Notices
 
 

  

User Tag List

Thread: How does the Quattro system work?

Results 1 to 4 of 4
  1. How does the Quattro system work? 
    #1
    Join Date
    May 2007
    Location
    Poole
    Posts
    83
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)
    Okay so this might be a question answered elsewhere - but I couldn't find it.

    How does Audi's Quattro system operate? Is it like the permanent 4WD in say a Freelander which is actually a front wheel drive car unless the front lose power then a viscous coupling takes the power to the back, or is it a bit more sophisticated than that.

    If anything my A6 Q feels like more link a RWD car than a FWD.

    Is there somewhere on the web that explains all this?

    Sorry bit of a geeky question really...
    ========================================
    Julian Whitehead
    2001 A6 Avant 2.7T Q
    Swing Unlimited | www.subb.co.uk | www.myspace.com/swingunlimitedbigband
     
    0 0 0
     

  2. #2
    Join Date
    Jun 2007
    Location
    Austin Texas
    Posts
    61
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)
    Quote Originally Posted by webchem View Post
    Okay so this might be a question answered elsewhere - but I couldn't find it.

    How does Audi's Quattro system operate? Is it like the permanent 4WD in say a Freelander which is actually a front wheel drive car unless the front lose power then a viscous coupling takes the power to the back, or is it a bit more sophisticated than that.

    If anything my A6 Q feels like more link a RWD car than a FWD.

    Is there somewhere on the web that explains all this?

    Sorry bit of a geeky question really...
    Your car is permanent AWD with power transfering to the wheels with the most traction, but if you want to know more look here:::>

    Longitudinal quattro systems
    In the original quattro system, the engine and transmission are situated in a longitudinal position. Power is sent through the transmission to a mechanical center differential which splits it between the front and rear axles.

    After 1987, the inclusion of a Torsen (torque-sensing) center differential, instead of a manually-locking one, allowed engine power to be redirected to individual axles as driving conditions warranted. Under ideal conditions (i.e., grip is equal in both front and rear axles) power is split between front and rear (50/50 in many, though not all, versions). In extreme conditions (i.e., when grip varies from front to rear), a maximum of 66-80% (depending on the transmission or model) of the engine's power can be directed to the front or rear axles. The mechanical nature of the Torsen centre differential helps prevent wheel slippage from occurring by diverting power to the axle that has more grip. In comparison, viscous coupling and electronically controlled differentials that are used in other all-wheel drive systems are reactive since they only redirect power once wheel slippage has occurred. The advantage is felt under acceleration while turning since the power transfer between axles is less sudden, reducing the chance of spinning.

    The Torsen-based quattro system also offers an advantage in the opposite function of distributing power to the wheels: engine-braking. When engine-braking is used to slow the car down, the resulting loads on the front and rear axle are stabilized by the Torsen system in exactly the same way that engine power is diverted - mechanically. This allows the spreading of the engine-braking load on the tires among the four wheels. The Torsen-based quattro-equipped vehicle is able to execute a more stable high-speed turn under deceleration with less risk of spinning due to loss of grip in the front or rear axles.

    However, this configuration of the quattro system does have some limitations. With placement of the engine-transmission assembly in a fore/aft position (longitudinally) there arises the need to place the front axle well behind the engine, leading to a common criticism of Audi vehicles: being nose-heavy. In other words, the ideal 50/50 weight distribution cherished by many driving enthusiasts is not possible. Recently the centre differential has been adapted to a 40/60 front/rear static split (i.e. when grip is equal on both front and rear axles), allowing more rear-wheel-drive-like handling characteristics. This was first introduced in the 2006-model RS4 and shortly thereafter in the Q7 SUV. It is planned to be incorporated in all future quattro-equipped cars which use longitudinal-mounted engines.

    The power split between left and right wheels has been acheived through the various iterations of the quattro system by various combinations of open, limited slip, and eventually electronically locking differentials. See quatto generations below.


