It was 30 years ago today that Audi launched the Quattro. Dr Ferdinand Piëch, Development Director of the original Quattro, presented the car at the Geneva Motor Show on 3 March 1980. In his speech he stated, “This is the dawning of all-wheel drive in roadgoing passenger cars.”
Power for the Quattro came from a super sweet inline five cylinder engine that had a character all of its own. By today’s standards the 200bhp headline figure is quite modest. But, three decades ago, having a coupé derived from a family sedan that could accelerate to 100km/h in 7.1 seconds was big news.
So, too, was the addition of all-wheel drive to the world rallying scene where the Quattro left an everlasting legacy by winning the World Rally Championship in 1983 and 1984.
Memories of the Quattro have been revived with the recent launch of the TT RS, featuring a 2.5-litre inline five cylinder that sounds sublime.
For more on the original Quattro check out the AUSmotive past master feature. As well, you can read Audi’s extensive press release below which covers the both the history and future of its quattro technology.
Always a born winner – 30 years Audi quattro
quattro technology from Audi has an anniversary to celebrate: The spotlights homed in on the first Audi quattro at the Geneva Motor Show on March 3, 1980. Its appearance signaled the start of a winning streak in motor sport and on ordinary roads that still continues today. Now, 30 years on, Audi is taking the wraps off the next generation of its successful technology.
The technology of quattro
How much performance can front-wheel drive develop? That was the question in winter 1976/77 during the test drives that Audi developers were conducting in Sweden. The camouflaged prototypes with their 170 hp five-cylinder engines put in a worthy performance. But they were left standing when pitted against a high-wheeled vehicle with 75 hp engine that was equipped with driver-engaged all-wheel drive – the Iltis military off-road vehicle that Audi was developing as the successor to the Munga.
Cars which distribute their propulsive power between all four wheels can generate a higher cornering force at each wheel than rear-wheel-drive or front-wheel-drive vehicles. Their traction and cornering behavior are superior. A sporty Audi car with permanent all-wheel drive and plenty of engine power – that would be the perfect solution, thought the engineers.
The project got off the ground in the early part of 1977 as “Development Order 262”. It was masterminded by three young engineers: Technical Director Dr. Ferdinand Piëch, Project Manager Walter Treser and Jörg Bensinger, Head of the Chassis Testing. The prototype bore the internal codename A1 – it was a modified first-generation Audi 80 with a slightly elongated wheelbase and the five-cylinder turbo engine of that would be fitted in the future Audi 200. The rear suspension comprised a second McPherson front suspension layout, rotated through 180 degrees.
In trials in deep snow on the Turracher Höhe in Styria, Austria, in January 1978 the test vehicle with the license number IN – NC 92 was able to demonstrate just how good its traction was. The definitive go-ahead was given by Volkswagen Board of Management Chairman Toni Schmücker in May 1978. One of the project engineers knew of a steeply sloping field in Stammham, near Ingolstadt. The local fire department was called in to saturate it from top to bottom. Schmücker climbed into the A1, and drove effortlessly all the way up the slope.
Meanwhile the wife of Volkswagen Development Director Ernst Fiala had been driving the A1 around in city traffic in Vienna, but complained that it felt tense on tight bends: “The car hops,” is how she put it. On bends, the front wheels describe a slightly larger arc than the rear wheels, so they need to be able to rotate faster. That was not possible on the prototype because its axles were rigidly connected. Audi’s developers focused on two priority objectives: The all-wheel drive was to be permanent, and it had to function without a separate transfer case and second propshaft at the front.
The hollow shaft – a stroke of genius by Audi
Franz Tengler, Head of Department in Transmission Design, had an idea that was as simple as it was practical: a 263 millimeter (10.35 in) long, hollow-drilled secondary shaft in the transmission, through which the power flowed in two directions. From its rear end, the shaft drove the cage of the manually lockable center differential. The differential transmitted 50 percent of the power via the propshaft to the rear axle, which in turn had its own differential lock. The other half of the drive torque was transferred to the front axle’s differential along an output shaft rotating inside the hollow secondary shaft.
