Torsen
1453010
224839495
2008-07-10T17:25:11Z
66.163.19.99
/* Torsens in front and/or rear axles */
[[Image:Audi quattro AWD system.jpeg|thumb|250px|Torsen differential from an [[Audi]] [[quattro (four wheel drive system)|quattro]]]]
'''Torsen''', (full name '''Torsen traction'''), is an [[automotive]] part, a [[limited slip differential]]. It was invented by [[United States of America|American]] Vernon Gleasman<ref name="theautochannel.com">{{Cite web|url=http://www.theautochannel.com/news/2004/11/19/285488.html|title=Inventor Of Automotive Technologies - Vernon Gleasman's Legacy|accessdate=2008-05-17|work=theautochannel.com}}</ref> and manufactured by the Gleason Corporation.
Torsen is a contraction of '''''Tor'''que-'''Sen'''sing''.
''TORSEN'' and ''TORSEN Traction'' are registered [[trademarks]] of JTEKT Torsen North America Inc (formerly Zexel Corporation, formerly Gleason Power Systems).
Torsen differentials can be utilised in one or more positions on a [[motor vehicle]]:
* '''centre''' - used to apportion appropriate [[torque]] distribution between front and rear axles on a [[four-wheel drive]] vehicle.
* '''rear''' - used to apportion appropriate torque distribution between left and right sides in rear axles. This may be on either a [[rear-wheel drive]] or four-wheel drive vehicle.
* '''front''' - used to apportion appropriate torque distribution between left and right sides in front axles. This may be on either a [[front-wheel drive]] or four-wheel drive vehicle.
As an example, on a four wheel drive vehicle, it may use either one, two, or three Torsen differentials.
==Types of Torsen==
There are currently three types of Torsen differentials.
# The original ''Torsen T-1 (Type A)'' uses crossed axis [[helical gear]]s to increase internal [[friction]]. The Type I can be designed for higher torque bias ratios than the Type II, but typically has higher backlash and the potential for Noise, Vibration, and Harshness (NVH) issues, and requires a precise setup/installation.
# The later ''Torsen T-2 (Type B)'' uses a [[gear|parallel gear]] arrangement to achieve a similar effect. There is also a specialist application of the T-2, known as the ''T-2R (RaceMaster)''.
# The latest ''Torsen T-3 (Type C)'' is a [[planetary gear|planetary type]] differential, in that the intended [[torque]] split is not 50:50. The Type C is available as single or twin version, the Torsen twin C differential has front and center differential in the same unit.<ref name="autozine.org">{{Cite web|url=http://www.autozine.org/html/Alfa/Brera.html|title=Alfa Romeo Brera|accessdate=2008-05-17|work=autozine.org}}</ref>
The Torsen T-3 will be employed as the centre differential in all future non-[[Haldex Traction]] [[Audi]] models with [[quattro (four wheel drive system)|quattro]] [[four-wheel drive]], current applications: [[Audi S4|2008 Audi S4 (B7)]], [[Audi RS4|Audi RS4 (B7)]], and [[Audi Q7]]. [[Alfa Romeo]] uses Torsen C twin differential in [[Alfa Romeo 156|Alfa Romeo 156 Crosswagon]] Q4 and then in [[Alfa Romeo 159|159]], [[Alfa Romeo Brera|Brera]] and [[Alfa Romeo Brera|Spider]] Q4 models. Also [[Toyota]] uses a Torsen T-3 in the center differential of the [[Toyota 4Runner]] and [[Lexus]] [[GX470]], with manual locking feature, and [[General Motors|GM]] has a Torsen T-3 centre differential in the (non rear drive) [[Chevrolet Trailblazer|Chevrolet TrailBlazer SS]].
==How they work==
The Torsen differential works by supporting a torque imbalance, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR). When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to 75% while the other side would have to only handle 25% of applied torque. During acceleration under asymmetric [[traction]] conditions, so long as the higher traction side can handle the higher percentage of applied torque, no relative [[wheelspin]] will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the [[angular acceleration]] of the faster output side of the differential.
