W engine

A W engine is a type of reciprocating engine arranged with its cylinders in a configuration in which the cylinder banks resemble the letter W, in the same way those of a V engine resemble the letter V.

Three different configurations have been called W engines:

The classical W engine uses three banks of cylinders, all connected to one crankshaft.

One of the first W engines was the Anzani 3-cylinder, built in 1906, to be used in Anzani motorcycles. It is this W3 engine which also powered the Blériot XI, the aircraft used by Louis Blériot when, on 25 July 1909, he made the first flight across the English Channel. Shortly afterward the W3 configuration was changed to a 120°-angle, three-cylinder radial engine configuration as the original W3 engine's replacement.

The 1917 Napier Lion aircraft engine was an early W12 engine. Lorraine built the 12Ed and 18Ka aero-engines of 450 horsepower (336 kW; 456 PS) and 650 horsepower (485 kW; 659 PS) in the early 1920s, while Isotta-Fraschini built the 18-cylinder Asso 750 and Asso 1000 of 820 horsepower (611 kW; 831 PS) and 1,100 horsepower (820 kW; 1,115 PS) in the late 1920s. At the same time the 500 horsepower (370 kW) Farman 12We wa used by many aircraft; Farman also built a W18.

A three-bank W12 design was also pursued by Audi, which later abandoned the project. Volkswagen Group built an experimental W18 engine for Bugatti's EB 118 and EB 218 concept cars, but the design was determined to be impractical because of the irregular firing order required by the three rows of six cylinders.

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