Auto Union Type 52 is finally built – after 90 years

Auto Union AG, the merger of Audi, DKW, Horch, and Wanderer in 1932, was a well known participant in motorsport in the 1930s, especially Grands Prix. Its Silver Arrows became legendary as pioneering racing cars, setting records that took a while to beat.

Just as a lot of racing technologies are transferred to production models that the public can buy today, back then Auto Union also had an idea to make a street-legal sportscar version with the 16-cylinder engine used in the racing cars.

It was to be called the Type 52 and arose from a project which the automaker commissioned the Stuttgart design office of Ferdinand Porsche to carry out. This was related to the new 750 kg formula used in the Grands Prix held from 1934 to 1936 and a racing car was to be developed for it which began to legendary Silver Arrows.

These powerful cars had futuristic designs, not to mention revolutionary technology. While Mercedes-Benz favoured front-mounted engines, Auto Union was the first to place the engine behind the driver. This mid-engine layout remains the standard in Formula 1 cars today.

While developing the first Silver Arrows, Auto Union Porsche’s design office also considered a sports sedan that would be legal for road use. The concept papers called the vehicle ‘Schnellsportwagen’ (apparently its intended marketing name) and its form is what we would today consider as a classic Gran Turismo model.

The Auto Union Type 52, as the project came to be known, was intended to be sold to customers for driving in long-distance races such as the Mille Miglia or in sportscar events such as the endurance races at Spa-Francorchamps or Le Mans. There was also talk of the car being a factory racing car.

By the end of 1933, the Porsche design office presented the first design sketches and in 1934, the project managers decided to build a prototype for testing. However, for reasons that are not known, that never took place and the project was abandoned in 1935.

However, the documents were kept in the archives of Audi and Porsche, detailing much of groundbreaking work on paper. Clearly, it was based on the technology of the Grand Prix racing car that was developed at the same time. The chassis from the Type 52 was designed as a ladder frame with a mid-mounted engine. The drivetrain of the Type 22 was used, but the compression of the powerful 16-cylinder engine was reduced to allow the car to run on regular fuel.

At the same time, the engineers reduced the gear ratio of the Roots supercharger. The Type 52’s engine was to draw around 200 ps from 4.4 litres of displacement at 3,650 rpm. Its maximum torque of 436 Nm was achieved at a moderate 2,2350 rpm.

Compared to the Grand Prix legend, this was a reduction in output, but the excellent performance of around 200 km/h (as calculated by the engineers – without computers) shows that the Schnellsportwagen would have lived up to its name. In its day, it would have been one of the most powerful street-legal machines on the road and certainly would have been dominant in sportscar races.

The significance of the Schnellsportwagen is recognised up till today and Audi decided that the abandoned project should be revived – not as a new production model but as a showpiece of the technologies and design excellence.

The automaker commissioned Crosthwaite & Gardner, a British company specialising in producing historic racing models and supplying parts, to build the Auto Union Type 52. The restoration specialists had only the surviving archive documents, plans, and design sketches for reference as no pictures of a finished model exist.

During Auto Union’s dissolution in the Russian occupation zone following World War II, most of the historic Grand Prix racing cars disappeared, as did many files and photographs. However, the documents provide a clear vision of the direction of development and the goals the engineers were pursuing.

After multi-year work, the Schnellsportwagen was completed in 2023. All components are custom-made, handcrafted specifically for the model. While the original engine, transmission, and open 5-speed gearbox were taken from the racing cars, the engineers chose different technical solutions for the suspension and damping. Instead of a combination of transverse leaf springs and friction dampers used for the Type 22, the Type 52 uses longitudinal torsion spring suspension in combination with hydraulic dampers.

During development, the 132-litre fuel tank was relocated under the seats. In the racing cars, the significantly larger tank is located directly behind the driver in the vehicle’s centre of gravity, giving the Silver Arrows an ideal weight distribution whether the tank was full or empty. Both the Type 52 and the Type 22 use drum brakes behind all 4 wire wheels.

“One insight that came out of our intensive exchange is that the developers in the 1930s would probably have had to adjust some of the technical details in the course of testing, too,” said Timo Witt, Head of Audi’s historical vehicle collection.

“Similarly, we had to lengthen the Auto Union Type 52’s wheelbase compared to the original design documents because it was technically unavoidable in combination with other components such as the front suspension, engine, steering, and transmission. The interior is inspired by the Auto Union Grand Prix racing cars, with a modern interpretation of colours and fabrics,” he explained.

At over 5 metres long, the 1930s Type 52 built in the 21^st century makes an impact with its design that is clearly from a different era. Its elongated silhouette reflects how its engineers designed the car for optimal aerodynamics and maximum performance.

Unlike the Grand Prix cars it was to be based on, the Schnellsportwagen is more suited for everyday driving – as the original concept was meant to be – with an overhead roof, headlights, and room for luggage, plus space for the two spare tyres.

But that is where the 3-passenger car’s comfort features end. As is typical for a racing car, the Type 52 driver sits in the middle, with the rear passenger seats slightly offset to the sides. With three passengers, 70 kgs of luggage, and 150 kgs of equipment, the technical data sheet lists the car’s total weight at 1,750 kgs, with an unladen weight of 1,300 kgs.

None of the documents specified the colour the car would have had at the time. So, Audi Tradition again took the racing car as the foundation and chose Cellulose Silver for the finish.

When it came to the engine that would power the Type 52, Audi however consciously decided to deviate from the designers’ original plan. A decision was made to use the 16-cylinder engine from the Auto Union Type C; its output was not restricted to the Type 52 to ensure compatibility with the Grand Prix racing cars. For that reason, the engine runs on a special methanol mixture.

The Type 52 built by Crosthwaite & Gardner is considered as the closest approximation to the Schnellsportwagen Auto Union Type 52 that was imagined some 90 years ago but never became a reality. Its first public appearance is at the Goodwood Festival of Speed in England this week.

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