The hollow shaft permitted all-wheel drive that was virtually tension-free, light, compact and efficient. The vital breakthrough was that the elegant quattro principle was no longer merely suitable for slow all-terrain vehicles and trucks, but also very specifically for sporty, fast passenger cars, and furthermore for volume-produced models.
All that remained was to decide on a name for the new car. One suggestion under consideration was “Carat”, an acronym of the German for “Coupé All-Wheel Drive Turbo”. Project Manager Treser came up with a better idea – and the quattro was born.
The first Audi quattro
“We wanted to symbolize a car that stands firmly on the ground. It was meant to put the emphasis on what it was capable of doing, not on what it looked like. That formal concept was a success because it was good, correct and honest,“ remarked former Design Chief Hartmut Warkuß about the first quattro.
Derived from the Audi 80 Coupé but clad in a body with angular edges, on March 3, 1980 the white-painted two-door car stood on an elevated turntable, adorned with a flower arrangement, in the middle of an indoor skating rink close to the Geneva showground. The five-seater had a compact wheelbase of 2,524 millimeters (99.37 in) and measured 4,404 millimeters (173.39 in) in length. Development Director Dr. Ferdinand Piëch was intensely aware of what an auspicious occasion this was. His speech concluded with the declaration: “This is the dawning of all-wheel drive in roadgoing passenger cars.”
147 kW (200 hp) and 295 Nm (217.58 lb-ft) – the Audi quattro driving machine
The Audi quattro was an uncompromising driving machine. It was powered by a five-cylinder turbo engine with a sonorous roar, installed longitudinally up front in typical Audi style. The two-valve power unit had a displacement of 2,144 cm3, and its boost pressure of 0.85 bar and charge-air intercooling helped it deliver 147 kW (200 hp) and 285 Nm (210.21 lb-ft) of torque. The quattro, weighing just under 1.3 tons (2,866 lb), sprinted from 0 to 100 km/h (62.14 mph) in 7.1 seconds and on to a top speed of around 220 km/h (136.70 mph). Its starting price of 49,900 marks, at that time a tidy sum, included forged 6 J x 15 wheels with 225/50 tires as standard, along with sports seats and front fog lamps.
Production started at the end of 1980 – in the special-work production hall N2 at Ingolstadt, where it was built predominantly by hand. Audi had initially planned to build only a very small run of 400 to enable the competition car to obtain homologation for the World Rally Championship. But the revolutionary drive concept and its extremely dynamic performance captivated the public from the very first day on, and the brand had difficulty keeping up with demand. When production of this car line finally ceased in May 1991, 11,452 units had been built.
Over this period of eleven years, Audi made various attentive refinements to the quattro. The interior gradually became more comfortable, without diluting its strictly functional character. The driving area was given digital displays in the style of the time, and for a while featured an acoustic function for warnings; Patricia Lipp, Bavarian Radio’s traffic news announcer, supplied the voice. The chassis, too – control arms, McPherson struts and disk brakes on all wheels – was gradually refined, eventually acquiring an anti-lock brake system.
The Sport quattro with shorter overall length and wheelbase appeared in 1984, as the homologation model of the new rally car. Its newly developed four-valve turbo engine with the aluminum engine block achieved an output of 225 kW (306 hp), with Kevlar and other lightweight materials cutting the body’s overall weight. The price tag of the “short version”, as the Sport quattro was known in public, meant that it was reserved for an exclusive clientele: 203,850 marks. Audi built 224 of this supercar. Four-valve technology was adopted in regular production in 1989, in a rather more toned-down version developing 220 hp.
The most important change arrived in the late summer of 1987. As well as an engine with marginally increased displacement that developed 200 hp, as before, the model now feature the Torsen differential; the worm gear replaced the manual differential lock. The name Torsen was a contraction of the two words torque and sensing.
The transmission distributed the propulsive power continuously, as required, diverting up to 75 percent of the torque to whichever pair of wheels achieved better grip. Thanks to the Torsen differential, which only locks up under load, the anti-lock brake system remained permanently available.
quattros in motor sport
The idea of the rally car was as long-established at Audi as the concept of the production quattro, and began to take shape as early as 1977. The Ingolstadt manufacturer made its first steps towards World Rally Championship glory with a front-wheel-drive Audi 80; by a feat of diplomacy it persuaded the competition’s governing body to accept all-wheel drive. The first quattro competition cars were tried out as prototypes in 1980. In the same year, the VW Iltis developed and entered by Audi won the Paris-Dakar Rally, with four driven wheels.
