2011 Audi A8 L W12.
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The new A8 is a concentrated high-tech package that confirms the Audi claim to technical leadership – “Vorsprung durch Technik”. And now the brand is introducing the top version of its flagship model. The A8 L W12 quattro, with a long wheelbase and a twelve-cylinder engine, sets new standards of luxury, dynamism and efficiency in the top automobile manufacturing league. The Audi A8 L is being launched with a twelve-cylinder engine, but by the end of the year will be available with all the engines currently offered for the A8.
The Audi A8 L W12 quattro: Splendor and efficiency.
Twelve cylinders are the ultimate engine configuration, a tradition that still applies in the large luxury car class. The first-generation A8 was available with an engine of this type from 2001 on, and a developed version could be obtained from 2004 on in the following model. Audi’s engineers have now thoroughly revised the W12. Its displacement has been increased, and gasoline direct injection boosts its output and its efficiency.
The 6.3 FSI engine has an output of 368 kW (500 hp) and delivers its peak torque of 625 Nm (460.98 lb-ft) at engine speeds at 3,250 rpm. It gives the long-wheelbase Audi A8 the kind of performance normally expected of a sports car: it sprints from 0 to 100 km/h (62.14 mph) in only 4.9 seconds and effortlessly reaches its governed top speed of 250 km/h (155.34 mph).
A fascinating flow of power is available in every situation, but the fuel consumption too sets new standards: the EU cycle test result is only 12.0 liters per 100 kilometers (19.6 US mpg), a figure well below that of competitors’ cars with V12 engines. The previous 6.0-liter engine, which had a power output of 331 kW (450 hp), recorded a fuel consumption of 13.6 l/100 km (17.3 US mpg) – the difference of 1.6 l/100 km is equivalent to a 12 percent improvement.
The engine is known as the W12 because of its unusual layout: it has four rows of three cylinders with a 15-degree included angle between the two offset rows of cylinders in each broad cylinder block. The V angle between the two blocks is 72 degrees. This layout makes the W12 engine exceptionally compact: only just over 50 centimeters (19.69 in) long and therefore distinctly shorter than a V8. Height and width are both in the region of 70 centimeters (27.56 in).
The W12, in its latest form with a displacement of 6,299 cc, is an undersquare design. Its bore and stroke are 86.0 and 90.4 millimeters (3.39 x 3.56 in) respectively. Compared with the previous version the engineers have enlarged the cylinder bore. The forged crankshaft has a 12-degree angle of crankpin offset, so that the mixture in the 12 cylinders is ignited at the ideal interval of 60 degrees. The engine therefore runs exceptionally smoothly, and the car’s occupants are unlikely to sense any of this supreme power at work unless it is at high engine speeds and severe loads.
The W12 engine weighs only 247 kilograms (545 lb), an impressive value to which the crankcase makes a major contribution. This is a lightweight, high-strength aluminum-silicon alloy casting with a gray cast iron lower cross-member into which the bearing pedestals are embedded. The pistons are forged from a high-strength light alloy and have angled crowns because of their V position in the cylinder blocks.
Each of the W12 engine’s aluminum cylinder heads contains two camshafts; these can be repositioned hydraulically by an amount equivalent to 52 degrees of crankshaft rotation. Altogether, the four camshafts operate 48 valves by way of low-friction roller cam followers, and are themselves driven by chains from an intermediate shaft.
For use in the long-wheelbase A8, Audi’s engineers have converted the W12 engine to FSI gasoline direct injection. This involved considerable modifications to the cylinder heads. Fuel is injected into the combustion chambers at a pressure of up to 130 bar. A high 11.8:1 compression ratio boosts power output and efficiency. The inlet ports are specially shaped to impart swirl to the incoming airflow and make combustion more efficient.
The W12 engine’s low fuel consumption compared with its competitors is to a large extent due to Audi’s modular efficiency platform. These are used in the entire A8 model line. The crankshaft and timing chains have been intensively optimized to reduce friction, and a recuperation system recovers energy that would otherwise be wasted when the car is braked. The innovative thermal management system shuts down the coolant circuit for a time after the cold engine has been started. This warms up the engine oil more rapidly and shortens the operating period in which friction is still high.
