NSU Wankel Spider 1965
We like the way NSU has introduced the Wankel engine. It's not in a "dream car" making the rounds of the auto shows. It's not in fifty hand-built prototypes being loaned to selected families for market evaluation. Although it could have been, it's not even in a very special sporting machine with a price unrealistically keyed to its unquestionable novelty value. The Wankel engine you can buy is in a good-looking little two-seater with competitive performance at a commercial price. A better start than that it couldn't possibly have.
Our time spent in the Wankel-powered NSU Spider has confirmed our conviction that the engine is applicable to better things than lawnmowers, fire pumps, power surfboards, and so on. We therefore share NSU's opinion that it is the most serious rival, so_ far, to piston engines in small and medium-size cars.
The fact that NSU is producing the Wankel Spider is not just a gimmick to promote further licensing agreements for the rotary piston engine, which has admittedly proved a highly remunerative business over several years (Curtiss-Wright and Toyo Kogyo paid up $2,000,000 each for full manufacturing rights, and about ten other firms including Daimler-Benz, Alfa Romeo and Citroen have paid NSU sums of about $50,000 for the right to share experimental information prior to negotiations about manufacture). NSU is also determined to remain a car manufacturer in its own right, as the Swabian firm used to be during the period 1906-1933, and has been again since 1956, when the Prinz was announced.
The first Wankel-engined production car, however, has turned out to fall short of the expectations which early communiques from the factory and and independent technical analyses led us to nurture. It's not at all the magic 15,000-rpm earthbound brother of the space ship that we dreamed about, but a rather ordinary and untemperamental small sports car with the performance of a normal 1100cc roadster. When NSU built its first Wankel-engined prototypes, they were fitted with Volkswagen transaxles which were not ideally matched to the power range. The Spider has a new all-synchro transmission designed for the Wankel engine, and the factory still limits the maximum rpm to 6000. This is in the interest of longevity, as experience has proved that seal tip wear increases sharply with a rise in rotational speed.
The result, of course, is a car that can be driven just as a conventionally-powered one, with the same controls and the same functions. In order to get similar results, some driving -adjustments are required, because there's next to no torque below 3000 rpm-to keep engine noise and vibration at an acceptable level, the driver should shun anything under 3000 rpm like the plague. The engine will idle with average smoothness at 750 rpm, but it goes through a period of great heaving about 1100 rpm" before it reaches that level. It sounds as if it's about to stall, but it doesn't. It's just a shake period, accentuated by the softest motor mounts known to man.
Caught at the traffic lights with the revs below the magic 3000, there's nothing to do but wait for them to swoop up (or slip the clutch for what seems like an entire quarter-mile). On the track, the car should do wonders for any driver willing to keep the revs permanently above 4000, which is where the racing power comes in. And, of course, the engine won't break if taken beyond the red-line-it just revs and revs to about 7500 with the existing carburetion, feeling smoother and healthier as the needle goes deeper into the red. NSU plans to sell a homologation quota- in order to qualify the car for the 1965 season-and they are probably praying that SCCA will put it in Class G.
NSU also argues that constant design work is going on (as distcinct from development work, we surmise) to find some more torque, or at least to spread what they have a little lower on the scale.
Many will wonder whether NSU is really- justified in releasing this car for sale at this point. But for a small operation like NSU it's an important fact that no number of miles with factory drivers can replace a year's time in the hands of the average buyer. The success of this method of customer participation in the development of the car is naturally contingent upon the service and warranty attitude of the factory. On past record, NSU will not let this become a source of worry to its customers.
Another reason for the urgency of producing the Spider is the recent introduction by Toyo Kogyo of a prototype Mazda sports car with a two-chamber Wankel engine (while NSU has stuck with the single-chamber unit). NSU does not object to the excellent progress Toyo Kogyo has made with the Wankel system, especially since the licensing agreements call for a two-way flow of information. Naturally, however, NSU would like to be first on the market with the engine on which it has literally staked its future.
