Quattro - AbsoluteAstronomy.com

Quattro

Encyclopedia

quattro is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

) is the name used by Audi AG

Audi

Audi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....

to indicate that four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

(4WD) technologies or systems are used on specific models of the Audi automobile

Automobile

An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

s.

The word "quattro" is a registered trademark

Trademark

A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...

of Audi AG, a subsidiary of the German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

automotive

Automotive industry

The automotive industry designs, develops, manufactures, markets, and sells motor vehicles, and is one of the world's most important economic sectors by revenue....

concern

Concern (business)

A concern is a German type of business group. It results from the merger of several legally independent companies an economic entity under unified management. These associated companies called "Group" companies....

, Volkswagen Group

Volkswagen Group

Volkswagen Group is a German multinational automobile manufacturing group. , Volkswagen was ranked as the world’s third largest motor vehicle manufacturer and Europe's largest....

.

Quattro was first introduced in 1980 on the permanent four wheel drive Audi Quattro

Audi Quattro

The Audi Quattro is a road and rally car, produced by the German automobile manufacturer Audi, now part of the Volkswagen Group. It was first shown at the 1980 Geneva Motor Show on 3 March.The word quattro is derived from the Italian word for "four"...

(often referred to as the Ur-Quattro - "Ur-" being German for "ancient" or "great" as in "great-grandfather"). The term quattro has since been applied to all subsequent Audi 4WD models. Due to the nomenclature

Nomenclature

Nomenclature is a term that applies to either a list of names or terms, or to the system of principles, procedures and terms related to naming - which is the assigning of a word or phrase to a particular object or property...

rights derived from the trademark, the word quattro is now always spelled with a lower case "q", in honour of its former namesake.

Other companies in the Volkswagen Group have used different trademarks for their 4WD vehicles. While Audi has always used the term "quattro", Volkswagen

Volkswagen

Volkswagen is a German automobile manufacturer and is the original and biggest-selling marque of the Volkswagen Group, which now also owns the Audi, Bentley, Bugatti, Lamborghini, SEAT, and Škoda marques and the truck manufacturer Scania.Volkswagen means "people's car" in German, where it is...

-branded cars initially used "syncro", but more recently, VW uses "4motion
4motion
4motion is a registered trademark of Volkswagen AG, used exclusively on Volkswagen-branded automobiles which utilise four-wheel drive systems. Volkswagen has previously used the term "Syncro" for its 4WD models....

". Škoda

Škoda Auto

Škoda Auto , more commonly known as Škoda, is an automobile manufacturer based in the Czech Republic. Škoda became a wholly owned subsidiary of the Volkswagen Group in 2000, positioned as the entry brand to the group...

simply uses the nomenclature "4x4" after the model name, whereas SEAT

SEAT

SEAT, S.A. is a Spanish automobile manufacturer founded on May 9, 1950 by the Instituto Nacional de Industria , a state-owned industrial holding company....

uses merely "4". None of the above trademarks or nomenclatures defines the operation or type of 4WD system, as detailed below.

Longitudinal systems

Volkswagen Group

Volkswagen Group is a German multinational automobile manufacturing group. , Volkswagen was ranked as the world’s third largest motor vehicle manufacturer and Europe's largest....

has been developing four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

(4WD) systems almost since its inception during the Second World War

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. The Volkswagen Kübelwagen

Volkswagen Kübelwagen

The Volkswagen Kübelwagen was a military vehicle designed by Ferdinand Porsche and built by Volkswagen during World War II for use by the German military...

, Volkswagen Schwimmwagen

Volkswagen Schwimmwagen

The VW Type 128 and 166 Schwimmwagen were amphibious four-wheel drive off-roaders, used extensively by the German Wehrmacht and the Waffen-SS during the Second World War...

and Volkswagen Kommandeurwagen were all military vehicles which required all four road wheel

Wheel

A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

s to be "driven", the latter being a 4WD Volkswagen Beetle

Volkswagen Beetle

The Volkswagen Type 1, widely known as the Volkswagen Beetle or Volkswagen Bug, is an economy car produced by the German auto maker Volkswagen from 1938 until 2003...

. Their military, and four wheel drive experiences later aided them in designing the Volkswagen Iltis

Volkswagen Iltis

The Volkswagen Type 183, more commonly known as the Iltis , is a military vehicle built by Volkswagen for use by the German military and under licence by Bombardier for the Canadian Forces and Belgian Army...

for the German military (Bundeswehr)

Bundeswehr

The Bundeswehr consists of the unified armed forces of Germany and their civil administration and procurement authorities...

in the 1970s. The Iltis utilized an early form of 4WD, which would later become synonymous with "quattro".

In that original quattro system, later found in road-going passenger cars, the engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

and transmission

Transmission (mechanics)

A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

are situated in a longitudinal

Longitudinal engine

In automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....

position. Torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

is sent through the transmission to a mechanical centre differential (commonly abbreviated to "diff") which apportions (distributes) the torque between front and rear driven axle

Axle

An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...

s. 4WD was permanently active.

After 1987, Audi

Audi

replaced a manually-locking centre differential with the Torsen

Torsen

Torsen is a type of differential used in automobiles. It was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. Torsen is a contraction of Torque-Sensing...

