In 1959, NSU developed the KKM 250, a larger version of Fröde’s initial KKM 125 that produced roughly as much power as NSU’s contemporary 583 cc (36 cu. in.) piston engine. The following year, the company installed a KKM 250 in a Prinz sedan and allowed journalists from German automotive publications to try it. This was followed months later by a Sport Prinz fitted with a further refined, more powerful 386 cc (24 cu. in.) KKM 400.
Both of these test mules were crude, but they helped to establish the Wankel engine as a viable prospect — important to the ongoing sales of patent licenses (NSU’s major source of development money) and the company’s relationship with its understandably nervous shareholders.
At the Frankfurt International Auto Show in the fall of 1963, NSU unveiled its first rotary-powered production car, the NSU Wankel Spider. The Spider was just what journalists who had driven the earlier prototypes expected of a Wankel-powered NSU: a ragtop conversion of the Sport Prinz coupe with a radiator stuffed under the bonnet to cool the rear-mounted 498 cc (30 cu. in.) KKM 502 engine. Fitted with a single two-throat Solex carburetor, the KKM 502 had 50 PS DIN (37 kW) and 52 lb-ft (71 N-m) of torque, about 15% more than the 996 cc (61 cu. in.) OHC four then being prepared for the new Prinz 1000. The price tag was DM 8,500, equivalent to about $2,125 at the contemporary exchange rate.
The Spider was not sold in large numbers, but it gave NSU useful field experience with the new engine. That was fortunate because the rotary still had significant issues. To prevent cracking around the spark plug, the rotor housing was aluminum, which was chrome-plated for hardness. Because using durable materials like cast iron for the apex seals would score the chrome surface, NSU (like Toyo Kogyo) opted for carbon seals, which had a relatively short life. When the apex seals became too worn, the engine would lose power, requiring a complete teardown to replace the seals. Oil consumption also remained high, although NSU tried to soften the blow by saying the engine’s oil use obviated the need for periodic changes; the manual recommended simply topping off the oil supply as needed.
The Wankel Spider demonstrated that the rotary did work as an automotive engine, but the KKM 502’s practical lifespan was still short and its real-world behavior left much to be desired. For a moderately priced, low-volume sports car, such deficiencies might be excusable (reliability was not the strong suit of most contemporary sports cars, even ones with perfectly conventional engineering), but expectations were different in the executive class in which the Typ 80 was expected to compete.
Nonetheless, NSU was now committed. When the four-cylinder Prinz 1000 debuted at Frankfurt in 1964, Von Heydekampf announced that NSU’s future engine development would focus exclusively on the Wankel.
TYP 80 TO RO80
NSU announced the production version of the Typ 80 in early 1965. After considering and discarding a variety of possible names (mostly for trademark reasons), NSU christened the new model Ro80, “Ro” for Rotary, “80” for the type number.
At that time, the Ro80 was still in the relatively early stages of its development. Final wind tunnel testing did not take place until September of that year and road testing of early prototypes didn’t begin until the following spring. It should be remembered that the Ro80 was a genuinely all-new design that shared very little with NSU’s other models, all of which (save the Spider) had rear-mounted, air-cooled engines. The Ro80 was considerably more sophisticated than the Prinz or Sport Prinz, featuring not only front-wheel drive but also power-assisted ZF rack-and-pinion steering, fully independent suspension (MacPherson struts in front, semi-trailing arms and coil springs in back), and ATE-Dunlop disc brakes all around (mounted inboard at the front) with a proportioning valve to limit rear-wheel lockup.
The Ro80 was initially slated to use a two-rotor version of the KKM 502 used in the Wankel Spider, but ongoing issues with the Spider’s seals led to the development of the extensively redesigned KKM 612, also of 995 cc (61 cu. in.) swept volume, but trading the rotor housing’s previous chrome plating for a new ElNiSil (electrodeposited nickel-silicon carbide) coating, developed by MAHLE GmbH under the trademark Nikasil. (It has subsequently seen widespread use as a coating for aluminum pistons and later aluminum cylinder bores for reciprocating engines.) The KKM 612 engine also used cast iron apex seals, which NSU hoped would wear better and have better detonation resistance than the Spider’s carbon seals while greatly reducing frictional losses. (See the sidebar on the following page.)
