Rotary Revolutionary: The NSU Ro80

In 1967, the small German automaker NSU introduced what would be its final and most ambitious product: the remarkable Ro80. It was NSU’s first and last luxury car, a sophisticated, highly aerodynamic sedan powered by a Wankel rotary engine. The Ro80 survived for 10 years, generating critical acclaim and controversy in roughly equal measure. In this installment of Ate Up With Motor, we take a closer look at the turbulent and sometimes troubled history of the 1967-1977 NSU Ro80.
1970 NSU Ro80 badge © 2012 Andrew Buc (used with permission)
Photo © 2012 Andrew Buc; used with permission


NSU was founded in 1873 in the small town of Neckarsulm, at the union of the Neckar and Sulm rivers in the German state of Baden-Württemberg. Like many early automakers, the company started off in a very different field, in this case sewing and knitting machines. (NSU was originally an acronym for Neckarsulm Strickmachinen Union, Neckarsulm Sewing Machine Co.) NSU started building motorcycles in 1901 and automobiles in 1905, followed a few years later by trucks.

Although the company produced some successful and rather sporty cars in the 1920s, the onset of the Depression led NSU to sell its automotive business to Fiat (which used the NSU-Fiat brand into the mid-1930s) and focus exclusively on motorcycles and motorbikes. It was not until the mid-1950s that NSU once again turned its attention to automobiles, introducing the NSU Prinz in 1957. While NSU had offered four- and six-cylinder cars back in the 1920s, the Prinz was a rear-engined mini-car powered by a decidedly motorcycle-like air-cooled, two-cylinder engine.

1960 NSU Prinz III front 3q © 2008 Charles01 CC BY-SA 3.0 Unported
A 1960 NSU Prinz III sedan. The rear-engined Prinz was a very small car: 123.8 inches (3,145 mm) long on a 78.8-inch (2,000mm) wheelbase, weighing less than 1,200 lb (540 kg). Until the arrival of the Prinz 1000, the sole engine was a 583 cc (36 cu. in.) SOHC inline two-cylinder engine making 20 PS DIN (15 kW). The slightly more expensive Prinz 30 had the 30 PS (22 kW) engine from the Sport Prinz coupe. Cars sold in the U.S. market were rated at 26 or 36 SAE gross horsepower (19 or 27 kW). (Photo: “NSU Prinz ca 1960” © 2008 Charles01; resized 2012/2014 by Aaron Severson and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

NSU introduced its first four-cylinder postwar car, the NSU Prinz 1000, at the 1964 Frankfurt auto show, but managing director Gerd Stieler von Heydekampf had already set his sights on bigger game. The West German economy had improved markedly in recent years, and buyers were graduating from mopeds and tiny bubble cars to larger and more luxurious sedans. NSU’s market share was only modest as it was. If the company didn’t evolve, its future looked gloomy.

In late 1962, NSU commenced work on a new model known internally as Typ 80. As originally conceived, it was to be in the same class as the Ford Taunus P4. Design targets were an engine output of 80 PS (79 hp, 59 kW), a weight of 800 kg (1,765 lb), and a price of 8,000 DM — about $2,000 at the contemporary exchange rate. Like the Taunus, the Typ 80 would have monocoque construction and front-wheel-drive, developed by chief engineer Ewald Praxl. The new model’s styling, meanwhile, was the responsibility of in-house designer Claus Luthe, who had joined NSU in 1956 after stints at Fiat and the bus maker Spengler.

Luthe’s design, commenced in early 1963 and completed as a full-size model that September, was exceptionally clean and airy, with a large, six-light greenhouse that made the car look smaller than it actually was. Space utilization was excellent, but the Typ 80 was far less boxy than most contemporary German sedans, leading to (unfounded) rumors in later years that it was actually designed in Italy like NSU’s earlier, Bertone-styled Sport Prinz coupe. The Typ 80’s most impressive attributes were its aerodynamics; in the interests of maximizing fuel economy, low drag was an important part of the design brief. Subsequent wind tunnel tests at Stuttgart Polytechnic Institute revealed a drag coefficient of 0.355, outstanding for the era.

