Engines

Superior power and high efficiency – the new A8 makes its debut on the market with a choice of two strong V8 engines, one gasoline and the other a TDI. A second diesel engine with six cylinders will follow a little later. The power spectrum of the three engines lies between 184 kW (250 hp) and 273 kW (372 hp) – during driving they never fail to impress with their superior power and mighty but discreet propulsion. All engines feature direct fuel injection, and consume up to 22 percent less fuel than their respective predecessors.

The engines in the A8 have intelligent elements from Audi’s modular efficiency system on board. During deceleration the recuperation system converts the kinetic energy to electric power, which is buffered in the battery. In the innovative thermal management a computer monitors numerous actuators for the ideal distribution of the heat flows between the engine, transmission and interior in any situation. After the cold start the engine is temporarily fully uncoupled from the cooling circuit, considerably shortening the warm-up phase with its high loss of friction.

The 4.2 FSI draws 273 kW (372 hp) of power from 4,163 cm3 displacement, generating its maximum of 445 Nm (328.22 lb-ft) torque at 3,500 rpm. It accelerates the A8 from zero to 100 km/h in 5.7 seconds, with the propulsion ending (as in all engine variants) at the electronically controlled speed of 250 km/h (155.34 mph). In the EU cycle the strong gasoline engine is content with 9.5 liters/100 km (24.76 US mpg) – a reduction by 1.4 liters or 13 percent compared with the predecessor, at a power increase of 16 kW (22 hp). The CO₂ emission rate is only 219 g/km (352.45 g/mile).

The most important reason for this enhanced power is the reduction of internal friction, especially in the chain drive for the camshafts and auxiliaries. The controlled oil pump with changeover between two pressure stages operates with high efficiency. Like all gasoline engines from Audi, the V8 has FSI direct injection. It allows a high compression of 12.5:1, for increased power and efficiency.

800 Nm (590.05 lb-ft) torque: the 4.2 TDI
The 4.2 TDI is another high-tech engine. Its displacement of 4,134 cm3 yields 258 kW (350 hp) and a hefty torque of 800 Nm (590.05 lb-ft), already available at speeds between 1,750 and 2,750 rpm. The V8 accelerates the A8 like a sports car. The sprint from rest to 100 km/h (62.14 mph) is accomplished in 5.5 seconds. The output has increased by 18 kW (24 hp) and 150 Nm (110.63 lb-ft), while the standard consumption has dropped by 1.8 liters/100 km – a full 19 percent. The new A8 4.2 TDI still consumes only 7.6 liters/100 km (30.95 US mpg), corresponding to CO₂ emissions of 199 g/km (320.26 g/mile).

The enhanced performance results above all from increased pressure of the common rail system, which now injects at 2000 bar. The reduction of the internal friction was another focus of development; the two turbochargers and the exhaust gas recirculation system have also been largely overhauled.

The two V8 engines are to be joined by a six-cylinder version shortly after
the market launch – the 3.0 TDI has also been thoroughly overhauled. It mobilizes 184 kW (250 hp) from its 2,967 cm3 displacement and draws 550 Nm (405.66 lb-ft) onto the crankshaft at 1,500 to 3,000 rpm – 13 kW (17 hp) and 100 Nm (73.76 lb-ft) more than previously.

The V6 diesel brings the A8 from 0 to 100 km/h (62.14 mph) in 6.6 seconds. On the average it needs only 6.6 liters of fuel per 100 km (35.64 US mpg) – an improvement of 1.9 liters/100 km or 22 percent. Per kilometer it emits merely 174 g CO₂ (280.03 g/mile). The standard 3.0 TDI operates with a start-stop system. It switches off the engine when the A8 comes to a standstill, and restarts the engine as soon as the driver’s foot leaves the brake.

At a later point in time Audi will add a second variant of the V6 TDI with 150 kW (204 hp). Driving exclusively the front wheels, its efficiency is exemplary. In the EU driving cycle the new engine needs only 6.0 liters/100 km (39.20 US mpg), corresponding to CO₂ emissions of 159 g/km (255.89 g/mile).

The equipment, data, and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.