(torque sensing) Type 1 ("T1") centre differential. This allowed engine torque to be automatically directed to individual axles as driving conditions, and grip warranted. Under 'normal' conditions (where grip in both front and rear axles is equal), torque is split between front and rear with a 'default" 50:50 distribution in many, though not all, versions. In adverse conditions (i.e., when there is variation in grip between front and rear), a maximum of 67-80% (depending on the transmission, or model of Torsen diff) of the engine's torque can be directed to the front or rear axles. The fully automated mechanical nature of the Torsen centre differential helps prevent wheel slippage

Wheelspin

A wheelspin, occurs when the force delivered to the tire tread exceeds that of available tread-to-surface friction and one or more tires lose traction.Standard differentials always apply equal torque to each wheel...

from occurring, by diverting torque instantly, without any discernible notice to the vehicle occupants, to the axle which has more grip. This method of operation can be described as proactive

ProActive

ProActive is Java grid middleware for parallel, distributed, and multi-threaded computing. It is developed by the OW2 Consortium, including INRIA, CNRS, University of Nice Sophia Antipolis, and ActiveEon...

. Furthermore, unlike the various types of electronically operated differentials, Torsen has no requirement for electronic data, from sources such as road wheel speed sensors

Wheel speed sensor

A wheel speed sensor or vehicle speed sensor is a type of tachometer. It is a sender device used for reading the speed of a vehicle's wheel rotation...

; it therefore has an element of "fail-safe

Fail-safe

A fail-safe or fail-secure device is one that, in the event of failure, responds in a way that will cause no harm, or at least a minimum of harm, to other devices or danger to personnel....

", unlike designs such as Haldex Traction, should one of the wheel speed sensors develop a fault. In comparison, viscous coupling

Viscous coupling unit

A viscous coupling is a mechanical device which transfers torque and rotation by the medium of a viscous fluid. It is made of a number of circular plates with tabs or perforations, fitted very close to each other in a sealed drum. Alternate plates are connected to a driving shaft at one end of the...

, and electronically controlled centre differentials that are used in other four-wheel drive systems are reactive, since they only redirect torque after wheel slippage has occurred. The advantage is felt under hard acceleration

Acceleration

In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...

, including whilst cornering

Cornering force

Cornering force or side force is the lateral force produced by a vehicle tire during cornering.Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length...

, since the torque transfer between axles is seamless, thus maintaining stable vehicle dynamics

Vehicle dynamics

Vehicle dynamics refers to the dynamics of vehicles, here assumed to be ground vehicles. Vehicle dynamics is a part of engineering primarily based on classical mechanics but it may also involve chemistry, solid state physics, electrical engineering, communications, psychology, control theory,...

, and considerably reducing the chance of losing control of the vehicle.

The Torsen-based quattro system also offers an advantage, in the opposite function of distributing torque to the road wheels, namely engine braking

Engine braking

Engine braking is where the retarding forces within an engine are used to slow a vehicle down, as opposed to using an external braking mechanism, for example friction brakes or magnetic brakes....

. When engine braking is used to slow the car down, with Torsen-based systems, the resulting "reverse-torque" loads on the front and rear axle are equally stabilised, in exactly the same way that engine "propulsion" torque is apportioned fully mechanically autonomously. This allows the spreading of the engine braking effect to all four wheels and tyres. The Torsen-based quattro-equipped vehicle is able to execute a more stable high-speed turn under deceleration, with less risk of losing control due to loss of grip in the front or rear axles.

This configuration of the quattro system, however, does have some limitations:

With placement of the engine and transmission assembly in a fore/aft position (longitudinally), the front axle is placed rearwards behind the engine, which leads to the criticism of some Audi vehicles as being nose heavy, though the system still leads to better weight distributions than transverse mounted engine packages as in Mitsubishis and similar cars. This allows for a better weight distribution of 55:45 (F:R).
The nature of the Torsen is akin to that of a limited slip differential in that, rather than actively allocating torque (as a computer controlled clutch can do), it supports a torque difference across the differential (the torque bias ratio/TBR), from the side with the least grip to the side with the most. Hence by nature the Torsen is limited in the amount of torque that can be supplied to the axle with the most grip by the torque available at the axle with the least amount of grip. Therefore if one axle has no grip, regardless of the TBR, the other axle will not be supplied substantial torque. In the extreme, for a centre differential implementation, complete loss of traction on a single wheel will result in very limited torque to the other three wheels. Audi responded to this limitation for the first Torsen-equipped cars by adding a manually-locking rear differential and then later replaced this feature with Electronic Differential Lock (EDL), which is the ability to use the individual wheel brakes (monitored by the ABS sensors) to limit individual wheel spin. EDL was implemented across both front and rear (open) differentials to operate at speeds < 80 km/h. This has the effect of increasing torque from a single low-traction wheel hence allowing more torque to be passed by the Torsen to the remaining high-traction wheels.
While the standard (Type 1 or T1) Torsen supports a static torque ratio of 50:50; i.e., input torque is supported equally across both output shafts, the T1 has a Torque Bias Ratio (TBR) of 2.7–4:1; i.e., it allows about 3 to 4 times the torque to be supplied to the most tractive output shaft than that is available on the least tractive shaft or, a torque split of between 25% to 75%. However, by nature the T1 Torsen is locked under most circumstances (output shafts locked together). Only when the TBR is reached (i.e., there is a greater torque difference across the output shafts than can be supported by the TBR) do the output shafts turn relative to each other, and the differential unlocks. This characteristic results in a relatively free torque movement between both outputs of the (centre) differential, within the limits of the TBR. Thus the static torque distribution of the T1 Torsen in a centre differential installation, rather than being 50:50, will mirror the weight distribution (both static and dynamic) of the vehicle due to the traction available at either (front:rear) output shaft. In a standard car, this is desirable from the perspective of stability, acceleration and traction, but can be undesirable in terms of handling (understeer). While the standard quattro Torsen T1 with 2.7:1 TBR is more than sufficient in most conditions, Torsen T1 differentials with higher TBRs (4:1) are available and can further limit understeer by supporting a wider torque split. A better solution, however, is to apportion a torque split directly between both output shafts (front & rear) and for this reason Audi has adopted the Type 3 (T3) Torsen design in the latest generations of quattro.