1969 NSU Prinz 1000 © 2006 Eastfrisian (Heinz Janssen?) CC BY-SA 3.0 Unported
The NSU Prinz 1000, introduced in 1964, was a four-cylinder version of the redesigned Prinz 4, introduced in 1961 and bearing a strong resemblance to the Chevrolet Corvair. The Prinz 1000 was powered by a 996 cc (61 cu. in.) four-cylinder engine — still air-cooled — initially with 43 PS DIN (32 kW). This was followed a year later by the Prinz 110, powered by a larger, 1,177 cc (72 cu. in.) engine, and later by an assortment of sporty TT and TTS models with more powerful dual-carburetor engines, modified suspensions, and uprated brakes. (Photo: “NSU Prinz 1000” © 2006 Eastfrisian (Heinz Janssen?); resized 2012/2014 by Aaron Severson and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

The full-size model, which was presented to NSU’s managing board in May 1964, was very close to the eventual production model in shape, but not dimensions. After considering the car’s likely cost, Von Heydekampf and the board selected a loftier target than the Taunus: the executive car market occupied by the likes of the Mercedes W110 (200/230) and BMW Neue Klasse sedans. To compete in that segment, the Typ 80 would be scaled up in size, weight, and price, the latter eventually rising from 8,000 to more than 14,000 DM (about $3,500).

You’ll note that we haven’t yet said a word about the Typ 80’s most significant and unusual feature, its rotary engine. However, even with a completely conventional powertrain, the Typ 80 would have been a very ambitious step for NSU, analogous to Honda proceeding directly from the original 1972 Civic to the six-cylinder Legend. BMW, of course, had developed its Neue Klasse sedans after several years of focusing on motorcycles and mini-cars, but BMW had also built larger, more prestigious cars like the 502, 503, and 507 throughout the fifties and early sixties (albeit not in large numbers). By contrast, NSU hadn’t built anything like a luxury car in more than 30 years.

Moving the project so far upmarket would have been a gamble no matter what, but what elevated it from bold marketing move to Citroën-like cliff-diving audacity was the Typ 80’s intended engine, NSU’s greatest and riskiest asset: the brainchild of inventor Felix Wankel.


We talked about the development and workings of the Wankel rotary engine in last year’s article on the early Mazda rotaries, but here is a recap for those joining us late.

Inventor Felix Wankel conceived the rotary engine while still a teenager and began filing patents on such engine designs in the 1930s, but his work on the rotary was interrupted by other projects and by the war. In 1936, Wankel joined the Deutschen Versuchsanstalt Für Luftfahrt (German Experimental Institute for Aviation), designing rotary valves for Daimler-Benz’s DB601, a 33.4-liter (2,020 cu. in.) V-12 for military aircraft, and later the Junkers KM8 torpedo engine. After the German surrender, Wankel spent time in prison for his military work, but he was released in 1946 and eventually allowed to return to practical research, establishing a new shop in Lindau, Bavaria.

Shortly afterward, Wankel’s old acquaintance Wilhelm Keppler arranged an introduction to Victor Frankenberger, NSU’s technical director, and NSU research chief Walter Fröde. On Fröde’s recommendation, NSU signed a consulting agreement with Wankel, first to apply Wankel’s rotary valve concept to motorcycle engines and subsequently to develop a unique rotary supercharger.

Throughout his consulting work, Wankel tried repeatedly to convince Von Heydekampf and the NSU board to fund the development of a rotary engine. However, NSU was far from over-capitalized, so it took three years and a great deal of cajoling before the board finally agreed.

NSU Quickly motorbike © 2009 Elmschrat CC BY-SA 3.0 Unported
One of the most popular NSU products for many years was the Quickly, a moped powered by a 49 cc (3 cu. in.) engine making a modest 1.4 PS (1 kW). In 1954, NSU fitted a Quickly with Wankel’s rotary supercharger, giving about 13 PS (10 kW) on 40 lb (2.8 bar) boost, and used the modified bike to set a number of speed records at the Bonneville Salt Flats. (Photo: “Nsu-quickly-1” © 2009 Elmschrat; resized 2012/2014 by Aaron Severson and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

Almost as soon as Wankel’s first DKM 54 (DKM for Drehkohlbenmotor, “Rotary Piston Engine”) prototype was running, Fröde concluded that it was hopelessly impractical for anything except perhaps stationary applications. Fröde and his staff in Neckarsulm soon developed an alternative design, the KKM (Kreiskolbenmotor, roughly, “Circuit Piston Engine”), which first ran on a test stand in 1958. Unlike Wankel’s DKM, in which both the rotor and the housing rotated around a stationary shaft, the KKM used a trochoidal rotor (shaped something like a three-lobed peanut) that traced a mathematically complex path along a cocoon-shaped stationary housing.

Wankel considered the KKM a bastardization of his concept, and Fröde’s design did sacrifice a measure of the DKM’s smoothness and exceptional rev potential, but the KKM was unarguably more useful. With much of NSU’s limited capital tied up in the launch of the Prinz, the entire project was hanging by a thread, and the board was definitely not willing to foot the bill for two engines, so Fröde finally convinced Wankel to accept the KKM. (It probably helped that the deal Wankel’s business partner Ernst Hutzenlaub struck with NSU later that year ensured that Wankel would share in the patent royalties either way. In fact, Wankel and Hutzenlaub received a substantial cut — initially 40% — of NSU’s rotary engine revenues, paid through a holding company called Wankel GmbH.)

