|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 engine-size category.
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.
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