Driving the new Volkswagen K70

From Motor Magazine, Week Ending October 3, 1970



To place the K70 we have to look briefly back into NSU history. When NSU marketed the R080 they were aware that its public acceptance might be a bit of a gamble, that they still had a great deal of piston engine manufacturing machinery to use and that there was a vast price gulf fixed between the inexpensive rear-engined models and the costly rotary-engined car. All this pointed to an intermediate model with a piston engine and this is how the K70 was born. It was announced very early in 1969 for the Geneva Show and then withdrawn again when VW took over NSU and formed the new subsidiary called Audi NSU Auto Union AG in April 1969.

Withdrawn but not suppressed. On the contrary, VW thought it was such a good car that they decided to give it their own name and produce it in very much larger numbers than NSU could possibly have afforded. In the meantime they have built a new factory at Salzgitter, not far from Wolfsburg, with a potential capacity of 500 K70s a day. And, of course, development has been continued by both NSU and VW.

We described and illustrated the K70 early this year (Motor, w/e March 7). To recapitulate briefly, it is designed very much after the lines of the Ro80 with front-wheel drive, a very long wheelbase and wide track, a short overhang body with rather similar lines, MacPherson Strut front suspension and irs by semi-trailing rear wishbones and coil spring /damper units. It has anti-roll bars at both ends, inboard disc brakes at the front and outboard drums at the rear with a pressure limiting valve and dual circuit operation. Steering is by rack and pinion but unlike the R080 (and contrary to earlier reports) it does not have power assistance.

The big difference, of course, is in the power unit which has a strong family resemblance to that of the Prinz 1000 series (but water-cooled) with a single chain-driven overhead camshaft operating V inclined valves in hemi-spherical heads through rocking fingers. The engine axis is longitudinal, the four-speed, all-synchromesh, all-indirect gearbox is behind the engine and the final drive is underneath it. Because of this the Ro80’s low bonnet line is not possible, even though the engine is canted 32° to the right to keep it low.

Two versions of the 82 X 76 mm. short stroke 1605 cc engine are available, both with five main bearings and a twin-choke side—draught Solex carburetter; one version has a compression ratio of 8:1 and gives 75 bhp (net) at 5200 rpm on 90 octane fuel, the other with 9.5 ratio needs 98 octane but gives 90 bhp at the same engine speed.

So much for the broad outline. Of course the last 18 months’ extra development has brought some further changes to the original design but most of these are of a very minor nature. The wheel size, however, has gone up from 13 to 14 in. and the 4.5j rims have 165SR radial tyres. Many of the engineering modifications have been inspired by VW’s production expertise and of these the most conspicuous is the change from a light alloy to a cast iron cylinder block.

The first public appearance of the K70 will be at the Paris Show but we recently had the chance to drive it for 150 miles in France. The question which obviously arises is, how does it compare with the Ro80, a car which has had rave test reports all over the world? In some ways it compares very well—it is a roomy five-seater car with an enormous boot of 24.5 cu.ft. capacity. It isn’t, of course, as fast. VW claim a maximum speed of 98 mph for the higher·powered version as against our test figure of 113 mph for the rotary car although the 0-60 mph figures are very similar. Road noise is very low and the K70 has that rigid, rattle-free feeling which adds so much to driving enjoyment on rough roads. The ride is generally good although it is characteristic of stiffly damped cars—a bit jerky at low speeds, but smoothing out at higher speeds.

Wind noise is also low and the ventilation system, a high flow, low velocity system, gives a draught-free air movement which is all you need up to quite high ambient temperatures. The engine is not as smooth as a Wankel but for a piston engine it is very smooth at high rpm, even if you take it right up into the red sector at 7000 rpm.

Probably the most disappointing feature relative to the Ro80 is the handling; the car is unusually stable, predictable and vice-free but the Michelin ZX tyres squeal at quite low cornering speeds and understeer builds up as you go faster until you can find yourself practically on full lock on sharp bends. We would want to try higher tyre pressures than the recommended 21 lb. all round—certainly much higher at the front on a car with 60 per cent of its unladen weight at this end.

Right hand drive K70s will not reach the UK until October 1971. In Germany, where the first batch will all be sold, its chief competitors will ironically be two other products of the VW group—the VW 411E and the Audi 100. No British price is yet available, of course, but the best possible estimate would put the current price at about £1600; in a year’s time it will probably be higher. Excellent though it is in many ways, it isn’t sufficiently distinguished we feel to command large British sales in this highly competitive price category. CHB

University Motors MGC

From Autocar Magazine, Week ending 17th December 1970



It is hard to say exactly what killed the MGC, but the most likely cause was the bad press the car received, together with its failure to sell in the USA. Our own road test, published in 16 November 1967, was far from enthusiastic about the engine, gearbox, handling and fuel consumption. Exactly when production ceased is hard to determine, but it was sometime last year. University Motors bought the last batch of cars and have been selling them successfully since. Their theory was that, with only a little attention, the model could be improved significantly and as they still have some 20 or so cars in stock, we decided to test one to find out for ourselves.