NSU special tools board © 2012 Andrew Buc (used with permission)
NSU enthusiast Jim Sykes owns a wide array of OEM parts, factory documentation, and other memorabilia, including this set of special tools, presumably for working on the Wankelmotor. (No, we don’t know what all of them are for!). (Photo © 2012 Andrew Buc; used with permission)

Although NSU began selling patent licenses almost immediately, beginning that fall with a deal with the aviation company Curtiss-Wright, the KKM had a long way to go before it would be a viable production engine. Fuel and oil consumption were inherently high; low-end torque was poor; and early engines suffered a host of serious maladies, including excessive exhaust smoke, seized bearings, heat-induced cracks around the spark plugs, and scored rotor housings (the infamous “chatter marks” that would also plague Toyo Kogyo’s development efforts). Probably the greatest challenge was the apex seals at the rotor tips, which were responsible for maintaining compression and preventing exhaust gases from mixing with the intake charge. Developing workable apex seals would be a major test for every user of the Wankel KKM design, including NSU itself.


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.

NSU Wankel Spider front © 2009 Berthold Werner CC BY-SA 3.0 Unported
Offered from 1964 to 1967, the NSU Wankel Spider was essentially a convertible version of the Sport Prinz coupe, trading the Sport Prinz’s air-cooled two-cylinder engine for a water-cooled KKM. Since the Wankel Spider was only a little more powerful than a four-cylinder Prinz 1000 and weighed 143 lb (65 kg) more, performance was decent but not extraordinary: 0-60 mph (0-97 km/h) in around 14 seconds and a top speed of perhaps 95–98 mph (153–158 km/h). (Photo: “NSU Wankel Spider BW 1” © 2009 Berthold Werner; resized 2012/2014 by Aaron Severson and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

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.

NSU Wankel Spider rear 3q © 2008 Berthold Werner CC BY-SA 3.0 Unported
The NSU Wankel Spider was 141 inches (3,580 mm) long on a 79.5-inch (2,020mm) wheelbase, weighing 1,543 lb (700 kg). The Spider was slightly longer and substantially heavier than a Sport Prinz coupe. At launch, the Wankel Spider initially listed for 8,500 DM (about $2,130) in Germany and $2,998 POE in the U.S. (Photo: “NSU Wankel Spider BW 2” © 2008 Berthold Werner; resized 2012/2014 by Aaron Severson and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

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.

1970 NSU Ro80 alloy wheel © 2012 Andrew Buc (used with permission)
These attractive alloy wheels were not standard on the NSU Ro80 — perforated steel discs with plain hubcaps were standard fit — but were a commonly specified option, priced at $260 in the U.S. Like the standard wheels, the alloy wheels are unfashionably small by modern standards: 5J rims wearing 175SR-14 Michelin XAS radials. (Photo © 2012 Andrew Buc; used with permission)

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.

1970 NSU Ro80 dashboard © 2012 Andrew Buc (used with permission)
The NSU Ro80 had a well-furnished but typically sober Teutonic interior (the colorful floor mats are not stock) even with the optional leather upholstery. Not readily apparent at this angle is one of the interior’s biggest selling points: a completely flat floor for maximum leg room, particularly in back. The interior’s major demerit was so-so ventilation in warm weather due in part to the lack of an interior fan. Note that there is no clutch pedal. The clutch is controlled by a touch-sensitive switch atop the shift lever. (Photo © 2012 Andrew Buc; used with permission)

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 (up to 2.2:1) and high stall speed (nominally 2,510 rpm) 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.

1970 NSU Ro80 side © 2012 Andrew Buc (used with permission)
The NSU Ro80 was 188.2 inches (4,780 mm) long and 69.3 inches (1,760 mm) wide on a 112.6-inch (2,860mm) wheelbase, standing 55.5 inches (1,410 mm) high. Curb weight with a full (22 U.S. gal., 85 L) tank of fuel was about 2,850 lb (1,290 kg), approximately 63% of which was on the front wheels. Cars sold in the U.S., like this federalized model, listed for a hefty $5,995, rising to more than $7,500 with air conditioning, leather upholstery, and other options. (Photo © 2012 Andrew Buc; used with permission)


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.

