When is a Volkswagen not a Volkswagen? When it’s an NSU. The K70’s fate forms a salutary tale.
There is an argument to be made that the Volkswagen motor company has thrived upon existential crises. Certainly they have experienced no shortage of them over their lengthy and mostly successful history. Having survived and prospered in the wake of the first of these in 1945, by the latter years of the 1960s, the Wolfsburg carmaker once again was faced with a serious reversal of fortune, with demand for the emblematic Beetle faltering, and little clear idea of how to move forward in its wake.
Yet this late in the decade, Volkswagen management appeared oblivious to the technological changes taking place across the wider industry, especially in the European market, where front-mounted engines were now very much the norm, and front-wheel-drive was in the ascendancy amongst more progressive carmakers.
One of these, previously wedded to the rear-engined layout, was NSU Motorenwerke AG, whose compact Prinz-series had proved a notable rival to the Beetle in Germany, if not elsewhere. The success of the smaller car emboldened NSU’s management to expand ambitiously. Having previously cleaved to what it knew best from its days as a motorcycle specialist, the company now embraced the very latest in technology, being at the vanguard of what was then regarded as the powertrain of the future – developing a version Felix Wankel’s rotary engine, which made its debut in the beautifully realised, if ill-fated RO80 model of 1967.
The costs of getting RO80 into production, coupled with the development of the rotary engine were to be balanced by the royalties NSU were set to derive from other carmakers.
Further to the flagship RO80 was its (slightly) smaller brother, dubbed K70 by dint of its reciprocating piston (kolben) engine. This model would sit smack within the mid-size saloon market, where the bulk of the volume could be gained. Designed along similar (if less aerodynamic) lines to that of its larger sibling under the direct supervision of Claus Luthe, the K70’s lines were crisp and modernist, if perhaps a little on the sheer side. (An estate model was also developed but never produced).
Technically, the K70 resembled its larger sibling in layout and chassis design, both designed under Ewald Praxl’s supervision. Struts and lower wishbones at the front, with what VW called a trailing wishbone axle aft. The front disc brakes were mounted inboard. The 1600 cc overhead camshaft engine was derived from the Prinz 1200 cc unit, and was offered in two outputs – 88 bhp, or 105 bhp (SAE). The engine was mounted well forward over the axle line, canted to the right, with the differential mounted directly beneath, and the four-speed manual gearbox in line behind.
With development complete, the K70 was on the verge of being introduced by NSU in March 1969. But behind the scenes, matters were unravelling. Pummelled by the warranty costs associated with the rotary engine’s teething troubles, and those associated with introducing two all-new models in quick succession, NSU essentially ran out of money. At this point Volkswagen stepped in, sensing an opportunity to gain valuable technical know-how from NSU’s engineers, not to mention production capacity from the Neckarsalum facility.
Allegedly pulled just prior to launch, the K70 vanished without trace while VW’s management pondered its fate. Complicating matters was the fact that Wolfsburg had recently introduced their own mid-sized offering with the rear-engined 411 model, not to mention the first-generation Audi 100, both of which were to a greater or lesser extent, direct rivals for the K70.
Volkswagen’s supervisory board merged NSU into Auto Union, creating Audi-NSU, and positioning it as the group’s technology leader, but as the business case for the Wankel began to evaporate amid protracted technical and in-service issues, coupled with the coup de grâce of the 1973 oil shock, the case for NSU in any shape or form was irretrievably lost.
Finally, it was decided to productionise K70 in September 1970 – the costs of axing it entirely most likely being prohibitive. Lightly restyled, it was therefore announced as perhaps the most advanced car to bear the Volkswagen name since its inception. “A surprise to everyone who doubted that VW would make it“, the carmaker rather disingenuously proclaimed in the sales material. Well received by the auto press, it achieved second place in that year’s Car of the Year contest, behind Citroën’s winning GS.
Volkswagen described the car as being “well ahead of its competitors“, and while that may or may not necessarily be an accurate reading, when it came to VW’s own 411 series, it most conclusively was. The contrast between the two cars is striking. The 411 represented Volkswagen’s hidebound approach to product strategy; their belief that an enlarged version of the engineering principles which underpinned the highly successful Beetle would suffice into the 1970s – an approach which echoed that of BMC, albeit in reverse.
Pitched against one another, the 411 gained a headstart in sales terms, meaning the K70, a car which required some explanation to traditional VW customers, (if not anyone else) such was its visual and technical novelty, struggled; a matter not aided by Volkswagen’s own lukewarm promotion of the NSU-developed orphan.
