The Three-Cylinder D.K.W. "Sonderklasse"

While on holiday in Germany recently I was given the opportunity by Auto-Union G.m.b.H. to try one of their new three-cylinder 900-c.c. two-stroke cars. This was a chance which I had hoped for ever since I heard of their new engine some time ago, as I have been a D.K.W. owner and enthusiast for the last fourteen years and an admirer of the remarkable little two-cylinder engine.

I have owned a 1945 F.5, a 1939 all-metal saloon F.7 and a 1939 fabric saloon F.8, which I converted into an aluminium panelled cabriolet. All these cars gave use extremely good service and my total journeys on them came to somewhere in the region of 175,000 miles. In addition, as Secretary of the D.K.W. Club in England, I have driven and tested many of the cars of our members, so the prospect of driving one of the latest models with an entirely new and more powerful engine was very pleasing.

Herr Schlager of Auto-Union and his wife called for my wife and myself at our hotel in Dusseldorf during the morning and we set off on our journey to Ingolstadt with four up and two large suitcases in the boot. The car was the de luxe saloon model with the large American-style rear window and had done approximately 25,000 kilometres since new. It had not been specially prepared in any way, in fact it had only come back the night before from a long trip.

On the Autobahn just outside Dusseldorf I took over the wheel and for the first few kilometres concentrated on getting the feel of the steering, the engine and the brakes. All three were extremely good, but the engine was exceptional. Constant high r.p.m. caused no distress or overheating and the faster we went the happier the engine seemed. However, more of that later.

A steady 100 k.p.h. was maintained most of the way down the Autobahn, occasionally the needle slipped up a bit to 110-115 k.p.h., but was firmly suppressed again. South of Limburg we turned off to Konigstein for lunch and then, after a little cross-country driving to avoid Frankfurt, came onto the Aschaffenburg-Wurzburg road. The piece of cross-country driving was particularly interesting as several stretches of the road (?) were really bad and I expected some complaints from the rear-seat passengers. Everybody was very comfortable, however, and had it not been for the cloud of dust behind us they would not have noticed anything wrong with the road. From the driver’s point of view the really bad pot-holes were avoided from habit rather than from necessity.

Once on the main road the speed was brought up to the 100-k.p.h. mark again and it was possible to test the high-speed cornering capabilities of the car on this section. As usual with front-wheel-drive cars the best way was to reduce speed to slightly below the maximum for the particular corner then accelerate fairly hard from about a quarter of the way round. Cornering in any other way produced some tyre squeal, but absolutely no uncertainty that the car would get round safely and on the line chosen by the driver. The majority of the bends, however, required no reduction of speed at all and the feeling was as if we were on invisible rails, a characteristic of a good front-wheel-drive car.

At Wurzburg we stopped for coffee on the terrace up the side of the hill overlooking the town and then, refreshed, set off for the final lap of our outward journey through Ansbach, Weissenburg, Eichstatt to Ingolstadt. This turned out to be our slowest section and destroyed any hopes we had of a good average speed for the journey, for, on the way, there was a stretch of road under repair through which only one vehicle at a time could pass. We arrived there at the same time as a large convoy of American Army lorries going the opposite way and it took over half an hour to get through against such opposition. Shortly afterwards darkness fell, but very little reduction of speed was necessary as the headlights were in keeping with the rest of the car and adequate for fast night driving. The distance recorded to Ingolstadt was exactly 550 kilometres and the running average, including the convoy delay but excluding meals, worked out at just over 60 k.p.h., although at no time was any attempt made to hurry unduly.

The following morning I was shown over the Auto-Union factory which is still very handicapped by reason of its dispersal in various parts of the town. Motor-cycle production is the main function of this factory, but the eight-seater bus and various forms of tradesmen’s vans are also manufactured here. Here also is the last stronghold of the two-cylinder engine which is still used for the vans. There is a service department for repairs and schools for servicing both personnel and apprentices.

After a most interesting morning in the factory, and a change of plugs for the car, we left Ingolstadt after lunch for Rothenburg, where we proposed to stay the night to break our return journey and see something of the countryside. With only a comparatively short distance to cover and plenty of time, we motored very easily to Ansbach (the stretch we had done in the dark the night before) and then turned off on the secondary road to the old town of Rothenburg. The distance was 135 kms. and we covered it in two hours 10 minutes, averaging 63 k.p.h.

At 10.00 hours next morning we left this peaceful town behind us, most reluctantly, and followed the twisting road along the Tauber River. This road provided a real test of the cornering powers of the car and was real “D.K.W. country.” Sharp almost continuous bends and corners, some very adversely cambered, fast climbs and sudden descents provided a perfect testing ground for brakes, steering and engine. Needless to say, the car came through with flying colours and the only possible criticism was the lack of an intermediate gear between second and top, a fault which is being rectified on future cars. Second gear will take you up to 75-80 k.p.h., if required, but on a long hill another gear to take in the speed range between 70 and 100 k.p.h. would give even better performance and make higher average speeds possible over hilly country. The synchromesh second was a delight to use and could be selected without the use of the clutch at any speed with the free-wheel in operation. Very sharp corners could best be taken by approaching with free engine and second gear selected, braking to the required speed and then using the lower gear to obtain the best acceleration from the corner.