The 500cc unit of the Spider is very compact and weighs only 275 ppunds complete with flywheel, starter, generator, carburetor and air cleaner, giving an unusually high power/weight ratio (4.29 lbs per bhp).
It has two cooling systems: the "engine housing is water-cooled and the piston is oil-cooled. The oil lubricates and is then consumed. No oil changes are necessary, but the engine needs occasional replenishment (approximately one quart per 1000 miles). The oil/ water heat exchanger is located next to the engine, while the water radiator is conventionally placed behind the grille. A thermostatically controlled fan is engaged if the airflow fails to keep water temperature within the normal operating range. Renault and Fiat, for instance, usually place radiators for rear-mounted engines in the back, but NSU interestingly moved it in front, in the avowed interest of improved weight distribution. The sheer size of it indicates that weight was at least one of their motives. Cooling capacity seems quite adequate, though there is a definite hot smell around the tail after a couple of hours' driving.
Ease of service is one of the major sales points of the Spider. Early estimates indicated that new seals and bearings would be needed after about 30,000 miles, but currently the factory seems confident of 60,000 trouble-free miles. It all stands or falls with the seals at the tips of the rotor apparently running the engine at its full capacity can cut their life in half. The engine has only one spark plug, and Bosch and Beru have produced special types that will take the continuous hot exhaust bath and give normal plug life.
One way of keeping the revs within reason was to fit a very long top gear, giving 107 mph at 6000 rpm. Aerodynamic drag won't permit the car to exceed 95 and even that figure can't be reached except on a long and empty freeway. Cruising at a steady 75 mph in top gear will keep the engine churning at an easy 4220 rpm-a point where it's free of vibration and the wind noise drowns it out completely. Winding up through the gears, it sounds almost like a high-revving aircooled two-stroke, which is quite pleasant to most ears, but on the overrun it persistently backfires. Incidentally, it gives almost normal four-stroke retardation on the overrun, and generally behaves like a normal four stroke unit except for the uncanny smoothness once it gets on the step.
On the step? Normally we would say "on the cam", but that seems a little silly when applied to an engine with precisely two moving parts: the rotor and its shaft. Probably the Wankel engine will engender a whole new jargon in automotive writing, i.e., undirectional motion, 'eccentric bearings, flame propagation, and other technical expressions used in previous reports on the Wankel engine
Under most highway conditions, the Wankel engine is practically inaudible, except for a slight whine at high rpm when the whistling of the wind and the gearbox clatter abate enough to let engine noise into the interior. Conversation is a shouting match above city speeds, and the general noise level of the car is enough to make both the driver and passenger physically tired after three hours or so.
If one cannot hear the Wankel engine, what's it really up to back there, under the rear trunk? Most of the time it's playing games with your hearing. Trying to drive the Spider without a tach would be a very frustrating experience until the driver learned to relax and let the engine work as close to peak power as possible. When it sounds like about 1200 rpm and the lack of torque is notable, a look at the tach will provide a surprise reading of 3000 or better. Feed a lot of throttle under 3000 and it just gulps and goes its gentle way.
The whole difficulty of driving the NSU Spider lies in holding engine speed high enough to get Wankel-style power, yet low enough to achieve reasonable longevity.
At first glance, the NSU Spider looks like nothing more than a "topless" Sport-Prinz, In the chassis, the two are really quite different. Front and rear suspension are taken from the Prinz 1000 (which differs from the Prinz 4 and the Sport-Prinz in having semi-trailing arm independent rear suspension in lieu of swing axles). The result is a far better-handling vehicle, giving moderate oversteer and higher ride comfort than one would expect from 12-inch wheels and a 79.5-inch wheelbase. .
The chassis combination, with disc brakes up front and light but firm rack and pinion steering, is more than capable of handling anything the 500cc Wankel engine can produce in the way of speed. All in all, it's a delightful small car to hurl about the narrow but well-paved roads of the Black Forest in Germany (as indeed it would probably have been with a hopped-up version of the single-overhead-camshaft one-liter NSU engine of the Prinz 1000).