In essence a fine, well rounded and capable car, the K70 however wasn’t perfect. Hampered by poor aerodynamics (a consequence of its compact but tall power unit – ironic given the RO80’s low bonnet line) and therefore a relatively heavy thirst for fuel, the VW-NSU, despite its obvious appeal, appeared anomalous within Volkswagen’s early ’70s car range – one which was otherwise dominated by dated, rear-engined, air-cooled offerings.
Along the banks of the Mittelandkanal however, frantic behind-the-scenes efforts to replace the traditional designs were taking place, with both rear and mid-engined fully-engineered prototypes being evaluated. As profits plummeted amid the European and US market’s rejection of the now hopelessly outclassed Beetle, desperate measures were enacted by newly appointed CEO, Rudolf Leiding, who immediately abandoned all attempts at a rear-engined approach.
Audi has been widely credited with the new generation of compact models which underpinned Volkswagen’s post-1974 revival, but author, Stuart Ager posits that it was NSU who was responsible for the basic designs for both Audi 50, (nee Polo) and Golf – both of which are said to have been on the drawing boards prior to the carmaker’s 1969 collapse. If true, it could be said that the takeover of NSU was perhaps the most astute (or fortuitous) act Volkswagen ever undertook.
The K70 was modified for 1973, gaining revised frontal bodywork, a larger 1800 cc engine, and trim details. Sales remained sluggish, largely owing to VW’s own ambivalence, and the advent the same year of the Audi 80-derived Passat model, a car which didn’t suffer from a not invented here stigma. The K70’s future was already sealed by then, and production ceased in 1975, with only around 200,000 built, alongside VW’s 411 at the Salzgitter facility. The RO80 struggled on until 1977, but it would not be until 1985 that the NSU name was excised entirely from Audi AG.
Mergers and acquisitions always incur some collateral damage, but in NSU’s case, it does appear they suffered a worse fate than most. Not only that, but with Volkswagen benefitting to a degree which could only be described as undeserving, a truly promising, highly innovative and commercially brave carmaker was snuffed out. History not only favours, but is frequently written by the winners. In this case however, VW deserves little honour. Both K70, and NSU itself deserved a better fate.
Source: SM-Accidental Death of an Icon : Stuart Ager/ VW
Driven To Write 
The official spelling of Ro80 is shown in the following advertisement (late cars had RO80 on their stick-on badges)
VW/Audi tried to use NSU hardware at some installations. At the beginning of Polo development there were prototypes using the NSU air cooled I4 up front – the NSU engine was rightfully considered as far too noisy when installed up front, it didn’t provide proper heating and was too expensive to make.
The elder brother of a former classmate was a NSU fanatic and had a collection of several dozen Prinz models, including rare TTSs he used for hill climb racing and of course he head to have a K70 and of course his K70 had to have a NSU logo in its grille (and of course the poor K70 had to be driven like he drove his TTs, flat out all the time).
The K70 always was criticised for its coarse and thirsty engine, its low top speed and for its rapid corrosion. On the other hand it was exceptionally roomy with an enormous boot and it was very comfortable and safe to drive, particularly when compared to the rear engined VWs.
Good morning Eóin. Although I very much liked the K70’s rectilinear design, I had always wondered why NSU didn’t simply reprise the lovely aero style of the Ro80 on its smaller saloon. I now understand it was simply because the engine and transmission package was far too tall to do so, which was a real shame. Also, I hadn’t realised how poor the K70’s aero performance was until Dave highlighted it recently.
Regarding the brochure, VW’s were lovely clean modernist designs back in the 1970’s, with simple consistent layouts, a handsome typeface and great photography. The image above of the K70’s front end, with the three smaller detail photos alongside, is typical, as is the large double-page single image with a white band of text below. They perfectly complemented the new generation of VW cars, bet even worked well with the Beetle:
Returning to the Ro80, the Wankel engine really was it’s Achilles heel and a number were replaced with Ford’s rough old V4, which was a travesty. That gets me thinking about a more suitable engine that might fit under that bonnet. What about the flat-six from the Boxster? It might give the car the turning circle of an ocean liner, but I could live with that!
The R0’s aerodynamic design was chosen to somewhat cover for the high fuel consumption of its Wankel engine and this particular design with the extremely low bonnet was possible only because the Wankel engine is barely larger than a shoebox, just like the old Cologne (not Essex) V4.
