This here is the long wheelbase version of the all-new, fourth-generation Audi A8 that will debut at the this month’s Beijing Motor Show in China with a new 6.3-liter W12 engine.

Ingolstadt’s flagship limo has an overall length of 5,267 millimeters (17.28 ft), meaning it’s 130 mm (0.43 ft) longer than the regular version. The wheelbase has grown by the same amount, to 3,122 mm (10.24 ft) while the height has increased by 2 mm (0.08 in) to 1,462 mm (4.8 ft). Width remains unchanged at 1,949 mm (6.39 ft).

All that extra length benefits rear-seat passengers who also get longer rear doors to further ease access.

For those that want the royal treatment, the German firm offers the option of two separate and power-adjustable seats that can be heated, ventilated and adjusted in a variety of ways including forward and back, seat cushion depth and seat back angle with top section adjustable separately.

Between the individual rear seats that are standard equipment in the A8 L W12 quattro, there’s a full-length console that extends back from the center tunnel to the rear shelf, and can be specified with several goodies such as a folding table or a refrigerator.

Rear passengers also get separate controls for the air conditioning that is controlled by 25 adjusting motors, while Audi also offers an entertainment system with two 10.2-inch screens.

The A8 L W12 quattro model is powered by a new 6.3 FSI W12 engine with 500HP and a peak torque of 625 Nm (460.98 lb-ft) at engine speeds at 3,250 rpm. With this powerhouse, the A8 L accelerates from 0 to 100 km/h (62mph) in just 4.9 seconds and reaches a governed top speed of 250 km/h or 155 mph.

It consumes 12.0 liters per 100 kilometers or the equivalent of 19.6 US mpg.

The W12 version features subtle visual cues that differentiate it from the other A8 L’s that will follow (with diesel and gasoline powertrains), including a unique radiator grille, chromed inserts of in the air inlets, and chromed applications on the exterior mirrors.

In the US, the 2011 model year A8 and A8L will go on sale in Fall 2010.