New Audi A8 3.0 TDI Quattro

Press Release

Long-distance specialist with sprinter qualities

The Audi A8 can now be ordered with a completely new six-cylinder TDI engine. Costing € 60,500, the A8 3.0 TDI quattro represents the addition of a further sporty version with the characteristics of a long-distance luxury saloon to the A8 range. The six-cylinder engine in the A8 3.0 TDI quattro develops 171 kW (233 bhp) at 4,000 rpm and summons up an impressive 450 Newton-metres of torque between 1,400 and 3,250 rpm. The lightweight luxury saloon with aluminium body is thus capable of sprinting from 0 to 100 km/h in just 7.8 seconds - a world best for a V6 diesel saloon - and goes on to a top speed of 243 km/h. The 3.0 TDI is the first production diesel model in the world to have the pioneering common rail fuel injection concept with piezo inline injectors. This permits up to five injection processes per operating stroke and an injection pressure of 1,600 bar. Piezo technology makes it possible to inject much smaller, more precisely metered amounts of fuel. Thanks to the higher speed of the injector needle, the system moreover responds twice as fast as other injectors. This effect is particularly important for brief intervals between the offset multiple injection processes, of which there may be up to five. The fuel is injected into the combustion chamber via 7-hole nozzles. They, too, play a major part in making the combustion process ultra-efficient and improving the quality of emissions, by distributing the fuel homogeneously throughout the combustion chamber. The V6 TDI belongs to Audi's new range of V engines and has a chain drive for camshafts and oil pump. The cylinder spacing in the new engine block is now 90 millimetres. The engine consequently measures a compact 444 millimetres in length. The engine block is made from vermicular graphite cast iron. This is one of the vital clues to the engine's low overall weight of just 220 kilograms - the 3.0 TDI is one of the lightest diesel V6s around. This benefits the power-to-weight ratio and the weight distribution in equal measure - two characteristics that are of central importance for the driving dynamics of the new A8 3.0 TDI quattro. Further distinguishing features of the engine include four-valve technology with low-friction roller cam followers, turbocharging with two charged air coolers, and electric actuation of the variable turbine geometry, with faster and more precise adjustment of the vanes even at intermediate stages. Particularly at low engine speeds, this builds up the boost pressure faster and thus achieves significantly better responsiveness. There are likewise continuously variable swirl flaps integrated into the intake tract. They can be used to adjust the air movement according to the prevailing engine speed and load. All these measures result not merely in high performance potential and an enormous torque plateau, but also in reduced fuel consumption and outstanding acoustic behaviour. Particularly in this discipline, the new engine now unquestionably serves as the benchmark in its class. And even with 6-speed tiptronic and permanent four-wheel drive, the A8 3.0 TDI quattro - the very first diesel in the luxury class to have controlled, cooled exhaust gas recirculation - undercuts the emission limits of the tough EU4 standard that will apply from 2006. It thus complies with the requirements for tax exemption for a limited period in Germany. One feature of the new engine that is undoubtedly as welcome as its efficiency at reducing emissions is its impressive fuel economy: the tank dispenses just 8.4 litres of diesel over 100 kilometres (overall fuel consumption). It therefore comes as no surprise to learn that the new A8 3.0 TDI quattro has an operating range of over 1,000 kilometres on a single tank of fuel. This is a figure that singles out the sporty saloon with TDI engine as the perfect long-distance vehicle . The first proud owners of the new Audi A3 3.0 TDI quattro will be taking receipt of their cars in April. Workshop
The Audi A8 3.0 TDI Quattro
with the world’s first
piezo inline common rail fuel injection system
from Bosch Technical speech
Richard Bauder
Head of Diesel Engine Development
Ladies and Gentlemen, It was Audi who began the success story of the direct-injection diesel engine for passenger cars in 1989, with its 5-cylinder inline engine. This had a swept volume of 2.5 litres and was available in a series of successful Audi models with power outputs up to 140 bhp. The first V6 TDI engine followed in 1997, also a 2.5-litre unit with a power output of 150 bhp and a maximum torque of 310 Nm. This generation of engines is still in active use with power outputs up to 180 bhp and torques of up to 370 Nm in various models, from the Audi A4 Cabriolet to the allroad quattro, and is therefore an important element in the Audi model programme. Today we are able to present to you our latest development, currently the world’s most powerful series-production V6 diesel engine for passenger cars, a 3.0-litre unit developing 233 bhp and 450 Nm of torque. Even without a particle filter, this new engine complies with the very tough EU4 exhaust emission limits when installed in luxury-class cars with automatic transmission and permanent all-wheel drive. This is an achievement of which we are particularly proud. The new V6 TDI is the first diesel in the new generation of Audi “V� engines with the distance between cylinders increased from 88 to 90 millimetres. This was necessary in order to obtain the increased swept volume of three litres. A significant feature of the Audi “V� engine family is the novel timing chain positioning at the transmission end of the engine. The chains drive the balancer shaft and the oil pump as well as the camshafts, and of course need no routine maintenance. This design principle makes the engine extremely short and compact. It is only 444 mm long – an impressive figure when we consider that some competitors’ engines are more than 700 mm long. The cylinder heads contain two overhead camshafts, one each for the inlet and exhaust valves. The valves are actuated by low-friction roller cam followers. To reduce mechanical noise, the camshafts are linked together by special zero-backlash gears. The engine block, with a 90-degree included angle between the cylinder banks, is a vermicular graphite iron casting. This material has twice the strength of conventional grey cast iron. As a result, it also weighs about 7 kilograms less than the block used for the previous engine. In combination with the main bearing deck and the aluminium sump, which is not exposed to ignition loads, this design principle permits optimum weight saving and in particular optimum acoustics. The complete engine weighs only 220 kg. It has a third-generation common-rail fuel supply system with piezo injectors from Bosch. This is a world first. It has a maximum injection pressure of 1600 bar; the high-pressure pump is located in the “V� of the engine and driven by a toothed belt. The novel piezo inline injectors can perform up to five injection stages on each injection stroke, and are notable for the very small amount of fuel they can deliver if necessary and the very low volumetric tolerances between the fuel deliveries. These are important factors in achieving the lowest possible emissions and an excellent operating noise pattern. The new 3.0 TDI engine has a turbocharger with variable turbine blade geometry. For the first time, the blades are moved by an electric actuating motor; this permits their position to be controlled more accurately. To avoid any unnecessary loss of exhaust heat, the manifolds and compensators have air-gap insulation. The combination of variable-blade turbocharger and air gap insulation ensures a spontaneous build-up of boost pressure and therefore of torque from the engine. Two air-to-air charge-air intercoolers are installed; these are mounted underneath the car’s headlights in order to obtain the best possible through-flow. To keep pressure losses and charge air temperatures to a minimum, the two intercoolers are arranged in parallel. Those were some of the main design highlights of the new V6 TDI engine.

