quattro – Audi’s lauded permanent all-wheel drive (AWD) system, due in part to historic success in motorsport, and in part to marketing – has sold its soul to the eco-devil! In the pursuit for efficiency Audi will be rolling out its newest generation of quattro, called ‘quattro with ultra’ (remember ‘quattro’ is spelt in the lower case) – and it’s no longer a permanent all-wheel drive.
Yip, you read that right – Audi’s famous AWD isn’t always going to be driving all four wheels, all the time. Instead, it’ll be a front-biased 4WD (four-wheel drive) system – much like the Haldex systems employed on the quattro-badged A3 and Audi TT. In fact the only difference – simply speaking – between the new quattro With Ultra system and Haldex is that the new Audi system will use longitudinally mounted engines, much like the current quattro does.
It’s all in the pursuit of 0.3 litres fewer used per 100km. That’s what Audi claims it will save on every quattro with ultra model as compared to conventional AWD-equipped models.
The first models to be equipped with quattro with ultra will be the new A4 allroad quattro making its debut in mid-2016.
How Does quattro With Ultra Work?
Under regular driving scenarios – any quattro with ultra equipped Audi’s will remain purely front-wheel drive. However, should slippage be detected on the front wheels, or should the system pre-empt slippage (apparently it can predict slippage before it occurs), a clutch pack and coupling system engages drive to the rear wheels to ensure all wheels receive torque.
An electronic motor engages a clutch pack (comprising 5 or 7 pairs of clutch-plates, model dependant), which engages the driveshaft to the rear axle. In this way, quattro with ultra can entirely decouple the rear axle and stop rotation of the drive shaft to reduce friction and improve efficiency.
This is in stark contrast to the previous self-locking centre differential – a mechanical planetary gear that responded to centripetal force to activate more drive to the rear if needed. The old system could divert up to 70% of the torque to the front axle, and 85% of it could be sent to the rear axle if needed.
The days of a 60:40 rear:front torque split are gone. There’s no word yet as to what percentage of the torque can be diverted rearwards though, and as the system only controls front-rear torque distribution, there isn’t any control of the torque split from left to right, meaning Audi will most likely equip models with brake-assisted torque vectoring rather than mechanical torque vectoring.
Predictive and Pre-emptive:
Audi claim the new system follows a 2-stage strategy to predict and pre-empt when all-wheel drive will be required.
Proactive level: At this phase, Audi claims the quattro with ultra systems will compute the point at which the inside front wheel will reach its grip limit during fast cornering. The calculation allegedly is completed 0.5 seconds prior to the grip limits being reached, at which point the system can be activated.
Predictive level: On this level, the quattro with ultra system utilises inputs based on the current style of driving to engage the AWD setup. It does this primarily by reading which ESC mode the driver is in and whether or not there is a trailer hitched to the vehicle.
When prediction doesn’t work?
If all else fails and the quattro with ultra system is unable to predict when AWD is needed, the system has a built-in reactive activation, which engages the rear axle when sudden shifts in traction occur – either the front wheels losing traction or suddenly gaining lots of it.
There’s hope for Audi yet…
It all sounds a bit faux, a bit Haldex, a bit old hat – and truth be told, it is. But, it’s not all bad news… or it might not be. It all relies on a big ‘if’ though. If Audi can recreate what Mitsubishi did with the Lancer Evolution’s S-AWC, then quattro with ultra might not be all bad.
To do this though, the pre-emptive systems will need to be able to sense and predict weight transfer through slight changes in yaw, braking, g-forces and changing road conditions. If Mitsubishi can do it, Audi can do it, right?
We can only hope so!
