Mercedes-Benz’s Abandoned M 950 Wankel Rotary Engine Project

Typically, when we think of legacy brands that have employed the use of the Wankel rotary engine in the past, Mazda is virtually the only automaker that comes to mind. After all, the Japanese marque first began using the odd motor type in the late 1960s on a mass-market scale, and popularized the Wankel’s use with models like the RX-7, RX-8, and the Cosmo. Sure, the Wankel has its downsides, but there are loads of rotary aficionados out there that seek out these older Mazdas solely for their mills.

The thing is, though, Mazda almost had a fierce competitor in the rotary engine world. Half a globe away, Mercedes-Benz was heavily considering using a version of a rotary engine, called the “M 950”, on a massive scale in the late 1960s and early 1970s. The German brand built quite a few rotary-powered concepts that took on the codename “C 111”. The nameplate denoted an experimental, wedge-shaped model that served as a test bed for many then-cutting-edge technologies, namely the rotary engine.

Related

FC RX-7: The Forgotten Version of Mazda’s Rotary Sports Car

The second-generation of Mazda’s beloved RX-7 is often left out of the conversation. Here’s why it shouldn’t be.

Close, But No Cigar

Mercedes-Benz M 950 Key Points

• Introduced in 1969
• Built in both three and four-rotor configurations
• Produced up to 349 horsepower
• Ultimately Proved Unreliable
• Program axed in 1970

Prior to Mercedes-Benz’s work beginning on their M 950 Wankel rotary engine, the German automaker was busy trying to figure out new, novel ways of powering their sporty models. Merc had become so enamored with the Wankel engine after Mazda had pioneered its development in 1961 that they created an entire department dedicated to its research a year later. A man called Wolf-Dieter Bensinger headed-up the then-new Wankel engine division, and work began on initial designs in mid-1969.

The first of these experimental engines to be produced was a tri-rotor iteration, which first saw use at the very end of 1969. In order to give their new engine a thorough test, Mercedes-Benz built a concept car to go along with it. The concept, coined the C 111, took on a traditionally Italian look commonly seen in supercars from the country in the late 1960s and early 1970s. After all, the small, wedge-shaped sports car with flip-up headlights had been made popular by the Italians just a couple of years prior.

Once installed into the C 111 concept, the three-rotor Wankel was given a series of stress tests to see just how well the new mill could perform in various circumstances, and under extreme stress. While the three-rotor Wankel proved to be insufficient in terms of power and performance, the four-rotor iteration – built at roughly the same time as the three-rotor version – was much more potent. Reportedly, a C 111 equipped with the quad-rotor Wankel reached a top speed of 186 mph. Not bad for a 55-year-old concept with an experimental engine.

Merc’s Wankel And Its Developmental Details Versus Mazda’s

The man behind the Wankel engine, Felix Wankel, initially developed the concept in the mid-1920s, but didn’t receive widespread attention for it until the early 1960s. Along with Mercedes-Benz and Mazda, several other legacy automakers were doing their own tinkering with rotaries at the time. When it comes to Merc’s design, Bensinger and his team envisioned the Wankel engine as more of a performance-oriented mill for use in high-octane sports cars, as evidenced by the Merc team’s dedication to producing high horsepower figures. Mazda, on the other hand, was focused more on bringing the Wankel to the mass market in a reliable and practical way.

The M 950’s Specs, Features, and Performance

Despite roughly seven years of development, Mercedes-Benz produced just two iterations of their Wankel engine that could be used for testing. The first three-rotor Wankel engine first saw use at the very beginning of 1970 within the aforementioned Mercedes-Benz C 111 concept car. Once installed, the C 111 equipped with the tri-rotor mill was able to produce a top speed of about 162 mph, thanks to a sum total of 280 horsepower and 289 lb-ft of torque. The tri-rotor Wankel measured in at approximately 3.6 liters of displacement.

However, the real “bread and butter” of the M 950 engine was its four-rotor iteration. The quad-rotor-equipped C 111 managed a top speed of 186 mph, but it was able to do more than just go quickly in a straight line. According to official Mercedes-Benz testing, the quad-rotor C 111 concept was capable of getting itself from a dead stop up to 60 mph in under five seconds, and produced 319 lb-ft of torque, along with its 349 ponies. With the extra rotor installed, the quad-rotor Wankel engine’s mass amounted to about 4.8 liters.

As far as the M 950’s testbed went, the C 111 featured a slew of then-unheard-of tech that helped it reach higher speeds, corner better, and achieve a higher level of passenger comfort, too. Its body shell was made up entirely of fiberglass to keep its weight to a minimum. Along with the trim waistline, the C 111 featured a few go-faster upgrades, like a fully independent suspension, along with anti-squat and anti-dive control built in, meaning the C 111 was more controlled under heavy braking and cornering.

We’ll lay out some more of the Mercedes-Benz C 111’s specs in the table below:

*Specs courtesy of Supercars.net

What Happened To The M 950 And How It Helped Mercedes-Benz

Unfortunately for Mercedes-Benz’s Wankel engine division, there was some not-so-promising writing on the wall shortly after the first M 950 engines were produced. Despite putting up impressive performance figures under the hood of the C 111 concept car, it became obvious that the Wankel engine was not particularly reliable. The motor struggled to stay alive at points, with frequent stalls being one of its hallmarks.

However, these issues didn’t deter Mercedes-Benz, at least not at first. The Wankel engine program continued, and a twin-rotor version was even planned for mass production. However, by 1972, these mass-production plans had not materialized, as no capital was allotted for this purpose. Even still, the Wankel program carried on until 1976, when it was finally axed. Daimler-Benz top brass were no longer interested in allocating much-needed funds to a program that was going nowhere after 14 years.

The project wasn’t a total loss, though. The C 111 concept did prove to be valuable in terms of learning and development. Its fully independent rear suspension and anti-squat and dive tech proved to be functional, and served as key features of Merc’s Active Body Control (ABC) tech that debuted in 1999. In short, the M 950 engine program was, largely, a failure. But, the first-gen C 111 concept proved successful.

Sources: Mercedes-Benz, Supercars.net