In 1959, NSU developed the KKM 250, a larger version of Fröde’s initial KKM 125 that produced roughly as much power as NSU’s contemporary 583 cc (36 cu. in.) piston engine. The following year, the company installed a KKM 250 in a Prinz sedan and allowed journalists from German automotive publications to try it. This was followed months later by a Sport Prinz fitted with a further refined, more powerful 386 cc (24 cu. in.) KKM 400.
Both of these test mules were crude, but they helped to establish the Wankel engine as a viable prospect — important to the ongoing sales of patent licenses (NSU’s major source of development money) and the company’s relationship with its understandably nervous shareholders.
At the Frankfurt International Auto Show in the fall of 1963, NSU unveiled its first rotary-powered production car, the NSU Wankel Spider. The Spider was just what journalists who had driven the earlier prototypes expected of a Wankel-powered NSU: a ragtop conversion of the Sport Prinz coupe with a radiator stuffed under the bonnet to cool the rear-mounted 498 cc (30 cu. in.) KKM 502 engine. Fitted with a single two-throat Solex carburetor, the KKM 502 had 50 PS DIN (37 kW) and 52 lb-ft (71 N-m) of torque, about 15% more than the 996 cc (61 cu. in.) OHC four then being prepared for the new Prinz 1000. The price tag was DM 8,500, equivalent to about $2,125 at the contemporary exchange rate.
The Spider was not sold in large numbers, but it gave NSU useful field experience with the new engine. That was fortunate because the rotary still had significant issues. To prevent cracking around the spark plug, the rotor housing was aluminum, which was chrome-plated for hardness. Because using durable materials like cast iron for the apex seals would score the chrome surface, NSU (like Toyo Kogyo) opted for carbon seals, which had a relatively short life. When the apex seals became too worn, the engine would lose power, requiring a complete teardown to replace the seals. Oil consumption also remained high, although NSU tried to soften the blow by saying the engine’s oil use obviated the need for periodic changes; the manual recommended simply topping off the oil supply as needed.
The Wankel Spider demonstrated that the rotary did work as an automotive engine, but the KKM 502’s practical lifespan was still short and its real-world behavior left much to be desired. For a moderately priced, low-volume sports car, such deficiencies might be excusable (reliability was not the strong suit of most contemporary sports cars, even ones with perfectly conventional engineering), but expectations were different in the executive class in which the Typ 80 was expected to compete.
Nonetheless, NSU was now committed. When the four-cylinder Prinz 1000 debuted at Frankfurt in 1964, Von Heydekampf announced that NSU’s future engine development would focus exclusively on the Wankel.
TYP 80 TO RO80
NSU announced the production version of the Typ 80 in early 1965. After considering and discarding a variety of possible names (mostly for trademark reasons), NSU christened the new model Ro80, “Ro” for Rotary, “80” for the type number.
At that time, the Ro80 was still in the relatively early stages of its development. Final wind tunnel testing did not take place until September of that year and road testing of early prototypes didn’t begin until the following spring. It should be remembered that the Ro80 was a genuinely all-new design that shared very little with NSU’s other models, all of which (save the Spider) had rear-mounted, air-cooled engines. The Ro80 was considerably more sophisticated than the Prinz or Sport Prinz, featuring not only front-wheel drive but also power-assisted ZF rack-and-pinion steering, fully independent suspension (MacPherson struts in front, semi-trailing arms and coil springs in back), and ATE-Dunlop disc brakes all around (mounted inboard at the front) with a proportioning valve to limit rear-wheel lockup.
The Ro80 was initially slated to use a two-rotor version of the KKM 502 used in the Wankel Spider, but ongoing issues with the Spider’s seals led to the development of the extensively redesigned KKM 612, also of 995 cc (61 cu. in.) swept volume, but trading the rotor housing’s previous chrome plating for a new ElNiSil (electrodeposited nickel-silicon carbide) coating, developed by MAHLE GmbH under the trademark Nikasil. (It has subsequently seen widespread use as a coating for aluminum pistons and later aluminum cylinder bores for reciprocating engines.) The KKM 612 engine also used cast iron apex seals, which NSU hoped would wear better and have better detonation resistance than the Spider’s carbon seals while greatly reducing frictional losses. (See the sidebar on the following page.)
