NSU Ro 80 (1967)



Ro 80 was famous for being the first mass production car featuring rotary (Wankel) engine. Unfortunately, that engine was also the cause of its failure, which killed not only the car but also its maker NSU.

Back in 1967, the Ro 80 was probably the most technologically advanced production car in the world. Its twin-rotor engine, invented and developed by German engineer Dr. Felix Wankel, was considerably smaller and lighter than conventional piston engines, and was renowned for turbine-smooth operation. Each combustion chamber displaced 497.5 cc thus the engine was equivalent to a conventional 2-liter unit. It produced 115 horsepower and enabled a top speed of 112 mph. The rest of the car was equally state of the art. Its body shell was shaped in the wind tunnel of Stuttgart Polytechnic, delivering an impressive aerodynamic drag coefficient of 0.355. Its modern design was well ahead of its time and foresaw the cars of the 1980s (in particular the game-changing 1982 Audi 100). Its 3-speed semi-automatic gearbox featured a torque converter and an automatic clutch triggered by a micro switch on the gearstick. It got all-independent suspensions, all-round disc brakes, rack-and-pinion power steering and front-wheel drive. Since Citroen DS, cars had never been so futuristic!



However, the radical decision to adopt Wankel engine turned out to be wrong and fatal. Not only it was thirsty, it suffered from excessive wear on rotor tip seals, causing leakage between combustion chambers, hence power loss, deteriorating fuel consumption and even complete crack down. The whole engine had to be rebuilt or even replaced as early as 30,000 miles! The reliability and durability problems led to huge warranty expenses while poor reputation drove customers towards rivals Mercedes and BMW. Although NSU had largely sorted the problems in later years, it was too late. The company was rescued by Volkswagen in 1969, merged with Auto-Union and formed the modern Audi. The Ro 80 itself survived until 1977, then the Neckarsulm factory was converted to assemble Porsche 924.



Reliability problems aside, contemporary road testers loved Ro 80 very much. Despite of lacking low-down torque and outright performance, they praised the car for smooth and quiet power delivery. The ride and handling was very good for a premium car. Its soft-setting and long-travel suspension delivered a French-style supple ride. Although understeered and rolled more in corners than some driver's cars, it offered good traction and roadholding. Excellent high-speed stability and minimal wind noise made it a great Autobahn cruiser. The power steering offered class-leading weighting, precision and feel. Inside, the cabin was spacious and the seats were comfy. Slim pillars and large windows afforded excellent visibility. No wonder it was elected as European Car of the Year in 1968. That happened before its reliability problems uncovered, of course.

No matter how brilliant it was, the Ro80 became the victim of its troublesome rotary engine. However, Wankel engine did not disappear from the world. Just a year after the demise of Ro 80, Mazda introduced RX-7. Having spent a lot of effort improving the design, the Japanese finally sorted out its sealing problems and made it practical for real-world use. What a pity NSU and Dr. Wankel did not do the same before fitting to the Ro 80.

Specifications

Model
 NSU Ro 80
Year of production
 1967-77
No. produced
 37,400 units
Layout
 Front-engined, Fwd
Engine
 2-rotor Wankel
Capacity
 2 x 497.5 cc
Power
 115 hp
Torque
 117 lbft
Gearbox
 3-speed semi-automatic
Suspension
 F: struts; R: semi-trailing arm
Weight
 1290 kg
Top speed
 112 mph
0-60 mph
 12.4 sec*

* Tested by CAR

The rise and fall of rotary engine

Felix Wankel originated the idea of rotary engine as early as the 1920s but full development was not started until 1954, when he persuaded NSU, a motorcycle manufacturer then, to fund the project.

In theory, the rotary engine has a lot of fascinating advantages. Firstly, the rotors spin in one direction, unlike pistons which change direction reciprocatingly, thus must be smoother and more energy efficient. Secondly, it uses fewer components – a twin-rotor Wankel engine compares favourably with a conventional 6-cylinder engine, and it saves considerable valve-gears and crankshaft components, thus it can be made smaller, lighter and simpler than piston engines. Thirdly, lacking valve-gear mechanisms and crankshaft leads to less vibration and noise.

NSU's rotary engine 

Dr. Wankel experimented his first rotary engine in NSU. It eliminated the imperfect eccentric movement of rotor by a revolving housing which was held by another housing. It was perfectly smooth, but too complicated to implement in an economical way. Therefore at last a more compromised design, with eccentric rotor and a single fixed housing was adopted. This is also the design that Mazda still uses today.

The first 498 cc single-rotor engine was introduced to the 1963 NSU Spider, a small roadster like Fiat 850 Spider. It was just a low-volume experimental project.

