During the exciting decades of technological advancement in the mid-20th century, the automotive world witnessed a surge of imaginative concept cars. While some, like the Chrysler Turbine Car with its jet engine aspirations or the nuclear-powered dream of the Ford Nucleon, remained firmly in the realm of concept, others pushed the boundaries of automotive engineering in more grounded, yet equally fascinating ways. Germany, a powerhouse of automotive innovation, was also deeply involved in this concept car frenzy. In the late 1960s, Mercedes-Benz embarked on an ambitious project: the creation of a versatile testbed designed to evaluate a wide array of cutting-edge technologies. The inaugural technology to take center stage was the rotary engine, a novel powerplant gaining traction after Mazda’s pioneering release of their first rotary-powered car just a few years prior. This Mercedes-Benz experimental marvel was designated the C 111, and its purpose extended far beyond simply exploring the potential of rotary engine technology for Mercedes-Benz.
Mercedes-Benz: A Legacy of Innovation
To truly appreciate the context of the C 111, it’s essential to understand the rich history of Mercedes-Benz. Tracing its origins back to the Benz Patent Motorwagen of 1895, the official Mercedes-Benz marque was established in June 1926 through the merger of Daimler Motoren Gesellschaft and Benz & Cie., the world’s oldest car company. This German luxury car manufacturer boasts a heritage steeped in motorsport success, particularly in early Grand Prix racing, and a reputation for off-road capability demonstrated by military vehicles like the Genadewagen, which evolved into the iconic G-Class. Mercedes-Benz has consistently been at the forefront of automotive luxury and technological innovation, exemplified by flagship models like the S-Class and SL. Today, Mercedes-Benz stands as one of the world’s leading automotive manufacturers, synonymous with quality, performance, and prestige.
Mercedes-Benz C 111: Key Highlights
- Debut Year: 1969
- Initial Engine: Three-rotor Wankel rotary engine
- Engine Placement: Mid-engine layout
- Body Style: Two-door berlinetta with gullwing doors
In the late 1960s, Mercedes-Benz was committed to exploring groundbreaking and unconventional automotive concepts. Instead of developing a series of disparate concept vehicles, they ingeniously decided to create a single, adaptable platform to test a multitude of innovative ideas. This platform was christened the C 111, and its initial mission was to showcase Mercedes-Benz’s foray into rotary engine technology.
While Mazda had already introduced rotary power to the market a couple of years prior, Mercedes-Benz unveiled the first C 111 at the 1969 IAA in Frankfurt, Germany. This striking concept featured a two-door berlinetta body style, reminiscent of a “small saloon,” accentuated by dramatic gullwing doors and a vibrant orange paint finish. At the heart of this revolutionary C 111 concept was a three-rotor Wankel rotary engine with a 3.6-liter displacement. Notably, unlike many engines of that era that relied on carburetors, this 3.6-liter Wankel engine incorporated advanced direct fuel injection technology, highlighting Mercedes-Benz’s commitment to innovation.
Building upon the initial C 111’s success, Mercedes-Benz presented the C 111-II in 1970, this time equipped with an even more potent quad-rotor Wankel engine. The addition of a fourth rotor increased the engine’s displacement to 4.8 liters. Reportedly, the C 111-II was capable of reaching a top speed of 186 mph, a remarkable velocity for a road car of that period. Despite their groundbreaking engineering and impressive performance, neither the original C 111 nor the C 111-II would ever progress to series production.
Power and Performance: C 111 Wankel Engines Compared
The development of both Wankel-powered C 111 concept cars was largely conducted in secrecy prior to the 1969 debut of the first iteration. Mercedes-Benz undertook the engine development in-house, without external assistance. The C 111 project was spearheaded by a compact two-person team. Bruno Sacco, who later ascended to become the head of design at Mercedes-Benz in 1975, led the overall project. Joseph Galitzendorfer was responsible for designing the C 111’s lightweight and aerodynamic fiberglass body.