In the first few days of 1981 Audi descended like a whirlwind on the World Rally Championship scene, which in those days was still rather modest in proportions. The quattro, at that time with a 310 hp engine, made its debut in the Austrian Jänner Rally, which did not count towards the World Championship. Local hero Franz Wittmann won at the first attempt, with a lead of more than 20 minutes over the runner-up.
At its World Championship debut in the Monte Carlo Rally, the quattro again demonstrated its superiority. On snow – ideal conditions for this car – Hannu Mikkola won the first six special stages and was only halted by an accident. Then, in the Swedish Rally, the Finn clinched the first win. The French driver Michèle Mouton became the first woman to win a World Championship heat in San Remo, and Mikkola emerged victorious again in the RAC Rally. At the end of the Audi model’s first year in action, it was placed third in the drivers’ standings.
By as early as 1982, the quattro was virtually unbeatable anywhere in the world; Audi redefined the benchmark with seven victories and captured the Manufacturers’ Trophy. Mouton won in Portugal, Greece and Brazil; only a breakdown in the penultimate heat in Côte d’Ivoire cost her the drivers’ title. However, Hannu Mikkola set the record straight in 1983 after winning in Finland, Sweden, Argentina and Portugal.
Triple win at “Monte” – the start to the 1984 season
The next year, too, began with a win. The newly recruited two-times World Champion Walter Röhrl won the Monte Carlo Rally ahead of his team colleagues Stig Blomqvist (Sweden) and Hannu Mikkola. At the finish, co-pilot Christian Geistdörfer congratulated his colleague with the remark: “Do you realize you’ve never driven so fast in your life?” At the end of the season Audi again dominated the manufacturers’ standings with seven wins, five of them by Blomqvist, who edged out Mikkola to become World Champion.
But 1984 was also the year in which rally competition entered a new orbit. The competitors exploited the very liberal regulations at that time in Group B to enter mid-engine cars that were purely functional pieces of machinery with very little resemblance to production models. The Ingolstadt team, too, considered switching to such a concept and a prototype was created. In the end, however, the project was abandoned – the longitudinally installed front engine was retained.
Audi’s new weapon was the Sport quattro with a wheelbase of just 2,224 millimeters (87.56 in) – an attempt to make the car lighter and more maneuverable by shortening it drastically by 300 millimeters (11.81 in). The “short version” was used from May in parallel with the old version, but took time to build up some momentum. Blomqvist had to wait until the penultimate heat in Côte d’Ivoire for the first win. Audi needed to turn up the heat.
July 1, 1985 was the date of the homologation of the final stage in its evolution, the S1. This model went down as a true colossus in the history of rally competition because of its extreme character. The aluminum five-cylinder engine officially developed 350 kW (476 hp) and 480 Nm (354.03) of torque; with a charge-air circulation system that kept the turbo engine constantly supplied, the real figure was probably in excess of 370 kW (over 500 hp), at around 8,000 rpm.
In the middle ratio the 1,090 kilogram (2,403.04 lb) S1 shot from 0 to 100 km/h (62.14 mph) in 3.1 seconds, and to 200 km/h (124.27 mph) in 11.8 seconds. When the driver stepped off the accelerator, the exhaust spat out meter-long searing tongues of fire. “It’s like riding on a bullet,” declared Walter Röhrl, “like an explosion. Everything happens so unbelievably fast you haven’t even got time to think.”
The first dual-clutch transmission – hi-tech in the S1
There were various differential locks to choose from for the quattro driveline – multi-plate, Torsen and conventional. In the last race of the season, the British RAC Rally, Walter Röhrl used a dual-clutch transmission that was actuated pneumatically by a long lever – a precursor of today’s S tronic.
The chassis comprised a tubular space frame paneled with sheet steel and plastic; to optimize the weight distribution the radiator, fan, battery and alternator were at the rear. Giant vanes scooped air onto the car on fast stretches, and the brakes could be cooled with splash water.
