W engines have been around since the dawn of the industry and the use a shape that looks like a “W” – one of the first, the W3 was built by Anzani, an Italian engineer in 1906 for use in a motorcycle but also ended up in Bleriot’s plane that crossed the English Channel. This motor used 3 banks of cylinders connected to one crankshaft.
Isotta Fraschini, another Italian luxury carmaker, were one of the first to build three bank W engines for cars and they used 18 cylinders! The VW Group also experimented with a similar 18-cylinder configuration for Audi and it also went in to a Bugatti concept. It was abandoned as being too difficult to get the timing right.
However, VW liked the idea of a W motor, especially after they had developed their VR6 engine that had a very narrow V - 15º instead of the normal 60 or 75º. This lead to them making a 4 bank W motor by mating the blocks together forming a W12 and it also used a single crankshaft for power delivery. This motor has been put into the Phaeton and Tuareg models as well as the Bentley Continental GT, albeit with twin turbos added!
This W motor is simplified by the use of the VR6 concepts as it only has two heads and two camshafts making it quite a simple design and easy to manufacture as the VR6 motors are already in production and they share most components.
VW also built a W16 motor for a Bentley concept car with a power output of over 680 horsepower. They then added quad turbochargers and fitted it into a Bugatti Veyron with a massive power output of nearly 1,000 horses!
And finally like many engine configurations, the W is destined to be found at the top end of the industry where large power outputs and multiple cylinder configurations are required. It provides no advantage for use in smaller cars where economy is the driving factor in the design.