Rotary Revolutionary: The NSU Ro80

THE TROUBLE BEGINS

The NSU Ro80 was an entirely new product from a company that hadn’t sold an executive car in conscious memory, powered by a bleeding-edge engine and rushed into production. What could possibly go wrong? In all fairness, if we discount the engine, the answer is “Surprisingly little”; even the curious Saxomat transmission was generally reliable. Der Wankelmotor, however, quickly established itself as a problem child, threatening to overshadow the Ro80’s other virtues.

1970 NSU Ro80 toolkit © 2012 Andrew Buc (used with permission)
All NSU Ro80s came equipped with this handy toolkit. The inclusion of a spark plug wrench and spare plugs is helpful, as plug cleaning and replacement were frequent chores for owners who drove regularly in stop-and-go-traffic. (Photo © 2012 Andrew Buc; used with permission)

Despite the rotary’s apparent simplicity, long-term testers soon complained that the KKM 612 could be frustratingly difficult to keep in proper tune. If the twin Solex carburetors were even slightly out of adjustment, the result would be hesitation and flat spots, which took a fine touch to correct. The spark plugs were another headache; the rotary had a unique flair for fouling its plugs in slow driving. The plugs’ position in the combustion chamber made it impossible to clear them with a burst of speed as one could with a piston engine, so the only recourse was to remove the plugs and clean or replace them. If most of your driving was on open roads, that was not a major concern, but regular urban commuting limited plug life to 5,000 miles (8,000 km) or less and the specified plugs cost were very expensive, 10 to 12 times the cost of a standard plug.

Those shortcomings were tolerable, if annoying, but they were followed by a rash of more serious engine problems, including failure of the apex seals and/or eccentric shaft bearings, often at less than 25,000 miles (40,000 km). Rather than attempting to repair or rebuild those engines, NSU generally opted to replace them (sometimes more than once) under and sometimes beyond the 20,000-mile (32,000-km) factory warranty. That was inevitably very expensive, and while NSU’s rather generous engine replacement policy was intended to appease nervous or angry customers, it actually served to drag down the car’s reputation.

1970 NSU Ro80 engine © 2012 Andrew Buc (used with permission)
The rotor housings of the NSU Ro80’s KKM 612 are aluminum castings, although the inner surfaces are plated with nickel silicon carbide. Despite the aluminum housing’s higher manufacturing costs, NSU and Toyo Kogyo considered it a necessity because tests with cheaper cast iron housings found that iron heat-cycled so much that the housings would crack around the spark plugs. This 1969 engine still has two spark plugs per rotor, replaced later in the year by single plugs. The latter was a compromise — NSU’s testing had found that dual plugs enhanced power and fuel economy — but greatly simplified the electrical system and substantially reduced costs. The later KKM 871/EA871 engine returned to dual plugs. (Photo © 2012 Andrew Buc; used with permission)

The root of the problem (aside from the Ro80’s overly hasty development) was that NSU had misjudged its customers’ real-world driving habits. The company apparently assumed that because the Ro80 was a large and thirsty car, most owners would use it in a relatively sedate fashion, mainly for long trips. In practice, the Wankel’s eagerness to rev encouraged owners to drive far more aggressively, with frequent excursions to or beyond the 6,500 rpm limit. While the engine was so smooth that it would exceed its redline without apparent complaint, such treatment exposed the limitations of the oil system, eventually leading to bearing damage. Stop-and-go driving, meanwhile, not only fouled the plugs, but also played hob with the engine’s clever three-piece, self-adjusting apex seals, particularly with liberal use of the manual choke.

While NSU subsequently made changes that at least mitigated the Ro80’s major weaknesses, the damage to the car’s image and the company’s bank account was considerable. NSU was already overextended and the Ro80’s massive warranty costs only made a bad situation worse. The ultimate price would be the company’s fiercely guarded independence.

SIDEBAR: Apex Seals of the KKM 612

Because they proved troublesome in early service, the apex seals of the NSU Ro80’s KKM 612 are much-maligned and often misunderstood. In fact, the design was quite sophisticated, although it suffered from the Ro80’s hasty development.

One of the major weaknesses of the Wankel Spider’s single-rotor KKM 502 engine was the rapid wear of its soft carbon apex seals. Those seals had been chosen to minimize chatter marks (scoring of the rotor housing surface), but had a short lifespan. Once the seals began to wear, engine performance deteriorated significantly until the seals were replaced, which required tearing down the engine.