Afterwards, Walter Röhrl described it as follows: “Forcing the quattro with its heavy engine up front into a bend was like wielding a mallet. On the other hand there was that indescribable traction, and I simply couldn’t shake off its fascination. All-wheel driving – that’s the ultimate experience for me.”
But the halcyon days of Group B were already numbered; the technically and organizationally draining race for supremacy had changed the world of rally driving for good. On narrow roads skirting along yawning precipices, across slick ice, rough gravel and oily asphalt, the familiar physical parameters began to develop cracks; hitherto familiar bends became tight and treacherous. And fans in Southern Europe, whipped up into a hysterical euphoria, made things even more dangerous. Like matadors facing a bull, they would stand alongside or on the track and wait until the very last moment to leap aside.
The final blow to Group B came in early 1986 when three spectators and two participants were killed in accidents in World Championship races in Portugal and Corsica. Audi, which in any case had substantially scaled back its involvement, pulled out of the series. The new mid-engine car developed for the scheduled Group S never entered the fray; the world federation FISA decided to switch to the close-to-production Group A regulations. Audi still participated in a few rallies in 1987 and Mikkola won the Safari ahead of Röhrl in a family sedan, the Audi 200.
The S1 nevertheless still enjoyed a final feat when its 440 kW (approx. 600 hp) helped Walter Röhrl to storm up the 156 bends of Pikes Peak in Colorado, the United States, to an altitude of 4,301 meters (14,110 ft) in 1987. He managed to get his racing car, fitted with a giant wing to increase downforce, into sixth gear on four occasions along the 19.99 kilometer (12.42 mile) sand and gravel track, and at his fastest was clocked at 196 km/h (121.79 mph).
On the back of wins by Michèle Mouton and Bobby Unser, this made it three wins in a row for Audi in America’s most famous hill climb, the “Race to the Clouds”. Röhrl’s time of 10:47.85 min lopped more than 21 seconds off Unser’s track record from the previous year.
Traction on asphalt – the switch to touring car competition
The triumphs on Pikes Peak whetted Audi’s appetite for more – it entered the American TransAm series for one year in 1988. The hood of the Audi 200 quattro concealed the five-cylinder turbo power unit from the World Rally Championship; its 375 kW (510 hp) propelled the American driver Hurley Haywood to the Championship title. With eight wins out of 13 races, Audi also captured the manufacturers’ trophy.
The next year, the works team switched to the IMSA GTO Series, with its even more liberal regulations. Outwardly, the GTO resembled the Audi 90 quattro but the outer skin was only a gesture of a plastic silhouette. Beneath it lurked an uncompromising driving machine, based on a floor pan made from carbon fiber composite material and a tubular space frame.
In its final evolutionary stage the five-cylinder engine, with 2.65 bar boost pressure and the thrust circulation system from the S1, developed around 530 kW (approx. 720 hp), and the four driven wheels were 36 centimeters (14.17 in) wide. Hans Joachim Stuck finished third in the championship with seven wins in 15 races, and the team managed second place in the manufacturers’ trophy.
In 1990 Audi switched to the German Touring Car Masters (DTM) with the brand’s top model, the V8 quattro. The luxury sedan’s 3.6-liter naturally aspirated engine achieved an output of 340 kW (462 hp). That, in conjunction with all-wheel drive, was sufficient to fend off the model’s lesser-powered but lighter challengers, despite its weight of 1,290 kilograms (2,843.96 lb).
Stuck won the championship in the first year, and in 1991 the young Frank Biela emulated his achievement in a heart-stopping final race at Hockenheimring. Following a dispute about the legality of the new crankshaft, the team withdrew the V8 quattro 1992 part way through the season. Audi had won half of all the 36 races staged in 1990 and 1991.
The brand enjoyed its most successful year ever in touring car competition in 1996. The A4 quattro Supertouring, with its 218 kW (296 hp) two-liter, four-cylinder engine, was an ultramodern racing car. The driver’s seat was positioned well back, the six-speed transmission had sequential shifting and the aerodynamics had been developed in elaborate wind tunnel tests.