The Wankel driver and passenger have new, semicontoured seats with good thigh and back support, some lateral steadying, and excellent fore-and-aft travel. The rake, however, is adustable only by thumb-screws at the bottom of the backrest. It's strictly a two-seater, although the room behind the seats is quite useful storage space for packages (or a small child). As in all other production NSU cars, footroom in the front is restricted by the wheel arches, so that the driver's clutch foot must be tucked under the pedals. But there's
enough headroom for tall drivers, and the doors open wide to facilitate entry and exit. Vision is good every where except to the rear quarters which are totally blind (a hard-top with rear quarter lights is rumored). The sloping hood hides a fair-sized trunk.
Instrumentation is generally aircraft-functional with large white-on-black speedometer and tachometer as the center of attention. The speedometer was an unforgivable 11.3 % fast on our test car at 60 mph, but the fuel gauge was accurate. We recorded 23 mpg on a stretch of highway plus some fast mountain driving, as opposed to the 35 mpg the factory claims for this car.
The net result of nine years of research on Wankel engines by NSU is an acceptable automobile for anyone interested in small sports cars. And it's not the final word from NSU, who have made considerable progress in multi-chamber engines since the Spider was first exhibited at the Frankfurt Auto Show in 1963. Field experience with the existing model will prove extremely valuable for NSU in the design of new models, and as production reaches higher levels, their confidence in the Wankel engine will be put to its final test.
NSU stock has been fluctuating wildly since the company first took the brave step of joining forces with Felix Wankel in 1957, reaching a peak in 1960 as a consequence of premature press reports, dropping after bankers verdicts, and reflecting each subsequent license contract and each stockholders' meeting. Future trends, however, will be determined by the success of the product rather than by rumors and guesswork, putting NSU in somewhat firmer control of its own stock values. Our experience with the NSU Spider seems to justify cautious optimism.
Water-cooled Wankel rotary piston engine, oil-cooled rotor, 3 main
Displacement.................... .30.3 cu in, 500 cc
Compression ratio................... .. .8.6 to one
Carburetion.............. .Single horizontal Solex 16-32 HHD
Valve gear... .. .:. Ports opened and closed by rotary piston
Power (SAE)........................ .. .64 bhp @ 5000 rpm
Torque........................... .54.25 Ibs-ft @ 3000 rpm
Specific power output............. .2.11 bhp per cu in, 128 bhp per liter
Usable range of engine speeds............................. .3000-6000 rpm
Electrical system............... .12-Volt, 44-amp-hr battery, 240 W generator
Fuel recommended. ... . . . . . . .. . Regular
Mileage........................... .. .20-30 mpgRange on 7.5-gallon tank.......150-225 miles
Zero to Seconds
30 mph.................. .. .. . . .. .. ... 5.0
60 mph................................. .. .15.0
70 mph..................................... .21.2
80 mph . . . . . .. . . . . . . . . . . . . .32.7Standing l/4-mile..........69 mph in 20.5
Unit-construction, all-steel body
Wheelbase............. .. . . . . .. . . .. .79.5 in
Track....................... .......... . F 49 in, R 48.3 in
Length..................................... ., .141 in
Width..................... .............. .. .. .60 in
Height....................................... .49.5 in
Ground clearance....................... .6.0 in
Dry weight. ... . . .. .. .. ............ .1485 Ibs
Curb weight . . . . ..................... .1545 Ibs
Test weight............... . . . .. ...... .1850 Ibs
Weight distribution front/rear........ . .47/53%
Pounds per bhp (test weight)....................... . . . .28.9
Suspension F: Ind., unequal-length wishbones, coil springs, stabilizer bar.
R: Ind., semi-trailing arms and vertical coil springs.
Brakes................................ .9-in discs front,
7.1-in drums rear, 196 sq in swept area
Steering.................................... Rack and pinion
Turns, lock to lock...... . . .. .. . . . . . . .3.0
Turning circle..................................... .32 ftTires.. . . . . . . . . . . . . . . . . . .5.00-12 Revs per mile.