1969 NSU Ro80 white front 3q © 2011 Wouter Bregman (used with permission)
Early European examples of the NSU Ro80 had single composite headlamps with glass covers, replaced in June 1970 with new headlights with separate elements for high and low beams. Note the shape of the body beneath the front bumper, part of the Ro80’s extensive aerodynamic development; a belly pan manages under-car airflow, an exotic and unusual touch for the late 1960s. (Photo: “NSU RO80 1969” © 2011 Wouter Bregman; used with permission)

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.

1970 NSU Ro80 rear 3q © 2012 Andrew Buc (used with permission)
During the early development of the Typ 80, NSU designers considered a number of configurations, including fastback and semi-fastback profiles. Surviving images of the latter show a surprising (and almost certainly coincidental) resemblance to the late-seventies Datsun B210, with up-swept, reverse-slant sail panels. The notchback production version’s high rear deck was dictated by aerodynamics, but paid dividends in trunk space. The Ro80’s boot is wide and, thanks to the independent rear suspension, quite deep, although some space is consumed by the spare tire. (Photo © 2012 Andrew Buc; used with permission)

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 2,750 lb (1,249 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 German magazine auto motor und sport managed 0–62 mph (0–100 k/h) in 12.5 seconds — 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 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.

1970 NSU Ro80 engine bay © 2012 Andrew Buc (used with permission)
The output of the NSU Ro80’s two-rotor KKM 612 engine has long been a matter of some confusion for English-speaking readers. In its original form, with two Solex carburetors, it was rated at 115 PS DIN (85 kW), equivalent to 113.5 hp; this is a net rating, with all accessories installed. U.S. cars carried an SAE gross rating (without accessories) of 130 hp (97 kW), quoted in some early reports as 136 hp (101 kW). A few English-language reports list an output of 128.5 hp, probably based on the mistaken assumption that the quoted gross output was in PS rather than hp (130 PS would be 128.22 hp). NSU quoted the same net torque output in all markets: 117 lb-ft (159 N-m) at 4,500 rpm. Note the twin distributors — this federalized car, manufactured in June 1969, still has two spark plugs per chamber. (Photo © 2012 Andrew Buc; used with permission)

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 12 to 18 mpg (U.S.; 13 to 20 L/100 km) depending on conditions, and it was actually better at high cruising 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 only required oil changes every 12,500 miles (20,000 km), 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.


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 with less testing than its designers would have preferred. 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. The 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 engine’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 the car were driven mostly 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 were very expensive, 10 to 12 times the cost of a standard spark 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 electrodeposited nickel silicon carbide. Despite the aluminum housing’s higher manufacturing costs, NSU and Toyo Kogyo considered it a necessity because heat-cycling would cause cast iron housings to 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.


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 to arrange 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 Genussscheine, profit shares, to NSU 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 and Audi products, including the Audi 100. Lotz decided to resurrect the project and transfer it to Volkswagen, albeit with many ostensibly 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 DIN (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 DIN (74 kW). (Photo: “1971 VW K70 L Front” © 2009 Kroelleboelle; resized 2012 by Aaron Severson and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)


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 117 PS DIN (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. NSU had almost certainly exited the American market 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 had 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 proved crippling. An NSU Ro80 was already an expensive car 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 2012/2014 by Aaron Severson 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 2012/2014 by Aaron Severson 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 form. 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 believed 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.


With its successor canceled, the NSU Ro80 expired in the spring of 1977, the final car leaving the assembly line on April 19. It was the last NSU production car, although NSU remained part of the corporate name until the mid-1980s and the marque is still owned by Volkswagen AG.

Ro80 production totals differ somewhat from source to source, but the most common figure is 37,402. (Some sources list 37,240, which makes us suspect that one or the other of these figures is actually a typographical error; your guess is as good as ours as to which!) Where most accounts agree is that the Ro80 was never profitable for either NSU or Audi. Even with lower warranty costs, it’s hard to see the car as a money-maker at such a low volume, despite a price that by the end of production had climbed to 23,620 DM (equivalent to more than $10,000).