The Torsen T3 centre differential combines a planetary gear set with a Torsen differential in a compact package developed for centre differential installations. Unlike the T2 Torsen where the torque split is a nominal 50:50, in the T3 Torsen the torque split, due to the use of the planetary gear set, is an actual asymmetric 40:60 front-rear torque split (i.e., when grip is equal on both front and rear axles, 40% of torque is sent to the front axle, and 60% to the rear). As with the T1 Torsen, torque will be distributed dynamically depending on tractive conditions, but with an actual (rather than nominal) static bias. The T3 allows handling characteristics and vehicle dynamics more akin to rear-wheel drive cars. This asymmetric Torsen was first introduced in the highly acclaimed 2006-model (B7) Audi RS4. It was then used in the 2006 manual transmission and 2007-model for B7 for both transmission types.S4

Audi S4

The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan...

. as well as the S5 and Q7. It is planned to be incorporated in all future quattro-equipped cars which use longitudinal-mounted engine layout.

The torque split across axles, between left and right wheels, has been achieved through the various evolutions of the quattro system, through a driver-selectable manually locking differential (rear axle only), and, eventually, through open differentials with Electronic Differential Lock (EDL). EDL is an electronic system, utilising the existing anti-lock braking system

Anti-lock braking system

An anti-lock braking system is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up and therefore avoiding skidding.An ABS generally offers...

(ABS), part of the Electronic Stability Programme

Electronic stability control

Electronic stability control is a computerized technology that may potentially improve the safety of a vehicle's stability by detecting and minimizing skids. When ESC detects loss of steering control, it automatically applies the brakes to help "steer" the vehicle where the driver intends to go...

(ESP), which brakes just the one spinning wheel on an axle, therefore allowing the transfer of torque across the axle to the wheel which does have traction.

Audi debuted a new generation of quattro in the 2010 RS5. The key change is the replacement of the Torsen Type "C" centre differential with an Audi-developed "Crown Gear" differential. Whilst this is superficially the same as a normal Open differential, adapted for a centre application, it has some key differences:

The central carrier and associated spider gears interface directly to two crown wheels connected to the front and rear drive shafts
The two crown wheels interface to the spider gears at different diameters, and so produce different torque when turned by the spider gears. This is engineered to produce a 40:60 static torque split front and rear.
Each crown wheel interfaces to the respective output shaft directly, whilst the spider carrier interfaces to each output shaft using a clutch pack which gives the unit the ability to control torque distribution over and above the static torque distribution.

If one axle loses grip, different rotational speeds arise inside the differential which result in an increase in axial forces that force the clutch plates to close. Once closed, the output shaft is locked resulting in the diversion of the majority of the torque to the axle achieving better traction. In the Crown Gear differential up to 85% of torque can flow to the rear, and up to 70% of torque can be diverted to the front axle.

The features of the Crown Gear differential provide the following benefits over the Torsen Type "C"

The ability to setup a more stable torque distribution, with full locking whereas the Torsen can only provide a torque distribution up to the Torque Bias Ratio; i.e., the Crown Gear differential can lock fully, regardless of bias ratio. Unlike the Torsen, the Crown Gear differential doesn't operate like a limited slip differential and can operate, fully locked, with no traction on one output shaft.
Easier integration into control electronics allowing four-wheel electronic torque vectoring with or without the active rear sport differential
Considerable reduction in size and weight (at 4.8 kg, some 2 kg lighter than the Torsen Type C)

The net result of this advance in quattro is the ability of the vehicle electronics to fully manage the vehicle dynamics in all traction situations, whether in cornering, acceleration or braking or in any combination of these.

Evolutions

Audi has never officially debuted quattro in specific generations—changes to quattro technology have generally been debuted with a specific range or model in the range and then brought into other models during appropriate points in the model cycle.

The exception to the above was the debut of the 2010 RS5 which was, amongst other things, heralded by Audi as the debut of a new generation of quattro.

quattro generation I

Used from 1981 to 1987 in Audi Quattro

Audi Quattro

turbo coupé, Audi 80

Audi 80

The Audi 80 is a compact executive car produced by the German car manufacturer Audi, from 1966 to 1996. It shared its platform with the Volkswagen Passat from 1973 to 1986 and was available as a saloon car/sedan, and an Avant...

B2 platform (1978–1987, Audi 4000 in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

n market), Audi Coupé quattro

Audi Coupé (B2)

The Audi Coupé is a two-door coupé produced and sold by Audi from 1980 to 1988. The car was an attempt by Audi to offer a cheaper version of its turbocharged, permanent four-wheel drive Audi Quattro - without turbochargers or four wheel drive. Later, quattro was added as an option...

B2 platform (1984-1988), Audi 100

Audi 100

The restyled C2 Audi 100 was launched in 1976, with an in-line five-cylinder engine...