The A4 quattro Supertouring entered seven national championships on three continents – in Germany, Great Britain, Italy, Spain, Belgium, South Africa and Australia. It won every single one of them. In the intensely competitive German STC Series, with a field of eight brands, Emanuele Pirro emerged on top, as did Frank Biela in Great Britain. Two years later, the European governing body largely banished all-wheel drive from touring car competition. It was simply too hard to beat.
quattros in production
It was not long before the first quattro from 1980 acquired siblings. From 1982, Audi launched five more all-wheel-drive versions – the Audi Coupé, the Audi 80/90 and the Audi 100/200, which set a new aerodynamics world record in the 1980s. The new versions reflected the fundamental principle of offering a quattro version in each car line, and were exceptionally popular with customers thanks to the good publicity generated by the motor sport triumphs.
The V8 model, initially with an output of 185 kW (250 hp) and subsequently rising to 206 kW (280 hp), appeared at the top of the range. The sedan was available exclusively with permanent all-wheel drive; customers likewise almost always ordered the quattro versions of its successor, the A8. For many years the top models in the luxury-class car line were simultaneously the most powerful production quattros built by Audi. At the start of 2009 the R8 5.2 FSI quattro high-performance sports car stepped into that role; it has a purpose-designed quattro driveline that directs the engine’s power in the first instance to the rear wheels.
In 1995 Audi also started to equip its high-torque TDI models with quattro drive – a really effective combination. The first such model was the A6 2.5 TDI quattro; its V6 developed 103 kW (140 hp). The current model range is very extensive. The basis comprises the A3 and A4 car lines – in which quattro drive is available right from the 1.8 TFSI and 2.0 TDI upwards. It culminates in the Q7 V12 TDI quattro – the most powerful diesel SUV in the world, with a mammoth output of 368 kW (500 hp) from a displacement of six liters.
The compact Audi models – the A3 and TT car lines – have likewise been available with permanent all-wheel drive since 1999. Their transverse engines mean that instead of the center differential, they have an electronic control system with a hydraulically actuated multi-plate clutch acting as an interaxle differential lock. Audi has successively refined this concept over the years – an extremely high-performance pressure accumulator now ensures that the power is redistributed in an instant if need be.
The active sport differential made its debut in the Audi S4 in 2008 and has since been used in other models. With the active sport differential, Audi elevates the driving dynamics and traction of the quattro permanent all-wheel drive system to a level unequaled by any competitor. The vehicle’s handling is sportily neutral when cornering at high speeds. It responds more directly to the steering, and the vehicle is also stabilized during load reversals. In addition to delivering significantly more driving fun, higher lateral acceleration is possible on bends. Considerably less steering effort is required of the driver.
Sporty and elegant – the Audi S models
From 1990 the S models helped to raise the dynamic image that the brand had acquired through its involvement in motor sport. A pioneering role was played by the S2 Coupé, the successor to the first quattro. Its elegant character was solid proof of how sportiness and refined style work together in perfect harmony. The new family grew rapidly, culminating in the appearance of the S8 in 2006. From the very start, quattro drive was an integral aspect of all S models. Audi currently has the S3, S4, S5, S6 and TTS car lines on sale.
The brand’s first RS model, the 1994 Audi RS 2 Avant, was also enthusiastically received by fans, with its abundant everyday suitability and a potent five-cylinder turbo engine. The RS 4 Avant from 2000 was powered by a V6 biturbo; the RS 6 (2002) was driven by a supercharged 4.2-liter V8. This was followed in 2005 by a new RS 4 that was propelled by a high-revving eight-cylinder naturally aspirated engine. In it, Audi unveiled a new evolutionary version of quattro drive – a center differential that distributed the engine’s power 40:60 between the front and rear wheels.
Today quattro GmbH, the AUDI AG subsidiary, builds exclusive series of five RS models. These are the RS 6 and RS 6 Avant with their biturbo-powered V10 power units (426 kW/580 hp), the TT RS and the TT RS Roadster with their supercharged five-cylinder engines (250 kW/340 hp) and the brand new RS 5 with its V8 naturally aspirated engine developing 331 kW (450 hp). Its quattro driveline now features yet another new technology – the so-called crown gear differential that increases traction yet further and produces outstanding handling characteristics.