1982 Audi 200 (C2) sedan front 3q © 2011 Charles01 CC BY-SA 3.0 Unported
Introduced in 1979, the Audi 200 was the most upscale version of the corporate C2 platform, with four-wheel disc brakes and trim comparable to that of the top-of-the-line Audi 100 CD. The standard engine was a 2,144 cc (131 cu. in.) inline-five with 136 PS DIN (100 kW), but the 200 was originally slated to offer the EA871 rotary engine, making about 170 PS (125 kW). Since that engine never made it to full production, Audi substituted a similarly powerful turbocharged version of the five-cylinder engine, introduced in February 1980. In the U.S., the turbocharged version was known as the Audi 5000 Turbo and had a more modest 130 SAE net horsepower (97 kW). (Photo: “Audi 200 C2 2144cc March 1982” © 2011 Charles01; resized 2012/2014 by Aaron Severson and used under a Creative Commons Attribution-ShareAlike 3.0 Unported license)

While the production Audi C2 (1976–1982 Audi 100/200/5000) never received the planned rotary engine, the C2 and subsequent C3 had a lot in common with the NSU Ro80 — and not just because stylist Claus Luthe was Audi’s design director during the C2’s development (although he’s generally credited only with the interior; the exterior was the work of Hartmut Warkuß). The Audi lacked the Ro80’s semiautomatic transmission, independent rear suspension, and inboard front brakes, and only the more expensive Audi 200 had rear discs, but in overall size, profile, ride and handling balance, and concern with aerodynamics, the Audi seemed to have studied at the feet of its NSU predecessor. (It’s also easy to see how the Audi 200 could have been the basis of a next-generation Ro80.) Although the NSU Ro80 remains obscure in the U.S., its Audi descendants had a strong influence on automotive design throughout the 1980s and 1990s, in America and Japan as well as in Europe.

1970 NSU Ro80 front 3q © 2012 Jim Sykes (used with permission)
Jim Sykes has owned our green photo subject, an early 1970 federalized NSU Ro80, since 1975, although it was idle for many years after its high-speed capabilities earned him several tickets. It still has its original twin-plug engine (although he does have a spare engine), and the only mechanical problem it has suffered has been a failed water pump. Jim says the Ro80 and other NSUs he’s owned over the years perform very well in his home town of Seattle because conditions are much like those of the area of Baden-Württemberg where the cars were originally built. (Photo © 2012 Jim Sykes; used with permission)

With its groundbreaking design and unusual powertrain, it’s tempting to characterize the NSU Ro80 as a car ahead of its time. In some ways that was true, but in others, the future the Ro80 presaged was not ours. The Ro80 was a car designed for an alternate world of light traffic, unrestricted Autobahnen, and moderately priced regular gasoline. For such conditions, the KKM 612 and Saxomat were a fine combination, superior in many respects to contemporary petrol and diesel reciprocating alternatives. However, by the mid-seventies, such a world was purely a fantasy for most drivers. The reality was gridlock, speed limits, and soaring fuel prices, an environment for which the Wankelmotor was considerably less than ideal.

Doubts about the Wankel’s reliability dogged the NSU Ro80 for many years, and the car’s rehabilitation (in the Soviet sense) was a lengthy process. A reputation for early engine failure does nothing good for residuals, so it’s little surprise that the Ro80’s resale values plummeted catastrophically in the 1970s. Since the rest of the car was generally quite sound, some owners resorted to engine swaps. A popular choice was the German Ford V-4, which rivaled the KKM 612 for compactness, if not power or refinement. Another obvious substitution was a two-rotor Mazda 12A or 13B; while many surviving Ro80s once again have rotary engines, not all were made in Neckarsulm.

Felix Wankel eventually sold his stake in the engine that bore his name: In the early seventies, he and Ernst Hutzenlaub sold Wankel GmbH to Roland Rowland’s Lonrho for a reported 64 million DM (about $25 million). Wankel’s lab in Lindau closed a few years later, after Wankel GmbH was sold again to Dankwert Eiermann and Jürgan Bax. By then, the auto industry’s interest in the rotary engine was rapidly fading. Development for nonautomotive applications like light aircraft continued into the 21st century, but by the time Felix Wankel died in 1988, Mazda was the last holdout in the auto industry. With the production of the final Mazda RENESIS engine in June 2012, the rotary engine’s passenger car career appears to be over unless Mazda is able to revive its currently inactive 16-X project.

1970 NSU Ro80 rear © 2012 Andrew Buc (used with permission)
A final note about the NSU Ro80 that didn’t fit anywhere else: In 1976, Ro80 designer Claus Luthe became design director of BMW, where he developed many familiar BMW models, including the E30 and E36 3-Series, the E28 and E34 5-Series, the E32 7-Series, and the E31 8-Series. Luthe died in 2008. (Photo © 2012 Andrew Buc; used with permission)

Back in 1956, before the NSU KKM was even invented, Ford Motor Company engineer Donald Frey (quoted a decade later in Motor Trend) opined that for a new engine design to seriously challenge the dominant four-stroke reciprocating (Otto-cycle) format, it was not enough to beat the Otto cycle in a few areas — the newcomer had to be superior in all or most respects. The rotary engine came closer than many challengers, but the Otto-cycle engine was able to close the gap in many of the Wankel’s areas of superiority faster than the Wankel’s limitations could be overcome.