C3 platform (1983–1987, Audi 5000 in North American market). Also, starting from 1984, used on the Volkswagen VW Passat

Volkswagen Passat

The Volkswagen Passat is a large family car marketed by Volkswagen Passenger Cars through six design generations since 1973. Between the Volkswagen Golf / Volkswagen Jetta and the Volkswagen Phaeton in the current Volkswagen line-up, the Passat and its derivatives have been badged variously as...

B2 platform (VW Quantum in the US market) where it was known as Syncro.

System type: Permanent four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

.

Open centre differential, manually lockable via switch on centre console.¹

Open rear differential, manually lockable via switch on centre console.¹

Open front differential, no lock.

¹ - ABS

Anti-lock braking system

disabled when locked.

How does the system perform: When all differentials are unlocked the car will not be able to move if one wheel of front and rear loses traction (is on ice or raised in the air). When center differential locked, the car will not able to move if two opposite front and rear wheels loses traction and one of another's wheels. When rear differential locked the car will not be able to move if two rears and one front wheel loses traction. When both center and rear differential are locked, the car will not be able to move when all four wheels loses traction.

quattro generation II

Starting from 1988 on older generation Audi 100 C3 platform and Audi Quattro

Audi Quattro

until the end of their production, and on new generation B3 platform (1989–1992) Audi 80/90 quattro, B4 platform (1992–1995) Audi 80, Audi S2, Audi RS2 Avant

Audi RS2 Avant

The Audi RS2 Avant was a limited edition, high-performance Audi five-door, five-seat estate car , manufactured from March 1994 to July 1995...

, C4 platform (1991–1994) Audi 100 quattro, Audi S4

Audi S4

The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan...

, earlier C4 platform (1995) Audi A6/S6.

System type: Permanent four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

.

Torsen

Torsen

Torsen is a type of differential used in automobiles. It was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. Torsen is a contraction of Torque-Sensing...

centre differential, 50:50 'default' split, automatically apportioning up to 75% of torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

transfer to either axle.

Open rear differential, manually lockable via switch on centre console located next to handbrake.¹

Open front differential, no lock.

¹ - ABS

Anti-lock braking system

disabled when locked, automatically unlocks if speed exceeds 25 km/h (15.5 mph).

How does the system perform: When rear differential is manually locked, the car will not be able to move if one front wheel and both rear wheels lose traction altogether.

quattro generation III

Used only on the Audi V8

Audi V8

The Audi V8 is a large luxury four-door, five-seat saloon , built by Audi AG at its Neckarsulm plant in Germany from October 1988 to November 1993, as the company's range-topping flagship model...

starting from 1988 to 1994.

System type: Permanent four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

.

V8 with automatic transmission:

Planetary gear centre differential with electronically-controlled multi-plate locking clutch

Torsen

Torsen

Torsen is a type of differential used in automobiles. It was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. Torsen is a contraction of Torque-Sensing...

type 1 differential rear.

Open differential front.

V8 with manual transmission:

Torsen

Torsen

Torsen is a type of differential used in automobiles. It was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. Torsen is a contraction of Torque-Sensing...

type 1 centre differential.

Torsen type 1 rear differential.

Open front differential.

How does the system perform: In on-road conditions the car will not be able to move if one front and both rear wheels lose traction altogether. Torsen effect with one wheel in the air still applicable to V8 with manual transmission, but will not happen on V8 with automatic transmission because center differential on this model offers 100% locking even when no torque is sensed on the spinning wheel. Manual transmission cars will have a more rear wheel drive feel to it due to torque being maintained to the outside rear wheel while cornering with torque applied, this will allows for better attitude during cornering and power on over-steer is easier to achieve.

quattro generation IV

Starting from 1995 on Audi A4

Audi A4

The first generation Audi A4 debuted in 1994, with production starting November 1994. It was built on the Volkswagen Group B5 platform, which it shared with the fourth generation Volkswagen Passat . It had a front-mounted longitudinal engine and front-wheel drive...

/S4

Audi S4

The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan...

/RS4

Audi RS4

The Audi RS4 quattro is the top tier and highest performing version of some specific generations of the Audi A4 range of automobiles. It is a sports-focused compact executive car , produced by Audi's high-performance private subsidiary quattro GmbH, in limited numbers, for German car manufacturer...

(B5 platform), Audi A6

Audi A6

The Audi A6 is an executive car marketed by the German automaker Audi AG, now in its fourth generation. As the successor to the Audi 100, the A6 is manufactured in Neckarsulm, Germany – and is available in saloon, and wagon configurations, the latter marketed by Audi as the Avant.All generations...

/S6

Audi S6

The Audi S6 is a high-performance version of the Audi A6, an executive car produced by German automaker Audi. It went on sale in 1994, shortly after the "A6" designation was introduced, replacing the "100" nameplate...

/allroad/RS6

Audi RS6

The Audi RS6 quattro, commonly referred to as the RS6, is the highest performing version, and top-of-the-line specification of the Audi A6, positioned above the Audi S6...

, Audi A8

Audi A8

The Audi A8 is a four-door, full-size, luxury sedan car manufactured and marketed by the German automaker Audi since 1994. Succeeding the Audi V8, the A8 has been offered with front wheel drive or permanent four-wheel drive, with multitronic or tiptronic automatic transmissions — and in short- and...

/S8

Audi S8

The Audi S8 quattro is a high-performance version of the German luxury automaker Audi's flagship car, the full-size Audi A8. The S8 is produced at Audi's Neckarsulm 'aluminium plant', and it was introduced in September 1994...

with both manual and automatic transmissions. Also on VW Passat B5

Volkswagen Passat

, where it was initially referred to as syncro, but by the time it reached US soil, it had been re-christened 4motion

4motion

4motion is a registered trademark of Volkswagen AG, used exclusively on Volkswagen-branded automobiles which utilise four-wheel drive systems. Volkswagen has previously used the term "Syncro" for its 4WD models....