Basically they are offering an MGC GT in standard paint, with wire wheels, delivered with number plates, seat belts and four months tax for £1,370. At the Motor Show in 1968, the listed price was £1,337 without any of these extras, or even a heater. By today's standards this is about £130 less than a Triumph TR6 coupe and not very much more than a GT6 delivered to the same specification.

To improve the appeal though, they are also offering a long list of extras, most of these being fitted to the test car. Added together these came to another £460, making the test car £1,830, or about as much as an Alfa Romeo 1300 GT or a little more than a BMW 2002. Some of these make so much difference as to be near essentials, while others like the stereo tape player and radio (£92) are pretty obvious luxuries.

Items like the Downton engine conversion make such a difference as to qualify as essential extras and the overall effect on the car leaves one wondering why it could not have been made like this in the first place, and if it had, would the fate of the model have been more successful? It would certainly have been much more enthusiastically received by our staff.

As a single item the Downton kit costs £l75 fitted. It comprises the usual kind of head improvement, coupled with special manifolds and a complete transformation of the induction system. In standard form the MGC is a real pig when cold, developing hardly any power until warm and never idling reliably. The Downton—converted car suffers from none of these troubles, pulling eagerly straight after a cold start. More than just this, the conversion gives the engine the "right" kind of sporty response, which it never displayed in standard form, climbing "on to the cam" at about 3,000 rpm with a real bark to its straight—through exhaust. In many ways it reminds one of the works rally Healey 3000, both in overall response and the noise it makes.

Actual improvements in acceleration time are not spectacular, but very worthwhile none the less. In top, for example, about 2sec is knocked off each 20-mph increment. Standing start times show similar slight improvements, and we could probably have made the differences greater if we had not been fooled by the rev counter, which over—read by almost 500 rpm at the top end.

As well as improving the performance, the conversion works wonders for the overall fuel consumption. Driving the car hard we got very nearly 20 mpg, which compares with only 17.5 mpg for the standard product.

The standard gearbox, with its enigmatic choice of ratios, remains unchanged, as does the final drive ratio with its long-legged 26.95 mph per 1,000 rpm in overdrive top. The test car was fitted with Cosmic light alloy wheels (£60 for five) which did little for the roadholding, but improved the appearance no end. They were fitted with the standard Dunlop radial-ply tyres.

Another worthwhile improvement came from the substitution of Koni dampers (£16 the pair, fitted) at the front and a 15in. dia. Motolita laather-trimmed steering wheel (£12 12s). Standard wheel size was 16.5in., so the steering becomes that much more responsive and the view out ahead that much better. Wooden packing strips under the seat runners also improved the driving position, which on the standard car was far too low for anyone much under 6ft tall.

Giving less leverage, the smaller wheel increases the already heavy steering effort, making fast cornering quite a muscular struggle. Excessive understeer from the extra nose weight of the six-cylinder engine makes the MGC a much less lithesome car than the MGB, but it is impressively stable in a straight line as compensation. Poor turning circles (almost 36ft between kerbs) hamper one when manoeuvring.

It would be wrong for a true sports car enthusiast to look at the MGC and expect it to be one better than the MGB. In the vital qualities of handling and engine response, it is no match for the four-cylinder car. But as a long—distance touring car, where a lot of the distance covered will be on motorways, it definitely has a place and in University Motors' guise begins to look much more attractive. At £1,545 (£1,370 plus the essential Downton conversion) it has few direct competitors, and anyone worried about spending this much on an obsolete model can take comfort in the fact that its rarity alone may one day make it a sought-after classic. According to factory records, only 2,199 MGC GTs have been delivered in the UK.

Wilson's Bedouin Executive GT

From Autocar Magazine, Week ending 17th December 1970



Rather disappointing engine conversion offers small gains in performance and mpg, and requires premium fuel. Tinted windows for a black world. Tape stereo and radio, and a television option, in an £1,892 10s 6d package deal

PROMPTED BY increasing demand for the more expensive motor caravans, Wilsons introduced earlier this year a number of modifications for the Bedford Bedouin coachbuilt design. All the items are available separately, or the whole caravan may be ordered with an even fuller list of options at a total price of £1,892 10s 6d. In this form it is called the Executive and has a distinctive matt radiator grille. There is also, at £100 extra, a conversion for the 2-litre engine. The Bedouin with the Executive specification in full, and with the GT engine, has been submitted by Wilsons Motor Caravan Centre for a brief test.