To avoid that problem with the Ro80, the KKM 612 engine adopted more durable cast iron seals of a clever self-adjusting, wear-compensating design. Each three-piece, spring-loaded apex seal was designed to allow combustion gases to pass under it, building up pressure that would force the tips of each seal closer to the rotor housing. Since that pressure was proportional to engine speed and throttle position, this design would theoretically maintain an optimal distance between the seal tips and the hard EINSIL rotor housing surface in all operating conditions. Not only did that promise a much greater lifespan for the seals, NSU tests found that it reduced internal friction by as much as 25% compared to one-piece soft carbon seals, a highly worthwhile improvement.

The weakness of this design lay in NSU’s mistaken assumptions about how owners would use the Ro80. In highway driving, which was apparently the principal focus of preproduction testing, the original seals worked as intended, but frequent stop-and-go driving produced an unanticipated problem: failure of the gas-operated self-adjustment feature due to rapid deterioration of the sides of the apex seals. This was precisely the opposite of what NSU engineers had anticipated; another reflection of the engine’s hasty development; given more time, the problem would likely have been identified before the car went on sale.

After reports began to come in from operational experience, NSU launched a crash program to do what they should have done before launch: evaluate the seals’ behavior in short trips (mostly between the Neckarsulm factory and the nearby village of Hasenmuhle) in real-world traffic with limited warm-up. This program yielded quick results: an interim seal design in late 1969, at the start of the 1970 model year, followed about a year later by an updated version of the original design, now using much harder Ferro-TiC (steel alloy bonded titanium carbide) material.

By most accounts, the Ferro-TiC seals were much more durable and largely addressed the KKM 612’s sealing problems. In the early seventies, Walter Fröde told the press that with the new seals, the Ro80’s engine replacement rate was now in the same realm as its German-made, piston-engined rivals, although he admitted it was still higher than NSU would have preferred.

ENTER VOLKSWAGEN

One of NSU’s ongoing challenges was that while Wankel licensing was a crucial source of revenue, the company was not unlike a minnow trying to do business with whales. The rotary engine had obvious value, but it undoubtedly occurred to some of NSU’s larger prospective licensees that it might be simpler to absorb the whole company and its patents rather than pay royalties. Von Heydekampf, however, had always refused to be intimidated, adopting a take-it-or-leave-it attitude toward negotiations. The NSU board strenuously resisted any attempts at outside takeovers, although Citroën did acquire about 10% of NSU through the two companies’ Comobil and Comotor joint ventures (a share acquired in 1968 by Fiat).

By early 1969, however, NSU’s position was becoming untenable, so von Heydekampf reluctantly entered discussions with Kurt Lotz, the new managing director of Volkswagen. Lotz, who had succeeded VW’s conservative Heinz Nordhoff in the spring of 1968, was still looking for Volkswagen’s post-Beetle direction and was very interested in expanding Volkswagen’s product range and production capacity. NSU needed capital very badly, but the Neckarsulm firm was still very reluctant to sacrifice any of its independence.

The compromise Lotz eventually struck with NSU was a merger with Auto Union (Audi), the Ingolstadt automaker in which VW had acquired a controlling interest back in 1964. The deal promised greater autonomy for NSU and did not require the approval of Volkswagen’s supervisory board, with which Lotz seldom saw eye to eye for various political reasons.

1970 NSU Ro80 front © 2012 Andrew Buc (used with permission)
The European NSU Ro80’s composite lights and headlight covers were not legal in the U.S., so federalized cars substituted quad sealed-beam headlights. RHD cars shared these lights from fall 1968 until June 1970. (Photo © 2012 Andrew Buc; used with permission)

The merger, announced in March 1969, created a new company, Audi-NSU-Auto Union, chaired by von Heydekampf and initially holding just under 60% of NSU stock. While a majority of NSU stockholders approved the deal, a small but vocal minority strenuously opposed it, and German law allowed those minority shareholders to demand significant concessions. Among these was an agreement providing genusscheine, profit shares, to NSU’s stockholders, giving them a substantial percentage (initially 40%, subsequently raised to almost 70%) of the company’s revenues from the Wankel engine for the next decade. Another concession was that Volkswagen would not be able to use the rotary engine in its own products without paying license fees to Audi-NSU-Auto Union.