Much the same could be said of the NSU Ro80. It went head to head with some of the toughest competitors in the business and acquitted itself far better than anyone really had a right to expect, but while the Ro80 was good enough to challenge the dominant players, it didn’t have enough of an edge to unseat them. By the time the bugs had been worked out, NSU’s rivals had improved too, leaving the Ro80 as the brave but risky alternative.

Would the Ro80 have been more successful if NSU had opted for a more orthodox design brief, perhaps with the alternative of a conventional piston engine? Maybe, maybe not, but one thing is certain: The results would have been far less interesting.



The author would like to thank Jim Sykes and Andrew Buc for their generous assistance and the use of their photos. (In the interests of full disclosure, Andrew has previously made financial contributions to Ate Up With Motor, albeit not specifically in connection with this or any other individual article.)


Our sources on the history of NSU, the Wankel engine, and the Ro80 included: “2 Car Test: Citroën ID20, NSU Ro80,” Autocar 1 May 1969, reprinted in NSU Ro80: A Brooklands ‘Road Test’ Limited Edition, ed. R.M. Clarke (Cobham, England: Brooklands Books, Ltd., 1999), pp. 36-41; R.F. Ansdale, “Wankel Progress,” Motor Trend Vol. 18, No. 2 (February 1966), pp. 29-31; “Audi 100 C2,” Unique Cars and Parts, www.uniquecarsandparts., accessed 15 August 2012; the Auto Editors of Consumer Guide, “1963-1966 NSU Wankel Spider,”, 24 July 2007, www.howstuffworks. com/ 1963-1966-nsu-wankel-spider.htm, accessed 7 October 2011, and “1967-1977 NSU Ro80,”, 29 October 2007,, accessed 7 July 2012; “Auto Test: NSU Ro80,” Autocar 13 July 1974, reprinted in NSU Ro80, pp. 71-75; Roger Bell and Anthony Curtis, “20,000 Miles on NSU Ro80,” Motor 28 September 1974, reprinted in ibid, pp. 76-79; Stuart Bladon, “Long-Term Report: NSU Ro80 Final report at 23,000 Miles,” Autocar 31 August 1972, reprinted in ibid, pp. 64-67, and “Smoky Rotaries,” Classic Car July 1987, reprinted in ibid, pp. 85-87; Griffith Borgeson, “NSU Wankel Comes of Age,” Motor Trend Vol. 19, No. 12 (December 1967), reprinted in ibid, pp. 10-13; Martin Buckley, “Brave new world,” Classic & Sports Car July 1995, reprinted in ibid, pp. 88-92; Charles Bulmer, “Serious Contender,” The Motor 9 September 1967, reprinted in ibid, pp. 5-9; “Buying Secondhand: NSU Ro80,” Autocar 26 November 1977, reprinted in ibid, pp. 82-84; “Car of the year–or decade? (Motor Road Test No. 5/68 – NSU Ro80),” The Motor 3 February 1968, reprinted in ibid, pp. 19-24; Wallace Chinitz, “Rotary Engines,” Scientific American Vol. 220, No. 2 (1969): 90–99; Richard Copping, VW Golf: Five Generations of Fun (Dorchester, Dorset: Veloce Publishing Ltd. 2006); Mike Covello, ed., Standard Catalog of Imported Cars 1946-2002, Second Edition (Iola, WI: Krause Publications, 2001); Anthony Curtis, “Classic Ro80,” Classic Cars August 1975, reprinted in NSU Ro80, pp. 80-81, and “Is cleanliness three-cornered?” New Scientist and Science Journal Vol. 49, No. 740 (25 February 1971), pp. 415-417; “Dual-Wankel coupe,” Popular Science Vol. 203, No. 2 (August 1973), p. 70; “Die Wankelmotoren von NSU,” Der Wankelmotor, 2000-2012, www.der-wankelmotor. de, accessed 13 August 2012; Jim Dunne, “Detroit Report,” Popular Science Vol. 210, No. 4 (April 1977), p. 56; J.L. Ellis and K. Mal, “New Developments in Powder Metal Sealing Elements,” Wear Vol. 32, No. 3 (1975): 327–342; John Ethridge, “Reciprocating Progress,” Motor Trend Vol. 18, No. 2 (February 1966), pp. 26-28; Nicholas Faith, Wankel: The Curious Story Behind the Revolutionary Rotary Engine (New York: Stein and Day, 1975); Joachim Fisher, “I Drove the Wankel-Engine Car at 90 MPH!” Popular Mechanics Vol. 116, No. 6 (December 1961), pp. 69-73, 218; Walter Froede (Fröde), “NSU’s Double Bank Production Rotary Engine,” SAE Technical Paper 680461 (New York: Society of Automotive Engineers, Inc., May 1968), and “The Rotary Engine of the NSU Spider,” SAE Technical Paper 650722 (New York: Society of Automotive Engineers, Inc., 1965);, “Giant Test: Jaguar XJ6, BMW 525, NSU Ro80,” CAR August 1974, reprinted in Jaguar XJ6 Gold Portfolio 1968-1979, ed. R.M. Clarke (Cobham, England: Brooklands Books, Ltd., 2008), pp. 107-115; “Giant Test: Lancia Beta 2000ES, Audi 100LS, Citroën CX2400,” CAR March 1977, pp. 54-59; “Giant Test: NSU Ro80 – Citroën DS23 – BMW 520,” CAR July 1973, reprinted with permission at Citronet, ed. Julian Marsh, 2009, www.citroenet., accessed 29 July 2012; John Goodman, “Nikasil® and Alusil,” Engine Professional Oct.