The Audi Q7 V12 TDI - the world’s most powerful diesel passenger car

The current generation of inline injectors use the piezo effect. When an electric current is created, piezo crystals expand in milliseconds. This expansion is then directly transported (inline) by the V12 TDI injectors – containing over one hundred piezo plates – to the injection nozzle needles without the use of mechanisms in between.

The number of injection processes per power stroke can be widely varied using piezo technology, in the case of the V12 TDI up to five injections.

In addition to the main injection, pre and post-injections are possible. Pre-injections reduce the acoustic hardness of the combustion procedure. Post-injections serve to increase the temperature of the emissions, helping regeneration of both standard-fit particulate filters.

Both turbochargers can be found on the exterior of the V-engine, each supplied with a cylinder bank. Thanks to its adjustable guide vane geometry, the complete gas emission stream is always fed through the turbines. The chargers respond even at low levels of revolution and reach high levels of efficiency.

Both turbochargers amass a charge pressure of up to 2.6 bar and are a key aspect of the exceptional torque levels of 1,000 Nm that are supplied to the V12 TDI constantly between 1,750 and 3,000 rpm. With its 368 kW (500 bhp), the diesel reaches a specific performance of 62 kW (84.3 bhp) per litre of engine capacity.

Two large charge air coolers reduce the temperature of the compressed air. The V12 comes with a double-flow exhaust system with two particulate filters. The suction unit is built in a similar way – each cylinder bank contains an air filter behind which an air mass meter is stored. Two control units manage what happens within the engine according to the master-slave concept.

The Audi Q7 V12 TDI will conform to the Euro 5 emissions class which will come into force in 2010 and demand a reduction of nitrogen oxide emissions. Aside from the precise analysis of the fuel injection system through the common rail system, the Audi engineers have focused especially on exhaust gas recirculation. At partial load, up to 50 % of emissions are recirculated through the air intake in order to reduce nitrogen oxide emissions. The large-dimension recirculation system is stored in the upper section of the V cylinder and includes a water cooler which reduces emission temperature significantly.

The Audi Q7 V12 TDI is impressive not only with regard to technology but also in terms of appearance. The most striking visual changes to the Audi Q7 are the underbody panels at the front and rear. The chrome-plated single-frame radiator grille evokes the tradition of the Audi S6 and S8. These two cars, with their V10 FSI engines, are the top sports models in their class. The V12 TDI features a powerful braking system which is every bit its equal.