Now for a few words about its combustion principle:

The biggest challenge was to outperform the tough EU4 exhaust emission limits in a luxury car with 6-speed automatic transmission and quattro driveline without the need for a particle filter. This called on the one hand for the very latest diesel engine technology, and on the other for special know-how in the thermodynamics of TDI engines. The 3.0 TDI is the first engine to use a completely revised Audi four-valve concept. The familiar star pattern of the valves has been modified so that each camshaft actuates two inlet and two exhaust valves. In conjunction with the controlled swirl flap, this permits the level of swirl to be extended, in other words the minimum and maximum degrees of swirl are farther apart. For the first time, the electronic swirl flap control system also permits intermediate positions to be selected. The six flaps are moved to the optimum setting in front of the spiral inlet ports in accordance with a mapped characteristic. This makes a major contribution towards keeping exhaust emissions low. At low engine speeds and loads, the minimum emissions flap is closed, so that the degree of swirl is high. At low engine speeds but when the load is high, an intermediate setting with moderate swirl significantly reduces emissions. At higher engine speeds and when peak performance is called for, the swirl flaps open fully and the degree of swirl is therefore low. Seven-hole injector nozzles are used. The blind-hole injectors produce a good spray pattern; they have micro-blind holes, which have the advantage of low dead volume and a high injection pressure. As a result, mixture preparation is more effective and combustion is highly efficient and creates very few emissions. For a luxury class car, it is obvious that an acceptable noise pattern is needed. Thanks to the piezo injectors and the single or double pilot injection volumes which they permit, combustion can be extremely smooth. Combustion noise is distinctly lower than from any known diesel engines. This is an impressive step forward in diesel-engine development that our customers will appreciate every time they drive the car. Good mixture formation and acoustics have enabled the compression ratio to be lowered to 17 : 1, which benefits both power output and emissions. The maximum absolute boost pressure is 2.3 bar.

A few words now about the performance of the engine and the car:

The 3.0-litre V6 TDI engine’s thermodynamic potential is evident in its power output, torque and emissions. At 233 bhp, the V6 TDI sets a new standard among all current six-cylinder passenger-car diesels in this The maximum torque of 450 Nm is reached at an engine speed of only 1400 rpm and remains constant at this high level all the way up to 3250 rpm. In addition, the new V6 can claim that the low exhaust emission values it achieves in the EU4 test are achieved solely by internal engine design measures. The particulate emissions are at an especially low level. Both fuel consumption and performance values are excellent. The overall average fuel consumption is 8.4 litres per 100 kilometres. The A8 3.0 TDI quattro accelerates from 0 to 100 km/h in 7.8 seconds and has a top speed of 243 km/h. With its new 3.0 V6 TDI engine, Audi once again demonstrates its TDI competence in a most impressive way. The three-litre engine, in addition to its qualities as a sprinter, has admirable acoustic properties and refinement, and will set a standard in its class that drivers will be able to sample and appreciate day after day.