The Little Engine that Never Was:
The General Motors Rotary Combustion Engine

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Last month Mazda ended, for the time being, production of Wankel rotary engines. Over the decades since the 1967 Cosmo’s L8A two-rotor, Mazda had built about 2 million Wankels. Since that announcement, epitaphs have being written for the engine that made Mazdas go “hmmmm”. Ironically, around the same time that Mazda stopped making Wankel rotaries I came across another Wankel engine that had it actually gone into production would undoubtedly have dwarfed Mazda’s rotary production numbers. I’m talking about the General Motors Rotary Combustion Engine and few prototype engines have come as close as it did to the factory floor without actually going into production.

In the early 1960s General Motors did some wacky, crazy things, like make the “rope drive” Pontiac Tempest, the overhead cam Pontiac six, the Oldsmobile Toronado’s unified powertrain FWD system and, of course, the rear engine, air-cooled Corvair. While the General’s retail offerings would get more and more mechanically conventional as that decade wore on, at the Warren Tech Center, the innovation continued.

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Not long ago, when following up a slightly exaggerated story by concept car collector Joe Bortz that some of the Motorama cars were electrically powered (they were, actually, with lead-acid batteries and starter motors, to get what were otherwise “pushmobiles” on and off the stage), the nice folks at the GM Heritage Center sent me a document from 1969 called Progress of Power, reporting on GM’s research into alternatives to the conventional gasoline powered Otto cycle engine. There were reports on turbines, EVs, Stirling engines, hybrid systems, experimental piston engines and even a couple of steam engines described in the document.

So GM was open to alternatives. Their checkbook was open too. When engineering heavyweights like Ed Cole and John DeLorean embraced Felix Wankel’s rotary engine design for it’s light weight, compact size and high specific output, GM paid Wankel’s American licensee, Curtiss-Wright, $50 million in 1970 for the rights to produce a Wankel rotary. GM then embarked on developing their own version of the Wankel, in an uncharacteristically public manner. The automaker announced that a two-rotor rotary would be available in the Chevy Vega no later than 1975. A couple of the ubiquitous “mid-engine Corvette” concepts (one later became the big-block powered Aerovette) had rotary power. GM’s Wankel project was high profile.

Not only did GM embrace the Wankel, but so did little American Motors, designing a complete and radical car, the Pacer, around the rotary’s compact dimensions. AMC also paid Curtiss-Wright a licensing fee, hoping to eventually build their own Wankels, but in the meantime planning on fitting the Pacer with engines bought from GM.

Development at GM proceeded but hit its first stumbling block as provisions of the Clean Air Act kicked in and engineers struggled to clean up the Wankel’s two-stroke like exhaust. It was thought that hurdle had been overcome but then the first oil crisis of the 1970s hit in 1973 in the wake of the Yom Kippur war. Not only is the Wankel notoriously dirty in terms of emissions, it’s also a bit of a gas hog. All that power and RPM come at a price. Still struggling to meet increasingly strict emissions standards and facing the prospect of selling an economy car with an uneconomical engine, in 1974 Ed Cole postponed the project, then retired. His successor as GM’s head engineer, Pete Estes, wasn’t nearly as enthused with the Wankel and he killed the project. In addition to the $50 licensing fee, at the time it was estimated that GM had poured another $150 million into the GMRCE project. That’s over a half billion dollars in today’s money and GM just walked away. They could afford taking that kind of technological flier back then.

The actual two-rotor GM Wankel engine, though, was about as close to production as an engine can get. The design had been fixed in 1972 and responsibility for mass production and meeting emissions standards had been assigned to GM’s HydraMatic division. That’s how I came across what looked like a production ready GMRCE at the Ypsilanti Automotive Heritage Museum. HydraMatic’s research and production facilities were located in Ypsilanti for decades. As you can see from the photos, the two spark plug per rotor engine looks like a production engine, not a prototype. Those are finished, smooth castings, made on production tooling, not machined and heliarc welded pieces of billet. The manifolds and ancillaries and their brackets look like production pieces as well.

Note the exposed cylinders and pushrods on this prototype Cadillac V12

To give you an idea of just how close to production the GM Wankel was, compare how finished it looks to these two prototype Cadillac OHC V12 engines from the “V Future” program in the 1960s originally intended to power the Olds Toronado and Cadillac Eldorado. In a period publicity photo of one of the engines you can see exposed cylinders and even what appear to be exposed pushrods (not sure what pushrods are doing in an overhead cam engine, but there they are). In another photo taken recently by Mac’s Motor City Garage at the GM Heritage Center, you can clearly see the massive amount of heliarc welding one would expect on a prototype. Compared to those, the GMRCE on display in Ypsilanti was very close to a production engine.

Photo of prototype Cadillac V12 at the GM Heritage Center courtesy of Mac’s Motor City Garage. Note all the heliarc welding typical of a prototype.

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One Response to The Little Engine that Never Was:
The General Motors Rotary Combustion Engine

  1. Pingback: A Pacer Racer? | Cars In Depth

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