To deal first with the engine conversion, we must confess to being a little disappointed. The modifications include a twin-choke Weber carburettor, higher compression ratio and revised induction. For the third time in our experience of the Bedford van, the bonnet release catch was not working, so we were only able to see the engine conversion by removing the cowling in the cab. This is enough to show the difficulty which lack of space makes in any attempt to modify the power unit, and the right angle junction in the air inlet cannot do much for efficient breathing. The table shows the small improvement in performance which resulted, and the gain in fuel consumption was offset by the need to use premium fuel instead of regular.

Not apparent from the figures alone is the fact that the vehicle felt much crisper and more responsive, and it was not until performance figures were taken that it was found that the improvements were more marginal than had been expected.

Air silencing was less effective on the modified engine, and a lot of induction hiss could be heard on light throttle openings, changing to a throaty roar under full power. The power brakes are a useful improvement on the Bedouin.

It is surprising how greatly the tinted windows alter the external appearance, but inside the effect is a little funereal, and the interior is very dark. Whatever the weather, you take your own dull day along with you. However, many people will no doubt value the privacy, especially when eating meals in the caravan, when one feels much less like a goldfish in a bowl. We were informed that the suppliers of the tinted glass have been requested to make it less dark on future production.

This is not the first time that a motor caravan has been offered with a tape stereo unit, but one would have thought that one of the combined tape and radio units would have been preferable to the two separate items listed at a total price of £86. Further, the stereo was not working, and both units were out of reach of the driver. Wilson's now offer Sony portable television as an alternative to the tape stereo and the tinted glass which seems a much more sensible option for a motor caravan. When this option is specified the Executive costs £1,869, showing a reduction of £23 10s 6d. There are difficulties of thief—proofing a television in a motor caravan, but half the battle is for the set always to be stored out of sight when not in use.

In the full specification of the Executive there are a number of lesser items, such as a fire extinguisher, gas refrigerator and tax for four months, in the attempt to offer a really comprehensive specification without extras; and the price has been maintained in spite of an increase in the basic cost of the Bedouin.

The idea of tailor—made modifications for a motor caravan is attractive, and there is considerable scope. This is quite a good start, but we would like to see some more practical refinements, such as the pressurized hot and cold water system of the Landliner, a conversion to servo-assisted disc brakes, and a more effective increase in power in future modifications. No doubt Wilson's will be looking again at the luxury market to see what further developments can be made for even greater comfort and refinement.

Rolls Royce make a Wankel

From Autocar Magazine, Week ending 17th December 1970.



Rolls-Royce Make A Wankel

Original two-stage diesel design

By J. R. Daniels, BSc

Alone among British firms, Rolls-Royce have shown an abiding interest in the Wankel principle. After six years of research. details are revealed which shows the originality of their work and its promise for the future

WE have long deplored the fact that Britain's motor industry has chosen, by and large, to ignore the Wankel engine. By following a policy of masterly inactivity they may be saving development effort and leaving themselves the option of taking up the rotary engine if it becomes really attractive; but this sort of approach is at present tightly controlled by the licensing arrangements centred on NSU. The only two British licence-holders to date are Perkins and Rolls-Royce, and only Rolls have done any serious development work. For a long time their approach was shrouded in secrecy, except for whispers that their thinking was highly original and intended primarily for application to military vehicles.

Details of their six—year development programme, however, have recently been given in a paper delivered to the Institution of Mechanical Engineers by F. Feller, C Eng, MIMechE. The story is something of a classic, starting with basic research on modified NSU engines and culminating in the design of a 350 bhp engine for military vehicle use. Even at this stage, Rolls-Royce regard the story as only half-written; much more development will be needed before the projected engine becomes a full production unit, even for the Army, while commercial prospects are even farther off.

The basic Rolls requirement was for an engine of small size and low fuel consumption. Existing standards were set by the opposed—piston two—stroke, and it was decided in 1964 by the Military Vehicles Engineering Establishment that it would be worth trying the Wankel engine as a diesel, for the sake of economy and the ability to operate on a wide range of fuels.

In fact, the Wankel in its familiar form makes a poor diesel. Its geometry makes it difficult to obtain a high enough compression ratio, and the long, thin combustion chamber has a poor surface—to—volume ratio (which results in high heat losses and poor combustion). Changing the geometry to push up the compression ratio results in a much bigger engine and an even worse surface-to-volume ratio, and so another solution was sought. The obvious answer was to pre—compress the ingoing air, by means of a Roots blower, a turbocharger, or a positive-displacement unit. Since the Wankel is itself a positive-displacement machine, the most elegant solution was to run two Wankels in series, as it were, with the first merely serving as a compressor for the second, in which combustion would take place. The first unit would then complete the thermodynamic cycle by acting also as the expansion stage for the exhaust gases.