In the short term, Lotz was more interested in NSU’s piston-engined Typ 70, which had been delayed and then briefly canceled around the time of the merger, first for lack of funds and then because the car would have competed directly with Volkswagen products, including the Audi 100. Lotz decided to resurrect the project and transfer it to Volkswagen, albeit with many ‘minor’ revisions that ultimately cost nearly twice as much as NSU had spent developing the car in the first place. It was launched in the fall of 1970 as the Volkswagen K70.

That move added to the displeasure of the minority stockholders, who were already infuriated by many provisions of the merger agreement, most particularly the rather modest option price set for NSU’s remaining stock. Led by the Israeli British Bank, the minority shareholders eventually took the matter to court, an acrimonious case not fully resolved until 1971, around the time Kurt Lotz resigned. NSU may have ended up in the belly of the whale — Audi, and by extension Volkswagen — but it left the whale with a certain amount of indigestion.

1971 Volkswagen K70 L front 3q © 2009 Kroelleboelle CC BY-SA 3.0 Unported
Although ultimately marketed as a Volkswagen, the K70 was developed by NSU to fill the sizable gap between the Prinz and the Ro80. Designed by Claus Luthe, the Volkswagen K70 was 174 in. (4,420 mm) long on a 105.9-inch (2,690mm) wheelbase, with front-wheel drive and inboard front disc brakes. The K70 was powered by a 1,605 cc (98 cu. in.) water-cooled four with 75 PS (55 kW), although the original design also had provision for the Ro80’s two-rotor KKM engine. Volkswagen never offered the K70 with rotary power, but from 1973, a larger 1,807 cc (110 cu. in.) piston engine became available, providing 100 PS (74 kW). (Photo: “1971 VW K70 L Front” © 2009 Kroelleboelle; resized and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

THE SURVIVOR

Following the merger with Audi, NSU continued developing the Wankel engine and working to resolve the Ro80’s problems. In the fall of 1969, the Ro80 received a new and much cheaper transistorized ignition system with a single coil and one spark plug per chamber along with an improved apex seal design. The latter was only an interim measure, followed in mid-1970 by a thorough update of the initial three-piece design using Ferro-TiC seals that NSU claimed were an order of magnitude more durable than the originals.

At the same time, the oil system was revised to provide better protection for the eccentric shaft bearings at high rpm, supplemented a year later by a dashboard buzzer to warn of over-revving. An automatic choke was added in 1972 and for 1973, the twin carburetors gave way to a single two-throat Solex 32DTI TS; output increased slightly, to 115 hp (86 kW) and 122 lb-ft (165 N-m) of torque. All cars now had emissions controls, including a thermal reactor similar to that used by Mazda, but NSU had never had much of a U.S. presence and we doubt that many Ro80s were formally imported after about 1970. It was almost certainly gone by the 1973 model year, as the Ro80 did not meet the new U.S. 5 mph (8 km/h) bumper standards.

1970 NSU Ro80 instrument panel © 2012 Andrew Buc (used with permission)
This U.S.-spec NSU Ro80’s dashboard includes a 140 mph speedometer (highly optimistic), an 8,000 rpm tachometer redlined at 6,500 rpm (although this car does not have the warning buzzer added in 1971), fuel and water temperature gauges, and a clock. Other functions are signaled by an assortment of multi-colored warning lights. The headlight dimmer, turn signals, horn, and wipers are controlled by steering wheel stalks. The labeling of the minor controls was originally criticized for being cryptic and confusing, so the symbols were extensively revised in 1970. Late (1974–1977) cars also used a larger typeface for the main dials. (Photo © 2012 Andrew Buc; used with permission)

Those changes made the Ro80 much more reliable than it had been (if still not wholly trouble-free), although its appetite for fuel, oil, and spark plugs was not abated. However, it was not easy to overcome the Ro80’s bad reputation, particularly with the alarming reports in the press and editorial cartoons in German magazines showing NSU drivers greeting each other with hand signals to indicate how many engines their car had had (a practice many English-language histories subsequently reported as fact). Sales for 1970 were down nearly 20% from the Ro80’s 1969 peak and 1971 sales fell a further 50%.

Business rallied in 1972 and 1973, but with the Wankel’s considerable thirst, the OPEC embargo in late 1973 and early 1974 was crippling. The Ro80 was already expensive to run and fuel shortages made its sales a very difficult proposition in Europe. Production dropped to fewer than 1,200 units in 1974 and about 1,800 in 1975. Constant price escalation probably didn’t help: the list price in Germany climbed from just under 18,000 DM (about $6,800) in the spring of 1973 to nearly 20,000 DM (about $7,700) by the fall of 1974. By mid-1975, the Ro80 had also disappeared from the U.K. except by special order.

