellion. In theory, that compact design and smooth operation were ideal for cars. He thought about installing such a powerplant in the Chevrolet Vega. Still, before that, he needed to promote it on a high-profile vehicle such as the Corvette. GM already had the twin-rotor engine to put it into the car. It was a 266-CID unit that the automaker rated at 180 hp. But Duntov knew the Wankel engine inside out and understood its strengths and flaws. He didn't like the surface-to-volume ratio inside the combustion chamber and didn't believe in its future. Moreover, the idea of using the same powerplant in a Corvette as the Chevrolet Vega was uncanny. Still, Cole had the upper hand as GM's president. As a result, the automaker built not one but two concepts: one with two and one with four rotors.

Related: The Story Of Zora Arkus-Duntov, The Godfather Of The Chevrolet Corvette

Finally, in October 1973, General Motors unveiled both prototypes at the Paris Motor Show: the twin-rotor and the four-rotor Corvette. The former featured a Pininfarina-designed bodywork mounted on a modified Porsche 914/6 platform. At the same time, the latter resembled the shape of the XP-895 concept car unveiled in 1972, which Jerry Palmer penned under the supervision of Bill Mitchell, GM vice president of design.

Visitors to the American stand received the vehicles with mixed feelings. Not only that the idea of a sports car with a mid-engine was relatively new, but the Wankel was still a mystery for most people. After the exhibition, both concept cars, the twin-rotor XP-897 GT and the four-rotor XP-882, traveled around car shows, trying to become popular. Unfortunately, they didn't convince too many potential customers that it was the right path for the Corvette. As a result, in October 1974, Ed Cole had to admit that his idea was defeated and pulled the plug on the project, citing emission issues. However, fuel efficiency was a much bigger part of the problem. Truth be told, the oil crisis had affected the global car market and the American one in particular. People couldn't afford the spiking price of gasoline, and a gas-guzzler vehicle was not exactly what they were looking for.

The American automaker hired Pininfarina to build the XP-897 GT in Europe since they had already made the gorgeous 1963 Chevrolet Corvette Rondine Coupe, meaning that GM had to pay import duty on it and didn't want to do that. As a result, the concept was placed in storage at Vauxhall facilities in Britain. It remained hidden there for almost a decade until a team of constructors discovered it during a remodeling process of that storage area. GM didn't want to get it back and had decided to send the car to the crusher. Fortunately, a British Corvette enthusiast, Tom Falconer, heard about the vehicle, got in touch, and convinced Chuck Jordan (GM head of styling) to sell him the concept without an engine installed. Falconer installed a mundane inline-four powerplant carried over from a Vauxhall Cavalier to move it around.

Manufacturer

GM

GM

Production Years

1972-1974

1973-1974

Configuration

Twin-Rotor

Four-Rotor

Displacement

266-CID

585-CID

Power

180 HP

420-HP

Torque

NA

NA

Fuel

Gasoline

Gasoline

Noteworthy Applications

XP-897 GT

XP-882

Fortunately, the idea of a mid-engine Corvette didn't die along with these two projects. In 1975, Bill Mitchell sent the XP-882 back to the design center to replace the four-rotor RCE with a more traditional small-block V8. By doing this, the original concept morphed into the XP-895 and featured a new powerplant behind its cabin. It was a 400 CID transversely-mounted engine paired with a Turbo Hydramatic gearbox. And that's how GM made the gorgeous 1976 Chevrolet AeroVette. The concept was supposed to become the fourth generation of the Corvette. But a quick reality check made by GM revealed that a front-mid engine vehicle would be cheaper to produce. Thus, the C4 reached assembly lines while the XP-895 was sent into a storage area to gather more dust. Luckily, the automaker didn't destroy the prototype and became part of the GM Historical Collection.

As for the other concept car powered by a twin-rotor Wankel engine, the XP-897 GT vehicle saved by Falconer still exists. In 1997 he installed a Mazda 13B engine behind the cabin, thus remaining more accurate to the original idea. The vehicle was displayed at the National Corvette Museum, and the last public appearance, with the engine running, was at the 2021 Concours d'Elegance of America. The twin-rotor 80-CID powerplant was carried over from a Mazda RX-7 and developed just 100 hp, almost half what the original 266-CID had on tap. Still, the beauty of the concept and the idea of a mid-mounted Corvette eventually paid off with the eighth generation of America's best sports car.

Felix Wankel developed the engine that bears his name to create a smoother-running powerplant. Thanks to his idea, the rotary engine doesn't need to convert the up-down piston movement into a rotating one via connecting rods and crankshaft. After developing this unit for the NSU RO80, the idea sparked interest from Mazda, which paid big bucks in developing a series of Wankel engines that powered various vehicles from the Japanese automaker, the most notorious being the legendary RX-7, which is a tuner's dream car.

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As Duntov believed, this kind of engine has some problems. Its surface area from the combustion chamber leads to incomplete fuel combustion and, therefore, to high emissions levels. But Mazda assessed most of the initial engine issues. Additional fuel-injection systems and catalytic converters allowed the Japanese automaker to successfully produce vehicles powered by Wankel engines. Still, despite constant improvements, it couldn't satisfy the stricter emission standards. Mazda had to accept that it could not make the powerplant cleaner and pulled the plug on it in 2012, along with the dismissal of the RX-8 sports car.

Still, there is hope for those looking to hear the specific sound of this rotary engine. Mazda announced that it will develop a new generation for it powered by hydrogen. That might work if the automaker will solve other problems, such as rotor sealing and lubrication.

Rotary engines couldn't couldn't meet emission requirements due to high levels of emissions and high oil consumption. As a result, they were banned from being offered on the market.

Mazda had to stop making rotary in 2012 engines due to high fuel and oil consumption. In addition, these Wankel powerplants had several issues with chamber sealing and lubrication and were not exactly environmentally friendly.

Rotary engines are good since they provide a smooth power delivery, a broad rev-band, and a unique sound. On the downside, they are not very good in terms of fuel efficiency or torque.

Rotary engines are unpopular since they are difficult to understand and work on them. Moreover, users always have to carry a pint of oil with them. There are also other particular requirements for shutting the engine off. All of these made customers drive away from them.

Tudor started his career in automotive journalism over 25 years ago as a contributor in a small editorial team of a printed magazine. Later, he evolved and led several car magazines as editor-in-chief, produced his TV broadcast, and traveled worldwide to car events from Italy to Pikes Peak, and from Laguna Seca to the Sahara Desert. Tudor continued learning and completed rally-driving and off-road schools. He also reviewed more than a thousand cars in his career before joining the HotCars team.