One of the outstanding innovations in the history of the car manufacturer Audi and a cornerstone of the brand identity is the all-wheel drive known as Quattro.
The technology that was once exotic in car construction has reached the ripe age of 40 this year and can look back on a correspondingly long history of success. In the past few decades, the southern German car manufacturer produced almost 11 million cars with all-wheel drive technology. The Quattro drive has been continuously developed and differentiated since it was launched in 1980.
This is probably one of the reasons why cars with Quattro lettering remain in demand. In the first nine months of the current year alone, almost 500,000 Audis with the technology title were built. Even in the electric future, Quattro will remain an integral part of the brand essence.
In the beginning there was the polecat
The Quattro story began with winter driving tests in Scandinavia at the end of 1976. A contract development for VW, the Iltis military off-road vehicle, proved to be superior to future Audi models in terms of driving dynamics on snow and ice.
“The idea for the Quattro also came from the fact that a VW Iltis with all-wheel drive had clear traction advantages during the winter test drives and drove the large-motorized vehicles around the ears,” says Dieter Weidemann, Head of Development All-Wheel Systems at Audi. Those responsible at the time were convinced of the idea of being able to transfer this all-wheel drive technology to a road vehicle. The most promising appeared to be the combination with a powerful turbo engine, which ultimately led to the series production of the Quattro sports coupé with 147 kW / 200 PS and all-wheel drive technology presented in 1980.
The original Quattro, which was actually planned in small series and then built over 11,000 times by 1991, impressed both with its sheer performance and the exotic combination of all-wheel drive at the time, which was actually reserved for off-road vehicles and commercial vehicles.
First Quattro revolution in the mid-1980s
The drive of the original Quattro was, however, still closely related to that of the Iltis. Initially, a system with a rear and middle differential lock, which was problematic in some points for car use and which could be switched from one another manually and mechanically, was used.
In the mid-1980s, says Weidemann, alternative technologies were then developed with self-locking Torsen differentials, which, thanks to a clever internal gearing, made it possible to transfer drive forces continuously as required to the axle with the higher traction and to relieve the load on the axle with less traction . In the Audi V8 from 1988, it was also possible for the first time to combine a four-speed automatic transmission with the Torsen all-wheel drive.
From 2005 the Torsen C followed with a rear-heavy 40:60 basic distribution. There was already a strong emphasis on driving dynamics. The current generation of Torsen CSM not only allows high traction and driving dynamics, but thanks to its compact design and the use of special materials it can save significantly in weight and installation space compared to previous versions.
With all the hardness over the Nordschleife
On the way to the Torsen CSM, northern Scandinavia in particular remained an important playground for the Audi engineers, where all-wheel drive technology was further practically tested and refined.
Developers like Dieter Weidemann and his colleague William Wijts have repeatedly compared vehicles with series production against development vehicles with modified technology in practical tests. It was tested and tuned until the new variant drove better than the production version.
This iterative development process also includes visits to the Nürburgring Nordschleife, as this track offers very different conditions with high centrifugal forces, high lateral acceleration and high temperatures in a very short time. This shows whether the system can handle it and whether the oiling is working. Another important component in the development is the strength test of the systems on a test site near Ingolstadt in order to test performance and durability under extreme loads. All-wheel drive technology is exposed to the highest loads, the highest torques and the most abrupt changes in the coefficient of friction.
Quattro is not always Quattro
Today Audi offers a range of all-wheel drive systems, all of which bear the name Quattro, but which set different technical accents. Models with longitudinally installed front engines are available with the classic Quattro as permanent all-wheel drive, in which a self-locking, purely mechanical center differential with a power distribution of 40 to 60 percent front / rear ensures a slightly rear-biased, sporty driving behavior.
The power distribution is variable to a certain extent, because the system can direct up to 70 percent of the power to the front axle and up to 85 percent to the rear axle. In the case of particularly sporty models, a sport differential is also used on the rear axle, which also allows the torque to be distributed on a wheel-by-wheel basis.
The focus is on efficiency
In 2016, Audi introduced the Quattro system with ultra technology, trimmed for efficiency, which can switch between all-wheel drive and pure front-wheel drive with the help of clutches, depending on the situation. If the power is not required on the rear axle, a multi-plate clutch located directly at the end of the transmission decouples the cardan shaft.
A separating clutch integrated in the rear axle differential can also shut down the rear part of the drive train. Should the sensors determine the need for power on the rear wheels, this will be made available again immediately. With normal driving style, the all-wheel drive shares remain low due to the decoupling of the rear drive train and thus the additional consumption. According to Weidemann, this is just 0.2 liters compared to normal front-wheel drive.
Haldex coupling for the Audi R8
Audi also calls the all-wheel drive systems with Haldex clutch Quattro. This solution, which is also used in many other vehicles of the VW Group, for vehicles with transversely installed engines, relies on a hydraulic multi-plate clutch for the highly variable distribution of the drive torque. Incidentally, a multi-plate clutch has also been used in the R8 mid-engine sports car since 2007, although it variably distributes torque from the rear axle to the front axle.
The next chapter
Last year, Audi ignited the latest Quattro stage, which is used in the all-electric E-Tron models. The mechanical transmission components of the aforementioned systems are not used here.
Instead, the software management of the drive motors on the front and rear axles alone ensures intelligent and performance-enhancing, fully variable torque distribution. While only the rear axle is driven during normal driving, the motor on the front axle can be activated if necessary. In addition, in the sporty E-Tron S models, two drive units mounted on the rear axle act as a sport differential. They act on one rear wheel each with the necessary force. Audi calls the result Quattro 2.0. (Text: mh / sp-x, tv | Pictures: Thomas Vogelhuber | Manufacturer)