The compressor stage must actually be larger than the combustion stage, since the initial compression depends directly on the relative size of the two units. In effect, one chamber of the compressor feeds air into the much smaller chamber of the engine proper. The basic compression ratio of the combustion stage is thus multiplied by the ratio of the displacements of the two units.

Physically, the compressor does not have to be very much bigger than the engine to give a multiplication of two or three. Together, the two-stage engine turns out to be little bigger than the equivalent single—stage one (since, as already explained, the latter must be made much bigger to obtain the same compression ratio). At the same time, the two-stage engine has a much better——i.e. lower surface—to-volume ratio.

Work was thus concentrated on the two-stage layout, with a three-rotor design as a back-up. This had separate rotors of simpler design to serve as the inlet compression and exhaust expansion stages. In the event, this alternative was not needed, but after a period in engineering limbo it is now being studied as an advanced exercise by the Royal Military College of Science.

Basic studies

Aside from the design of the two-stage engine, a great deal of basic research has been done on both combustion and on apex seal design. The combustion research resulted from the decision to use direct fuel injection rather than to` have a pre-combustion chamber in the wall of the rotor housing; there were. several design disadvantages, including leakage past the tip seals and difficult starting, which overruled the possible advantages of pre—combustion.

Combustion conditions in a Wankel are very different from those in a conventional reciprocating engine. Instead of the nice, stable column of air in the centre of the combustion chamber, and the very low piston speed around top dead centre when the fuel injection takes place, the chamber and its charge of air are travelling past the injector very fast indeed. These conditions are not necessarily worse for combustion; it was just that the engineers were working in a field where very little was known, compared with the extensive work which had been done on the reciprocating engine. Such work as had been done on the Wankel related to the petrol-burning, spark—ignition engine.

Using a small NSU Wankel engine as a test bed, 30 different combustion chamber shapes were tried, along with six different fuel injector positions. Some of the combinations were incompatible, but even so, over 100 different arrangements were tried before the best chamber shape was arrived at. In this design, the fuel is injected into a relatively wide recess carefully shaped to induce air swirl. Air for the combustion process comes from above the trailing half of the rotor, and squirts into the area through a narrow delivery channel.

It must be emphasized that this research applies to the Wankel in its diesel form, and it remains to be seen how much of it may be applied to the four-stroke petrol engine.

Seal research

While the combustion test work was going on, the little Wankel engine had to be modified to withstand diesel operating conditions. An early change was made from carbon to steel tip or seals, and it was found necessary to make new seal springs out of Nimonic 90 nickel alloy.

Early studies showed signs of misfiring which were soon traced to seal misbehaviour. Since the seals cannot be a perfect fit in their rotor-tip slots, they were tilting and jamming. The solution here (also adopted by NSU before the appearance of the Ro80) was to machine slots in the leading face of the seal to admit high—pressure gas underneath it and force it upwards into contact with the rotor housing. Later, a tendency of the seals to lose contact with the rotor housing as they passed into a lower-pressure area was overcome by recessing the trailing edge of the slots. This resulted in a 30 per cent improvement in low-speed fuel consumption. A further development was the use of a stepped apex seal, retaining the advantages of the recessed slot while also reducing the seal mass.

Again, these studies were carried out with the diesel engine in mind; but it would be surprising if designers of passenger-car Wankels did not take them into account in future.

Engine developments

The first Rolls—Royce development engine was the R1 which was conceived purely as a research tool. With a compressor stage of 1,126 c.c., and a combustion stage of 500 c.c., it produced over 50 bhp and achieved specific fuel consumptions of better than O.5lb/bhp/hour. Among other things, it was used to develop the best inter—porting arrangement between the two stages.

The R2 engine was the alternative three-stage layout, built but not investigated in detail. R3 refers to a combustion stage only, which is being used as a basic unit to build up a range of engines; it has a displacement of 1,216 c.c., and has produced 180 bhp at 4,500 rpm under test conditions.

The remaining engine of which details may be given is the 2—R6. This is a military engine formed of two banks of a two—stage engine. Each high pressure (combustion) stage has a displacement of 1,265 c.c., and is fed by a low-pressure stage of 3,250 c.c. The design power is 350 bhp at 4,500 rpm, for a weight of 939lb-a spectacular power-to-weight ratio for a diesel.

Rolls—Royce emphasize that this engine is not even running as yet, and that it will be some years before it sees even military service. But it is encouraging to see at least one British firm indulging in advanced and original Wankel research.