Skip to main content
Original Issue


A British authority drives a fascinating dream car and predicts that its system of rotors (inset) will supplant the time-honored reciprocating piston engine at Mercedes-Benz

All big automotive firms have research and development departments, though with some the end product hardly seems to justify the outlay. At the Daimler-Benz factory in Stuttgart, Germany, research and development has always been very strong, and during the period 1952-55, when Mercedes-Benz cars were sweeping all before them on the motor-racing circuits of the world, it could justifiably have been renamed the racing department. All the brains and technology available at Daimler-Benz were put into the project "motor racing" under Director Rudolf Uhlenhaut, with results that still may be seen in the engineering of the passenger cars.

When the racing department reverted to normal research and development work for passenger cars, there was no lessening of activity or experimentation, but, naturally, the outside world and the customers saw only the end products. Such advances as fuel injection, greater braking efficiency, safer chassis structures, improved handling, better suspension systems were the result of work done by Uhlenhaut's experts. Uhlenhaut had no objection to people studying his racing cars, as they would be obsolete before they could be copied. What he did not permit was any breach of security in the experimental department.

This week Daimler-Benz is displaying a new experimental car to the world at the Frankfurt Auto Show. Its engine is not the traditional reciprocating piston engine to be found in nearly all the cars on the road today. It is instead a rotary piston engine, and to me the fact that Daimler-Benz has put it on public view is one of the most significant events in motoring history. I have driven the car, I have discussed the engine at length with the engineers, I have considered the company's legendary reputation for engineering integrity—after all, its roots go right back to the beginning of the automobile and of the reciprocating engine, to the pioneers Gottlieb Daimler and Karl Benz—and at the same time its great caution about new concepts, and the sum of my impressions is that this car contains the engine of the future for Daimler-Benz.

The automotive world has felt the need for a new prime mover for some time now. Gas turbines, steam power and electrical sources of energy are occupying many engineering minds, while rotating pistons have been with us experimentally for a long time. The engine of the German designer Felix Wankel—in which a triangular rotor revolves in a specially shaped chamber, uncovering inlet and exhaust ports as in a two-stroke engine but operating on the four-stroke Otto cycle—had been in the embryo stage for many years. Eventually it was taken up by the German NSU company, which transformed it into practical fact and then sold the patent rights to other firms. Toyo-Kogyo of Japan produced it in two-rotor form in the Mazda car, while NSU went ahead with its two-rotor Ro80.

Daimler-Benz bought an option on the patent. At that time I said to Uhlenhaut, "You've not done that to bury the idea." His reply was, "Of course not. It is an interesting engine." It is this concept, in three-rotor form, that Daimler-Benz has introduced at Frankfurt in a mid-engined, two-seater sports car called the Mercedes C-111. It is designed along the classic lines of the Le Mans-winning Ford GT40 and obviously could go into limited production. At the moment, however, it is being shown as a research and development vehicle, or public test bed, for the rotary engine.

Coming from a small and adventurous manufacturer, the C-111 would have drawn admiration. That an apparently staid and conservative company like Daimler-Benz should produce it has laid the automotive world by the ears. It would have been a pity if the NSU Wankel had proved to be a failure; if the Mazda had failed we could describe it as an Oriental adventure. But by tradition Daimler-Benz must not fail, and so this engine from Stuttgart is a serious portent of what must come. The car is here for all to see, for some to drive and maybe even for some to own. This can mean but one thing: in Stuttgart the reciprocating piston engine is as dead as the dodo. The funeral will not be today, indeed it may not be tomorrow, but the only question is just when it will finally lie down.

What is this rotary Wankel engine and why? To the development engineer, the rotating piston engine is just beginning its useful life, whereas the orthodox reciprocating engine has long been past its prime. For equal capacity the Wankel engine can be produced at about two-thirds of the weight of a conventional engine and in about half the space; it poses far fewer problems of balance and smooth running, has unlimited development possibilities in the rpm sphere and already in its infancy at Daimler-Benz is producing 330 hp (SAE) from 220 cu. in. of displacement in production form. The piston and running chamber can be produced as a single unit or in any multiples thereof. NSU started with one chamber, Mazda went to two, Daimler-Benz to three. The next steps undoubtedly will be four, five or six, depending on how much power is wanted—and each addition takes up very little extra space.

As for the rotary engine's bad reputation in regard to air pollution, this may be said: normally if only 500 cars are produced you do not have to comply with antipollution rules. If 5,000 are produced then you do. Mercedes is aware of all the rules, and however many cars are produced the company will adjust to them.

[In Detroit a senior automotive engineer who has studied and tested the Wankel concept said Mercedes would have to be making giant strides indeed if it were close to solving emission and other problems of volume production—problems which, in his view, are formidable.]

To anyone involved in the motor-racing world there is today only one place for the engine. That is the mid-engine position, just ahead of the rear axle and just behind the driving compartment, and that is where Uhlenhaut has put it in the C-111. Even USAC and Indianapolis have come round to this way of thinking; Ford and Chevrolet have shown that in sports cars they also agree. "For the ultimate in road holding and handling there is no argument against the mid-engined sports car," said Uhlenhaut, "and our compact Wankel fitted neatly into the whole concept." It would also fit neatly into the concept of a traditional front-engine sedan, but that is neither here nor there at the moment. Having driven Porsche, Ford, Lotus, Rover, Lamborghini, Ferrari and de Tomaso cars of the mid-engined coupe layout, I am convinced of the validity of that concept for sports car motoring, and from the time I saw the first single-rotor NSU Wankel experimental engine many years ago I was sold on it, too. To get the two concepts in one vehicle, as with the C-111, was more than I had expected.