1976 or 1977 NSU Ro80 front 3q © 2007 Rudolf Stricker CC BY-SA 3.0 Unported
There were very few external changes to the NSU Ro80 over its 10-year lifespan, making identifying the model year based on external cues very difficult. Post-1970 European cars like this one had a plastic (rather than aluminum) grille and new headlights with separate elements for high and low beams. This car’s rubber bumper inserts mark it as a 1976 or 1977 model. (Photo: “NSU RO80 front 20070502” © 2007 Rudolf Stricker; resized and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

By then, NSU’s piston-engined cars were all dead, replaced on the assembly lines by Audi products. The K70’s days were numbered: its execution had been flawed, its performance was disappointing, and being sold as a Volkswagen meant that NSU’s original plan to offer it with a rotary engine (perhaps as an answer to the BMW 2002) never came to fruition. The K70 finally died in May 1975, having sold around 211,000 units.

The joint ventures between NSU and Citroën also came to nothing. The sole product of the Comobil venture was the Citroën M35 (essentially an Ami 8 with a single-rotor Wankel engine), a road-going research project of which only a few hundred were built. Comotor’s two-rotor KKM 622 engine (derived from the Ro80’s KKM 612) was a costly flop, used only in the ill-fated Birotor version of the Citroën GS, and plans to sell the engine to other automakers never materialized.

Despite all that, the NSU Ro80 was not dead. It received more changes in mid-1975, including new taillights and new bumpers, and in 1977 the Saxomat transmission received new internal gear ratios. The latter modification foreshadowed Audi-NSU’s ambitions for a second-generation Ro80 — something that had been rumored in the press for several years. The new Ro80 was to feature a larger, more powerful engine with a geometric displacement of about 1,500 cc (92 cu. in.), aimed at six-cylinder piston-engined rivals.

1976 or 1977 NSU Ro80 rear 3q © 2007 Rudolf Stricker CC BY-SA 3.0 Unported
Some sources describe the NSU Ro80’s 1976 exterior changes as a facelift, which is probably overstating the point. Other than the rubber bumper inserts front and rear, the principal changes are new taillights with integral fog lamps and a relocated rear license plate (now above rather than below the bumper). In certain markets, 1976–1977 cars also had a two-piece rear bumper. (Photo: “NSU RO80 rear 20070502” © 2007 Rudolf Stricker; resized and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

NSU’s original plans were for the new Ro80 to use a three-rotor version of the KKM 612 engine, the KKM 619, giving a total displacement of 1,493 cc (91 cu. in.). Further investigation suggested that it would be easier and cheaper to create a new two-rotor engine using a larger rotor diameter to give the same 1,493 cc swept volume. The result was the KKM 871 (known as EA871 in Audi/Volkswagen parlance), which was good for 170 to 180 PS (125 to 132 kW) in preproduction trim. The big engine, prototypes of which were tested in Audi 100 development mules, provided much better performance than the smaller KKM 612 and attracted interest from a number of other automakers. Two EA871A engines, de-rated to 150 PS (110 kW), even found their way into prototypes of the RFP Fanliner, a small acrobatic aircraft.

While the EA871 project enjoyed some support within NSU-Audi — leading to plans to use the new engine in the new C2-platform Audi 100/200 as well as a new Ro80 — technical director Ferdinand Piëch was increasingly skeptical about the Wankel’s viability in the European market. Piëch felt (correctly, as it turned out) that diesel was a better bet than the rotary, which still suffered from relatively poor thermal efficiency and inherently heavy fuel consumption. (Based on the SAE thermal equivalency formula, the EA871 would have been comparable to a 4.5-liter (273 cu. in.) piston engine and probably very thirsty by European standards.) Although Piëch eventually succeeded in ending Wankel development, it was not a universally popular decision. According to writer Martin Buckley, some senior company executives continued to favor cars powered by preproduction EA871 engines well into the 1980s. A few EA871 engines later found their way into private hands.

46 Comments

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  1. I believe this is the most comprehensive NSU story ever published in America.
    The research for the article is top notch.

  2. When I moved to Boulder, Colorado, in January 1972, there was an NSU dealership downtown with a Ro 80 in the showroom. I had read some articles about the car and knew what it was, and I don’t know why I didn’t stop in for a closer look at this one. I remember it being burnt orange. I don’t know if it was an incoming ’72 or a leftover ’71.

