A W engine is a type of piston engine where three or four cylinder banks use the same crankshaft, resembling the letter W when viewed from the front.
W engines with three banks of cylinders are also called "broad arrow" engines, due to their shape resembling the British government broad arrow property mark.
The most common W-type engine is the 4-bank type, with the Volkswagen Group experimenting with the Passat W8 and it’s 4.0 liter, 4-bank W8 engine and later implementing the concept with their Bentley division, creating a 6.0 liter W12 in both naturally aspirated and turbocharged variants. Due to the pre-existing VR-type engine only needing one cylinder head despite having two banks of cylinders, a Volkswagen 4-bank W-type engine is structured more similarly to a conventional 2-bank Vee engine as opposed to a “true” W engine.
W engines are significantly less common than V engines. Compared with a V engine, a W engine is typically shorter but wider. In Volkswagen’s case, this allows for superior packaging in engine compartments intended for 6 and 8 cylinder engines, the Passat W8 being one such example.