Early Ro80 engines mostly failed because the leaf springs behind the rotor tip seals lost their tension and in turn the engine lost most of its compression (other than a reciprocating piston engine a Wankel will still run in this condition with reduced power which makes it the favourite engine for snow mobiles). NSU had ordered their dealers to replace the engine in case of any fault so NSU could investigate the reasons for the defects. That’s why some Ros got five or six new engines under warranty, particularly when the car was used under adverse conditions like inner city or short distance driving. Most engines could be repaired quickly and cheaply by replacing the rotor tip seals but this didn’t help the warranty costs. the K70 was a fine car which had a strong but small community of followers who bought it because it was a modern VW unlike the 411 (four doors, eleven years too late).
From corresponding with a few NSU Ro80 clubs (more specifically Ro80 Club International), it seems some NSU technicians studied the use of a conventional piston engine and ‘played’ with a flat-six Boxer engine, but the NSU officials stopped this, since they thought it to be undesirable.
As far as existing engine conversions are concerned it seems Audi engines were a common swap, likely the Mercedes-Benz M118-derived EA831 that was used in the Audi 100 C2 and Volkswagen LT that with further modification found its way into the Porsche 924.
Since the Ford V4 was a common swap and despite the following being a narrow-angle V4, it would have been fascinating to see whether a Fulvia V4 could fit into the R080.
As for the K70, can understand the engine being tall and based on the previous air-cooled engine though it seems unfortunate the K70 engine never evolved to become NSU’s equivalent of the EA831 unless a great degree of NSU thinking ultimately found its way into both EA111 and EA827.
I seiously doubt that an EA831 would fit under the R080’s low bonnet and the same goes for the Fulvia engine, which also is very tall where you least want it, around the cam drive. Look at the high bonnet line of any Fulvia.
(The other way round was popular. Audi built at least seventy 100 C2 with the KKM 871 and up to 180 PS for board members which were very popular as fast comfortable transport).
The Ford V4 was chosen because it was extraordinarily compact even if it was the complete opposite of everything the Wankel was. The K70 engine really was NSU’s parallel to the EA831: modern and powerful, noisy and thirsty. The K70 LS’ 1.8 engine definitely was one step too far and stretched the engine beyond its sensible limits, even if Friedel Münch enlarged it even further for his motorcycles. VW didn’t improve on the K70’s noise insulation in short intervals for nothing, the latest K70s had around thirty of forty kilograms more of sound deadening material than the first. At anything above 120 kph the K70 engine sounded very strained which is no wonder considering the aerodynamics.
The mention of Audi inline-4 engines being installed in Ro80s comes from correspondence with Ro80 Club International, however it is not specified exactly which inline-4 engines out of EA831 and EA827 though presume it was not without some extensive modifications.
In recent years it seems a number of V4-powered Ro80s have been converted back to rotary engines as reliability has significantly improved, with a number of Ro80’s being equipped with the marine rotary engine type R135 which has about 135 hp instead of 115 hp.
There’s a significant number of Ro80s with the KKM 871 and 170 to 180 PS. Some of then are ex-NSU works prototypes, some are retrofit conversions and all are very much sought after.
Here’s a picture of a Ro with KKM 871. Look at how incredibly small such a Wankel engine is – just the two grey stripes left and right of the oil filler neck (the trochoids) and that’s about it.
https://www.ro80club.org/sites/default/files/photos/rotary/P1010051.jpg?1276244014
Here’s a question I’m sure you can answer, Dave or Bob: why do Wankel engines have such heavy petrol consumption? I would have thought that, with so few moving parts, frictional losses would be minimal and the energy contained in the petrol would be very efficiently turned into motive power. What am I missing?
Hi, Daniel,
when you look at the following video
you see a couple of things.
The Wankel combustion chamber has an extremely unfavourable relation of surface to volume, leading to high heat dissipation to surrounding surfaces and therefore thermodynamic losses. A Wankel rotor gets very hot and needs active cooling, either by guiding the intake mixture through it (Fichtel&Sachs, Norton) or by oil cooling it (NSU, Mazda, Comotor).
The combustion chamber is rectangular and very oblong, preventing any kind of swirl in the mixture, making flame spreading slow and combustion inefficient.
You see that at the moment the spark plug fires the combustion chamber has the shape of a ‘B’, preventing quick spreading of the flame front. Later it takes the form of a half moon, ending sickle shaped. This permanent change of shape prevents any kind of stable combustion and leads to what Wankel engineers call the ‘rich nucleus’, residual unburnt mixture at the trailing part of the combustion chamber. The result are enormous amounts of unburnt hydrocarbons in the exhaust and uneven running under partial load or on the overrun, just like a two stroke. When you look at the ignition timing of a late type Mazda engine with timing jumping between retarding and advanced seemingly at random just to reduce this rich nucleus.
Hi Dave. That’s a really good explanation, thank you, much appreciated!