    I think the dealership was still there when I left Boulder in August 1973, but I hadn’t really been keeping tabs on it.

    1. It’s possible — I wasn’t able to find any definitive answers on how long NSU had U.S. franchises or what happened to those places after NSU pulled out. Did they get Audi franchises? Did they just go away? If anyone has more specific information, I’d be very curious.

      As I said in the text, it’s hard for me to see NSU sticking around long after MY 1973. By that point, the Prinz and other models were out of production, and I don’t know of any attempts to make any of NSU’s cars (including the Ro 80) compatible with the U.S. bumper standards.

  3. Regarding Ro80 interior storage, there’s plenty. There’s a large “magazine” shelf below the 5 band radio and glove box.
    The front seat backs have two large pockets for those sitting in the rear seats.

    1. Fair enough. I should note that the complaints about interior storage came chiefly from British critics, who were accustomed to having a whole array of door bins and oddments trays on even little cars like the Mini. I think they looked at the Ro 80’s large and uncluttered interior as a missed opportunity in that respect. (Of course, for one accustomed to British luxury cars, the Ro 80 was a little plain inside, but large enough to provoke fits of agoraphobia…)

      1. I ran a ’74 model Ro80 in the mid eighties, bought when they were
        practically worthless and I have been a Wankel fan ever since. The Ro80 interior was then criticised for it’s “Germanic” plainness but not by me; I have never gone for the leather / wood / wool interiors that Brits. are supposed to like.
        I loved the space, the quiet, the view through those huge windows, the ride, the fine steering and superb brakes. And of course that fantastically smooth engine! My car had 47000 odd miles when I acquired it, definitely on the original engine. There were some starting issues at first but these were fixed with a change to NGK spark plugs. I think I got about 20 miles from a UK gallon, not good but the engine did encourage full throttle. Sadly it had to go in the end due to rust.

        1. Well, the Ro 80 may not have matched cars like the XJ6 for that British men’s club feel, but from a packaging standpoint it was really no contest. When [i]Car[/i] compared the Ro 80 to the BMW 525 and Jaguar XJ6L Series II in 1974, they made the usual complaints the NSU looking too stark, but they had to admit that Ro 80 was roomier than even the long-wheelbase Jag.

  4. I guess the story comes full circle with the Wankel-engined, hybrid concept, the Audi A1 e-tron.

    (By the way came across the site some weeks ago and I have to say the stories are excellent, and very informative, especially for European people)

  5. Aaron,

    GREAT article, as always. Love your research and your writing. Have a small correction to your apex seal diagram captions: The part labeled "sealing bolt" is actually a corner seal:

  6. Thank you again, do you read my mind? I have reflected upon the Ro80 many times with Mazda ceasing production of a rotary engined auto. I was so enthused by your article that I had to share it at work. I thought that my description of a rotary combustion engine would be perfectly understandable. This was not the case.I did, however, garner some understanding of my interest when I E-Mailed an image of the Ro80. Even a complete non car person offered a comment that it could not be that old.Indeed.

  7. I always thought the RO80 was one of the sharpest designs of the ’60’s and wanted one, despite the problems with the early Wankel. Still a stunning looker and a real pioneer!

  8. Absolutely terrific article!

    But one little “gotcha”….. You wrote “The rotor housings of the KKM 612 are aluminum castings, although the inner surfaces are plated with nickel silicone carbide.”

    Looks like you fell into the Silicon-Silicone trap! Silicone is a rubbery material familiar to most people as bathtub caulking. It is also what attaches the tiles to the space shuttle. There is no such thing as Silicone Carbide!

    The above quote should have read “silicon carbide”…. a very hard crystalline substance.

    But none of the above detracts from the excellent piece on the Ro80!

    1. That was a typographical error in the photo caption; I’m well aware of the difference between silicon and silicone, and you’ll note that it was spelled correctly in the first instance in the text.

  9. Thanks again Aaron, a lot of stuff I did not know about the RO80, I've only seen one.

  10. [quote=Administrator]It’s possible — I wasn’t able to find any definitive answers on how long NSU had U.S. franchises or what happened to those places after NSU pulled out. Did they get Audi franchises?[/quote]

    Just speculating, but on general principles, I wouldn’t think that NSU dealers would automatically be grandfathered in. I’d think that Audi would need to feel the need for another dealership in that area and would need to see the ex-NSU dealer as a worthy candidate for the franchise.