    [edit] Transverse quattro systems
    In some recent quattro-equipped models using a transverse engine and transmission positioning (i.e., TT Coupe and Roadster, and A3), power is sent primarily to the front axle. As a result, quattro badged cars using this configuration cannot be said to have a "permanent" all-wheel drive system. A Haldex electrohydraulic center limited-slip "coupler" (i.e. not a differential in the true sense) may divert up to 50% of the power to the rear axle as conditions warrant. The power split between left and right wheels is achieved through limited slip differentials with electronic locking. This system is also available in other Volkswagen Audi Group (VAG) A-platform Volkswagen, Seat, and Skoda vehicles, such as the Golf R32, re-named as 4motion. The exception among is among VAG B-platform models, such as the B5 Passat, which uses the aforementioned Torsen-based system since it uses a longitudinally-mounted engine.

    Advantages of the Haldex-based quattro system over the Torsen-based system are: a slight increase in fuel economy (due to the decoupling of the rear axle when not needed thereby reducing driveline losses due to friction), and a more balanced front/rear weight distribution (due to the location of the Haldex centre "differential" in the rear axle).

    Disadvantages of the Haldex system are: the vehicle has inherent front-wheel drive handling characteristics (as when engine-braking, load is only applied on the front wheels, and due to the reactive nature of the Haldex-based quattro and slight lag time in the redistribution of engine power).


    [edit] quattro generation I
    Used from 1981 to 1987 in Audi Quattro turbo coupe, Audi 80 B2 platform (1978-1987), Audi 100 C3 platform (1983-1992), Audi 4000, Audi 5000 in the American market.

    What: Permanent all wheel drive.

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

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

    Open front differential, no lock...

    ¹ - ABS disabled when locked.

    How: When two differentials are locked, up to 100% of torque can be transferred to either axle. The car will not move if one front wheel and both rear wheels lose traction.


    [edit] quattro generation II
    Starting from 1988 on older generation Audi C3 platform and Audi Quattro turbo coupe until the end of their production and on new generation B3 platform (1989-1992) Audi 80/90 Quattro, B4 platform (1992-1995) Audi 80, Coupe Quattro, Audi S2, Audi RS2, C4 platform (1991-1997) Audi 100 Quattro, Audi S4, earlier C4 platform (1995-1998) Audi A6/S6.

    What: Permanent all wheel drive.

    Torsen center differential, 50/50 split, automatically locking with up to 80% of torque transfer to either axle.

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

    Open front differential, no lock.

    ¹ - ABS disabled when locked, automatically unlocks if speed exceeds 25 km/h (15 mph)

    How: When rear differential is manually locked the car will not move if one front wheel and both rear wheels lose traction, but this is valid if all wheels are on the ground. Note that due to the constructive feature of the Torsen (TORque SENsing) differential if no torque is sensed on one axle the Torsen works as open differential e.g. if one front wheel is raised in the air the Torsen differential will not lock, all power is transferred to the wheel in the air and the car will not move.


    [edit] quattro generation III
    Used on Audi V8 starting from 1990.

    What: Permanent all wheel drive

    V8 with automatic transmission:

    Planetary gear center with electronically-controlled multi-plate locking clutch

    Torsen differential rear.

    Open differential front.

    V8 with manual transmission:

    Torsen differential middle.

    Torsen differential rear.

    Open differential front.

    How: The car will not be able to move if one front and both rear wheels lose traction. The Torsen effect with a front wheel raised in the air will not happen on V8 with automatic transmission. If the front axle loses traction the multi-plate clutch is automatically locked transferring up to 100% of torque to the rear axle.


    [edit] quattro generation IV
    Starting from 1996 on Audi A4/S4/RS4, Audi A6/S6/Audi_RS6, Audi A8/S8 with both manual and automatic transmissions. Also on VW Passat B5 4motion. Manually locking rear differential replaced by Electronic Differential Lock (Difflock imitation, detects wheelspin via ABS sensors and applies brakes to spinning wheels thus transferring torque via open differential to another wheel which has more traction)[1]. EDL works at speeds up to 40 km/h (25 mph), on more powerful versions such as S4/S6/S8 - up to 80 km/h (50 mph). In addition to EDL, Audi A8/S8 limits engine rpm when excessive wheelspin occurs.


    What: Permanent all wheel drive.

    Torsen center differential, 50/50 split, automatically locking with up to 80% of torque transfer to either axle. Some recent vehicles [2006+ B7 RS4] have a 40/60 front/rear torque split rather than 50/50

    Open rear differential, Electronic Differential Lock.

