Straight-eight Engine - Performance and Racing Cars

Performance and Racing Cars

Despite the shortcomings of length, weight, bearing friction, and torsional vibrations that led to the straight-8's post-war demise, the straight-8 was the performance engine design of choice from the late 1920s to the late 1940s, and continued to excel in motorsport until the mid-1950s. Bugatti, Duesenberg, Alfa Romeo, Mercedes-Benz and Miller built successful racing cars with high-performance dual overhead camshaft straight-8 engines in the 1920s and 1930s.

The Duesenberg brothers introduced the first successful straight-8 racing engine in 1920, when their 3 L engine placed third, fourth and sixth at the Indianapolis 500. The following year one of their cars won the French Grand Prix, while two others placed fourth and sixth in the race. Based on work the company had done on 16-cylinder aircraft engines during World War I, the overhead camshaft, three-valve-per-cylinder engine produced 115 brake horsepower (86 kW) at 4,250 rpm, and was capable of revving to an astonishing (at the time) 5,000 rpm. No Grand Prix engine before the war had peaked at more than 3,000 rpm.

Bugatti experimented with straight-8 engines from 1922, but in 1924, he introduced the 2 L Bugatti Type 35, one of the most successful racing cars of all time, which eventually won over 1000 races. Like the Duesenbergs, Bugatti got his ideas from building aircraft engines during WWI, and like them, his engine was a high-revving overhead camshaft unit with three valves per cylinder. It produced 100 bhp (75 kW) at 5,000 rpm and could be revved to over 6,000 rpm. Nearly 400 of the Type 35 and its derivatives were produced, an all-time record for Grand Prix motor racing.

Alfa Romeo were the first to react to the engineering problems of the straight-8: in their racing car engines for the P2 and P3 and in their Alfa Romeo 8C 2300/2600/2900 sports cars of Mille Miglia and Le Mans fame the camshaft drive had been moved to the engine centre, between cylinders #4 and 5, thus reducing the aforementioned limitations. The straight-8 was actually built as a symmetrical pair of straight-4 engines joined in the middle at common gear trains for the camshafts and superchargers. It had two overhead camshafts, but only two valves per cylinder.

The Alfa Romeo straight-8 would return after World War II to dominate the first season of Formula One racing in 1950, and to win the second season against competition from Ferrari's V12-powered car in 1951. The Alfa Romeo 158/159 Alfetta was originally designed in 1937 and won 47 of 54 Grands Prix entered between 1938 and 1951 (with a six-year gap in the middle caused by the war). By 1951, their 1.5 L supercharged engines could produce 425 bhp (317 kW) at 9,300 rpm, and could rev as high as 10,500 rpm. However, the engines were at the end of their potential, and rule changes for the 1952 season made the Alfettas obsolete.

Mercedes-Benz would create the last notable straight-8 racing cars in 1955, with the championship-winning W196 Formula One racing car and the 300SLR sports racing car. The 300SLR was famous for Stirling Moss and Denis Jenkinson's victory in the 1955 Mille Miglia, but notorious for Pierre Levegh's notorious accident at the 1955 24 Hours of Le Mans. The 300SLR was the final development of the Alfa Romeo design of the early 1930s as not only the camshaft, but now also the gearbox was driven from the engine's centre. Engineers calculated that torsional stresses would be too high if they took power from the end of the long crankshaft, so they put a central gear train in the middle (which also ran the dual camshafts, dual magnetos, and other accessories) and ran a drive shaft to the clutch housing at the rear.

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