    You’ll notice that on the license plate frames of Jim’s car, it says Lake City. Lake City is a neighborhood in the northeast corner of the city of Seattle proper, and Lake City Way is a major arterial through the area.

    I moved to Seattle in 1981, and I have dim memories of seeing a billboard for an NSU dealership on Lake City Way in the early ’80s. It was a couple of miles south of the commercial strip in the heart of Lake City, where the dealership would presumably have. Of course, at this point the billboard didn’t necessarily mean that the dealership was still around.

    1. Well, my thought process was that while Audi might not have been keen to give out new franchises to ex-NSU dealers, NSU-Audi did have to deal with U.S. franchise laws, which tend to favor the franchise holder in such situations. If NSU dealers did NOT switch to Audi at some point, it’s hard to see how they would have stayed in business, since I’m pretty sure that by the start of the 1974 model year (fall 1973) there were no NSU cars still in production that met U.S. regulations

      1. All NSU dealers in America sold other imported cars. Most sold other German cars. The largest was Overseas Imports in Livonia, Mich. Their main line was Italian cars because the owners were Italian. I asked about the why they sold NSU’s and was told they respected the NSU marque and they liked to quick and nimble cars that were easy to work on… he said one can change a clutch in 30 minutes. Which is true.

        1. At least in the U.K., the “book” time for a clutch job was listed as 5.3 hours, although that was still not bad for a FWD car and a good deal shorter than a Citroën DS (which was 12 hours) or a Rover 2000/2200 (which was over 10 hours), both engine-out jobs.

          1. I think the 30-minute clutch change applied to the rear-engine air-cooled NSUs.

  11. Lake City Auto Imports was located at 91st and Lake City Way, which is in Seattle City limits. I bought my Ro80 from one of the owners who was going through a divorce and need to liquidate assets. I paid full market value at the time.
    After having three kids and having three citations in so many years I decided to retire the car till I wised up.
    The car set in my shop untouched for over 30 years. I went through the car and changed all fluids, wiped off 30 years of dust with a diaper to prepared it for Seattle’s huge 2010 Greenwood Car show. Out of 900 cars entered the Ro80 came in number 27 of 30 awards. My car won Best of Class. There were so many fine cars in the show I would have been happy to be in the top 100. Being a judge at a car show is a tough job.

  12. What an excellent piece of research here. I have an RO80 myself. It was apparently brought over by a US military officer. I have attended the Essen Techno Classica show a few times, and looked for an RO 80 in Germany, but they are hard to find even there, and then of course there is the rust issue. I was stationed in Wiesbaden in 1970-72, and I remember seeing them exit the autobahn, with trails of blue smoke following them as they de-accelerated. I have also found a few Birotors for sale in France – the factory tried to buy every single car back to destroy them, but a few slipped through their fingers. Now that would be a find!

  13. Hi ROers, I am sitting on 3 Ros in Stuart Florida.
    A 1976 in super condition silver. A 1971-2? in good condition orange, great black vynil interior.
    And a 1969 ceased engine, avacado green.
    Actually looking to sell the 71 & 69 if anyone is interested. Email me. Rust minimal in the two for sale.

    1. Hi,

      I just read your post from Jan, 2013. Do you still have the 2 RO80 for sale ?
      I am interested in getting one. I am in California.

      Rainer

  14. nice write up by Aaron ..
    Jim your car looks fantastic
    Too bad no company ever put Bentele’s direct injection technology from 1962 into action.
    [U.S. Patent No. 3,246,636]

    1. I regret that for space reasons I haven’t been able to get into Curtiss-Wright’s Wankel development, either here or in the Mazda article. C-W did a lot of work on the Wankel over the years.

      One thing that’s worth mentioning that I didn’t exactly spell out is that NSU’s license agreements gave NSU access to its licensees’ rotary development information. NSU didn’t always implement the ideas that its licensees came up with (NSU and Toyo Kogyo went their own ways on a number of points), but Fröde et al were definitely fully aware of those developments.

  15. The lights! The lights!

    Our family had RO80s from about 1975 to 1980, when I was 9 to 14.

    The things I remember as outstanding were brakes, headlights, bootspace, interior space and silence, and that they are quite roly-poly, the amount of fuel used, and the cost of spares.

    This was a Brit car with the sealed beam halogen lights.

    No one wants them in less than pristine condition, so our 3 cars (1 had last run in 1980, the others were non runners for rebuild and parts bought back in 1980), so all 3 were cut up and scrapped last year when we moved to a smaller house.