I had asked in the comment section of another posting (which is currently inaccessible for discussion) about:
https://www.liquidpiston.com
I wanted to invite a critique from our resident technical experts to help further our understanding as about this clever “inverted Wankel” design, which has not caught on despite attempting to address the major, seemingly fatal flaws which have led to the Wankel’s ultimate demise and disappearance from the marketplace.
I’ve just found such a critique, which furthers my understanding and could be of interest to others here. With the caveat that the following video is -not- “safe for work”, I’ll share it here:
The K70 is the car I grew up on n, my father had a bright orange one between 1978 and 1981. My mother had a penchant for finding good bargains, and those cars being orphaned was an incredible bargain in the late 70’s. My mother had a red K70, replacing a VW 412 Variant my father had recently crashed. When they divorced my father bought his own first car, a bright orange K70, and through I was only four years old at the time, I remember the moment we went to the dealer to get it delivered, and the salesman parked it in front of us in this very dim lit parking garage and my fathers unbridled joy of finally getting his own car. In retrospect, it must have been a very odd choice in the communist circles he belonged, I remember friends of the family most having Renault’s, like the Renault 12 and 16 and above all the R4. Or the odd older Volvo, Mercedes, or Citroen. The K70 must really have been the odd man out in those circles.
Hi Ingvar. Great recollections, thank you. I imagine that you must be one of a vanishingly small number of people (other than those directly connected with VW) who have experience of both the Type 4 and the K70. VW traditionalists would have bought the former, while early adopters would have favoured the latter.
Incidentally, there’s a companion piece to this one on the Type 4 coming up very shortly. Stay tuned to DTW!
I’m looking forward to the Type 4! Of course, I don’t remember the 412 because I was too young, but I’ve heard stories they dressed the rear cargo area as a sort of play area for me with a mattress I could sleep on. This was the 70’s to and before anyone had ever heard of child safety, but apparently I slept very well just above the engine, hearing the engine noise putting me to sleep. Before I was born they had a VW double cab pickup, so I guess they were loyal to Volkswagen. Both my parents later strayed towards Toyota, and for my mother these last 15 years towards Citroen.
I’m old enough to have experienced most of these cars when they were new, either as a passenger or as occasional driver of somebody else’s car.
VW’s ‘Nasenbären’ (coatis) were quite popular in ‘Variant’ estate form because driven by some aerodynamic miracle the estate with its pronounced Kamm rear was considerably faster than the saloon and was driven accordingly by sales reps. Up to 85 PS was considerable power in a family car at that time.
The standard fitment of an engine-independent heater (that could be upgraded to a parking heater at very little cost) made the 411/412 quite attractive in comparison to other air cooled VWs which only heated in summer but made you scrape ice from the inside of the windscreen in winter. The 411 was a reliability nightmare because of its electronic injection with a control unit as large as a big shoebox under the passenger seat but this was cured by enlarging the engine from 1.7 to 1.8 litres and fitting carburettors for the 412 which also had an even longer nose and an even larger boot up front.
If it had really been as dangerous as they say today, we all would not be here anymore…
And, as my father told me, NSU brought more technical substance to Audi than was later said. Without NSU, Audi would not have become what it became after. NSU was more or less the technical think tank of the 1960s – in terms of automotive technology. Without the takeover of NSU – a fortunate coincidence – Volkswagen would not have survived, because they were technically at the end of the cul-de-sac. The Type 4 says it all.
Without rose tinted spectacles themrootmof Audi’s success as wellas VW’s survival was the Audi 80, Ludwig Kraus’ brainchild and he came from Mercedes.
What a sad yet highly interesting story. In another universe we might be eulogising over the exceptional staying power of Herr Wankel’s engine and NSU, as we do say a Hemi or the Rover (Buick) V8 along with perennial strugglers Jaguar or TVR.
But some excellent reminiscing from Ingvar as well as detailed knowledge from Dave & Bob, thank you.
I was the Ro80 Engine coordinator at the NSU importers in shoreham Sussex in 1970. Used to send the replacement Warranty engines in the passenger seat space of sold P4s and 1200s to dealers. Remove the seat and swing the Wankel unit in on a small crane. I could manhandle the old units in wooden crates quite easily. I am a small bloke too! I loved the Ro80 and spent happy hours talking to guys in the technical dept. understanding little but enjoying it all none the less.
I do also remember that there were 2 types of Ro80 engine. the 2 plug and the 4 plug?
