Audi uses the "ultra" badge for particular models that are tuned to be efficient. Up until now, they have all been front-wheel-drive, which isn't a problem considering the most powerful has 218 PS. However, the Germans needed something different for the A4 Allroad, which is a go-anywhere wagon. So the first quattro ultra drivetrain was developed.
Up until now, quattro stood for permanent all-wheel drive, which is great for traction but bad for fuel consumption, as any S4 owner will tell you it's rare to get more than 20 mpg. The new quattro ultra is different because it's permanently AVAILABLE all-wheel-drive, meaning it's not on all the time.
If you want it to, the system works like the regular quattro setup should. However, the A4 Allroad's computer can decide to use only the front wheels. Using a couple of clutches at the end of the transmission casing, the prop shaft to the rear is de-coupled. The rear prop shafts are also cut from the differential case at the back. Sounds too complicated? Look at the image above - everything that's green is off.
The car can turn back to AWD in just 250 milliseconds, which is a funny way of saying a quarter of a second or about the time it takes to change one gear. However, Audi has designed the quattro ultra almost never to be reactive. Instead, the car tries to think ahead and engage AWD before you need it. For example, if you have the traction control off or in Sport mode, Audi knows power needs to go to the back because you want to have fun. There is also a reactive function that Audi says "rarely occurs in practice." Sudden ice on the road is a good example.
Just like cylinder deactivation, this latest ultra system doesn't make a huge difference. While the A4 Allroad is 5% more efficient, the 0.3 liter/100km drop in fuel consumption is negligible. But it beats the heck out of having an FWD car!
This technology should become available in other Audi models. We think the next one to get it is the Q5, followed by the next A6, A7 and A8.
Mihnea's favorite cars have already been built, the so-called modern classics from the '80s and '90s. He also loves local car culture from all over the world, so don't be surprised to see him getting excited about weird Japanese imports, low-rider VWs out of Germany, replicas from Russia or LS swaps down in Florida. Full profile
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