. Also used on the Volkswagen Phaeton

Volkswagen Phaeton

The Volkswagen Phaeton is a full-size luxury sedan/saloon manufactured by German automaker Volkswagen, and is described by Volkswagen as their "premium class" vehicle...

and Volkswagen Group D platform sister vehicles. The Volkswagen Touareg

Volkswagen Touareg

The Volkswagen Touareg is a mid-size crossover SUV produced by German automaker Volkswagen since 2002. The vehicle was named after the Tuareg people, a Berber-speaking group in North Africa...

used 4Xmotion with a separate transmission, PTUs

Power Transfer Unit

In aviation, a Power Transfer Unit is a device that transfers hydraulic power from one of an aircraft's hydraulic systems to another in the event that second system has failed or been turned off....

and front axles.

The manually locking rear differential from the earlier generations was replaced with a conventional open differential, with Electronic Differential Lock (EDL) (which detects wheelspin via ABS road wheel speed sensors, and applies brakes to the one spinning wheel, thus transferring torque via open differential to the opposite wheel which has more traction). EDL works at speeds up to 80 km/h (49.7 mph) on all quattro models (on non-quattro models: up to 40 km/h (24.9 mph).

System type: Permanent four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

.

Torsen

Torsen

Torsen is a type of differential used in automobiles. It was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. Torsen is a contraction of Torque-Sensing...

type 1 centre differential, 50:50 'default' split, automatically apportioning up to 75% of torque transfer to either front or rear axle.

Open rear differential, Electronic Differential Lock (EDL).

Open front differential, Electronic Differential Lock (EDL).

quattro generation V

Starting with the B7 Audi RS4

Audi RS4

and the manual transmission version of the 2006 B7 Audi S4

Audi S4

The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan...

. It was adopted in the entire S4 lineup in 2007. and become the standard fitment on all quattro Audis with longitudinal engine layout until replaced in the 2010 RS5.

System type: Permanent asymmetric four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

.

Torsen type 3 (Type "C") centre differential, 40:60 'default' split front-rear, automatically apportioning up to 80% of the torque to one axle using a 4:1 high-biased center differential. With the aid of ESP, up to 100% of the torque can be transferred to one axle.

Open rear differential, Electronic Differential Lock (EDL).

Open front differential, Electronic Differential Lock (EDL).

Vectoring quattro system

Audi's new sport differential, debuted 'torque vectoring' to quattro generation V. The Audi sport differential allowed the dynamic allocation of torque across the rear axle of the debut vehicle: the B8 (2008) S4, and is now an optional addition to all quattro vehicles, which continue to use the 40:60 asymmetric Torsen (Type "C") centre differential. The sport differential replaces the normal open rear differential while the front axle still rely on an open differential with EDL.

The torque vectoring rear axle differential is designed and manufactured by Audi and is being offered on Audi A4, A5, A6 and their derivatives (including RS models). The Sport Differential selectively distributes torque to the rear axle wheels thereby generating a yaw moment, which improves handling and also stabilizes the vehicle when it oversteers or understeers, thereby increasing safety.

The sport differential operates by using two superposition ("step up") gears at the differential, which are operated via multi-plate clutches each side of the differential crown wheel. When required by the software (using lateral and longitudinal yaw sensors, the ABS wheel sensors, and a steering wheel sensor), the control software (located in a control unit close to the rear differential), actuates the relevant clutch pack. This has the effect of taking the output shaft drive through the step-up gear to the attached wheel, while the other shaft continues to drive its wheel directly (i.e., the clutch pack not actuated). The higher speed output shaft produces increased torque to the wheel, producing a yaw (turning) moment. In normal operation increased torque is delivered to the wheel on the outside of the turn thereby increasing the vehicles turning moment, in other words, its willingness to turn in the direction pointed by the steering wheel.

quattro generation VI

Audi debuted the 6th generation of quattro in the 2010 RS5. The key change in generation VI is the replacement of the Torsen Type "C" centre differential with an Audi-developed "Crown Gear" differential. With the new "Crown Gear" center differential, up to 70% of the torque can be applied to the front wheels while up to 85% can be applied to the rear wheels if necessary. The net result of this advance in quattro is the ability of the vehicle electronics to fully manage the vehicle dynamics in all traction situations, whether in cornering, acceleration or braking or in any combination of these.

BorgWarner

The Audi Q7

Audi Q7

The Audi Q7 is a full-size luxury crossover SUV unveiled in September 2005 at the Frankfurt Motor Show. Production of the Q7 began in autumn of 2005 in Bratislava, Slovakia. It is the first SUV offering from Audi and went on sale in 2007. Later, Audi's second SUV, the Q5, was unveiled as a 2009...

, the platform-mate of the Volkswagen Touareg

Volkswagen Touareg

The Volkswagen Touareg is a mid-size crossover SUV produced by German automaker Volkswagen since 2002. The vehicle was named after the Tuareg people, a Berber-speaking group in North Africa...

and Porsche Cayenne

Porsche Cayenne

The Porsche Cayenne is a five seat mid-size luxury crossover manufactured by the German manufacturer Porsche since 2002, with North American sales beginning in 2003. Its platform was developed by Porsche and is shared with the Volkswagen Touareg and the Audi Q7. It is the first V8-engined vehicle...