    Open front differential, Electronic Differential Lock.

    How: In on-road conditions the car will not move if all four wheels lose traction. Torsen effect with one wheel in the air will not happen on quattro IV because Electronic Differential Lock will apply brakes to spinning wheel and Torsen differential will transfer torque to rear axle.

    In off-road conditions (wheels in the air and an obstacle restricting the vehicle from moving forward) the car will not move further when one front and one rear wheels lose traction. The reason of this behavior is that Electronic Differential Lock is not a replacement for mechanical differential lock and it is not able to transfer enough torque to another wheel. The car will end up spinning one front and one rear wheel with crackling EDL trying to stop them from spinning.


    [edit] Haldex AWD
    Where: Starting from 1998 quattro has become just a trade mark and it does not indicate that all wheel drive system with Torsen differential is used on the vehicle any more. Vehicles with transverse engine mounting (Audi A3/S3 quattro, Audi TT quattro) are equipped with Haldex automatic all wheel drive. The same type of automatic all wheel drive is used on VW Golf/Bora/Jetta 4motion (Mark IV 1998-2005, Mark V 2003-), VW Sharan 4motion (2001-) and other Volkswagen AG vehicles with transverse engine mounting – Seat and Skoda.

    What: Automatic all wheel drive.

    Haldex multiplate clutch with electronic control acting as a center differential.

    Open rear differential, EDL on some models (not proved).

    Open front differential, EDL.

    How: Normally front wheel drive vehicle. In normal driving conditions 100% of torque transferred to front axle. When slipping occurs, Haldex multiplate clutch locks and up to 100% of torque is automatically transferred to rear axle. Haldex clutch offers instant activation – it locks as soon as one driveshaft travels just 1/8 of a turn further than the other. Front wheels do just 1/4 of a turn before AWD is activated. Accompanied by EDL on front wheels, in on-road conditions the car will not move if both front and one rear wheels lose 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 system is more reactive than preventative; the Torsen's even power split under non-slipping conditions makes slipping less likely to start, while the Haldex's greater torque split under slipping conditions is helpful for recovery.

    Haldex Electronic Control Unit disengages the clutch as soon as brakes are applied to allow ABS work properly; it also disengages the clutch when handbrake is pulled to allow “handbrake turns”. When performing tight low-speed turns (e.g. parking) the clutch is disengaged by Electronic Control Unit to avoid wind-up in transmission.


    [edit] Haldex aftermarket applications
    The Haldex centre differential is often used as upgrade to an aftermarket AWD conversion on older FWD volkswagens. It is said to be capable of withstanding larger power outputs than the also commonly used syncro system.

    The conversion is carried out by way of a syncro rear axle and associated live suspension system being fitted to a suitable project car (i.e. A VW Corrado or Golf mk2), and then fabricating a custom bracket to hold the Haldex centre differential.

    Enthusiasts often either use the OEM ECU and engine management from a newer VAG car to control the Haldex centre clutch using the standard yaw, steering angle and acceleration sensors - or can buy aftermarket controllers that supply the relevant Pulse Width Modulation to actuate the clutch and transfer drive to the rear wheels either via simple variable dial or based on Throttle Position (TPS) calculations


    [edit] 4motion
    4motion is Volkswagen's trademark name for it's four wheel drive system, but it functions the same as quattro (subject to application). It is available in A-platform Volkswagen, Seat, and Skoda vehicles, such as the Golf R32, in Haldex form, on which Audi's Haldex quattro is based. The exception among Volkswagen models would be the B5 Passat, which uses the aforementioned Torsen-based system since it uses a longitudinally-mounted engine (identical to quattro found in the A4).


    [edit] syncro
    syncro was the brand name of VW's older four wheel drive system. It, like 4motion, was not just one type of system. It was used in the B2 Passat (Quantum in the US), and was a re-brand of the Audi 4000 quattro Torsen system. It was also available on the transverse-engined Golf and B3 Passat, in a Haldex-like system, with viscous coupling. It acted like a front wheel drive system until slippage occurred, in which case the viscous differential would lock, and there would be an even 50:50 power split. It also came on Vanagons with a viscous coupling system, though it was flipped around, acting as a rear-biased system until slippage occurred. The viscous coupled systems have no relation to quattro.


