Throughout the history of the internal combustion engine, there have been some ingenious engines developed. Almost any layout and configuration you can think of has been tested, with varying degrees of success. We know about single cylinder engines, flat fours, five strokes and the now famous piston-less Wankel engines. In cars though, we generally now use well-established engine layouts like inline four, V6/8 and V12 engines.
VW took inspiration from an early 20th-century British aircraft engine builder and pioneered the use of a W12 configuration in automotive applications. The result is a powerful, butter smooth engine that delivers impressive fuel economy.
W12 Engine History
The W12 engine is a twelve-cylinder piston engine layout, which was first used by British engineering company and aero engine builder D. Napier & Son. The twelve-cylinder engine it built was called the Napier Lion and it featured three banks of four pistons. At the time, this was one of the most powerful engines in the world. A number of other manufacturers adopted the layout through the 1920s and 30s.
In the late 80s, two separate Formula One teams experimented with a W12 engine. One was only tested privately and never entered into an official race. The other, built by a former Ferrari engineer, attempted to attract potential racing customers. When the company failed to do so, they bought an F1 chassis and tried to enter F1 in 1990 as an independent race team. The engine was highly unreliable and down on performance, in 14 attempts, the W12 never made it out of pre-qualifying.
VW would later experiment with the W engine layout for automotive use, starting with a W8. The W engine derives its name from the configuration of the pistons, which when viewed from the front, appear to resemble the letter W. Volkswagen started work on the W8, the experience gained later proved instrumental in the development of W12 engines. W8’s were fitted to VW Passats longitudinally, that is, with the front of the engine at the front of the car.
The W8 can be thought of as two narrow V4 engines melded together. The VR4 engines it’s based upon use a very narrow-angle between pistons of 15 degrees. The four banks of pistons then share one crankshaft. This makes for a very compact engine, which will fit in the same space as a traditional V6.
In 1991, Audi unveiled a W12 engines concept car, called the Audi Avus. The show car was fitted with a dummy engine, however, made from painted plastic and wood.
It wasn’t until a decade later that VW demoed its W12 engine, then fitted in a mid-engined, rear wheel drive concept car. The engine had a 6.0-litre displacement and produced 600hp. A week before its debut at the Tokyo motor show, the W12 concept car broke a 24-hour world endurance record, covering 4,400 miles at an average speed of 183.45mph.
This engine can be thought of as two VR6 (narrow-angle V) motors joined together at 72 degrees to one another. Unlike earlier W12 layouts, it uses four rows of three cylinders, as opposed to three rows of four. Sometimes, this configuration is referred to as a WR12 engine.
VW is the only motoring group in the world to use a W12 layout. The reason for doing so is that this layout is highly space efficient. Rather than combining two V6 engines lengthwise, the W12 halves the motor length, meaning it can be mounted transversely. This means that car designers can create AWD sedans and coupes.
Engine Specification
| Identification / Part Number Prefix | 07C |
| Engine Displacement | 366.0 cubic inches, |
| Configuration | 72° W12 engine. |
| Bore x Stroke | 3.31 in x 3.55 in |
| Stroke Ratio | 0.93:1 |
| Compression Ratio | 10.7:1 |
| Cylinder Block | Homogenous monoblock, die-cast from hypereutectic ‘Alusil’ aluminum-silicon alloy |
| Crankcase | Torsionally stiff crankcase with high-resistance piston liners. Die-forged steel crank with seven main bearings. Constant firing order as per V6 engine. |
| Cylinder head | Cast aluminium, four valves per cylinder, 48 total. 2 x double overhead camshaft. |
| Aspiration | Dual electronic throttle bodies cast magnesium alloy intake manifold. Bentley models are twin turbocharged. |
| Fuel | Common rail fuel distribution with multi-point sequential indirect fuel injection. NGK spark plugs. Mapped direct injection also. Knock sensors and permanent lambda control. |
| Dimensions | 20.2in long, 28.1in height, 28 in wide. |
Power output and models
Currently, the W12 engine is fitted to the following models.
- Audi A8L W12 (384.4 cu in with 493bhp and 463 lb-ft torque at 4,750 rpm
- Bentley Continental GT (353 cu in with twin turbos and 626hp. 664 lb-ft @1,350 to 4,500 rpm
- Bentley Continental Supersports (353 cu in with twin turbos and 700hp. 750 lb-ft @1,350 to 4,500 rpm
- Bentley Continental Flying Spur (353 cu in with twin turbos and 626hp. 605 lb-ft @2,000 rpm
- Bentley Bentayga (353 cu in with twin turbos and 600hp. 664 lb-ft @1,350 to 4,500 rpm
- Volkswagen Phaeton W12 until 2011 (366.0 cu in. 444 bhp. 413 ln-ft @ 2,750 – 5,200 rpm)
Power gains with tuning
It’s possible to further increase the power of this large engine by adjusting parameters on the engine control module. With ETG’s (ECU Tuning Group) software, the Bentley Continental GT will make 681 Horsepower and 651 LB-FT of torque. Additionally, changes to throttle and transmission maps further enhance performance.
W12 Factory Video
A YouTube channel filmed the W12 production from start to finish. It’s a fascinating watch and surprising to see a lot of hand finishing and traditional build methods still in use at the Bentley Crewe factory.
by Ben Gribbins