Uhlenhaut said, "We are just going for a test drive in the C-111 to try out some small things. Why don't you come along?" I was in the passenger seat almost before he had buckled his seat harness. Uhlenhaut, at 63, still drives harder and faster than I have ever been able to do, and as we left the factory gates he floored the accelerator. The smooth hum from the Wankel engine became hard and purposeful as the speed went up to 7,000 rpm. "We are just on the threshold of this power unit," he said, as he released the 330 hp and reached peak rpm in the intermediate gears. "It has unlimited possibilities." The manual, five-speed gearbox he explained as a purely temporary expedient. A fully automatic transmission is obviously in the future for this engine and, ultimately, an infinitely variable transmission so that the engine can run at almost constant speed. After a few miles and a demonstration of the car's good manners over a poor-surfaced, undulating road, Uhlenhaut gave me the car and said, "Off you go, it is not difficult to drive. This is aimed at being a sports car that any enthusiastic driver can manage, not a racing car that needs a specialist driver."

With no camshafts, poppet valves or valve gear, there is virtually no mechanical noise from the Wankel engine, but the very quick uncovering of the exhaust ports and the free gas flow give rise to a lot of exhaust noise—as with orthodox two-stroke engines—that has to be subdued by large mufflers. Intake gas roar is also loud, for the same reasons, though once again good mufflers reduce this. The feeling of the engine on the accelerator pedal is very much like a two-stroke engine, and the exhaust note adds to this feeling. With relatively low rotating masses the inertia is low and torque is poor at very low rpm so that 2,500 rpm are needed when taking off from a standstill in low gear. Once over that figure the engine really surges upward, and the car accelerates with that constant pressure on the seat that is typical of all high-performance sports cars. Apart from a very slight delay on the throttle response, it would be difficult to know that you had a Wankel engine in the car. It runs like a dynamo, and there is no feeling of stress from the engine at peak rpm, unlike some reciprocating engines that let you know orally and physically when they are flat-out. From 5,000 rpm the engine really surges on up to 7,000 rpm, and you need to keep a wary eye on the tachometer. On the C-111 the driving position is orthodox, with an adjustable seatback so that it can be fairly upright for those who prefer it that way. In all our discussions Uhlenhaut emphasized that this was nothing way out or freaky, but an advanced and practical vehicle. When I suggested that a sports Mercedes-Benz was long overdue to carry on the traditions of the SSK and 300SL models, he agreed.

Although Daimler-Benz has not been racing mid-engined cars, as have Ford, Ferrari, Lotus and Porsche, the company does not seem to have missed a thing, and the C-111's balance and handling more than matched up to my personal, rather stringent, standards. For me the satisfaction of the balance of a mid-engined sports coupe is its directional stability and the way you can make such a machine change direction very suddenly, without any subsequent drama—as when making high-speed traffic maneuvers on open highways or in mountain country where corners appear frequently and in different directions with very little warning. The C-111 came out well on handling, except when I experimented near the limit of tire adhesion and I found the front wheels wanted to "plow" straight on in an understeer attitude. Commenting on this, Uhlenhaut said, "Try the car again after lunch; at the moment we are experimenting, and we have no antiroll torsion bar on the rear suspension." Of course, he was right, for with modern suspension systems you can make adjustments to suit any taste, and the afternoon tests removed my only criticism of the car's handling.

Afterward, in the sunny countryside of southern Germany, I chatted with Uhlenhaut about sports cars, high-speed driving, automotive engineering, racing and manufacturing problems. This man, whom I first got to know well in 1955 when I joined the Mercedes-Benz racing team to passenger Stirling Moss in his classic Mille Miglia victory, does not change. It did not seem possible that it was 14 years ago that we sat together on the side sill of a gull-wing 300SL Mercedes-Benz coupe in Italy and talked high-speed driving. Here we were in 1969 doing the same thing, only this time on the side sill of a gull-wing Wankel-engined C-111. "Times don't change very much," I remarked. "Then you produced your desmodromic valve, fuel-injected SLR engine; today you have produced this three-rotor Wankel engine. It is the engineering confidence which is significant to me."

"The only thing that changes," said Uhlenhaut, "is that we are getting older. But we must not let it show."

As he drove me back to the factory, traffic conditions limited our speed to 135 mph, though the car is geared for a maximum of 160. Dr. Liebold, the engineer in charge of the development of the C-111, was following us in a 300SEL 6.3-liter V8 sedan, keeping pace with his chief, and I recalled a test day in 1955 when Moss and I were in our racing 300SLR, cruising the German Autobahnen at 135 mph, and Engineer Kosteletsky, who was shepherding us, kept pace in a gull-wing 300SL sports car. Now the 1970 gull-wing sports car was leading, and a production sedan was keeping right up. I would call that progress.