Targa Florio 1922: Successful racing premiere of the supercharged engine 100 years ago

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On 2nd April 1922, 100 years ago, Daimler-Motoren-Gesellschaft (DMG) entered three different Mercedes vehicles in the XIII Targa Florio in Sicily with great success. The Mercedes 115 PS Grand Prix racing car takes the overall victory as well as two other placings. Count Giulio Masetti is the first to cross the finish line of the famous road race in his private racing car after 6 hours, 50 minutes and 50.4 seconds.

At the same time, the Italian racing driver took class victory for racing cars ahead of works drivers Christian Lautenschlager (2nd in class and 10th overall, co-driver Ernst Hemminger) and Otto Salzer (4th in class and 13th overall, co-driver August Grupp) in identical cars.

The three Mercedes 115 PS Grand Prix racing cars are based on a design from 1914: with this model, DMG dominates the French Grand Prix on 4 July 1914, which ends with a triple victory for the brand bearing the star. The Grand Prix racing cars are technically updated for the mission in Sicily.

The 1922 Targa Florio also saw the world premiere of racing cars with supercharged engines, which paved the way for Mercedes-Benzʼs motor racing successes in the years that followed: the class win for production cars with over 4.5 litres of displacement went to Max Sailer in a Mercedes 28/95 PS with compressor (6th place overall), followed by Christian Werner in a vehicle of the same type with a 7.3-litre engine but without compressor (2nd place in class and 8th place overall).

With third place in the class of production cars with a displacement of up to 1.5 litres (20th place overall), Paul Scheef in a Mercedes 6/40/65 PS finally rounded off the Mercedes success in the 432-kilometre road race in Sicily, his co-driver being Jakob Krauss. This brilliant première of competition cars with mechanical charge air compression by a Roots supercharger is a harbinger of the great successes of the Mercedes-Benz supercharged touring cars of the S family in the 1920s and early 1930s as well as the Grand Prix racing cars of the first Silver Arrow era from 1934 onwards.

Pioneer of compressor technology in motor racing

The 1922 Targa Florio thus also became a triumph for the DMGʼs chief designer at the time, Paul Daimler. He was responsible for the naturally aspirated 4.5-litre engine of the Grand Prix racing car with four-valve technology from 1914 as well as for the new supercharged engines. Paul Daimler knew the principle of the rotary piston blower for charge air compression from aircraft engine development. In September 1919, he undertook the first tests on the automotive use of mechanical superchargers on a slide-valve engine from the Mercedes-Knight 10/30 PS, and driving tests followed as early as the beginning of October.

Because a Knight engine and a supercharger cannot be combined efficiently, Daimler turns to valve-controlled engines with mechanical supercharger. As early as 1921, DMG presented the first two passenger cars with compressor engines, but production of the Mercedes 6/25 PS and 10/40 PS series vehicles with the innovative power unit did not begin until 1923.

For the pioneering use of supercharger technology in the Mercedes competition cars at the 1922 Targa Florio, Paul Daimler chose as the basis the Mercedes 6/20 PS (four-cylinder engine with 1,568 cubic centimetres of displacement and supercharger) presented in 1921 and the Mercedes 28/95 PS (six-cylinder engine with 7,280 cubic centimetres of displacement) – Max Sailer was already successful with this second model at the 1921 Targa Florio (2nd place overall and class victory for production cars with up to 5 litres of displacement). The Mercedes 6/20 PS is a perfect basis for the “Voiturette” racing car with 1,499 cubic centimetres of displacement.

This is because the use of a supercharger was considered from the very beginning of its development. According to the official chronicle of then Daimler-Benz AG, the racing car is the first supercharger model used in a race. The 1.6-litre production engine with two V-shaped hanging valves per cylinder is transformed into the 1.5-litre M 65134 racing engine with two overhead camshafts, vertical shaft and four-valve technology. It has an output of 33 kW (45 hp) without supercharger and 49 kW (67 hp) with supercharger. By comparison, the Mercedes 6/25 PS, the standard version of the 6/20 PS of 1923, produces 15 to 18 kW (20 to 25 hp) without supercharger and 28 to 29 kW (38 to 40 hp) with the mechanical supercharger switched on.

In the Mercedes 28/95 PS, the on-demand supercharger is located on the left-hand side of the engine and is driven from the rear end of the crankshaft via spur gears and an engageable and disengageable multi-disc clutch. Compared to the production car, the racing car with supercharger can be recognised, among other things, by the special routing of the exhaust pipe with specially cut-out rear wing. The output of the M 10546 engine in the production car is 66 kW (90 hp), in the “Sport” version used at the 1921 Targa Florio it is 81 kW (110 hp). With supercharger, the six-cylinder car now makes another significant leap in output to 107 kW (145 hp).

Count Giulio Masetti wins the road race in Sicily with a Mercedes 115 PS Grand Prix racing car, which bears starting number 40 and is painted in the Italian racing colour red

The crowning achievement of the DMGʼs second Sicily outing in succession was Count Giulio Masettiʼs victory with the Mercedes 115 PS Grand Prix racing car on 2nd April 1922. The Italian racer receives the King of Italyʼs gold medal, the Coppa Polizzi and the Coppa Termini for overall victory, the fastest lap and the fastest overall time to date at a Targa Florio. The racing car, which dates from 1914 and has a 4.5-litre sixteen-valve engine, proves to be at least on a par with the newer designs in the road race.

Among other things, it is around 720 kilograms lighter than the new Mercedes 28/95 PS with supercharger, which gives it an advantage on the winding course in the Madonie. Albert Heeß, head of DMG engine design before the First World War, writes about the modifications to the car for the 1922 Targa Florio: “The engine is the same as that used for the ‘Grand-Prix 1914ʼ race in France, and differs only in that it has been given light-alloy pistons in place of the cast iron ones. This increased the maximum speed on the brake from 3,200 to 3,600 and the output at n = 3,000 from 104 to 109 hp.”

Daimlerʼs engine was a decidedly progressive development in 1914. Therefore, after the outbreak of the First World War, a vehicle located in London was closely examined at the instigation of W. O. Bentley. Bentley is so convinced of the valve train that he adopts this solution for his own first design, which also serves as a template for Rolls-Royce aircraft engines of the First World War.

Arriving in Sicily on their own power

Not only in the race itself, but already on the journey to Sicily, the Mercedes racing cars proved their performance and reliability 100 years ago. Because, from Untertürkheim, the team travelled all the way to the south of Italy on its own power, as documented by historical photographs in the Mercedes-Benz Classic archives. Among other things, they show the racing cars lined up at the Untertürkheim plant before the departure (equipped with number plates and wings), the drive through Stuttgart admired by numerous spectators and the passage through Rome – including a visit to DMGʼs representative “Auto Palaces M. Morescalchi – Automobili Mercedes”.

If you study the pictures more closely, you can see the difference in colour between the cars that took off in Stuttgart and the vehicle of the later winner, Count Masetti: the factory racing cars were painted in Germanyʼs racing colour, white. In the black and white photo, Masettiʼs privately registered car with the starting number 40 has a dark colour – the red of the Italian racing cars.

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