Bada Bing

I had a chance to test drive an A7 TDI at a promotional event at my local dealership and was very impressed with the smoothness and power of the 3.0 TDI engine. Looking at the window stickers of their showroom cars, I noticed that the A8L TDI is rated at 406 lb-ft, while the A6 & A7 TDI models are rated at 428 lb-ft. Also, Audi USA website shows a significant 0.9 second difference between these models (A8 at 6.4 vs 5.5 second for the A6/A7). I doubt that the A8 is more than a couple hundred pounds heavier. Do you know why the flagship model gets a detuned version of the 3.0 TDI engine?

MP4.2+6.0

If you check back, I think you will find the higher power/torque motor starts with the Q5, and then is spreading around. Look at the Cayenne TDI and you'll find the same lesser performance one, another oddity and tied in turn to the Q7. The Cayenne TDI underneath is also Audi quattro, not Porsche flavor AWD like all the gas Cayennes. Q5 weighs what an A8 does basically; it's no lightweight at all. Meanwhile, yep buy the 50-75% more expensive Cayenne (especially after the option gouging) and get less performance in TDI's than the Q5 TDI and not much more interior space, and then find out its also Audi quattro in disguise underneath.

Normal obvious explanations for this sort of thing are they've got too many parts or production capacity hanging around for the other flavor, so it keeps getting used. Or, it's a motor emissions compliance thing, though that makes much less sense if both motors are getting shipped into the same market, especially with the same basic eight speed ZF tranny and driveline. Odd though to do it when they are just intro'ing a TDI model here, but figure likely it backtracks into how it was first installed into the original Euro offerings.

Another kind of piece of junk drivetrain example frankly when I look at it is the hybrid in the A8. Actually having one (of the few) in the Q5, how in the world did they conclude to strip out the quattro (which is in the Q5 of course), downgrade it back to NiMH apparently (lithium ion in Q5 and thus both smaller and lighter for same capacity), and then for kicks drop the battery back right in the middle of the inadequate-to-start-with D4 trunk instead of under the floor/in place of spare (a la Q5 and with a smaller battery pack form factor to start). Owning a D3 W12, it all makes about zero sense they would do something more advanced on the much more basic A4/A5/Q5 platform, and then do a hack almost laughable job on it for the D4. Somehow thus no surprise "Art" in Engineering got displaced in stuff like this by Fritz in Beancounting and motor regulatory compliance.

jakematic

Best explanation yet...
Skimping on the flagship isn't going to make people rush to that particular combo - at least it doesn't for me and diesel is very high on my wish list.

Same goes for CoD in the new W12 in my book.