Hispano-Suiza H6

The Hispano-Suiza H6 was an ultra-luxurious automobile from the 1920s. Introduced at the 1919 Paris Motor Show, the H6 was produced until 1933. Roughly 2,350 H6, H6B, and H6C cars were produced in total.

The H6 engine featured a straight-6 inspired by designer Marc Birkigt's work on aircraft engines. It was an all-aluminium engine displacing 6.5 litres. Apart from the new overhead camshaft, it was essentially half of Birkigt's aviation V12 design. The billet crankshaft was milled from a 317 kg (700 lb) block of steel to become a sturdy 16 kg (35 lb) unit.

One of the most notable features of the H6 was its brakes. They were power-assisted, the first in the industry, and were driven with a special shaft from the transmission. When the car was decelerating, its own momentum drove the brake servo to provide additional power. This technology was later licensed to other manufacturers, including arch rival Rolls-Royce.

The 1922 H6B was slightly more powerful, and an 8.0 litre engine appeared in 1924's H6C. The similar 9.5 litre V12 took over after 1933, though this car used a more-conventional pushrod engine.