Next step was to put the technology into a mass production car. The 1967 Ro 80 seemed to be a winner. It had all sorts of advanced technology and futuristic design to win European Car of the Year award, but its 115 hp twin-rotor engine was found to be unreliable soon. Rotor tip sealings worn out quickly, increasing fuel consumption, decreasing power, causing oil leak and breakdown. This cost NSU substantial money on warranty and established a bad reputation for Wankel engines. To a large extent, NSU’s financial trouble and eventual acquisition by Volkswagen was driven by the Wankel engine. It has never produced rotary engines since then.

However, before that happened Wankel engine technology had already attracted the attention of the world. To raise development budget, NSU sold its license for United States to an aircraft engine maker called Curtiss-Wright, which then sub-licensed to General Motors, Ford and other car makers.

GM's effort

General Motors was the most eager player besides NSU and Mazda. It obtained worldwide license from NSU in 1970, then displayed two prototypes in 1973, i.e. Chevrolet Corvette 2-Rotor and Corvette 4-Rotor, both were mid-engined. Having invested a lot of money on rotary projects, GM estimated 80 percent of its production in 1980 would be powered by rotary engines.

The real production car, Chevrolet Monza, was to be launched in 1974, but the plan was hit by the newly announced smog regulations for 1977, which was so strict that GM feared the rotary engine could have problems to comply with. Eventually, Monza appeared with conventional engines. The prospect of rotary programme became uncertain, and virtually dead when its supporter, Ed Cole, president of GM, retired in September 1974.

Citroen, Mercedes and Nissan

Citroen collaborated with NSU and created 2 rotary-engined cars, Ami 6 and GS Bimotor. Both were installed with NSU's engine. However, they were short-lived and limited in numbers.

Mercedes was another giant European car maker to experiment Wankel engines. Mid-engined exotic concept car C111 stunned the world in the 1969 Frankfurt motor show. 3-rotor and 4-rotor version output 320 hp and 405 hp, respectively. But it did not come true.

Nissan took a Wankel license in 1970 and created a prototype in 1972. It planned to produce a small sports car at the rate of 120,000 cars per year, but eventually cancelled after the 1973 oil crisis.

Mazda - the only survivor

Mazda, called Toyo Kogyo then, obtained the license from NSU in 1960. Originally it wanted to put NSU's engine directly to its vehicles, but after experienced delivery delay and disappointing vibration and fuel consumption, it designed its own Wankel engines from scratch. 

Why was Mazda so eager to develop this technology? Because in the 1960s the Japanese government wanted to merge car makers in order to enhance international competitiveness. To retain independence, Mazda believed developing a unique technology would help.

Its first rotary-powered car, Cosmo, went into low-volume production in 1967. That was a 2-seat GT like the original Ford Thunderbird. Twin-rotor each displaced 491 cc, capable of pumping out 110 hp, later upgraded to 130 hp. It was a true 200 km/h grand tourer. 5 years of production totalled 1,519 units.

Having experimented the technology, Mazda became confident to put Wankel engines into mass production. In 1968, it launched a 4-seat coupe called R100, which was derived from the mass-produced Familia sedan. Powered by 10A twin-rotor engine and output 100 hp. It was shipped to the USA in 1970 and became a hit. Mazda created a rotary boom there with more rotary cars – R130, RX-2 and RX-3, all were based on the R100. In 1971, Mazda produced the 200,000th rotary cars!

The prospect was bright, and the company planned to produce 100% rotary cars by 1975. But the oil crisis changed that overnight. Since rotary  engines were well-known for thirsty, sales in the US dropped by half in 1974 and did not recover to the 1973 level until RX-7 was launched. Wankel engines for econo cars became out of the plan, thus its application was limited to RX-7 in the following 20 years. The only exception was the 1992 Cosmo, which was a modern version of the original Cosmo powered by a 280 hp twin-turbo 3-rotor Wankel engine. Its sales was bounded in Japan.

In 2003, Mazda introduced the next generation Wankel engine called RENESIS (which meant Rotary Engine Genesis) on its new 4-seater coupe RX-8. While the previous rotary engines employed side intake ports and peripheral exhaust ports, the new one switched to side ports for both intake and exhaust. This lengthened the expansion stroke and enhanced thermal efficiency. It also enabled larger exhaust area, enhancing breathing and power output. Emission was also significantly improved by the design. The RX-8 achieved considerable sales success, if not matching the early RX-7 in the good old days. Nevertheless, as the world pursued green motoring harder and harder, its thirst of fuel became a big hurdle to sales. Following its end of life in 2012, Mazda's rotary engine production came to a stop.

 
Copyright© 1997-2012 by Mark Wan @ AutoZine