The Wankel Citroens 1970-75

Updated: 6 days ago

One fascinating aspect of automobile history is that it's not a straight path. In fact, there have been many technological dead-ends, inventions that, for a fleeting, shining moment in time, seemed destined to change the industry... Only for them to fade away and be forgotten.



The German Felix Wankel had been working on rotary engine concepts since before WWII patenting one in 1934. Still, it was only when his work caught the attention of the small motorcycle and automaker NSU that Wankel got the funds and resources to put his ideas into practice.

By the time NSU put the first Wankel-engined car on the market, in 1964, this revolutionary engine design had become the darling of the entire automobile industry. But why?

The rotary engine developed by Felix Wankel and NSU was virtually free from vibration, could spin much faster and produce much more power than all the piston engines available at the time, all with a dramatic reduction in complexity, weight, and bulk.

The French carmaker Citroen had been an innovator for its entire existence, so it was only natural for its president, Pierre Bercot, to approach NSU about its "marvel" engine. But Citroen didn't simply buy a license like pretty much every automaker was doing: it went further, establishing a joint-venture with NSU called Comobil in 1964.

Meanwhile, NSU and Citroen went a step further, establishing a new, more ambitious joint-venture company called Comotor in 1967.

The purpose of Comobil was to study the application of NSU rotary engines into Citroen-designed cars, leading to the experimental M35 program of 1970.

Although the M35 looked remarkably like an Ami8, it actually was a bespoke vehicle built by Heuliez on behalf of Citroen, which sold it to a select group of customers to gather real-world data about the Wankel engine in service. Equipped with hydropneumatic suspensions and powered by a single-rotor water-cooled engine made by NSU, the M35 was an expensive proposition, costing as much as an ID 19. That's probably one of the reasons why only 267 cars were made instead of the 500 Citroen had planned.

The oil crisis shook the automotive industry to its core, especially the small, financially overstretched Citroen, which would lose its independence by the end of '74.

Meanwhile, NSU and Citroen went a step further, establishing a new, more ambitious joint-venture company called Comotor in 1967. Its mission was the mass production of rotary engines in a purpose-built factory built in the Saar region of then-West Germany.

The Comotor factory was equipped for high-precision manufacturing of 1000 Wankel engines per day, and its first product was the KKM624: a liquid-cooled twin-rotor engine, which was an evolution of the KKM612 NSU fitted to its Ro80 flagship.

The rationale behind the Comotor factory and its twin-rotor engine was to sell rotaries to other manufacturers as well: the idea was that the whole industry was to abandon piston engines soon... Which turned out to be a colossal miscalculation.

Citroen launched the GS Birotor in September 1973 at the Frankfurt motor show, a top-of-the-line variant of its popular GS model equipped with the Comotor twin-rotor engine. But just a month later, OPEC countries sent oil prices skyrocketing, plunging Western economies into recession as retaliation to the American support of Israel during the Yom Kippur war.

GS Birotor production lasted only one year, and it was only ever offered on the French market.

The new political and social climate brutally exposed one of the Wankel's weakest points, high fuel consumption, making rotary cars unsalable overnight.

The oil crisis shook the automotive industry to its core, especially the small, financially overstretched Citroen, which would lose its independence by the end of '74.

Production of the GS Birotor at the Rennes-La-Janais factory started in March 1974, but by then, the program was dead in the water. Birotor production lasted only one year, and it was only ever offered on the French market.

Although it looked very much like a standard GS to the casual observer, the Birotor was a heavily re-engineered car: the whole front end of the GS was redesigned to take the new running gear. The Comotor 130Hp, twin-rotor engine was fitted transversely in a bespoke subframe. The front suspension was redesigned entirely and bore striking similarities with the layout of the contemporary CX. The GS Birotor had wider track front and rear and flared wheel arches to match, and its interior was better appointed than the ordinary GS, to justify its substantially higher price.

By April of 1976, Peugeot completed its acquisition of a virtually bankrupt Citroen, creating the PSA Group. To avoid having to support the 861 GS Birotor it sold, Citroen sought to take them all off the road and destroy them, by offering substantial discounts on new models to their owners. Thankfully not all of them accepted, allowing a few to survive to this day in the hands of hard-core Citroen enthusiasts.




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