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.
Many of the first versions of the W formation engine went into aircraft during the earlier years of powered flight – engineers were clearly looking for maximum power and the thought patterns were obviously around more cylinders equals more power!
Isotta Fraschini, another Italian luxury carmaker, were one of the first to build three bank W engines for cars and they used 18 cylinders! Many years later, the VW Group also experimented with a similar 18-cylinder configuration for Audi and it also went in to a Bugatti concept however it was abandoned for 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 Touareg models as well as the Bentley Continental GT, albeit with twin turbos added!
4 bank W engines weren’t new when VW built their version. In the 1930s and then during World War 2, Allison in the US and Daimler-Benz in Germany were developing 4 bank aero engines by mating two smaller engines together using a common crankcase with the shafts geared down to one propeller shaft.
The VW 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 the Bugatti Veyron with a massive power output of nearly 1,000 horses!
W formation engines have also been found in motorcycles. I have seen pictures of Moto Guzzi’s development W4 which was also two twins merged together and Yamaha had a pseudo W4 in the old 500cc racing – during the early 1990s. It seems to be more a V however some commentators called it a W.
Finally, like many large engine configurations, the W is destined to be found at the top end of the industry or racing, 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. The VW Group are the only ones that seem to have persevered with this formation for road use in several of their brands either as production or concept cars.