What is the difference between Audi's on-demand four-wheel drive and full-time four-wheel drive?
3 Answers
Audi's on-demand four-wheel drive and full-time four-wheel drive differ in the following aspects: 1. Different concepts: Audi's on-demand four-wheel drive means the four-wheel drive system is activated when appropriate, otherwise, it operates as a two-wheel drive system; full-time four-wheel drive is always in a four-wheel drive state. 2. Different applicable conditions: Audi's on-demand four-wheel drive vehicles are convenient to operate and widely used in urban SUV models; full-time four-wheel drive is applied in off-road desert conditions. Audi's sedan models include the A6L, A4, A3, A7, and A8L. Taking the 2021 Audi A6L as an example, it is a mid-to-large-sized car with body dimensions of 5038mm in length, 1886mm in width, 1475mm in height, a wheelbase of 3024mm, a minimum ground clearance of 117mm, and a body weight of 1800kg.
I've been driving Audis for over a decade and know both four-wheel-drive systems inside out. The permanent all-wheel drive is like a tireless bodyguard, with all four wheels constantly at work. The Torsen differential distributes power with precision, providing exceptional grip in rain or snow. As for the on-demand four-wheel drive, it tends to slack off during normal driving, with just the front wheels pulling to save fuel. Only when you turn the steering wheel sharply or the tires slip does the rear wheel come scrambling to help. The difference? For city driving, on-demand four-wheel drive is sufficient and more fuel-efficient. But if you frequently tackle mountain roads or face snowy northern winters, the stability of Torsen-based permanent all-wheel drive in corners is something electronic systems simply can't match. Oh, and permanent all-wheel-drive cars are generally 80-100kg heavier, and tire wear tends to be faster.
Last week, I finally understood this while helping my bestie test drive cars. Full-time four-wheel drive means all four wheels are always providing power, like the old Q7's mechanical system which is super reliable. The Q5L with on-demand four-wheel drive usually acts like a two-wheel drive car, only engaging the rear wheels when it detects slippage, and you can see the power distribution animation on the dashboard. The salesperson said the on-demand system saves 1-2 liters of fuel, but there's a half-second delay when crossing bridge seams in rain or snow. I ended up choosing the A6 allroad with full-time four-wheel drive—it just goes 'thud' through puddles, which feels really reassuring. Though the tires are a bit pricey, so changing them hurts the wallet a little.