, does not use the same underpinnings of either previous model. BorgWarner

BorgWarner

BorgWarner Inc. is a United States-based worldwide automotive industry components and parts supplier. It is primarily known for its powertrain products, which include manual and automatic transmissions and transmission components, , turbochargers, engine valve timing system...

instead provides the 4WD system for this more off-road appropriate SUV. A Torsen Type 3 (T3) differential is used.

Transverse systems

Since Volkswagen Group

Volkswagen Group

Volkswagen Group is a German multinational automobile manufacturing group. , Volkswagen was ranked as the world’s third largest motor vehicle manufacturer and Europe's largest....

's first mainstream transverse

Transverse engine

A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...

engined

Internal combustion engine

vehicle in 1974, four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

(4WD) has also been considered for their A-platform family of cars

Automobile

An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

. It was not until the second generation of this platform that 4WD finally appeared on the market. The mid-1980s Mk2 Golf syncro

Volkswagen Golf Mk2

The Volkswagen Golf Mk2 succeeded the Mk1 as Volkswagen's volume seller from 1983 and remained in production until late 1992. In comparison to its predecessor, its wheelbase grew slightly , as did exterior dimensions . Weight was up accordingly by about...

, with its transverse engine and transmission

Transmission (mechanics)

positioning, still had most of its torque sent primarily to the front axle. Vehicles using this configuration therefore cannot be said to have a "permanent", or "full-time" four wheel drive system.

Attached to the transaxle

Transaxle

In the automotive field, a transaxle is a major mechanical component that combines the functionality of the transmission, the differential, and associated components of the driven axle into one integrated assembly....

is a Power Transfer Unit

Power Transfer Unit

In aviation, a Power Transfer Unit is a device that transfers hydraulic power from one of an aircraft's hydraulic systems to another in the event that second system has failed or been turned off....

(PTU), which is connected to a rear axle

Axle

through a propeller shaft. The PTU also feeds torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

through itself to the front axle. At the rear axle, torque was first sent through a viscous coupling before reaching the final drive gearset. This coupling contained friction plates and an oil just viscous enough so that pressure affected how many plates were connected and active (and therefore, how much power was being delivered to the rear wheels).

Starting with the Mk4 generation A4-platform, the viscous coupling has been dropped in favour of a Haldex Traction electro-hydraulic limited-slip "coupler" (LSC) or clutch

Clutch

A clutch is a mechanical device which provides for the transmission of power from one component to another...

. The Haldex Traction LSC unit is not a differential and therefore cannot perform in the true sense like a differential

Differential (mechanics)

A differential is a device, usually, but not necessarily, employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it...

. A Haldex Traction unit may divert up to a maximum 100% of the torque to the rear axle as conditions warrant. Many people are confused with the torque distribution on Haldex-based systems. Under normal operating conditions the Haldex clutch operates a rate of 5% torque transmission. Under adverse conditions where the cars road wheel speed sensors have determined that both front wheels have lost traction the Haldex clutch can lock at 100% clamping force, meaning all torque is transferred to the rear axle. The torque split between left and right wheels is achieved with a conventional open differential. If one side of the driven axle loses grip, then the Electronic Differential Lock (EDL) component of the ESP controls this. EDL brakes a single spinning wheel, therefore, the torque gets transferred across the axle to the opposite wheel via the open differential. On all transverse engine cars with the Haldex-based four wheel drive system, the EDL only controls front wheels, and not the rear.

The main advantages of the Haldex Traction LSC system over the Torsen-based system include: a slight gain in fuel economy (due to the decoupling of the rear axle when not needed, thereby reducing driveline losses due to friction), and the ability to maintain a short engine bay and larger passenger compartment due to the transverse engine layout. A further advantage of the Haldex, when compared to just front wheel drive variants of the same model, is a more balanced front-rear weight distribution (due to the location of the Haldex center "differential" next to the rear axle).

Disadvantages of the Haldex Traction system include: the vehicle has inherent front-wheel drive handling characteristics (as when engine braking

Engine braking

Engine braking is where the retarding forces within an engine are used to slow a vehicle down, as opposed to using an external braking mechanism, for example friction brakes or magnetic brakes....

, load is only applied on the front wheels, and due to the reactive nature of the Haldex system and slight lag time in the redistribution of engine power), and the Hadex LSC unit also requires additional maintenance, in the form of an oil and filter change every 60000 kilometre (whereas the Torsen is generally considered to be maintenance-free). Another important disadvantage of the Haldex system is the requirement for all four tyres to be of identical wear levels (and rolling radii), due to the Haldex requiring data from all four road wheel speed sensors. A final significant disadvantage is the reduction in luggage capacity in the boot (trunk), due to the bulky Haldex LSC unit necessitating a raised boot floor by some three inches.

Viscous Coupling

Important note: This 4WD system was used only on Volkswagen

Volkswagen

branded vehicles, and was never used on any Audi

Audi

cars except Audi R8 model.

The aforementioned viscous coupling 4WD system was found in the Mk2 generation of transverse-engined A2-platform vehicles, including the Volkswagen Golf Mk2

Volkswagen Golf Mk2

and Jetta

Volkswagen Jetta

Although the Golf had reached considerable success, in the North American markets, Volkswagen observed that the hatchback body style lacked some of the appeal to those who preferred the traditional three-box configuration...