Safe and sporty: Transmission.
The transmission makes a major contribution to ensuring the high efficiency of the Audi A8 L. The eight-speed tiptronic shifts smoothly and quickly, with the individual gears closely spaced but with a generous overall spread from low to high. Gear shifts are performed electronically (“shift by wire”) from an elegant yacht-style selector lever or at steering wheel paddles.
The center differential, the main component in the quattro permanent all-wheel drive train, divides the torque flow from the engine in a sporty manner, with 60 percent to the rear axle and 40 percent to the front in regular driving conditions. But if the situation changes, up to 60 percent of the torque can be sent to the front, or 80 percent to the rear. An optional sport differential splits the torque input actively between the left and right rear wheels.
Maximum precision: Chassis.
Thanks to its advanced chassis design, the long-wheelbase Audi A8 brings together the silky, refined smoothness of a true luxury car and the handling of a sport sedan. The wheel control arms are made of aluminum. The front suspension uses five locating arms at each wheel; the controlled-track wishbone rear suspension ensures a supremely comfortable ride. The servotronic power steering system has a direct operating ratio and operates at high efficiency.
The adaptive air suspension with controlled damping is standard equipment and is integrated into the Audi drive select dynamics system. With this system the driver can choose between four different operating settings of the engine, the eight-speed tiptronic transmission, the servotronic power steering, the optional sport differential and the Audi pre sense basic safety system. An additional module is the dynamic steering system, which varies its gear ratio steplessly according to road speed.
The A8 L W12 quattro runs on 19-inch alloy wheels with a 15-spoke design reserved for this model, and size 255/45 tires. As an optional extra 20-inch wheels can be chosen, and even 21-inch wheels can be obtained from quattro GmbH.
The A8 L W12 quattro, the new top model, naturally has a high-performance brake system, with ventilated disks at all four wheels. The front disks are 400 mm (15.75 in) in diameter, with 356 mm (14.02 in) disks at the rear. To dissipate heat and reduce weight, stainless steel pins connect the steel friction rings with the aluminum disk centers. The calipers have a matt black paint finish.
Dynamic intelligence: Communication and assistance systems.
This large sedan features an exemplary control concept. Although there are so many functions available, they can be selected in an easily understood, ergonomically correct way. Two large monitor screens, one on the instrument panel and one on the center console, acts as control centers and display their information as high-resolution 3D graphics.
The A8 has a pioneering innovation on board: the optional MMI navigation plus, which operates with the aid of a high-capacity hard disk, has a touch-sensitive control panel known as MMI touch. The driver inputs his or her navigation destination or a telephone number simply by writing the letters or numerals on the pad with a finger. Acoustic feedback makes this possible without taking one’s eyes of the road.
The high-end navigation system cooperates with the assistance and safety systems in an innovative way. It registers the topography of the road in advance and makes this data available to the control units for the automatic transmission, headlights and adaptive cruise control with Stop & Go function. Thanks to their advanced intelligence, these systems can identify complex scenarios and offer the driver support in good time.
The adaptive cruise control system operates at any speed up to 250 km/h (155.34 mph) and responds even more flexibly and smoothly than before.
The Audi side assist system, which helps the driver to change lanes, and Audi lane assist which detects any departure from the chosen lane, also have new and additional performance features.
The night view assistant uses a thermal imaging camera to identify persons on the road ahead of the car. If it considers the situation to be potentially dangerous, the image of the person on the road is shown in red and a warning signal is heard. The Audi pre sense safety system is also closely linked to the assistance systems. It is available in several stages: the full version brakes the car automatically in order to minimize the consequences of a nose-to-tail collision.
In the multimedia area, Audi can also supply many attractive modules. These include a Bang & Olufsen Advanced Sound System with an output rating of more than 1,400 Watts and 19 speakers, and the Rear Seat Entertainment system. This has an MMI control panel on the console between the rear seats and provides access to all the infotainment functions on board this large luxury sedan.
The new Online services in cooperation with Google use the car phone to capture news and current information on the weather or points of interest (POI) from the Internet. Later this year an UMTS module will be available: this fast data link can supply images and information from Google Earth to the monitor screen and combine them with the navigation route. The driver can use all these services with his or her cell-phone contract.
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