Like the early Mazda rotary engines, the KKM 612 had dual ignition coils and two spark plugs per chamber, giving a total of four; both plugs were set to fire simultaneously. With two Solex 18/32 HHD two-throat carburetors, the KKM 612’s output was 115 PS DIN (85 kW) and 117 lb-ft (159 N-m) of torque, more than twice the output of the Spider’s single-rotor engine. For all that, the two-rotor engine was very compact and quite light, with a dry weight of only 265 lb (120 kg). (Mazda’s contemporary 982 cc (60 cu. in.) L10A engine, with side intake ports, was lighter still, but had only 110 PS (81 kW) and 96 lb-ft (130 N-m) of torque.)
While the two-rotor engine was considerably more powerful than the Typ 80’s original specification, the Ro80’s weight had also risen by more than 50%, which also raised new questions about what transmission the car should use. NSU had considered using an unusual hydrostatic transmission, but concluded that it was not sufficiently refined for production. A conventional four-speed gearbox also proved less than satisfactory because it highlighted a weakness of the KKM engine’s peripheral intake ports: an annoying driveline ‘snatch’ on the overrun (i.e., with the throttle closed and the clutch engaged, allowing the engine to be driven by the car’s momentum rather than the other way around), caused by exhaust gas being drawn back into the intake charge. A fully automatic transmission would have avoided that problem, but was apparently ruled out because it would have sapped too much engine power.
The alternative NSU finally chose was the three-speed Saxomat, a semi-automatic transmission made by Fitchel & Sachs, similar to the four-speed Sportomatic unit then used by Porsche. The Saxomat transmission was essentially a fully synchronized three-speed manual gearbox (with an overdrive top gear) with both a dry-plate clutch and a torque converter that shared the engine’s oil supply. The plate clutch was operated by a vacuum servo, controlled by a switch in the top of the shift lever; simply touching the gearshift knob would disengage the clutch.
The Saxomat transmission offered two major advantages for the Ro80. First, the torque converter largely eliminated the overrun snatch because there was no direct mechanical connection between engine and gearbox; the gearbox input shaft was driven by the converter turbine. Second, the converter’s additional low-speed torque multiplication (2.3:1 at stall) helped to compensate for the Wankel’s mediocre low-end torque and reduced the need to shift in gentle driving.
The Ro80 was a very promising package, but it represented a great deal of new ground for NSU, and there were serious questions about whether the car was ready for public consumption. According to writer Dieter Renkin, Ewald Praxl asked Von Heydekampf for more time for testing prior to series production, but by the time pilot production began in August 1967, NSU’s back was against the wall. NSU’s existing cars were selling reasonably well (more than 100,000 units in both 1966 and 1967), but the company was no longer in the motorbike business and had invested nearly all of its available resources in the Ro80 and the follow-on Typ 70 (a smaller piston-engined car intended to debut at the 1969 Geneva show as NSU’s answer to the BMW 1600/1602). That fall, Von Heydekampf freely admitted to the press that NSU was betting everything on the Ro80. The company simply couldn’t afford to wait any longer for launch.
THE NSU RO80 DEBUTS
The new car made its public debut at the Frankfurt show in September 1967. The NSU Ro80 was not the world’s first two-rotor production car — that honor went to the Mazda Cosmo Sport, which went on sale earlier that year, two and a half years after it bowed at the 1964 Tokyo Motor Show — but the NSU was the first rotary-powered production sedan, arriving about two months before the public introduction of Mazda’s Familia Rotary Coupé (R100). The Ro80 went on sale shortly afterward with a starting price of 14,150 DM (about $3,550), raised a nominal 40 DM ($10) in early 1968. That price put the Ro80 a full 1,000 DM (about $250) above a Mercedes 230 sedan and almost 2,300 DM ($580) more than a six-cylinder Opel Commodore — an ambitious price tag indeed.