. It was also found on the Volkswagen Type 2 (T3)

Volkswagen Type 2 (T3)

The Volkswagen Type 2 was the third generation of the Volkswagen Transporter and was marketed under various nameplates worldwide – including as the Transporter or Caravelle in Europe, Microbus in South Africa and as the Vanagon in North and South America.Larger and heavier than its...

(Vanagon in the US), Mk3 generation of Golf

Volkswagen Golf Mk3

The third-generation Volkswagen Golf Mk3 was a car launched in Europe in November 1991 , and in North America in the spring of 1993. The delay in North America was due to Volkswagen's decision to supply U.S. and Canadian dealerships with Mk3 Golfs from the VW plant in Puebla, Mexico...

and Jetta, 3rd generation of Volkswagen Passat

Volkswagen Passat

B3 (which was based on a heavily revised A-platform), and the Volkswagen Eurovan

Volkswagen Eurovan

The Volkswagen Transporter T4 is a van produced by German automaker Volkswagen Commercial Vehicles between 1990 and 2003, succeeding the Volkswagen Type 2 and superseded by the Transporter T5....

.

Note that the Vanagon system was RWD-biased, due to the vehicle being rear-wheel drive by default; the engine and transaxle were in the rear, whereas the viscous coupling was found in the front axle near the final drive. This 4WD system was known as Syncro on all vehicles.

What: Automatic four wheel drive (on demand).

A viscous coupling installed instead of a centre differential, with freewheel

Freewheel

thumb|Freewheel mechanismIn mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft...

mechanism to disconnect the driven axle when braking.

Open rear differential (mechanical differential lock optional on Vanagon).

Open front differential (mechanical differential lock optional on Vanagon).

How: Normally a front-wheel drive

Front-wheel drive

Front-wheel drive is a form of engine/transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitudinal engine arrangement generally found in rear-wheel drive and...

vehicle (except Vanagon, see above). In normal driving conditions 95% of torque transferred to front axle. Because viscous coupling is considered to be "slow" (some time is needed for silicone fluid to warm-up and solidify), 5% of torque is transferred to rear axle at all times to "pre-tension" the viscous coupling and reduce activation time. The coupling locks when slipping occurs and up to near 50% of torque is automatically transferred to rear axle (front in Vanagon). In on-road conditions the car will not move if one front wheel and one rear wheel lose traction.

The freewheel

Freewheel

segment, installed inside the rear differential, lets rear wheels rotate faster than front wheels without locking the viscous coupling and preventing ABS

Anti-lock braking system

from applying brakes to each wheel independently. Because of the freewheel, torque can be transferred to rear axle only when vehicle is moving forward. For four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

to work when reversing

Reversing (Vehicle maneuver)

Reversing is the process of driving a vehicle in the reverse direction in order to maneuver. Rear view mirrors are standard equipment for this endeavor. Extremely large or luxury vehicles may have in addition technical aids such as backup cameras...

, a vacuum-actuated "throttle control element" is installed on the differential case. This device locks the freewheel mechanism when in reverse gear. The freewheel mechanism unlocks when the gear shift lever is pushed to the right pass the 3rd gear. The freewheel is not unlocked immediately after leaving reverse gear on purpose - this is to prevent the freewheel from cycling from locked to unlocked if the car is stuck and driver is trying to "rock" the car by changing from 1st to reverse and back.

Disadvantages of this four wheel drive system are related to actuation time of the viscous coupling. 1: When cornering under acceleration on a slippery surface, rear axle is engaged with delay causing sudden change in the car's behaviour (from understeer to oversteer). 2: When starting on a sandy surface, front wheels can dig into the sand before all wheel drive is engaged.

Haldex

Starting from 1998, the Swedish

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

Haldex Traction LSC unit replaced the viscous coupling. Haldex is used by Audi

Audi

on the quattro versions of the Audi A3

Audi A3

The Audi A3 is a small family car produced by the German automaker Audi since 1996. Two generations of A3 exist, both based on the Volkswagen Group A platform, which they share with several other models such as the Audi TT, Volkswagen Golf, Volkswagen Caddy and Volkswagen Touran as well as SEAT...

and Audi S3, and the Audi TT

Audi TT

The Audi TT is a two-door sports car manufactured by the German automaker and Volkswagen Group subsidiary Audi since 1998.The Audi TT has been produced in two generations. Both generations have been available in two car body styles; as a 2+2 Coupé, or two-seater Roadster...

. It is also used by Volkswagen

Volkswagen

in the 4motion

4motion

versions of the Mk4 and Mk5 generations of Volkswagen Golf

Volkswagen Golf

The Volkswagen Golf is a small family car manufactured by Volkswagen since 1974 and marketed worldwide across six generations, in various body configurations and under various nameplates – as the Volkswagen Rabbit in the United States and Canada , and as the Volkswagen Caribe in Mexico .The...

, Volkswagen Jetta

Volkswagen Jetta

, and the Golf R32, Volkswagen Sharan

Volkswagen Sharan

The Volkswagen Sharan is a large MPV produced by the German automaker Volkswagen since 1995.-First generation :The name Sharan is derived from a Persian word meaning "Carrier of Kings"....

, 6th generation VW Passat (also based on the A-platform) and Transporter T5. On the Audis, the trademark holds, and are still referred to as quattro, whereas the Volkswagens receive the 4motion name. The Škoda Octavia

Škoda Octavia

The Škoda Octavia is a small family car produced by Czech automaker Škoda Auto since 1996, its name revived from a model originally produced between 1959 and 1971. The current Octavia is available in five-door liftback and station wagon....