Miltenburg on the Main was our stop for lunch and thence to Darmstadt, where we had a little competition from another three-cylinder D.K.W. which, unfortunately, turned off after a short time. The Autobahn outside Frankfurt was reached at 16.40 hours and I set out to see how many kilometres could be put into an hour with 900 c.c. and a full load on a fairly undulating road. We were passed only once in the first hour, and that by a new 220 Mercédès, and covered 92 kms. The second hour produced some brisk clashes with some of the faster cars, the drivers of which looked somewhat surprised to be challenged by a D.K.W. and even more surprised to find how fast they had to go to get away. This hour produced only 88 kms., due to some rather extensive road repairs and weekend traffic, but 180 kms. in two hours without any distress or overheating from the engine is, in my opinion, exceptional for a car of this capacity. Cruising at 120 k.p.h. seemed just as easy as at any other speed and the maximum reached on the level on two or three occasions was 130 k.p.h. The engine was smooth and vibrationless throughout.

We reached Dusseldorf well before dark after a run of 435 kms., making a total for the whole trip of 1,120 kms. and an average running speed, in spite of some sightseeing on the way, of just over 63 k.p.h.

My impressions of the three-cylinder car as a result of this trip are:

(i) It is vastly superior in performance to the two-cylinder model and, in fact, to any other standard four-seater saloon car of equivalent capacity that I have ever driven.

(ii) Its acceleration is extremely good, even with full load, and the engine is smooth and quiet at all speeds above slow-running.

(iii) There is plenty of room for four large people to ride in comfort for long distances. Baggage space in the boot is also generous.

(iv) Suspension is extremely good, the amount of body movement, even on a bad road, is very small and there is no tendency for the car to lurch on corners.

(v) Steering is very positive at all speeds. It is fairly high geared, and there is absolutely no “kick-back” on the wheel. The high gearing and the front-wheel drive make the steering heavier than is usual with the conventional type of rear-drive car, but not so much so as to be tiring on a long run. The car never gave me a moment’s uneasiness on corners at any time.

(vi) The driving position was good and the pedals well placed, but the gear lever on the steering column needs to be brought nearer the wheel. With the present arrangement the right hand has to be taken off the wheel to change to any gear and it is quite possible to foul the trafficator lever when so doing. Either the gear lever should be cranked upwards or it should be mounted higher up the column.

(vii) The gears are very easily selected and the clutch is unnecessary when changing down to second gear when running on free-wheel. A four-speed box will make a good deal of difference to performance in billy country and will enable the top gear to be raised slightly and second to be lowered for even better acceleration. The clutch is smooth and light in operation.

(viii) Brakes are very good and stood up to fairly hard usage well; with free-wheel in operation and a full load this was most important.

I would like to emphasise that at only one stage, the last two hours on the Autobahn, was any attempt made to maintain a high average speed, at all other times the driving was in keeping with the feelings of the party. In spite of this the average speed was remarkably high over the whole trip, the admirable road-holding of the car enabling the cruising speed to be maintained even on winding or rough roads. Altogether, the three-cylinder car was an exceedingly pleasant vehicle to drive and its performance for a car of 900 c.c, is really outstanding. Fuel consumption worked out at about 34 m.p.g. over a distance of 700 miles.

Since writing the above I have had the opportunity of testing the very latest model with the four-speed gearbox. It has, as anticipated, made a great improvement to the overall performance and the ratios are very well selected. Top gear has been raised slightly and third takes in that critical speed range on which I previously commented, also second has been lowered. The new gearbox is actually being made by Auto-Union, the three-speed was a Z.F. product, and is synchromesh on all except first. gear. The only possible criticism against it is that it is a little noisy in the intermediate gears which have a distinct whine. I spoke to Auto-Union about this and they said that this particular gearbox was one of their very first productions and they already had several small improvements which they thought would eliminate the fault entirely.

Technical Data
Engine: Three-cylinder in-line, two-stroke of 896 c.c.
Bore, 71 mm.; stroke, 76 mm.
Compression ratio, 6.5 to 1.
H.P., 34 b.h.p. at 4,000 r.p.m.
Maximum r.p.m., 4,250.
Roller-bearing crankshaft and big-ends.
Lubrication, petroil, 25 to 1.
Watercooled.

Gearbox: Synchromesh on all except first gear. Ratios:
Three-speed box
1 : 15.85 — 1st
1 : 7.51— 2nd
1 : 4.41 — top
1 : 14.53 — Reverse

Four-speed box
1 : 18 — 1st
1 : 10.45 — 2nd
1 : 6.3 — 3rd
1 : 4.25—Top
1 : 22.1 — Reverse
Differential ratio: 1 : 4.72.

General: Empty weight, 870 kg.
Suspension, independent front with single transverse spring and wishbones. Rear, single transverse spring with dead axle.
Shock-absorbers, telescopic hydraulic.
Steering, rack-and-pinion.
Electrics, Bosch six-volt standard, 12-volt system can be supplied if required. Separate dynamo and starter.

Body styles, Standard saloon.
Standard saloon with sunshine roof.
De Luxe saloon.
Drophead coupé (four-seater).
Drophead coupé (two-seater).
Station wagon.