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The W engine is an engine configuration in which the cylinder banks resemble the letter W in the same way a V engine resembles the letter V. There have been two entirely different implementations of this concept.
The Original "three-bank" Design
The classical W engine uses three banks of cylinders. The 1917 Napier Lion aircraft had a first W12 engine. Later, a W12 design was also pursued by Audi, who later abandoned the project. An experimental W18 engine was produced by Volkswagen for Bugatti's EB 118 and EB 218 concept cars, but the design was determined to be impractical because of the irregular firing sequence required by the three rows of six cylinders.
The Modern "four-bank" Design
The Volkswagen Group (VAG) created the first successful automotive W engine with the introduction of their W12. It combined two narrow-angle VR6 engines around a single crankshaft for a total of four banks of cylinders. For this reason, the four-bank configuration is sometimes, and more accurately, referred to as a "VV" ("vee-vee" or "double-vee") to distinguish it from the traditional three-bank "W" design.
The W-12 is used in the Volkswagen Phaeton, the Audi A8 and the Bentley Continental GT - though in the latter application, the engine has been highly modified by Bentley and fitted with twin KKK turbochargers. As a result, it produces considerably more power than the original version.
The narrow (15°) angle between bank pairs makes this engine resemble a V12 in that it has just two cylinder heads and two sets of camshafts.
VAG went on to produce a W16 prototype which produced 623 horsepower (465 kW) for the Bentley Hunaudières concept car. A quad-turbocharged version of this engine will go into production in 2005 powering the 1001hp Bugatti Veyron 16.4. A W8 engine was also produced for use in the VW Passat.
The major advantage of these engines is packaging, i.e., they contain high numbers of cylinders but are relatively compact.
Related Topics
See Also
External Links
Volkswagen's VR6 and W-engines (http://autozine.kyul.net/technical_school/engine/tech_engine_packaging.htm)
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