W18 engine

A W18 engine is an eighteen cylinder piston engine in a W configuration. Recent W18 engines powered the Bugatti EB 118, Bugatti EB 218 and Bugatti EB 18/3 Veyron concept cars in the late 1990s. This engine featured three banks of six cylinders set 60 degrees apart.

VAG also developed a variation of this engine - it retained the 18 cylinders but instead of three cylinder banks, it had four. This confused many who saw the specification in print at motor shows since 18 isn't evenly divisible by four. The design was loosely based on the concept Volkswagen used for its V5 engines which had one bank with three cylinders and one bank with only two. Essentially the four-bank W18 was two V9 engines (one bank of five cylinders and one band of four) mated to a common crankshaft. Ultimately the design proved to be impractical.

An earlier example is the Isotta-Fraschini "Asso 750" used to power the Italian Savoia-Marchetti S-55 seaplanes flown by Italo Balbo into Chicago in 1933. This engine used the same layout as the above-mentioned Bugatti - basically a vertical six with two adjacent banks set at 60 degrees each to make a W-18.

W12 engine

A W12 engine is a twelve cylinder piston engine in a W configuration. Some prototype W12 engines have used three banks of 4 cylinders (Broad arrow concept) though none have ever gone into production. They were, however, briefly and unsuccessfully used in the 1990 F1 World Championship by the Life team. All production W12 engines to date (April, 2005) use four banks of three cylinders (two narrow-angle V6 engine blocks), coupled to a common crankshaft.

At the 2001 Tokyo Motor Show, Volkwagen showcased the W12 Coupe, a mid-engined, rear wheel drive supercar powered by a 6 L W12 engine producing 600 hp. A week before, the W12 Coupe broke the world 24 hour endurance record. A total distance of 7085.7 kilometres (4402.8 miles) was covered at an average speed of 295.24 km/h (185.45 mph), breaking the old record by 12 km/h (7.5 mph). Production of the W12 Coupe was considered but is currently cancelled.

Volkswagen Group currently produces W12s based on two of its narrow-angle VR6 engines. The narrow angle of each set of cylinders allows just two camshafts to drive each pair of banks, so just four are needed in total. Note that this design differs from the W18 engine that Volkswagen produced for its Bugatti concept cars of 1998 and 1999. Due to this distinction, the VW Group's W12 engine is sometimes described as a "WR12".

The VW W12 is used in some high-end luxury models:

* Audi A8
* Bentley Continental GT
* Bentley Continental Flying Spur
* Volkswagen Phaeton
* Volkswagen Touareg

W8 engine

A W8 engine is an eight cylinder piston engine in a W configuration, or two juxtaposed V4 engine blocks, coupled to one crankshaft.

The VW W8 can be imagined as flat plane crank V8 made with VR4s instead of inline 4s, with a reduced Vee angle of 72 degrees instead of the customary 90. This design is short enough to fit where only a V6 could fit. Volkswagen Group currently produces a W8 based on its VR6 engine. The VW W8 was used in the Volkswagen Passat for a time, but sales were minimal. The 2006 redesign, with its engine re-orientation, was no longer equipped with the W8, and the 'large' 3.6 liter VR6 has replaced its position.

The W engine

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 three entirely different implementations of this concept: one with three banks of cylinders, one with four banks, and one with two banks of cylinders and two crankshafts.


The Original "three-bank" Design

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

One of the first W engine was a W3, built by Anzani in 1906 to be used in their motorbikes. It is this W3 engine which also powered the Blériot XI, the aircraft used by Louis Blériot when on the 25th of July, 1909, he made the first ever successful flight across the English Channel.

The 1917, Napier Lion aircraft had a first W12 engine.

Later, a three-bank W12 design was also pursued by Audi, who later abandoned the project. However, the Volkswagen Group later 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.


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 resemble a V12 engine, in that it has just two cylinder heads and two sets of camshafts.

VAG went on to produce a W16 engine prototype which produced 623 horsepower (465 kW) for the Bentley Hunaudières concept car. A quad-turbocharged version of this engine went 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, that is, they contain high numbers of cylinders but are relatively compact.


The Motorcycle "two-bank" Design

A very rare type of W engine is found in motorbikes of the MotoGP class. These are 2-stroke, 500 cc V engines with two banks of two cylinders and two separate crankshafts, one per bank of cylinders, thus constituting a sort of "W" form. The angle between the banks varies from 60 to 75 degrees.

There are two major advantages of these engines over the more traditional straight-4 or V4 engines. The first is the width of the engine: a V4 engine will be narrower than a straight-4 engine with the same displacement, but a W4 with its two crankshafts will be even smaller. The second advantage is that the W4 lacks the need for a balance shaft; it will run smoothly if the two crankshafts rotate in opposite directions. This is a weight advantage over the V4 engine, which will need a balance shaft.

Examples of these type of W4 engines are the Yamaha YZR500 and the Cagiva GP500 motorbikes.

These types of engines should not be confused with the U engine, which also has two banks of cylinders and two crankshafts, but which is made by combining two similar straight engines. The U engines lack the advantages the "W"-form of the engine has in terms of width and weight.


The Motorcycle "One-bank" Design

The Feuling W3 is a patented 180 hp, three-cylinder air-cooled engine and may be the shape of things to come for those who fancy power cruisers. The W3 is an engine with 50 percent more displacement than Harley's Twin Cam 88 with the 95-cubic-inch factory upgrade kit installed. Taking inspiration from radial aircraft engines, a central, master connecting rod with two slave rods, one on each side of the central rod, direct the three 4.0-inch pistons through the cylinders. Cory Ness built his chopper using a Feuling W3 engine on a "Biker Build Off" episode. The design has already been tested in a 185-cubic-inch (3032cc) form and a 245-cubic-inch (4015cc!)drag racer was planned. Jim Feuling passed away in December 2002. The company was for sale july 2004 and still listed the W3 among its products.

Type: air-cooled, 3 cylinder 45 degree x 45 degree Displacement, bore x stroke: 142 cu. in. (2327 cc), 4.0 in. x 3.75 in. (101.6 mm x 98.4 mm)