In the 30 years between 1980 and the end of 2009, Audi has built 3,296,917 cars with permanent all-wheel drive. In recent years, across all car lines quattro versions have consistently accounted for more than one-quarter of the total; in 2009 the figure was 34.0 percent. The A4 and A6 are the most successful Audi car lines in terms of sheer units; the same applies to their quattro versions. Including its predecessor car lines, 1,132,186 of the A4 had been supplied with permanent all-wheel drive by the end of 2009; the total for the A6 is 1,109,155.
Worldwide, Audi is the leading premium-segment manufacturer of passenger cars with permanent all-wheel drive. The current model range includes 126 quattro versions. The Q5, Q7, R8, A4 allroad quattro, A6 allroad quattro and all S and RS models are supplied exclusively with all-wheel drive.
Tire tracks in the snow being contemplated reverently by an aged Eskimo, who then turns to his grandson and says: “Audi – quattro.” The snow-covered ski jump that the Audi 100 CS quattro drives up without any external assistance – over quattro’s 30-year history Audi has made a whole range of TV commercials that highlight the mystique of quattro and the emotions it arouses. Some of these films have become true classics.
The idea of the ski jump commercial took shape in 1986. In tests on a Tyrolean glacier an Audi 100 quattro conquered a 39 degree uphill gradient – so the ski jump in the Finnish resort of Kaipola, 300 kilometers (186.41 miles) north of Helsinki, was slightly gentler at 37.5 degrees, though still more than 80 percent. A crane hoisted the car onto the outrun, where it was secured in three different ways – by a concealed steel cable, by a braking device beneath the front end, and by a retaining net on the outrun.
Professional rally driver Harald Demuth, who had previously driven the quattro in competitive racing, only needed this braking device to halt at the top. He effortlessly drove the Audi 100 CS quattro under its own power up the 78-meter (255.91 ft) jump – virtually blind, because his car’s nose was pointing steeply up into the sky.
The commercial came to be regarded as one of the all-time best moments in Audi advertising, and is still talked about today; Audi shot a remake in early 2005 with an A6 4.2 quattro, for which a construction team specially renovated the Kaipola jump that had last been used in 1994. Typically for the brand, the overall strategy in the advertisement was and is focused unequivocally on the products. And there is simply no doubting their credibility, because thanks to their motor sport successes the quattros have had a bigger impact on the Audi brand than any advertising campaigns costing millions could have achieved.
The quattro versions are outwardly almost indistinguishable from their front-wheel-drive counterparts. They are no mere peripheral members of the model range, they are the driving force behind this highly advanced technical brand and an integral part of it. The term quattro means more than traction – it represents emotion, driving safety and sportiness, it stands for engineering expertise and a dynamic spirit.
Success story – quattro GmbH
In its sheer exclusivity, this special Audi lifestyle is also the hallmark of the product range of quattro GmbH, which was established in Neckarsulm in 1983. The Audi subsidiary has operated as a vehicle manufacturer since 1996. quattro GmbH currently has over 700 employees and runs its own development and production operations, e.g. for the R8 high-performance sports car and the Q7 V12 TDI performance SUV.
Fascination – quattro show cars
Another instrument that Audi uses to nurture the fascination of quattro is spectacular design studies. In fall 1991, the brand unveiled two sports cars with mid-engine and permanent all-wheel drive in rapid succession at the Frankfurt and Tokyo Motor Shows – the quattro Spyder and the Avus quattro. The large show car in particular, with its outer skin of polished sheet aluminum and W12 engine, is still vividly remembered. In 200 there followed another dramatic study – the “Rosemeyer” was a tribute to the Grand Prix racing cars built by Auto Union in the 1930s.
The show cars that stole the limelight in 1995 were rather closer to the reality of everyday driving: The TT quattro, in Coupé and Roadster versions, was not far removed from the production version. In 2001 the all-wheel-drive concept cars Pikes Peak, Nuvolari and Le Mans quattro served to pave the way for the later Q7, A5 and R8.
In recent years the primary purpose of Audi show cars has been to showcase new directions in driveline technology. The e-tron, one of the stars of the Frankfurt Motor Show in 2009, is a fast sports car with purely electric drive. Its output of 230 kW (313 hp) is used to drive all four wheels – in typical Audi fashion. 30 years after going into production, the quattro idea is more dynamic and emotional than ever.
