The Mercedes-Benz W196 was the Mercedes-Benz Formula One entry in the 1954 and 1955 Formula One seasons, winning 9 of 12 races entered in the hands of Juan Manuel Fangio and Stirling Moss.
Firsts included the use of desmodromic valves and fuel injection developed by Mercedes engineers through experience gained on the DB 600 series of engines used on the Messerschmitt Bf 109 fighter and others during World War II.
The 300SLR was derived from the W196 for the 1955 World Sportscar Championship season
The new 1954 Formula One rules allowed engines of 2.5 litres naturally aspirated or, alternatively, 0.75 litres supercharged. The expected target range for competitive engines was 250 to 300 bhp (190 to 220 kW).
Mercedes' 1939 2-stage supercharged 1.5 litre 64.0×58.0 mm V8 (1,493 cc or 91.1 cu in) gave 278 bhp (207 kW) at 8,250 rpm with about 2.7 atm (270 kPa) pressure. Halving this would have only produced 139 bhp (104 kW).
Studies by Mercedes showed that 290 bhp (220 kW) at 10,000 rpm could be achieved from 0.75 litres with a supercharger pressure of 4.4 atm (450 kPa). 390 shp (290 kW) would have been developed with 100 hp (75 kW) being required to drive the supercharger. Fuel consumption would have been 2.3 times higher than a naturally aspirated engine developing the same power. Since 115 bhp/l (86 kW/l) at 9,000 rpm was being developed by naturally aspirated motorcycle racing engines, it was decided that a 2.5 litre engine was the correct choice. This was a significant change of philosophy, since all previous Mercedes-Benz Grand Prix engines since the 1920s had been supercharged.
The 2,496.87 cc (152.368 cu in) straight 8 (76.0×68.8 mm) gave 257 bhp (192 kW) at the 1954 French GP which was its first race. During 1955, this had increased to 290 bhp (220 kW) at 8,500 rpm. The 2,981.70 cc (181.954 cu in) sports car (78.0×78.0 mm) gave 310 bhp (230 kW) at 7,500 rpm and was a bored and stroked version of the F1 engine complete with desmodromic valves and fuel injection. Variable length inlet tracts were experimented with and four wheel drive considered. An eventual 340 bhp (250 kW) at 10,000 rpm was targeted for the 2.5 litre F1 motor.
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