Like the early Mazda rotary engines, the KKM 612 had dual ignition coils and two spark plugs per chamber, giving a total of four; both plugs were set to fire simultaneously. With two Solex 18/32 HHD two-throat carburetors, the KKM 612’s output was 115 PS DIN (85 kW) and 117 lb-ft (159 N-m) of torque, more than twice the output of the Spider’s single-rotor engine. For all that, the two-rotor engine was very compact and quite light, with a dry weight of only 265 lb (120 kg). (Mazda’s contemporary 982 cc (60 cu. in.) L10A engine, with side intake ports, was lighter still, but had only 110 PS (81 kW) and 96 lb-ft (130 N-m) of torque.)
While the two-rotor engine was considerably more powerful than the Typ 80’s original specification, the Ro80’s weight had also risen by more than 50%, which also raised new questions about what transmission the car should use. NSU had considered using an unusual hydrostatic transmission, but concluded that it was not sufficiently refined for production. A conventional four-speed gearbox also proved less than satisfactory because it highlighted a weakness of the KKM engine’s peripheral intake ports: an annoying driveline ‘snatch’ on the overrun (i.e., with the throttle closed and the clutch engaged, allowing the engine to be driven by the car’s momentum rather than the other way around), caused by exhaust gas being drawn back into the intake charge. A fully automatic transmission would have avoided that problem, but was apparently ruled out because it would have sapped too much engine power.
The alternative NSU finally chose was the three-speed Saxomat, a semi-automatic transmission made by Fitchel & Sachs, similar to the four-speed Sportomatic unit then used by Porsche. The Saxomat transmission was essentially a fully synchronized three-speed manual gearbox (with an overdrive top gear) with both a dry-plate clutch and a torque converter that shared the engine’s oil supply. The plate clutch was operated by a vacuum servo, controlled by a switch in the top of the shift lever; simply touching the gearshift knob would disengage the clutch.
The Saxomat transmission offered two major advantages for the Ro80. First, the torque converter largely eliminated the overrun snatch because there was no direct mechanical connection between engine and gearbox; the gearbox input shaft was driven by the converter turbine. Second, the converter’s additional low-speed torque multiplication (2.3:1 at stall) helped to compensate for the Wankel’s mediocre low-end torque and reduced the need to shift in gentle driving.
The Ro80 was a very promising package, but it represented a great deal of new ground for NSU, and there were serious questions about whether the car was ready for public consumption. According to writer Dieter Renkin, Ewald Praxl asked Von Heydekampf for more time for testing prior to series production, but by the time pilot production began in August 1967, NSU’s back was against the wall. NSU’s existing cars were selling reasonably well (more than 100,000 units in both 1966 and 1967), but the company was no longer in the motorbike business and had invested nearly all of its available resources in the Ro80 and the follow-on Typ 70 (a smaller piston-engined car intended to debut at the 1969 Geneva show as NSU’s answer to the BMW 1600/1602). That fall, Von Heydekampf freely admitted to the press that NSU was betting everything on the Ro80. The company simply couldn’t afford to wait any longer for launch.
THE NSU RO80 DEBUTS
The new car made its public debut at the Frankfurt show in September 1967. The NSU Ro80 was not the world’s first two-rotor production car — that honor went to the Mazda Cosmo Sport, which went on sale earlier that year, two and a half years after it bowed at the 1964 Tokyo Motor Show — but the NSU was the first rotary-powered production sedan, arriving about two months before the public introduction of Mazda’s Familia Rotary Coupé (R100). The Ro80 went on sale shortly afterward with a starting price of 14,150 DM (about $3,550), raised a nominal 40 DM ($10) in early 1968. That price put the Ro80 a full 1,000 DM (about $250) above a Mercedes 230 sedan and almost 2,300 DM ($580) more than a six-cylinder Opel Commodore — an ambitious price tag indeed.
Even without the rotary engine, the Ro80 would have been a great achievement. The aerodynamics were probably the best of any contemporary production car; only the Porsche 911 and Citroën DS21 even came close. The Ro80’s chassis was also superb. Despite its skinny Michelin tires, the combination of wide track, low center of gravity, and fine steering made for excellent handling. The ride was outstanding as well, thanks to long wheel travel, well-tuned spring and damping rates, and low unsprung weight.
As was typical for German luxury cars, the Ro80’s interior did not approach American, British, or French standards of plushness, but it was tasteful, roomy, and well-made. The body had a reassuring sense of solidity, and assembly quality was high. There were nits that could be picked — the labeling of minor controls was rather cryptic (resolved in 1970), the seats needed more lateral support (ditto), and the ventilation system would have benefited greatly from an interior fan — but the Ro80 was nonetheless genuinely impressive, particularly considering it was NSU’s first executive car.
