Roads considered challenging enough to be a test of mettle for thoroughbred competition cars on the Azores rally have been chosen to provide a baptism of fire for the quattro system
underpinning the all-new Audi A3. Journalists have been able to assess the dynamic capabilities of all-wheel-drive versions of the advanced new compact hatchback on these roads, which snake around the island of São Miguel in Portugal’s Azores archipelago, ahead of the car’s world public debut at next month’s Geneva Motor Show.
In a place where volcanoes once created a whole chain of islands and where there is a high level of volcanic activity, Audi is demonstrating the core of its DNA: quattro drive. The all-wheel drive system fittingly makes its first appearance in one of the most emotive versions of the fourth generation A3, and represents the latest stage in the evolution of this successful technology, which in Audi models with transverse engine installations is based around an electro-hydraulic multi‑plate clutch.
Managed by precisely tuned software, the system not only maximises stability, grip, and driving pleasure, but is also extremely efficient. Supported by the adaptive suspension and the progressive steering, it delivers composed, surefooted and incisive driving characteristics that impress over tight winding roads and varied mountain and valley stretches in particular.
The clutch is located at the end of the prop shaft, in front of the rear axle differential – a position that benefits the axle load distribution in particular. Inside is a package of plates that operate in an oil bath. Its metal friction rings are arranged behind one another in pairs – one ring of each pair is rigidly meshed with the clutch housing, which rotates with the prop shaft; the other ring is meshed with the short output shaft to the rear axle differential.
Audi tailored the electronic torque distribution control specifically to suit the new A3 and integrated it in the Audi drive select dynamic handling system. It takes the data of the suspension sensors into account and detects not only the driving conditions and road properties but also the driving style. The control unit uses this data as a basis to calculate a torque distribution that provides optimum efficiency and passes the value on to the clutch. This is particularly efficient.
The all-wheel drive distributes the torque with full variability between the front and rear axles. During normal driving operation, the majority of the engine’s power is transmitted to the front wheels. When driving off or when the front axle has little traction, the clutch diverts the torque at lightning speed: In this case, an electric axial-piston pump is activated, which applies up to 44 bar of hydraulic pressure to the clutch plates. The more the clutch plates are pressed together by this pump, the more drive torque is transmitted to the rear axle – the maximum is 100 percent. The clutch can already transmit part of the torque to the rear axle when the driver begins to make quicker turns of the steering wheel during more challenging driving. As soon as the driver accelerates, the torque presses the A3 into the corner. During load changes, the distribution of torque allows precise turning into the bend, which further increases driving dynamics.
