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| Company type | Division |
|---|---|
| Industry | Automotive |
| Founded | 1980 |
| Headquarters | Germany |
Area served | Worldwide |
| Owner | Volkswagen Group |
| Parent | Audi |
Quattro (meaningfour inItalian and stylized asquattro) is the trademark used by theautomotive brandAudi to indicate thatall-wheel drive (AWD) technologies or systems are used on specific models of its automobiles.[1]
The word "quattro" is a registeredtrademark of Audi AG, a subsidiary of theGerman automotive enterprise,Volkswagen Group.[1]
Quattro was first introduced in 1980 on the permanent four-wheel driveAudi Quattro model, often referred to as theUr-Quattro (meaning "original" or "first"). The term quattro has since been applied to all subsequent Audi AWD models. Due to the nomenclature rights derived from the trademark, the word quattro is now always spelled with a lower case "q" by the manufacturer, in honour of its former namesake.[citation needed]
Other companies in the Volkswagen Group have used different trademarks for their 4WD vehicles. While Audi has always used the term "quattro",Volkswagen-branded cars initially used "syncro", but more recently,[when?] VW uses "4motion".Škoda simply uses the nomenclature "4x4" after the model name, whereasSEAT uses merely "4" ("4Drive" more recently[when?]). None of the above trademarks or nomenclatures defines the operation or type of 4WD system, as detailed below.
Volkswagen Group has been developingfour-wheel drive (4WD) systems almost since its inception during theSecond World War. TheVolkswagen Kübelwagen,Volkswagen Schwimmwagen, andVolkswagen Kommandeurswagen were allmilitary vehicles which required all four road wheels to be "driven", the latter being a 4WDVolkswagen Beetle. Their military and four-wheel drive experiences later aided them in designing theVolkswagen Iltis for theGerman military (Bundeswehr) in the 1970s. The Iltis utilized an early form of 4WD, which would later become synonymous with "quattro".[2]
In that original quattro system, later found in road-going passenger cars, theengine andtransmission are situated in alongitudinal position.Torque is sent through the transmission to a mechanical centredifferential[3] (commonly abbreviated to "diff") which apportions (distributes) the torque between front and rear drivenaxles. 4WD was permanently active.
After 1987, Audi replaced a manually locking centre differential with theTorsen (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 rearaxles 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 90-100% (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 preventwheel slippage from occurring, by diverting torque instantly, without any discernible notice to the vehicle occupants,[4] to the axle which has more grip. This method of operation can be described as proactive. Furthermore, unlike the various types of electronically operated differentials, Torsen has no requirement for electronic data from sources such asroad wheel speed sensors; it, therefore, has an element of "fail-safe", unlike designs such asHaldex Traction, should one of the wheel speed sensors develop a fault. In comparison,viscous coupling and electronically controlled centre differentials that are used in other four-wheel drive systems are reactive, since they only redirect torqueafter wheel slippage has occurred. The advantage is felt under hardacceleration, including whilstcornering, since the torque transfer between axles is seamless, thus maintaining stable vehicle dynamics, 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, namelyengine braking. 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 stabilized, 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:
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 T1 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 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 torear-wheel drive cars. This asymmetric Torsen was first introduced in the highly acclaimed 2006-model (B7)Audi RS4. The Type 3 torsen was used in the Audi S4 and RS4 B7 manual transmissions from 2006 to 2008, as well as the S6, S8, and Q7 models from 2007.
The torque split across axles and 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 existinganti-lock braking system (ABS), part of theElectronic Stability Programme (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.[5]
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:
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 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.
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".
Used from 1981 to 1987 inAudi Quattro turbo coupé,Audi 80 B2 platform (1978–1987, Audi 4000 inNorth American market),Audi Coupé quattro B2 platform (1984–1988),Audi 100 C3 platform (1983–1987, Audi 5000 in North American market). Also, starting from 1984, used on the VolkswagenVW Passat B2 platform (VW Quantum in the US market) where it was known asSyncro.
System type: Permanentfour-wheel drive.
Open centredifferential, manually lockable via switch on centre console.¹
Open rear differential, manually lockable via switch on centre console.¹
Open front differential, no lock.
¹ABS disabled when locked.
How the system performs: When all differentials are unlocked, the car will not be able to move if one wheel (front or rear) loses traction (is on ice or raised in the air). When the center differential is locked with the rear differential unlocked, the car will not be able to move if one front wheel and one rear wheel lose traction. When the rear differential is locked with the center unlocked, the car will not be able to move if both rears or one front loses traction. When both center and rear differentials are locked, the car will not be able to move if both rears and one front lose traction.
Starting from 1988 on older generationAudi 100 C3 platform andAudi 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, C4 platform (1991–1994)Audi 100 quattro,Audi S4, later C4 platform (1994-1997)Audi A6/S6.
System type: Permanentfour-wheel drive.
Torsen centredifferential, 50:50 'default' split, automatically apportioning up to 75% oftorque transfer to either axle.
Open rear differential, manually lockable via switch on centre console located next to handbrake.¹
Open front differential, no lock.
¹ABS disabled when locked, automatically unlocks if speed exceeds 25 km/h (16 mph).
Used only on theAudi V8 starting from 1988 to 1994.
System type: Permanentfour-wheel drive.
V8 withautomatic transmission:
Planetary gear centre differential with electronically controlled multi-plate locking clutch
Torsen type 1 differential rear.