Much of the press attention, of course, focused on the Ro80’s powertrain, which drew considerable interest and mixed reviews. The free-revving nature and smoothness of the rotary engine elicited much praise, but while the engine’s power output compared favorably with that of a 2-liter (122 cu. in.) carbureted piston engine, torque was meager below about 3,000 rpm. The torque converter helped a bit, but the Ro80 had widely spaced gears and around 2,850 lb (1,290 kg) of curb weight, which made for sleepy low-speed performance, particularly if one followed NSU’s suggestion to leave the transmission in second for most city driving. Most testers reported 0-60 mph (0-97 km/h) times of around 14 seconds through the gears. While brake-torquing (revving the engine against the brake in neutral at launch) could trim a second or so off that time, the Ro80 was not well-suited for drag strip starts. The Saxomat transmission wasn’t much help in that regard; achieving smooth shifts took practice, and some testers found that fast changes could beat the synchros.
The Ro80 came into its own at autobahn speeds, where the relatively short overall gearing (3,200 rpm at 60 mph (97 km/h) in top) put the engine into a richer part of its torque curve, providing much brighter acceleration and snappy passing response. The rotary remained uncannily smooth all the way to redline, and with the well-suppressed wind and road noise, drivers were well-advised to keep a close eye on the (rather optimistic) speedometer. Claimed top speed was about 112 mph (180 km/h), a respectable figure for the Ro80’s size and price, and very few cars of the time were as stable or comfortable at high speeds.
Even in relatively brief road tests, the NSU rotary engine displayed a few disagreeable habits, including recalcitrant cold starting, but the biggest complaint was fuel economy. On an absolute scale, the Ro80’s fuel consumption was not disastrous for the era, ranging from 13 to 18 mpg (U.S.; 18 to 13 L/100 km) depending on conditions, and it was actually better at high speeds than many piston-engined rivals. However, the bottom line was that the KKM 612 was a 995 cc (61 cu. in.) engine with fuel economy comparable to a 4,235 cc (258 cu. in.) Jaguar.
Added to the rotary engine’s prodigious appetite for oil and spark plugs, such consumption made the NSU Ro80 rather expensive to run for European buyers. (In that, it was probably fortunate that the Ro80 was not in the Taunus/Cortina class, where the rotary engine’s thirst would have been an even greater marketing problem.) One consolation was that, as with the Wankel Spider, the Ro80 did not require routine oil changes, although it was imperative to keep the oil supply full.
Still, the new model made a good first impression, and its combination of merit and novelty earned it the European Car of the Year award. Initial 1967–68 sales totaled around 6,400 units — not bad for the price, particularly considering that right-hand-drive models were not available until the fall of 1968 and the Ro80 was not certified for U.S. emissions standards until mid-December 1969.
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I believe this is the most comprehensive NSU story ever published in America.
The research for the article is top notch.
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.
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.
In 1978 my friend Tom Hoskins found a place in downtown Washington DC, a block from Union Station, known as Allied Light Cars. The owner claimed he was the official importer for NSU in the USA, but I’m not so sure that boast is accurate! Allied had closed a couple of years earlier, just locked the doors & shut off the lights. When the building was up for sale, Tom managed to grab everything that wasn’t nailed down, but once he realized the amount of work involved, he contacted me, as I had the land, truck & trailer, and storage buildings.
I ended up with about 20 NSU cars, mostly 1100 sedans, a couple of TT & TTS cars, and 2 Spyder Wankles. Plus a HUGE parts inventory, from small mechanical stuff to complete body panels & doors. I ended up selling the 2 Spyders to Myron Vernis in Ohio, probably 35 years ago. [Vernis bought the 2 spyders and a 1958 DKW Munga from me!] Sadly, the entire parts inventory [except for some of the rarer items that sold quickly] was destroyed in a huge lightning-induced fire in 1995. I recently found a few NSU engine gasket sets [2 & 4 cylinder], that I sent to Jeff Lane in Nashville.
I never found anything concerning the Ro80, no parts, literature, repair or parts books, nothing. This made me think if he WAS the official importer, yet there was nothing concerning the Ro80, perhaps he didn’t elect to bring them into the country. This could possibly be the reason they are hard to find in the US today. We’ll probably never know for sure.