The table below provides a comparative overview of the specifications for the two Wankel-engined C 111 variants:
| Model | 1969 Mercedes-Benz C 111 | 1970 Mercedes-Benz C 111-II |
|---|---|---|
| Engine | 3.6-Liter Tri-Rotor Wankel Rotary | 4.8-Liter Quad-Rotor Wankel Rotary |
| Horsepower | 280 hp @ 7,000 rpm | 349 hp @ 7,000 rpm |
| Torque | 289 lb-ft @ 4,000–5,500 rpm | 317 lb-ft @ 4,000–5,500 rpm |
| Compression Ratio | 9.3:1 | 9.0:1 |
| Specific Output | 77.78 hp per liter | 72.71 hp per liter |
| Top Speed | 162 mph | 180 mph |
After rigorous testing and evaluation of the Wankel engines in the 11 C 111 prototypes built, Mercedes-Benz engineers concluded that the rotary engines, while powerful, did not meet the company’s stringent standards for long-term durability and reliability. While the C 111 project itself continued to evolve, the rotary engine program was ultimately discontinued. Despite the allure of exceptional speed, a luxurious interior, and a futuristic design embodied by the C 111 and C 111-II, these models were destined to remain as significant milestones in automotive history, rather than production vehicles.
Beyond Rotary Power: The Versatility of the C 111 Program
The cancellation of the Wankel engine program did not spell the end for the C 111 initiative. Instead, it demonstrated the platform’s inherent versatility. While eleven C 111s were initially equipped with rotary engines, the twelfth prototype explored a completely different powertrain direction. This variant, known as the C 111-IID, replaced the rotary engine with a turbocharged version of Mercedes-Benz’s successful 3.0-liter OM 617A five-cylinder diesel engine. When it debuted in 1976, the C 111-IID produced 187 horsepower and was immediately put to the test, breaking endurance records at the Nardo Test Track in Italy.
In 1978, Mercedes-Benz engineers further refined the C 111-IID’s diesel engine. Through further development, they boosted the engine’s output to 227 horsepower. This enhanced version was designated the C 111-IIID and returned to the Nardo Test Track, where it proceeded to shatter nine more diesel endurance records. The diesel-powered C 111 achieved an astonishing run at Nardo, covering 9,941 miles at an average speed of 156 mph over a continuous 64-hour period. This was a resounding success, although it would be several decades before Mercedes-Benz actually introduced a production AMG diesel model.
Beyond diesel experimentation, two C 111 prototypes were also selected to evaluate V8 engines. Mercedes engineers replaced the rotary engines in these prototypes with a 3.5-liter V8 engine. Instead of pairing it with the typical four-speed automatic transmission associated with the 3.5-liter V8, Mercedes opted for a five-speed manual gearbox. Further V8 testing culminated in the C 111-IV. This iteration featured a heavily modified 4.8-liter version of Mercedes-Benz’s 4.5-liter V8, enhanced with twin turbochargers, resulting in a remarkable 493 horsepower. In 1979, the C 111-IV achieved a top speed exceeding 250 mph at the Nardo Test Track, showcasing the platform’s incredible performance potential.
Mazda’s Rotary Revolution: Paving the Way
Mazda holds the distinction of being the first automaker to bring rotary engine technology to the mass market. In 1967, the Japanese manufacturer launched the Cosmo, a compact, two-seater sports car powered by a small 1.0-liter twin-rotor Wankel engine producing a modest 110 horsepower. However, the Cosmo’s lightweight construction, tipping the scales at just 2,072 pounds, reportedly made it an exceptionally engaging and enjoyable car to drive, particularly on winding mountain roads.
Mazda not only pioneered mass-market rotary engines but also became synonymous with this technology. The Mazda RX-7 is arguably responsible for bringing the rotary engine into the global car enthusiast spotlight. While rotary engines generally are not as durable as conventional piston engines, they are known for their high-revving nature and exceptional power-to-weight ratio.
Mazda’s commitment to rotary technology continues to this day, and we can only speculate about the direction AMG might have taken if Mercedes-Benz had proceeded with their rotary engine development plans for production vehicles.
Sources: Mercedes-Benz, Mazda
