During the exhilarating period of technological advancement spanning the 1940s through the 1960s, the automotive world witnessed the birth of some truly outlandish concept cars. From the Chrysler Turbine Car with its jet engine aspirations to the Ford Nucleon envisioned as a nuclear-powered vehicle, these concepts pushed the boundaries of imagination and engineering.
Germany, too, was deeply involved in this era of radical concept development. In the late 1960s, Mercedes-Benz embarked on an ambitious project: the creation of a versatile experimental platform designed to evaluate a wide array of cutting-edge technologies. The initial focus of this program was the exploration of the rotary engine, a technology gaining traction after Mazda’s groundbreaking release of their first rotary-powered car just a few years prior. This Mercedes-Benz experimental vehicle was christened the C 111, and its significance extended far beyond just rotary engine development, becoming a symbol of innovation and forward-thinking engineering.
Mercedes-Benz C 111: Pioneering Innovation Beyond Rotary Power
The Mercedes-Benz legacy, dating back to the Benz Patent Motorwagen of 1895, officially solidified in June 1926 with the merger of Daimler Motoren Gesellschaft and Benz & Cie., creating Daimler-Benz. This German automotive giant is renowned for its rich motorsport heritage in early Grand Prix racing, its off-road mastery exemplified by military vehicles like the G-Wagon (originally Genadewagen, now G-Class), and its unwavering commitment to luxury and technological innovation seen in models like the S-Class and SL. Today, Mercedes-Benz stands as one of the world’s leading automotive manufacturers.
Mercedes-Benz C 111 – Key Highlights:
- Debut Year: 1969
- Initial Engine: Three-rotor Wankel rotary engine
- Layout: Mid-engine configuration
In the late 1960s, Mercedes-Benz was at the forefront of automotive innovation, exploring groundbreaking concepts, some of which were entirely novel to the industry. Rather than pursuing a series of disparate concept vehicles, Mercedes opted for a unified platform to rigorously test a broad spectrum of their innovative ideas. This platform, designated the Mercedes-Benz C 111, was first conceived to showcase Mercedes-Benz’s advancements in rotary engine technology.
While Mazda had introduced rotary power to the market a couple of years prior, the Mercedes-Benz C 111 made its grand entrance in 1969 at the IAA in Frankfurt, Germany. It captivated audiences with its striking two-door berlinetta body style, evocative of a “small saloon” in Italian, accentuated by iconic gullwing doors and a vibrant orange paint finish. At the heart of this revolutionary C 111 concept was a sophisticated three-rotor Wankel engine, boasting a displacement of 3.6 liters. Unlike most engines of the era that relied on carburetors, this 3.6-liter Wankel engine incorporated advanced direct fuel injection, showcasing Mercedes-Benz’s commitment to advanced engineering.
The following year witnessed the unveiling of the Mercedes-Benz C 111-II, an evolved iteration featuring a quad-rotor Wankel engine. The addition of a fourth rotor increased the engine’s displacement to 4.8 liters, significantly boosting performance. Reportedly, the C 111-II was capable of reaching a top speed of 186 mph, an astonishing figure for a road-legal car of that period. Despite their technological prowess and groundbreaking design, neither of these initial Mercedes-Benz C 111 concepts would progress to series production.
Power and Performance of the Rotary-Engined Mercedes-Benz C 111 Prototypes
The development of both Wankel-powered Mercedes-Benz C 111 concepts was shrouded in secrecy prior to the debut of the first version in 1969. Mercedes-Benz undertook the engine development in-house, relying entirely on their internal expertise. The C 111 project was primarily spearheaded by a dedicated two-man team. Bruno Sacco, who later became the head of design at Mercedes-Benz in 1975, led the overall project. Joseph Galitzendorfer was responsible for crafting the C 111’s lightweight and aerodynamic fiberglass body.
The following table outlines the specifications of the two Wankel-engine Mercedes-Benz C 111 prototypes:
| 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 extensive testing and evaluation of the 11 Mercedes-Benz C 111 prototypes equipped with Wankel engines, Mercedes-Benz engineers concluded that these engines, while powerful, did not meet the company’s stringent standards for long-term durability and reliability. Consequently, while the C 111 program continued to evolve, the Wankel engine project was effectively discontinued for production vehicles. Despite the allure of exceptional speed, luxurious interiors, and futuristic styling, the Mercedes-Benz C 111 and C 111-II were destined to remain as iconic prototypes, living on in automotive history.
Beyond Rotary: The Expanded Scope of the Mercedes-Benz C 111 Program
The Mercedes-Benz C 111 initiative, despite the decision to discontinue the Wankel engine program for production, pressed forward with unwavering momentum. While eleven C 111 vehicles were equipped with rotary engines, the twelfth prototype took a significant detour in powertrain development. Instead of a rotary engine, this C 111 variant was fitted with a turbocharged version of Mercedes-Benz’s highly successful 3.0-liter OM 617A five-cylinder diesel engine. Designated the C 111-IID, this diesel-powered prototype produced 187 horsepower upon its debut in 1976 and was immediately deployed to the high-speed Nardo Test Track in Italy to pursue endurance records.
In 1978, Mercedes-Benz engineers further refined the C 111-IID’s engine. Through meticulous enhancements, they boosted the engine’s output to 227 horsepower. This upgraded prototype, renamed the C 111-IIID, returned to the Nardo Test Track and shattered nine diesel endurance records. The diesel C 111 achieved an astonishing feat at Nardo, covering 9,941 miles at an average speed of 156 mph over a grueling 64-hour period. This resounding success, however, did not immediately translate into production diesel AMG models; it would take decades before Mercedes-Benz introduced a diesel AMG variant.
In addition to the diesel experimentation, two Mercedes-Benz C 111 chassis were chosen to evaluate V8 engines. Mercedes-Benz engineers replaced the rotary engines in these prototypes with a 3.5-liter V8 engine. Instead of the typical four-speed automatic transmission paired with the 3.5-liter V8, these C 111 V8 testbeds were equipped with a five-speed manual gearbox. Further V8 development culminated in the C 111-IV. This iteration featured a heavily modified 4.8-liter version of Mercedes-Benz’s 4.5-liter V8, enlarged and augmented with twin turbochargers, resulting in a staggering 493 horsepower. In 1979, the C 111-IV reached a top speed exceeding 250 mph at the Nardo Test Track, further cementing the Mercedes-Benz C 111’s legacy as a platform for extreme performance exploration.
Mazda’s Rotary Pioneer: The 1967 Cosmo
While Mercedes-Benz explored rotary engine technology extensively with the C 111, Mazda achieved a significant milestone by bringing rotary power to the mass market first. In 1967, the Japanese automaker introduced the Mazda 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, contributed to its reputation as an exceptionally agile and enjoyable car to drive, particularly on winding Japanese mountain roads.
Mazda not only pioneered the mass-market rotary engine but also became synonymous with this unique engine technology. The Mazda RX-7 is arguably responsible for bringing the rotary engine into the spotlight of car enthusiasts worldwide. While rotary engines are generally considered less durable than conventional piston engines, they offer impressive high-revving capabilities and exceptional power density.
Mazda’s commitment to the rotary engine continues to this day, reigniting the passion for this unique technology. One can only speculate about the trajectory of AMG and Mercedes-Benz performance vehicles if the company had pursued its initial rotary engine ambitions as intensely as Mazda.
Sources: Mercedes-Benz, Mazda