The Owner of Allied told me the Spyders were 2 special examples, as one was the first example to be imported to America, and the other one was the last one imported. Both cars were red, & had never been titled! The first car was the one the car magazines used for their road tests. It had a rare factory hardtop.
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.
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…)
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.
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.
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)
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.
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!
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!
That was a typographical error in the photo caption; you’ll note that it was spelled correctly in the first instance in the text.
Thanks again Aaron, a lot of stuff I did not know about the RO80, I've only seen one.
[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.
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
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.
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.
I think the 30-minute clutch change applied to the rear-engine air-cooled NSUs.
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.
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!
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]
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.
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.
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
Thanks for the corrections — I’ve amended the text.
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.
Thanks, Dan. I redacted your phone number so that random spammers don’t use it to bug you.
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.
Interesting! It’s always neat to see the unexpected places cars end up. Thanks for the info.
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.
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.
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.
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.
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?
No one told me there would be math…
Four cylinders – one bang every 180 degrees of the flywheel.
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.
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.
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.
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.
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.
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.
Regarding the NSU Spider (and even the NSU Sport-Prinz), were non-Wankel versions considered such as regular and TT/TTS spec 996-1177cc NSU air-cooled OHC engines?
Not so far as I know. That might have been a logical development if NSU had considered the Sport-Prinz or the Spider a commercial priority, which I’m not sure they did. I don’t know that the Sport-Prinz was ever a big seller, and the Spider was pretty clearly a short-term expedient: “How can we create a ‘new’ model to showcase our first production rotary engine without investing a lot of money in anything other than the engine, which we’re still trying to make work?” The fact that the Spider and Sport-Prinz were dropped about the time the Ro80 debuted is probably indicative in this regard. It’s possible (speaking strictly speculatively now) that NSU might eventually have developed replacements, offering both piston and rotary engines, but NSU just didn’t have a lot of money and the Ro80 and K70 were their principal priorities at that time.
Interestingly it seems Citroen themselves also looked at air-cooled Flat-6 and water-cooled Flat-4 engines for the Citroen CX (as opposed to the earlier Flat-6 attempt with the Citroen DS), which goes back to the idea that both Citroen and NSU should have collaborated on Flat engines instead of going bankrupt trying to develop the Rotary engine.
Info elsewhere suggests a Citroen CX prototype featured a water-cooled 95 hp 1654cc Flat-4 engine that may or may not be connected to collaboration between Citroen and Fiat owned Lancia whose Flat-4 engines were later used in the Lancia Gamma.
NSU assuredly did not go bankrupt developing the rotary engine, royalties on which were one of their major sources of income throughout the sixties, through the point VAG acquired them. (Neither did Citroën, for that matter, although the failure of the Comotor joint venture and the GS Birotor certainly didn’t do them any favors.) The Ro80 would have been been a financial strain for NSU even if it had had a conventional engine, and if the engine had been newly developed, expensive teething problems would not have been unlikely, with similar results.
The impression one gets from NSU when quickly delving into its history is the fact they sold their recently completed Heilbronn car factory to Fiat in the Great Depression (leading to NSU-Fiat / Neckar), before deciding to enter the car market once again almost 2 decades later in the post-war era.
To what extent were NSU handicapped by the loss of the Heilbronn factory and had a way been found for NSU to survive the financial problems caused by the Great Depression without selling the Heilbronn factory and leaving the car market (or a way was found for NSU to regain the NSU-Fiat factory in the post-war aftermath), to what degree would their position have been strengthened relative to its post-war domestic rivals or later real-life partner Citroen?
I really don’t know. There are so many overlapping hypotheticals involved that one could probably do a whole Ph.D. thesis on a subject like that; it’s certain well beyond my knowledge of European industrial history.
I will say that a resource you can’t afford to use is ultimately not much of a resource. For instance, if you have a fancy, expensive car — even a very nice car — for which you can’t afford the insurance, the maintenance costs, the taxes or registration fees, or the fuel, it’s not going to do you a lot of good, no matter how nice it might be if you could afford those things.
If this site is still active, any ROers please reach out to me.
I have a 1976 silver RO in Stuart Florida.
Mazda are introducing a rotary hybrid in Dec 2023. It will have a rotary range-extender turning only the generator. Rotary engines are far more efficient, with greater longevity, when running at a constant speed at their ‘sweet spot’. They are 25% more efficient when running on hydrogen/ Japan aims to be a hydrogen society.
So the rotary is not dead in cars.