  16. Very nice article and it is difficult to find well researched information about NSUs in general.
    A couple of corrections:
    1) the figure for the number of Spiders produced is 2x – the correct number is ~2,475
    2) The Spider always had only a single spark plug in production. It did not use a coil, but had an early electronic ignition which utilized an electron tube to generate the necessary hot spark.
    2) The Ro80 never had 2 distributors (Maxda’s did, though) – the early 2 plug per rotor engine (I have one) had a single distributor with four plug wires and two for the coils. The distributor rotor has two contacts opposite each other to fire the 2 plugs

    1. JJ,

      Thanks for the corrections — I’ve amended the text.

  17. hey,i have read the comments on this site and find some quite interesting.the ro80 was and is a unique auto,i know i owned four or five and even drove one coast to coast;california to new jersey years ago. bought the first one from dec auto in boulder,co. and the last one was converted to a 12a mazda. still have a parts and repair manual in english along with usa headlite assembly and amber directional lens for usa. give me a call to chat about the car and experiences of owning and driving one.

    1. Thanks, Dan. I redacted your phone number so that random spammers don’t use it to bug you.

  18. I have been seeing an Ro80 on the road here in Barbados fairly frequently of late,and a couple of weeks ago I met the owner, whose name is John King, at a classic car show.
    He said an English expatriate imported the car around 2002 (and I do recall seeing it once or twice in the north of the island back then. The expat sold it to a local car collector, who drove it for about 75 miles before putting it in storage. John bought it in 2013 after seeing it at a classic car show and has been using it as his daily driver since then.
    This car is a 1974 model and uses the upgraded NSU engine. John says the engine works well and he has only changed the water pump on it. He noted that it was not the most fuel efficient car and required oil changes every 1000 miles or so, but he said the frequent oil changes were advantageous in that they ensured the engine was always properly lubricated and the oil was clean.
    Cosmetically, it was resprayed in the original light blue, and the cloth inserts in the upholstery were changed, but everything else was original and all the accessories, including the electric sunroof, were in good working order.
    John added that cricket legend and Barbadian National Hero, Sir Garfield Sobers, brought the first Ro80 into Barbados in the early 1970s when he was at the height of his cricketing career. It was a 1972 model, whichi he kept for a couple of years. Eventually it passed through the hands of several owners until, to the best of his knowledge, it was scrapped some time in the late ’70s or early ’80s.

    1. Interesting! It’s always neat to see the unexpected places cars end up. Thanks for the info.

    2. Please send me photo of the Ro80 in Barbados for our archives.

      BTW-My grandfather 6 generations ago (1767-1790) had business dealings in Barbados….. he was the bookkeeper for a shipping firm…. their ship was named Barbados.

  19. Cannot help but wonder whether all that investment towards the Rotary by NSU would have been better spent on developing say a Lancia-inspired 2.0 narrow-angle V4 Twin-Cam engine for the NSU Ro80.

    1. Or buying engines from Lancia, which could have used the income! The difficulty, of course, is that controlling the rights to the Wankel engine was also a big part of the reason NSU had the money to develop the Ro80; rotary engine royalties were a major source of income for what was after all a very small company. A V-4 would still have cost them a lot to develop and wouldn’t have offered the same income potential.

      1. Apparently SAAB was a more likely candidate for the Lancia V4 engines until they went for the same unrefined / underpowered Ford V4 in the NSU Ro80 conversions for the SAAB 96, a pity really that the 96 never utilized the Fulvia V4.

        Also the Fulvia V4 was said to be at the limit capacity wise though a shelved 1600cc Fulvia V4 project with variable valve timing for rallying was looked into prior to the Lancia Stratos project.

  20. How many cylinders would an Otto-cycle engine need to have in order to have the same number of power strokes per revolution as a two-rotor Wankel?

    1. No one told me there would be math…

    2. Four cylinders – one bang every 180 degrees of the flywheel.

  21. From asking around the Ro80 Clubs, it seems that some within NSU did indeed investigate the use of a conventional Flat-6 engine for the Ro80 until it was stopped by NSU officials who found it undesirable.

    Unfortunately no further details of the Flat-6 prototype engine are available.

    Though the following is baseless speculation is on my part, it makes one wonder whether closer cooperation between NSU and Citroen beyond the Comotor join-venture or an alternate non-Comotor arrangement was considered.