NSU permanently modified the Ro’s engine. It started with a single plug, went to two and returned to one at the time it got the ceramic liners in the exhaust ports. NSU also switched between single and double exhausts and there are even more variations for ignition distritubutor and air filter/silencer. There are engines with and without Nikasil coated trochoids and stellite apex seals.
Most of these modifications were made to reduce the Wankel’s considerable thirst and the high amount of unburnt hydrocarbons in the exhaust gases. NSU also fought against the loud intake noise that’s characteristic for Wankels with circumferential inlet ports which open abruptly and make the intake sound like a shot and against the uneven running/’hunting’ that’s typical for Wankels under partial load and on the overrun and forced NSU to fit a torque converter to filter it out. They relatively quickly (but expensively by using nikasil and stellite) sorted out the problem of premature trochoid wear caused by apex seals with lame springs that led to chatter marks on the trochoid’s surface.
I remember the leaked images of the Ro80 before its’ introduction – front and rear views seemed to show two different cars. It took a few years before I realised how advanced it was.
In the early 70s there was a crashed Ro80 with German plates parked next to Cullotys Garage in Killarney Co Kerry. I asked Culloty about it because most of it was pristine, and I really wanted the front seats for my Landcrab ! He explained that the insurance company wasn’t inclined to take the wreck back to Germany, and no parts could be sold because import duty had not been paid. Eventually it became sleeping quarters for the local homeless…
Someone locally owned a K70, the only one I ever saw.
The R080 would be perfect for electric conversion since the replacement motor would physically be no larger than the rotary. The cooling system, exhaust, fuel tank, torque converter and clutch could all be eliminated.
I’ve been fortunate to have owned two of these great cars, a 70 dual round headlamp and a 73 with the sleeker lamps, alloy wheels and velor interior. My only problem during ownership was a leaking torque converter oil seal on the later car, this I sucessfully replaced myself without prior experience.
Great car the Ro80!
I have seen V4 conversions,horrible as they usually require modification to the grille and or bonnet.
The R080 would be perfect for electric conversion since the replacement motor would physically be no larger than the rotary. The cooling system, exhaust, fuel tank, torque converter and clutch could all be eliminated.
I’ve been fortunate to have owned two of these great cars, a 70 dual round headlamp and a 73 with the sleeker lamps, alloy wheels and velor interior. My only problem during ownership was a leaking torque converter oil seal on the later car, this I sucessfully replaced myself without prior experience, believe somewhere I still have the workshop manual!
Great car the Ro80!
I have seen V4 conversions,horrible as they usually require modification to the grille and or bonnet.
‘In this case however, VW deserves little honour’.
I think that’s perhaps a little rough on Volkswagen.
Realizing the irretrievable situation they were in, NSU had quietly been touring manufacturers’ boardrooms with a view to being taken over. Their preferred candidate was Citroën who weren’t keen. It would have been an interesting, if brief, liaison.
Why did Volkswagen agree to take them over? My guess is a wish to get their hands on the rights to the Wankel technology and licenses, on the assumption that this would have at least some success in future. Could there have been political pressure, too?
As for the other assets…
1) Ro 80 was gaining / had gained a poor reputation;
2) K70 competed with Volkswagen’s own range. Further, while its approach was novel by Volkswagen’s standards, it really broke little new ground in the market. I don’t think they were very keen on launching it;
3) the rest of the NSU range had a limited lifespan;
4) talented people / front wheel drive technology. Possibly attractive, but they had bought Audi a few years before which provided both. Also, at the time of the takeover, in 1969, I think they were still convinced that air-cooled, rear engined vehicles had a future;
5) extra production capacity?
6) at least there was the beginnings of the K50 / Polo.
Volkswagen could have waited until NSU went bust and picked through the remains. Did they want to be sure of heading-off competitors’ access to rotary technology, or were there other reasons we don’t know about?
Did not know Citroen was the preferred candidate for NSU, would have indeed been fascinating to see how Citroen would have benefited from NSU as well as whether Volkswagen would have still become what is in the present day without acquiring NSU (minus the K50 / Polo).
What role did NSU play in developing the EA111 and EA827 engines?
Guess the NSU Ro80 would have made a nice starting point for a 1.7-2-litre+ Flat-Four powered replacement for the Panhard 24 had Citroen not forced Panhard to stop producing cars.
My father had one from 1972 to 1975. It was a lovely car. I loved the glassy bright cabin and the exterior simplicity. It was replaced with a slightly gaudy FIAT 132 1600gls which only underlined the elegance of the k70 for me. There were no chrome stripes, it was all about shaped metal in a really simple three box design.
As modern car windows get smaller and smaller, the old K70 looks better and better. It must have a very high glass-to-metal ratio for a mass-produced car