Audi has introduced a production version of the Q7 V12 TDI full-size SUV concept shown in January 2007. (Earlier post.) The 6.0-liter twin turbo V12 TDI diesel engine generates an output of 368 kW (493 hp) and 1,000 Nm of torque (738 lb-ft).
|The 6.0-liter V12 TDI engine. Click to enlarge.|
The Audi Q7 V12 TDI quattro accelerates from zero to 100 km/h (62.14 mph) in 5.5 seconds and has an electronically capped top speed of 250 km/h (155.34 mph). The V12 diesel has a fuel consumption rating of 11.3 liters/100 km (20.82 US mpg).
The engine uses a Bosch 2,000-bar injection system with an eight-hole injector with hole diameters of 0.12 mm. The high pressure produces an optimum spray pattern inside the combustion chamber, which makes for a faster, more homogeneous and, as a result, more acoustically refined ignition process. The improved combustion efficiency increases power output while reducing both fuel consumption and emissions.
The fuel pressure and quantity can be adjusted according to requirements; the number of injection phases per power stroke can be varied up to a maximum of five with the piezoelectric technology in the V12 TDI. Main injection can be accompanied by both pilot and post-injection phases. Pilot injection lessens the harshness of the combustion sound, which is particularly noticeable at low engine loads.
Both turbochargers generate up to 2.7 bar of absolute boost pressure. Two large intercoolers reduce the temperature of the compressed air and thus increase the level of oxygen required for combustion. The V12 TDI features a dual-branch intake system. For each bank of cylinders there is an air filter, behind which an air mass meter is located.
Two ultra-fast control units manage events in the engine, sharing the workload according to a master/slave principle. The six-liter has adopted map-controlled swirl variation of the combustion air from its smaller TDI siblings. The electrically controlled flaps can be adjusted to ensure optimum swirl with respect to high performance and low emissions.
The exhaust system also has a dual-branch design; here Audi engineers focused their attention on exhaust gas recirculation. At partial throttle, up to 50% of the exhaust is fed back into the intake air in order to reduce NOx emissions. The large-dimension recirculation system, located at the top of the inner vee, incorporates a water cooler that uses map-based control to lower the temperature of the exhaust gas.