Chevy Experimented With A 2-Rotor Corvette In ’73 – Jalopnik

What’s the primary thought that involves your thoughts when somebody says Corvette? For some, it is a white Corvette C4 pushed by Burt Reynolds as he drives off into the sundown in a wonderful V8 symphony. We’re undecided when you have the identical imaginative and prescient, however it’s onerous to think about the Corvette with no massive V8 engine beneath the hood. And you’d in all probability by no means think about one with a rotary engine. But Chevrolet got here fairly shut to creating a two-rotor Wankel Corvette in ’73.

It was known as the XP-897 GT, a beautiful mid-engine two-seat idea sports activities automobile with a two-rotor Wankel engine meant as General Motors’ opening rotary act. Most of the credit score for the rotary Corvette goes to Ed Cole, GM’s legendary president and one of many visionaries behind the unique small-block V8. Ed noticed the rotary engine as a significant a part of the technological future and have become one among its greatest evangelists in America. He envisioned a compact, lighter, and extra highly effective engine that will be a greater match for the opposite mid-engine ideas (the XP-882 and 895) that had been already within the works. Spoiler alert: a mid-engine Corvette didn’t go into manufacturing till 2020. But it nearly turned a actuality within the early seventies due to the rotary XP-897 GT.

But why transfer from a confirmed V8 energy prepare? What made the Wankel extra appetizing than the V8? Why did not it take off? And what even is a Wankel engine?

It wasn’t simply Chevrolet trying to get into Wankel engines. AMC, Chrysler, Ford, and Mercedes-Benz had been trying on the Wankel rotary engine as if it had been the promised messiah. Even the Soviets made rotary-powered Ladas for the KGB. There had been many causes for this curiosity within the rotary engine. One was the motor’s inherent simplicity. Unlike conventional engines that should convert reciprocating movement of the piston into energy, the Wankel engine made its energy in a rotary movement. This meant that the motor wanted far fewer transferring components. As a consequence, it was lighter, smaller, less complicated, and extra refined than your conventional engine. It additionally supplied a superior power-to-weight ratio in comparison with the engines of that point.

The seventies additionally marked the arrival of Mazda, a model that proved the Wankel engine might work. The Japanese carmaker entered North America with its rotary Cosmo sports activities coupe, and continued the custom with its RX sequence of sports activities automobiles. Not desirous to be left behind, General Motors spent hundreds of thousands to make loads of rotary-focused strikes, from creating its personal engine designs to constructing prototypes for AMC. But, after all, the crowning glory of those efforts was the rotary Corvette.

Despite its professionals and cons, many preferred the thought of a Wankel rotary engine. It’s a unique idea that turns what we all know in regards to the typical four-stroke engine on its head. At its core, the elemental distinction between conventional and Wankel engines is reciprocating movement versus rotary movement.

A rotary engine has an oval-shaped housing with a triangular rotor rotating inside it, not like a traditional four-stroke engine, which has a tube-shaped combustion chamber with a piston transferring up and down. This rotor strikes contained in the oval chamber in a cool orbital sample, which leaves three distinct gaps between the facet faces of the triangular rotor and the housing. Instead of consumption and exhaust valves, the housing has ports. The Wankel engine makes use of the identical four-stroke cycle – i.e., consumption, compression, combustion, and exhaust. The distinction, although, is that each one three sides of the rotor concurrently ship their model of the combustion cycle. When one face is within the consumption cycle, the opposite is within the combustion cycle.

This distinctive approach of working has the Wankel motor full three combustion occasions inside one full rotation of the rotor. The Wankel engine can also be compact as there are fewer transferring components in comparison with a standard engine (no pistons, connecting rods, valves, or camshafts). With fewer components and a pure rotatory movement, you’ve gotten a vibration-free, easy, high-revving engine that feels far more superior than the rumbling V8s of the seventies.

Yes, the XP-897 GT sat on a modified Porsche 914/6 platform, which was particularly designed to deal with the brand new General Motors’ two-rotor Wankel engine. Why? Because Ed Cole needed a compact mid-engine chassis for his compact rotary engine. The Porsche platform’s wheelbase was lowered by 6.5 inches whereas the entrance and rear tracks had been widened. The idea automobile even featured Porsche suspension and brakes.

The engine was not a rebadged Mazda energy prepare. It was constructed in-house by GM, and it value the corporate an obscene quantity ($50 million again then) to license from Wankel and NSU. And it wasn’t made particularly for the Corvette, however was initially meant to debut within the Chevrolet Vega. The water-cooled twin-rotor engine displaced 266 cubic inches (or 4.4 liters) and delivered 180 horsepower.

The 914/6 was despatched to famed Italian coach builder Pininfarina. That firm labored its magic and created a glossy, low-slung sports activities automobile painted in silver, which featured silver leather-based seats. It was the best-looking Corvette of all time. Before showcasing it on the 1973 Frankfurt motor present, GM modified the XP-897 GT’s shade to a vivid crimson and the interiors went from silver to fawn leather-based. The idea automobile now sported gold-painted machined alloy wheels (which later got here to be often known as “Vector” wheels). After all these adjustments, Corvette gave this idea the identify of “Corvette Two-Rotor”.

In concept, the rotary engine was a masterpiece in automotive know-how. In follow, although, it was flawed. For starters, the combustion chamber design didn’t enable gasoline to cleanly burn, which resulted in poor gasoline financial system. Other challenges included the motor’s voracious urge for food for engine oil in addition to poor rotor seals, which frequently failed with disastrous penalties. Mazda soldiered on with rotary engine know-how, perfecting it as a lot as potential. Eventually, they gave up and dropped the rotary engine in 2012 after the RX-8. Mazda’s rotary engine is making a comeback, although, in a brand new, greener idea avatar.

There had been different components as to why the Corvette Two-Rotor did not make it to manufacturing. GM realized that the deeper they went in, the extra the once-pioneering rotary know-how felt like snake oil. The 1973 gasoline disaster and tightening emissions norms posed main hurdles. And the mid-engine structure, although revolutionary, was a fancy and dear train at the moment. By 1974, GM lastly shut down its Wankel engine improvement division.

So what occurred to the Corvette Two-Rotor Concept? GM saved it at Vauxhall’s Design Center in England for over a decade earlier than lastly deciding to scrap the automobile as an alternative of paying taxes to convey it again to the States. Thankfully, UK-based Corvette collector Tom Falconer satisfied GM to promote the idea automobile to him. Although he received his arms on the automobile, it ended up going with out the facility prepare. The enterprising Tom stuffed the engine hole with a Mazda 13B rotary and turned the idea right into a present automobile, permitting it to proceed surviving immediately.