Even without the rotary engine, the Ro80 would have been a great achievement. The aerodynamics were probably the best of any contemporary production car; only the Porsche 911 and Citroën DS21 even came close. The Ro80’s chassis was also superb. Despite its skinny Michelin tires, the combination of wide track, low center of gravity, and fine steering made for excellent handling. The ride was outstanding as well, thanks to long wheel travel, well-tuned spring and damping rates, and low unsprung weight.
As was typical for German luxury cars, the Ro80’s interior did not approach American, British, or French standards of plushness, but it was tasteful, roomy, and well-made. The body had a reassuring sense of solidity, and assembly quality was high. There were nits that could be picked — the labeling of minor controls was rather cryptic (resolved in 1970), the seats needed more lateral support (ditto), and the ventilation system would have benefited greatly from an interior fan — but the Ro80 was nonetheless genuinely impressive, particularly considering it was NSU’s first executive car.
Much of the press attention, of course, focused on the Ro80’s powertrain, which drew considerable interest and mixed reviews. The free-revving nature and smoothness of the rotary engine elicited much praise, but while the engine’s power output compared favorably with that of a 2-liter (122 cu. in.) carbureted piston engine, torque was meager below about 3,000 rpm. The torque converter helped a bit, but the Ro80 had widely spaced gears and around 2,850 lb (1,290 kg) of curb weight, which made for sleepy low-speed performance, particularly if one followed NSU’s suggestion to leave the transmission in second for most city driving. Most testers reported 0-60 mph (0-97 km/h) times of around 14 seconds through the gears. While brake-torquing (revving the engine against the brake in neutral at launch) could trim a second or so off that time, the Ro80 was not well-suited for drag strip starts. The Saxomat transmission wasn’t much help in that regard; achieving smooth shifts took practice, and some testers found that fast changes could beat the synchros.
The Ro80 came into its own at autobahn speeds, where the relatively short overall gearing (3,200 rpm at 60 mph (97 km/h) in top) put the engine into a richer part of its torque curve, providing much brighter acceleration and snappy passing response. The rotary remained uncannily smooth all the way to redline, and with the well-suppressed wind and road noise, drivers were well-advised to keep a close eye on the (rather optimistic) speedometer. Claimed top speed was about 112 mph (180 km/h), a respectable figure for the Ro80’s size and price, and very few cars of the time were as stable or comfortable at high speeds.
Even in relatively brief road tests, the NSU rotary engine displayed a few disagreeable habits, including recalcitrant cold starting, but the biggest complaint was fuel economy. On an absolute scale, the Ro80’s fuel consumption was not disastrous for the era, ranging from 13 to 18 mpg (U.S.; 18 to 13 L/100 km) depending on conditions, and it was actually better at high speeds than many piston-engined rivals. However, the bottom line was that the KKM 612 was a 995 cc (61 cu. in.) engine with fuel economy comparable to a 4,235 cc (258 cu. in.) Jaguar.
Added to the rotary engine’s prodigious appetite for oil and spark plugs, such consumption made the NSU Ro80 rather expensive to run for European buyers. (In that, it was probably fortunate that the Ro80 was not in the Taunus/Cortina class, where the rotary engine’s thirst would have been an even greater marketing problem.) One consolation was that, as with the Wankel Spider, the Ro80 did not require routine oil changes, although it was imperative to keep the oil supply full.
Still, the new model made a good first impression, and its combination of merit and novelty earned it the European Car of the Year award. Initial 1967–68 sales totaled around 6,400 units — not bad for the price, particularly considering that right-hand-drive models were not available until the fall of 1968 and the Ro80 was not certified for U.S. emissions standards until mid-December 1969.