4x4 and SEAT León

SEAT León

The SEAT León is a small family car built by the Spanish car manufacturer, and Volkswagen Group subsidiary SEAT, S.A. since October 1998.The two León generations are, or have been built upon two differing variants of the Volkswagen Group A platform, and they also share many other components with...

4 and SEAT Alhambra

SEAT Alhambra

The SEAT Alhambra is a large 7-seat MPV by the Volkswagen Group, sold under the SEAT brand.The Alhambra already spans two generations since 1996, and both of them are built at the AutoEuropa plant in Palmela, Portugal...

4 also used Haldex LSC, being based on Volkswagen Group

Volkswagen Group

Volkswagen Group is a German multinational automobile manufacturing group. , Volkswagen was ranked as the world’s third largest motor vehicle manufacturer and Europe's largest....

models. Curiously, the Bugatti Veyron

Bugatti Veyron

The Bugatti Veyron EB 16.4 is a mid-engined grand touring car. The Super Sport version is the fastest road-legal production car in the world, with a top speed of . The original version has a top speed of...

also utilizes Haldex, though with separate transmission, PTU and front and rear axles.

What: Automatic four wheel drive (on demand).

Haldex Traction LSC multi-plate clutch with ECU electronic control, acting as a pseudo center differential.

Open rear differential, no EDL.

Open front differential, EDL.

How: Normally front-wheel drive

Front-wheel drive

vehicle. A Haldex Traction LSC unit may divert up to a maximum 100% of the torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

to the rear axle

Axle

as conditions warrant. Many people find the torque distribution on Haldex Traction systems confusing. Under normal operating conditions, the Haldex LSC clutch operates at 5% (divide 5% between front and rear, and 97.5% torque goes to the front, and 2.5% goes to the rear). Under adverse conditions where both front wheels lose traction, the Haldex clutch can lock at 100% clamping force. This means, that since there is no torque transferred to the front axle, all torque (minus losses) must be transferred to the rear axle. The torque split between left and right wheels is achieved with a conventional open differential. If one side of the driven axle loses grip, then the Electronic Differential Lock (EDL) controls this. EDL brakes a single spinning wheel, and therefore torque gets transferred to the opposite wheel via the open differential. On all transverse-engined cars with the Haldex Traction LSC four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

system, the EDL only controls the front wheels, and not the rear.

In vehicles equipped with EDL on the front wheels only, the car will not move if both front and one of the rear wheels loses traction.

Again, due to limitations of Electronic Differential Lock (see quattro IV description above), in off-road conditions it is enough for one front and one rear wheel to lose traction and the car will not move.

The Haldex Traction system is more reactive

Reactive

Reactive may refer to:*Generally, capable of having a reaction*Reactance , the imaginary component of AC impedance*Reactive mind*Reactive programming...

than preventative, in that there must be a difference in slip (or rotational speed) of the two axle systems before the Haldex operates and sends torque to the rear axle. This is not the same as wheel spin, as the system can react in less than the full rotation of any wheel on the vehicle. The Torsen's permanent 'full-time' even torque split under non-slipping conditions makes slipping less likely to start.

The Haldex Electronic Control Unit (ECU) disengages the Haldex clutch in the centre coupling as soon as brakes are applied to allow ABS

Anti-lock braking system

work properly. When performing tight low-speed turns (e.g. parking) the clutch is disengaged by Electronic Control Unit to avoid "wind-up" in transmission. When Electronic Stability Programs (ESP) are activated the Haldex is disengaged to allow the ESP system to effectively control the vehicle. This applies under acceleration and deceleration conditions.

Haldex aftermarket applications

The Haldex Traction LSC centre coupling is often used as upgrade to an aftermarket four-wheel drive

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

conversion on older front-wheel drive

Front-wheel drive

Volkswagens. It is said to be capable of withstanding larger power outputs than the also commonly used viscous coupling system from a syncro vehicle.

The conversion is carried out by way of rear axle and associated live suspension system from a syncro vehicle being fitted to a suitable project car (i.e. a Volkswagen Corrado

Volkswagen Corrado

The Volkswagen Corrado is a hatchback coupé developed by German automaker Volkswagen and built by Karmann in Osnabrück, Germany, between 1 September 1988 and 31 July 1995....

or Volkswagen Golf

Volkswagen Golf

), and then fabricating a custom bracket to hold the Haldex rear coupling.

Enthusiasts often either use the OEM ECU and engine management from a newer Volkswagen Group

Volkswagen Group

Volkswagen Group is a German multinational automobile manufacturing group. , Volkswagen was ranked as the world’s third largest motor vehicle manufacturer and Europe's largest....

car to control the Haldex centre clutch using the standard ABS road wheel speed sensors - or can buy aftermarket controllers that supply the relevant pulse-width modulation

Pulse-width modulation

Pulse-width modulation , or pulse-duration modulation , is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches....

to actuate the clutch and transfer drive to the rear wheels either via simple variable dial or based on throttle position sensor

Throttle position sensor

A throttle position sensor is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the throttle valve butterfly....

(TPS) calculations.

External links

Audi.com corporate international portal
Independent grip. Intelligently applied Audi UK quattro page

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Longitudinal systems

Evolutions

quattro generation I

quattro generation II

quattro generation III

quattro generation IV

quattro generation V

Vectoring quattro system

quattro generation VI

BorgWarner

Transverse systems

Viscous Coupling

Haldex

Haldex aftermarket applications

See also

External links