Mercedes 150 hp "Semmering" racing car, 1908

Following the successful appearance of the Mercedes Grand Prix racing cars at the beginning of July 1908 at the Grand Prix de l'A.C.F. in Dieppe, further race opportunities soon arose: these were, first of all, the numerous contests on the Brooklands track in Weybridge in the south of England, which had opened a year earlier and for which an independent variant was developed under the internal designation "Brookland model". For races that were not subject to Grand Prix regulations, Paul Daimler had a very special engine built with a bore of 175 mm and a stroke of 160 mm. However, the considerably larger space requirement of the cylinders, while the spacing between the crank pins on the crankshaft remained unchanged, made it necessary for the four connecting rods, which had been modified accordingly at both eyes, to be positioned at a slight angle in the cylinder.

Unusual as this technical solution was, it worked very well. With a displacement of 15.4 litres, the extremely large-volume racing engine produced 150 hp/110 kW and, in combination with a Grand Prix chassis, resulted in the "Brookland racing car". Contrary to what the name might suggest, this car was not only used on the Brooklands track, but also competed in the renowned hill climb at Semmering near Vienna, which had been held for nine years and was scheduled for 20 September 1908. In addition to the unmodified version used in Dieppe, which had competed there in the Grand Prix class, Otto Salzer's "Brookland racing car" also contributed to an impressive victory in the open class "without limit of bore and weight". Salzer's average uphill speed was 81.2 km/h. Willy Pöge secured second place in this race in another Mercedes with the 150 hp engine. 

In 1909, the two Semmering racing cars in the open class received an even more powerful engine with a stroke of 180 mm and a capacity of 17.3 litres. Otto Salzer achieved another victory with this car on the Semmering in September 1909, clearly surpassing his record from the previous year with an average speed of 84.3 kilometres per hour. Willy Pöge also repeated his result from the previous year with second place.

According to credible sources, at least one of these engines was fitted with aluminium pistons in 1910, which resulted in a further increase in performance. However, it remains to be seen whether 180 hp/132 kW was actually achieved, as some sources claim. Camille Jenatzy achieved a top speed of 173.1 km/h over the kilometre with a flying start in such a vehicle on 16 July 1910 in a record attempt during the race week in the Belgian seaside resort of Ostend - the highest speed ever achieved with one of these racing cars.