With this extremely impressive power output, the new Audi A8 4.2 TDI quattro puts itself ahead of all the other diesel-engined cars on the international market. The entirely redeveloped 4.2-litre, eight-cylinder biturbo engine accelerates the lightweight saloon with its aluminum body from 0 to 100 km/h (0 – 62 mph) in just 5.9 seconds. The top speed is electronically restricted to 250 km/h. In addition to these dynamic qualities, the new power plant displays the kind of refinement that sets standards even in the top segment of the motoring world, and ennobles the A8 4.2 TDI quattro, turning it into the perfect long-distance touring saloon.
The new engine is also exemplary in terms of economy. Combined as standard with quattro permanent four-wheel drive and 6-speed tiptronic transmission, it uses on average just 9.4 litres of diesel fuel for every 100 kilometers. This means it will cover more than 950 kilometers (590 miles) on a full tank without a stop.
The Audi A8 4.2 TDI quattro is equipped as standard with a diesel particulate filter, which works without additives and consequently lasts the lifetime of the vehicle without servicing.
The A8 4.2 quattro has a chassis with air suspension and adaptive damping – otherwise known as Audi adaptive air suspension. It allows the vehicle to be driven either in a decidedly sporty fashion or with an extremely comfortable ride, just as the driver wishes.
The surfaces of the cylinder bores are treated using UV laser exposure. This special honing process ensures significantly reduced oil consumption in the TDI engine, and, as a result, a significant reduction in particulate formation during combustion.
In the 2005 year all A8 variants got the new wider and taller trapezoidal grille.
The forged crankshaft made of chrome molybdenum steel is offset in such a way that forces and moments of the first and second order are avoided – a decisive bonus delivering extremely low levels of vibration.
The cylinder head is made of aluminum, and two camshafts are used to operate the valves in each. They are driven via a maintenance-free chain drive, which also drives the oil, water and power-assisted steering pumps.
There are four valves per cylinder, for optimum charging of the combustion chamber. The valves on the new V8 are operated by roller cam followers with hydraulic valve clearance compensation. This low-friction drive technique plays a decisive part in reducing both the fuel consumption and the emissions of the 4.2-litre engine.
The use of roller cam followers is likewise beneficial to the engine's acoustics. In conjunction with the twisted-type and therefore virtually play-free camshaft drive, these followers are instrumental to the reduction in mechanical noise from the valve gear and contribute to the 4.2 TDI's outstandingly quiet running.
The rigid construction of the engine block and the unit’s effective encapsulation also help to lessen the sound emitted by the eight-cylinder engine.
The 4.2 TDI engine is currently the most powerful diesel engine to be found in any production saloon car. 240 kW (326 bhp) at 3,750 rpm are the new benchmark – an increase of no less than 51 bhp over its 275 bhp predecessor.
The A8 4.2 TDI quattro has the performance of a top athlete. This lightweight luxury saloon with its aluminum body takes only 5.9 seconds to sprint from a standstill to 100 km/h – making it quicker than any other diesel saloon on the international market. It is capable of a governed top speed of 250 km/h.
The torque gives the driver a feeling of pulling power in every speed range that is otherwise only to be experienced in a sports car. 650 Newton-meters between 1,600 and 3,500 rpm – this figure makes the A8 4.2 TDI quattro the Audi with the most torque of them all.
Source: Audi press