    Particularly if such cooperation between NSU and Citroen potentially connects back to the NSU Flat-6 prototype engine in the event the Flat-6 is somehow revealed to NOT be a unique in-house NSU design, but rather in essence a (possibly water-cooled) Flat-6 version of what became the air-cooled Citroen GS Flat-4 (via the earlier Citroen C-60 and F projects) or air-cooled 2-litre Panhard X4 prototype Flat-4 (later used on the Panhard AML) engines.

    Worth mentioning as well as that the water-cooled Volkswagen / NSU K70 engine was essentially a development of the air-cooled Inline-4 engine mounted in the rear of the NSU 1200, so it might be the case that water-cooling was considered for the NSU Flat-6 engine regardless of its true origin.

    1. Hard to say. One point worth considering is that, as Chevrolet found with the Corvair, air-cooled flat-fours and flat-sixes are to some extent different animals — at least in automotive applications, the cooling requirements are quite a bit different. With water-cooled engines, I imagine that developing a six from a four or vice versa would be somewhat easier.

      The upshot, I think, is that for NSU to develop a workable flat-six — assuming they did not have a production partner from which they could purchase or license an existing design — would have been a substantial additional investment in engineering and production resources, which wouldn’t necessarily have been any less risky than the Wankel. So, I can see why the NSU directors would be reluctant to go that way.

      1. Considering what happened to both NSU and Citroen, one cannot help but wonder whether they would have fared better had they not been fully committed to the Wankel Comotor joint-venture, but rather focused on more conventional engines.

        NSU had the 1.6-1.8 K70 engine that may or may not have been capable of being enlarged further to a 2-litre as well as the Flat-6 prototype engine.

        There was also the NSU K50 project aka Audi 50 / VW Polo that may have either used what became the VW EA111 engine from the outset or water-cooled developments of the air-cooled NSU Prinz/1200/etc engines, the latter assumes NSU remains independent from VW.

        Citroen meanwhile could have further enlarged its Flat-4 engine beyond 1299cc to around 1600cc or beyond, perhaps even find a use for the 2-litre Panhard Flat-4. Though there is also the fact that Citroen around that time owned Maserati as well.

        1. For Citroën, there’s a strong argument that they should have put more into modern four-cylinder engines, which ended up being a weak point in a couple of different areas. The 1.3-liter flat-four’s expansion potential is uncertain. People have taken them out to 1.6 liters, but as Julian Marsh’s excellent Citroënet site notes, Citroën was very wary of doing so for cooling reasons, which is fair. I don’t know that the Panhard engine was a reasonable modern alternative, but the reciprocating-engine GS could certainly have benefited from a bigger option, no argument there.

          As for NSU, they were dealing with the facts that (a) they were running out of money and (b) the Wankel was, while not quite their ONLY asset, the only one that was headline-worthy. They were a tiny company with something that, at least for a while, everybody was interested in. A me-too response to that class would have been technologically safer, but also sounds like a recipe for commercial oblivion.

          1. Agreed that Citroen should have developed modern water-cooled 4-cylinder engines, though they did look a transverse-mounted 1.6-litre water-cooled engine derived from the DS engine for Project F.

            Interested in reading up the Citroenet link on the uncertainty of further expanding the Flat-4 engine beyond 1.3-litres.

            Since the Citroen C-60 project did look at a 1.4-litre Flat-4 and assuming any relation exists between the Flat-4 and 2CV Flat-Twin engines, the Citroen Project F was to feature a 750cc Flat-Twin derived from the 2CV engine that doubled up as a Flat-4 creates a 1.5-litre Flat-4 (with some people even enlarging the 650cc 2CV Flat-Twin to as much as 800cc).

            Guess NSU had to take a risk with the Wankel if it was indeed in a dire position though was under the impression they did rather well in cars and motorcycles. Curious to know whether NSU did consider producing 4-door versions of their rear-engined NSU Prinz 1000 / NSU 1200 models.

          2. Regarding risk, the dilemma for small companies not exactly rolling in capital (or individuals in the same position) is that if you aren’t doing at least relatively well, you aren’t in a position to do anything financially risky. If you can’t pay your rent, you aren’t going to buy stock and you probably aren’t going to start a new business venture. Examining the history of the auto industry, innovation very often comes from companies that have had some success — enough to give them some money to play with — and that are looking to grow and bolster their position; that’s generally the most exciting and interesting phase of a company’s development. Established segment leaders don’t have much incentive to take risks and players who are struggling can’t afford to.

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