The next step: quattro drive with crown gear center differential
Over the 30 years since the debut of the first quattro, Audi has gradually increased its technology lead in the sphere of all-wheel drive. Not that the Ingolstadt engineers are content to rest on their laurels. At the Geneva Motor Show, the company is now presenting a new evolutionary stage – quattro drive with crown gear center differential and torque vectoring. This technology, which is even more efficient, precise and high-performance than the previous concept, is making its debut in the new Audi RS 5 high-performance coupé.
The self-locking center differential in the quattro driveline, positioned immediately at the transmission output, has the task of distributing the engine torque between the two axles in defined proportions. If one wheel of an axle starts to slip – for instance on a slippery surface – the differential without delay diverts most of the propulsive power to the axle achieving better traction.
The new center differential from Audi follows an innovative principle. Its cylindrical housing is driven by the transmission. Inside it there are two rotating crown gears that owe their name to the crown-like design of their teeth. This new gearing is called Evolvere. The rear crown gear drives the propshaft to the rear axle, and the front one an angular-running beveloid shaft that runs to the front axle’s differential.
The crown gears are driven by four straight-cut compensating gears arranged at angles of 90 degrees to each other. They are pivot-mounted on the axles that are fixed to the housing. This allows the equalization of speeds between the front and rear axles that is needed when cornering, for instance.
40:60 – the basic torque split between front and rear
When the front and rear axles are rotating at exactly the same speed, the two crown gears run at the same speed as the differential housing. But because of the special design of the teeth, they have different numbers of teeth and meshing points at different diameters. The lever effects are therefore unequal. With the basic torque split, 60 percent of the engine torque flows to the differential for the rear axle and 40 percent to the front. This permits very good traction and driving dynamics.
When drive torques are introduced via the gearing of the compensating gears, axial forces occur inside the differential. These force both crown gears outwards. This axial force is used to compress plate packages located behind the crown gears. The resulting locking torque redistributes the torques between the crown gears.
For example if the RS 5’s front wheels encounter a patch of snow, the speed of the front axle will momentarily rise. This produces a speed difference between the two crown gears and the housing. The self-locking effect in the crown gear center differential now immediately diverts the drive torque to whichever axle achieves better traction. Up to 85 percent of the drive torque reaches the rear wheels. In the opposite scenario – if the RS 5’s rear axle achieves less grip – the same happens in reverse; now up to 70 percent of the torque is diverted to the front axle.
With this broad torque distribution range the newly developed crown gear center differential surpasses its predecessors – traction becomes even better thanks to increased locking effect. Forces and torques are redistributed permanently without any time lag, and absolutely consistently. The driver can easily handle the situation. No control electronics or electromagnetic or hydraulic actuation are needed. The purely mechanical operating principle guarantees maximum efficiency and no-delay response.
Other strong points of the crown gear center differential are its compactness and low weight – at 4.8 kilograms (10.58 lb) it is up to 2.1 kilograms (4.63 lb) lighter. After making its debut in the RS 5, it will then become available in other models. This Vorsprung durch Technik impressively demonstrates the constant progress being made by quattro drive technology. It also increases Audi’s lead over its competitors.
For dynamic cornering – torque vectoring
Audi combines the crown gear center differential in the RS 5 – and in other models in which it will subsequently feature – with an intelligent software solution, torque vectoring. An evolutionary form of the ESP with electronic differential lock that is already fitted as standard in many front-wheel-drive models, it acts on all four wheels. The new system makes cornering even more precise and dynamic.
Using the driver’s steering input and desired level of acceleration, the control unit calculates the optimal distribution of propulsive power between all four wheels for each specific situation. If need be it marginally brakes the wheels on the inside of the bend – just slight application of the pads on the disks at minimal pressure is all that it takes.
This assistance is provided continuously and directly for high-speed cornering. The neutral handling range becomes noticeably broader and understeering when turning and accelerating is reduced. ESP action can take place later and becomes softer.
The new crown gear center differential with is constant, always precisely defined operating method permits responsive, precise torque vectoring action.
For greater lateral dynamics and more driving fun, the quattro driveline can be further enhanced with the sport differential that actively distributes power between the individual rear wheels. When the sport differential is active, torque vectoring applies only to the front axle.