Recently, Audi debuted a new variant of its famous Quattro all-wheel drive system, dubbed “Quattro with Ultra technology” or just “Quattro Ultra‘ for short. The idea behind this new Ultra system is to decouple the rear wheels, thus making the car front-wheel drive, for any time when maximum tractions isn’t needed. However, when extra tractions is needed, it can recouple the rear wheels and get things moving smoothly again. CNET’s Roadshow gives us a deeper look.
While that idea isn’t a very new one, being that multiple car companies have used similar features before, Audi does do some things a bit differently. First of all, it isn’t just the rear wheels that decouple. Audi’s Quattro all-wheel drive system uses a center-mounted Torsen (Torque Sensing) differential with a multiplate clutch that has a prop shaft going to a real differential. Attached to the rear differential is a dog-leg clutch that controls the power going to the rear wheels. During its fuel-saving “Ultra” mode, the multiplate clutch decouples the rear prop shaft from the transmission. But the dog-leg clutch also decouples the rear wheels from the rear differential.
What all of this does is reduce any amount of drivetrain lost from friction of the rear wheels spinning the rear prop shaft as they turn naturally. While it isn’t a huge amount of friction lost, it does help with fuel economy a bit and every little bit helps, especially today.
All of this technology is quite interesting but it means nothing if it doesn’t work well. According to the folks at CNET, who recently tested the system on the brand-new Audi Q5, claim that it works seamlessly. Technology like this can have a tendency to feel sloppy and jerky, but Audi’s Quattro Ultra is brilliant, smooth and imperceptible. Its ability to switch from front-wheel drive to all-wheel drive takes just 200 milliseconds, making it fast as well.
During their drive, CNET had an Audi engineer along with them. He showed them in real time just how much grip was available and how much was used on a variety of different surfaces. One thing that was noted was that they found themselves using front-wheel drive for over 90 percent of the time and only used the all-wheel drive for a very small amount of time. The all-wheel drive system did engage quite often, actually, but so briefly that the car was still mostly front-wheel drive. However, they never once noticed it change, despite it changing over often.
It’s an impressive system Audi’s developed and it’s surprising how good such a fuel-saving all-wheel drive system can be.