Audi introduced its Allroad Quattro in 2009. Now there's an off-road version based on the A4.Audi has renamed its "Quattro" system as "Quattro Ultra", to mark the change from permanent all-wheel drive to on-demand AWD. The new drivetrain system took around 5 years to develop. Sensors and a computer detect when a wheel might lose traction. Then the Ultra all-wheel drive engages -- within a quarter of a second!