–Nov. 2008: 18–22; Heiko Haupt, “NSU Ro80: Wankelmütiges Wunderwerk,” SPIEGEL 8 February 2006, de, accessed 11 August 2012; John B. Hege, The Wankel Rotary Engine: A History (Jefferson, NC: McFarland & Company, Inc., 2001); “His rare 1970 NSU is a mystery to most,” NWAutos, 27 May 2012, blog.nwautos. com, accessed 20 June 2012; “History of the Volkswagen K70/40 years of VW K70/NSU/AutoUnion,” autolatest, N.d., www.autolatest. ro, accessed 23 July 2012; Kay Hottendorff and Ard op de Weeg, The Fate of the Sleeping Beauties (Dorchester, Dorset: Veloce Publishing Ltd., 2010); Jan Hullegie,, 5 December 2007, www.ro80. nl/, accessed 14 August 2012; “It’s pull, not push, for the latest VW,” Popular Science Vol. 197, No. 4 (October 1970), p. 85; “First Road Test: The Revolutionary ’69 NSU Wankel Ro80,” Road Test October 1968, reprinted in NSU Ro80, pp. 28-33; “In 1978 the Ro80 may have a little competition,” advertisement, c. 1968, reprinted in NSU Ro80, p. 25; Richard A. Johnson, Six Men Who Built the Modern Auto Industry (St. Paul, MN: Motorbooks/MBI Publishing, 2005); David LaChance, “Whirl Premiere,” Hemmings Sports & Exotic Car #47 (July 2009); Brian Long, RX-7: Mazda’s Rotary Engine Sports Car (Revised 2nd Edition) (Dorchester: Veloce Publishing Ltd., 2004); Karl Ludvigsen, “How Big Are Wankel Engines?” Hemmings Sports & Exotic Car April 2008; Julian Marsh, “Citroën GS Birotor,” Citroënët, 2002, www.citroenet., accessed 21 August 2012; John Matras, Mazda RX-7 (Sports Car Color History) (Osceola, WI: MBI Publishing Company, 1994); Rob Maselko, “Feature Car: ur-TTS,”, 25 June 2007, fourtitude. com, accessed 15 August 2012; Patrick McNally, “The NSU Ro80,” Autosport 8 September 1967, reprinted in NSU Ro80, p. 14; Mazda Motor Corporation, “Mazda Spirit: The Rotary Engine,” 13 August 2007, www.mazda. com, last accessed 20 October 2011; Günther Molter, “Wankel-Powered NSU Spider,” Road & Track Vol. 16, No. 4 (December 1964), pp. 50–52; “Modern Motor road test: NSU Ro80,” Modern Motor December 1969, reprinted in NSU Ro80, pp. 48-52; Günther Molter, “NSU Ro80,” Road & Track Vol. 19, No. 2 (October 1967), reprinted in ibid, pp. 15-18; “MOTOR RACING joins the revolution,” Motor Racing, January 1969, reprinted in ibid, pp. 34-35; Jan P. Norbye, “The Front-Drive Cars in VW’s Future,” Popular Science Vol. 199, No. 4 (October 1971), pp. 10-12, “The View Down the Road,” Popular Science Vol. 206, No. 2 (February 1975), p. 52, The Wankel Engine: Design, Development, Applications, 2nd printing (Philadelphia: Chilton Book Company, 1972); and “Why Detroit Is Doing a Double Take on the Wankel,” Popular Science Vol. 198, No. 1 (January 1971), pp. 54-55, 112; “NSU-Audi,” Der WankelMotor, 2012, www.der-wankelmotor. de, accessed 13 August 2012; “NSU Wankel rotary engines and cars,” Craig’s Rotary Page, cp_www.tripod. com/rotary/ pg05.htm, accessed 13 August 2012; “NSU Wankel Spider,” NSU Prinz, 2008, www.nsuprinz. com, accessed 7 October 2011; Robert van Overbeeke, “Unilateral idealism,” GTO Magazine #6 (December 2007); Dieter Renkin, “Birth of the Ro80,” Classic & Sports Car July 1995, reprinted in NSU Ro80, pp. 92; Graham Robson and the Auto Editors of Consumer Guide, Volkswagen Chronicle (Lincolnwood, IL: Publications International Ltd., 1996); “Ro80 Reassessment,” CAR August 1970, reprinted in NSU Ro80, pp. 46-47; David Scott, “First Test: NSU’s Twin-Rotor Wankel-Powered Sedan,” Popular Science Vol. 191, No. 3 (September 1967), pp. 90-91, 203; Edoard Seidler, “Dr. Kurt Lotz: Vorstandsvorsitzender of Volkswagen: The man who thinks beyond the Bug,” Motor