he A6 3.0 TDI’s turbo-diesel has been redesigned from the ground up. Weight drops by 11.5 percent (55 pounds) compared with the engine it replaces . Some 13 pounds were trimmed from the crankcase alone, which now is made from a high-strength cast iron. Sundry rotating parts have been lightened as well. Other changes include a redesigned drive system for the camshafts and improvements to the common-rail injection system, intake and exhaust systems, turbocharger, and intercooler.

There will be two versions of the 2967-cc TDI engine, with programming being the only difference. The conservative tune makes 204 hp and 295 lb-ft of torque, with the more-powerful engine churning out 245 horses, its 369 lb-ft peaking at 1400 rpm. (The outgoing 3.0 as installed in our long-term Q7 TDI makes 225 hp and 406 lb-ft.) Although both will be available in the A6, we sampled only the more powerful one, which is the one more likely to show up in the U.S. In Germany, this version of the engine will come standard with Quattro all-wheel drive and Audi’s new eight-speed automatic transmission, but the exact equipment plan for the U.S. has not been finalized. Thus equipped, the A6 proved plenty quick as we charged up and down the narrow, hilly roads on Sicily. Regardless of grade or elevation, the car gains speed forcefully, making almost no sound unless you absolutely hammer it. The turbo rush seems omnipresent, with virtually no lag.
SOURCE: http://www.caranddriver.com/reviews/audi-a6-30-tdi-diesel-review