Open differential front.
V8 withmanual transmission:
Torsen 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.
Starting from 1995 onAudi A4/S4/RS4 (B5 platform),Audi A6/S6/allroad/RS6,Audi A8/S8 with both manual and automatic transmissions. Also onVW Passat B5, where it was initially referred to assyncro, but by the time it reached US soil, it had been re-christened4motion.[6] Also used on theVolkswagen Phaeton andVolkswagen Group D platform sister vehicles. TheVolkswagen Touareg used 4Xmotion with a separate transmission,PTUs 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 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 (50 mph), on all quattro models (on non-quattro models: up to 40 km/h (25 mph)).
System type: Permanentfour-wheel drive.
Torsen 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).[5]
Open front differential, Electronic Differential Lock (EDL).[5]
Starting with the B7Audi RS4 and the manual transmission version of the 2006 B7Audi S4. It was adopted in the entire S4, S6, and S8 lineup in 2007.[1]
System type: Permanent asymmetricfour-wheel drive.
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).[5]
Open front differential, Electronic Differential Lock (EDL).[5]
Audi's newsport 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 B7 (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.[5]
The torque vectoring rear axle differential is designed and manufactured by Magna Powertrain,[7] and is being offered on Audi A4, A5, A6 and their derivatives (includingRS models). TheSport 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.
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, braking, snow or in any combination of these. This system was later adopted by the A7, latest generation of the A6 and A8.
TheAudi Q7 (First generation), the platform-mate of theVolkswagen Touareg andPorsche Cayenne, does not use the same underpinnings of either previous model.BorgWarner instead provides the 4WD system for this more off-road appropriate SUV. A Torsen Type 3 (T3) differential is used.
Audi announced "Audi Quattro with Ultra Technology" in February 2016, it is a front-wheel drive biased system for use on platforms with longitudinally mounted engines.[8]
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SinceVolkswagen Group's first mainstreamtransverseengined vehicle in 1974,four-wheel drive (4WD) has also been considered for theirA-platform family ofcars. It was not until thesecond generation of this platform that 4WD finally appeared on the market. The mid-1980sMk2 Golf syncro, with its transverse engine andtransmission positioning, had most of its torque sent primarily to the front axle.
Attached to thetransaxle is aPower Transfer Unit (PTU), which is connected to a rearaxle through apropeller shaft. The PTU also feedstorque 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 generationA4-platform, the viscous coupling has been dropped in favour of aHaldex Traction electro-hydraulic limited-slip "coupler" (LSC) orclutch. The Haldex Traction LSC unit is not a differential and therefore cannot perform in the true sense like adifferential. A Haldex Traction unit may divert up to a maximum 100% of the torque to the rear axle as conditions warrant. Many people[who?] 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 car's 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 whenengine braking, 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 Haldex LSC unit also requires additional maintenance, in the form of an oil and filter change every 60,000 kilometres (37,000 mi) (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.
This 4WD system was used only onVolkswagen branded vehicles, and was never used on anyAudi cars exceptAudi R8 models.
The aforementioned viscous coupling 4WD system was found in the Mk2 generation of transverse-enginedA2-platform vehicles, including theVolkswagen Golf Mk2 andJetta. It was also found on theVolkswagen Type 2 (T3) (Vanagon in the US), Mk3 generation ofGolf and Jetta, third generation ofVolkswagen Passat B3 (which was based on a heavily revised A-platform), and theVolkswagen Eurovan.
The Vanagon system was RWD-biased, 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 asSyncro on all vehicles.
What: Automatic four wheel drive (on demand).
Aviscous coupling installed instead of a centre differential, withfreewheel 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).
Normally afront-wheel drive vehicle (except Vanagon, see above). In normal driving conditions, 95% of torque is 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.
Thefreewheel segment, installed inside the rear differential, lets rear wheels rotate faster than front wheels without locking the viscous coupling and preventingABS from applying brakes to each wheel independently. Because of the freewheel, torque can be transferred to rear axle only when the vehicle is moving forward. Forfour-wheel drive to work whenreversing, 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, past the third 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 first to reverse and back.
Disadvantages of this four-wheel drive system are related to actuation time of the viscous coupling.
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Starting from 1998, theSwedishHaldex Traction LSC unit replaced the viscous coupling. Haldex is used byAudi on the quattro versions of theAudi S1,Audi A3,Audi S3, and theAudi TT. It is also used byVolkswagen in the4motion versions of the Mk4 and Mk5 generations ofVolkswagen Golf,Volkswagen Jetta, and the Golf R32,Volkswagen Sharan,6th generation VW Passat (also based on the A-platform) andTransporter T5. On the Audis, the trademark holds, and are still referred to as quattro, whereas the Volkswagens receive the 4motion name. TheŠkoda Octavia 4x4 andSEAT León 4 andSEAT Alhambra 4 also used Haldex LSC, being based onVolkswagen Group models. Curiously, theBugatti Veyron 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: Normallyfront-wheel drive vehicle. A Haldex Traction LSC unit may divert up to a maximum 100% of thetorque to the rearaxle 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 LSCfour-wheel drive 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 morereactive 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 allowABS 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.
As part of Audi's celebration of quattro All-Wheel Drive technology, a TV commercial titled 'Ahab' was produced inspired by the American novel, Moby Dick. The ad debuted in the United States during 2012 NFL division playoffs.[9]
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