Trend Vol. 21, No. 8 (August 1969): 18–22, 96, and “Overseas Report: Who Wants NSU?” Motor Trend Vol. 21, No. 5 (May 1969): 46–47; Reinhard Seiffert, “NSU Ro 80: Wunderauto mit Schattenseiten,” auto motor und sport 3/1968 (3 February 1968): 20–29; “Statistische Daten,” Ro80-Club International, ro80club. org/das-auto/ statistische-daten, accessed 14 August 2012; Jason Torchinsky, “The Last Mazda Wankel Engine Has Been Built,” Jalopnik, 26 June 2012, jalopnik. com, accessed 29 June 2012; “Trail Blazer, White Elephant or Both?” CAR June 1972, reprinted in NSU Ro80, pp. 60-63; “Upheaval of an empire: How Lotz went out and Leiding came in,” Autocar 25 November 1971, pp. 44-47; Richard van Basshuysen and Gottlieb Wilmers, “An Update of the Development on the New Audi NSU Rotary Engine Generation,” SAE Technical Paper 780418 (Warrendale, PA: Society of Automotive Engineers, Inc., February 1978); Paul Van Valkenburgh, “NSU Ro80,” Sports Car Graphic October 1969, reprinted in NSU Ro80, pp. 42-45; “Volkswagen K70: Sad, unwanted child of a forced marriage,” The Independent 2 March 2004, uk, accessed 23 July 2012; Christian von Klösterlein, “Claus Luthe – eine Retrospektive,” Ro80-Club International, 2008, ro80club. org, accessed 14 August 2012; “West Germany: The Wankel Wager,” TIME 8 September 1967, p. 110; “What Car? tests/NSU Ro80: Yesterday’s car of tomorrow,” What Car? October 1974, reprinted in NSU Ro80, pp. 68-70; and the Wikipedia® entries for the Audi 100 (, accessed 15 August 2012), the German Audi 100 page (, accessed 15 August 2012), the German Audi 200 page “Audi 200” (, accessed 22 August 2012), Claus Luthe (, accessed 7 July 2012), Felix Wankel (, accessed 22 August 2012), Kurt Lotz (, 11 August 2012), NSU Motorenwerke (, accessed 14 August 2012), the German NSU Prinz page (, accessed 23 August 2012), NSU Ro80 (, accessed 7 July 2012), Rudolf Leiding, (, accessed 10 August 2012), Sulm (Germany) (, last accessed 7 September 2021), and Supervisory Board (, 11 August 2012).

Some historical exchange rate data for the dollar, the sterling, and the Deutschmark came from Lawrence H. Officer, “Exchange Rates Between the United States Dollar and Forty-one Currencies,” MeasuringWorth, 2011,, used with permission. Exchange rate values cited in the text represent the approximate equivalence of British, German, and U.S. currency at the time, not contemporary U.S. suggested retail prices, which are cited separately. Please note that all exchange rate equivalencies cited in the text are approximate; this is an automotive history, not a treatise on currency trading or the value of money, and nothing in this article should be taken as financial advice of any kind!



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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.

      1. Aaron,
        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.

  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. 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.

  6. 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!

  7. 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; you’ll note that it was spelled correctly in the first instance in the text.

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

  9. [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.

  10. 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.

  11. 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!

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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?

    1. 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.

  21. 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.

    1. 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.

  22. 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?

    1. 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.

  23. If this site is still active, any ROers please reach out to me.
    I have a 1976 silver RO in Stuart Florida.


  24. 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.

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