    [edit] References
    ^ VAG four-wheel drive systems and brand names.

    [edit] See also
    4MATIC - a four wheel drive system from Mercedes-Benz.
    All-trac - a four wheel drive system from Toyota.
    ATTESA-ETS - a four wheel drive system from Nissan.
    Retrieved from "http://en.wikipedia.org/wiki/Quattro_%28all_wheel_drive_system%29"
    Shawn Olsen Austin TX ACNA#1616
    //95 S6 RS2 // 02 A6 4.2 // 04 S4

     
    0 0 0
     

  3. #3
    Join Date
    May 2007
    Location
    Poole
    Posts
    83
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)
    Cheers, Should have thought of wikipedia!

    Will read and inwardly digest!
    ========================================
    Julian Whitehead
    2001 A6 Avant 2.7T Q
    Swing Unlimited | www.subb.co.uk | www.myspace.com/swingunlimitedbigband
     
    0 0 0
     

  4. #4
    Join Date
    Jun 2007
    Location
    Austin Texas
    Posts
    61
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)
    Quote Originally Posted by webchem View Post

    Will read and inwardly digest!
    The short version is under NORMAL conditions ..50% of your torque is to the front wheels and 50% to the rear wheels...and when driving in a straight line I think 25% torque goes to each wheel.

    Shawn Olsen Austin TX ACNA#1616
    //95 S6 RS2 // 02 A6 4.2 // 04 S4

     
    0 0 0
     

Similar Threads

  1. Bad day at work
    By gresty in forum Chat - Completely Off Topic
    Replies: 9
    Last Post: 11-10-2011, 09:56 PM
  2. Ipod and cd changer work around....will this work?
    By Ben in forum Chat - Completely Off Topic
    Replies: 1
    Last Post: 10-07-2007, 03:47 PM
  3. Making my key fob work (bora uk)
    By wulfrob1 in forum Bora - 1998 - 2005
    Replies: 1
    Last Post: 19-06-2007, 08:17 AM
  4. Work begins
    By madfella65 in forum Audi A4 - Archive Topics
    Replies: 17
    Last Post: 09-06-2007, 01:25 AM
  5. key fob doesnt work please help
    By mya3 in forum Audi A3 - Archive Topics
    Replies: 1
    Last Post: 27-02-2007, 11:54 PM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


 



  


Disclaimer: VW Audi Forum is an "independant enthusiast website", administered in line with guidelines supplied by VAG in the UK, and is in no way related to any of the Worldwide Volkswagen,Audi,Seat,Skoda,Bentley,Bugatti,Porsche or Lamborghini group of Companies. For official up to date information on any of there vehicles, please visit the official websites. Any comments made throughout this website, are the views of the respective poster, and in no way represent the views of the VW Audi Forum Administration, or the worldwide Volkswagen & Audi Group of companies.


VW Audi Forum do not vet and are not responsible for any information which is posted in this forum. All content is viewed and used by you at your own risk and we do not warrant the accuracy or reliability of any of the information.


Copyright: Certain "words", "phrases" and "Images" used on this website by the Administration are "Copyright" of Volkswagen GB, Volkswagen AG (Germany), Audi GB, Audi AG (Germany), Volkswagen Motorsport GB, Volkswagen Motorsport AG (Germany), Audi Motorsport AG (Germany), Volkswagen Racing GB, Bentley, Bugatti, Porsche and Lamborghini. No image can be replicated by anyone WITHOUT the relevant Companies written permission.


All trademarks and copyrights remain property of their respective owners.

No part of the VW Audi Forum website or forum may be reproduced without written permission from the site administration


PLEASE NOTE - PERSONAL ABUSE, ABUSE AGAINST THIS OR ANY OTHER WEBSITE OR ANY COMPANY WILL NOT BE TOLERATED. OFFENDERS WILL BE MODERATED OR EVEN BANNED.


This website and forum are best viewed at a minimum resolution of 1024 by 768.



  



- VW AUDI Forum - The #1 Volkswagen (VW) Group Forum - Volkswagen (VW) - Audi - Seat - Skoda - Bentley - Bugatti - Lamborghini - Porsche - Scania - MAN - Ducatti - VW Audi Forum -


- www.vwaudiforum.co.uk - www.vwaudiforum.co.uk -