NOTE: The TBR should not be confused with the uneven torque-split feature in the planetary-type Torsen III. The planetary gearset allows a Torsen III center differential to distribute torque unevenly between front and rear axles during normal (full traction) operation without inducing wind-up in the drivetrain. This feature is independent of the Torque Bias Ratio.
===Torsens in front and/or rear axles===
When attempting to turn with a torque sensitive differential, the outer wheel will need to rotate more quickly relative to the differential, and the inner wheel will rotate more slowly than the differential. Friction in the differential will oppose motion, and that will work to slow the faster side and 'speed up' the slower/inner side. This leads to asymmetric torque distributions in drive wheels, matching the TBR. Cornering in this manner will reduce the torque applied to the outer tire, leading to possibly greater cornering power, unless the inner wheel is overpowered (which is easier to do than with an open differential). When the inner tire (which has less traction due to weight transfer from lateral acceleration) is overpowered, it angularly accelerates up to the outer wheel speed (small percent wheel spin) and the differential locks, and if the traction difference does not exceed the TBR, the outer wheel will then have a higher torque applied to it. If the traction difference exceeds the TBR, the outer tire gets the tractive torque of the inner wheel multiplied by the TBR, and the remaining applied torque to the differential contributes to wheel spin up.
When a Torsen differential is employed, the slower-moving wheel always receives more [[torque]] than the faster-moving wheel. The Torsen T-2R RaceMaster is the only Torsen to have a preload [[clutch]]. So even if a wheel is airborne torque is applied to the other side. If one wheel were raised in the air, the regular Torsens would act like an [[open differential]] and no torque would be transferred to the other wheel. This is where the parking brake 'trick' can help out. If the parking brake is applied, assuming that the parking brake applies even resistance to each side, the drag to the airborne side is 'multiplied' through the differential and TBR times the drag torque is applied to the other side. So the ground side would see (TBR X drag torque) minus drag torque, and hopefully that can help restore progress either forward/backwards. In Hummer/[[HMMWV]] applications, there are both front and rear torsen differentials, so use of the main brakes will operate this 'trick' on both axles simultaneously.
===Notable Torsen users===
One of the most famous uses of Torsen differentials are in many of the various [[Audi]] [[quattro (four wheel drive system)|quattro]] models, notably excluding the [[Audi A3|A3 & S3]] and [[Audi TT|TT]] (which have [[transverse engine|transverse-mounted engines]] and use [[Haldex Traction]] 4WD systems).
It is also used, for example, in the [[Toyota Supra]] and [[Toyota Soarer]] (or [[Lexus SC|Lexus SC430]]), the B5 platform revision of the [[Volkswagen Passat]] [[4motion]] (based upon the Audi [[Audi A4|A4]]), and some versions of the [[Mazda Miata|Mazda MX-5/Miata]]. The [[Lancia Delta Integrale]] also had a Torsen differential.
The [[High Mobility Multipurpose Wheeled Vehicle|HMMWV or Humvee]] uses two Torsens, front and rear, with a normal manually lockable center differential (NVG242HD AMG transfer case) in the center.
==Torsen applications==
===Center===
* [[Alfa Romeo]]: [[Alfa Romeo 156|156 Crosswagon & Sportwagon]], [[Alfa Romeo 159|159]], [[Alfa Romeo Brera|Brera & Spider Q4]]
* [[quattro (four wheel drive system)|quattro]] versions of [[Audi]]:
** [[Audi Quattro]]
** [[Audi 80|Audi 80 & 90]], [[Audi S2#Audi S2 and RS2|Audi S2 & RS2]], [[Audi RS2 Avant]]
** [[Audi 100|Audi 100 / Audi 200 / Audi 5000]]
** [[Audi Coupé quattro]]
** [[Audi A4]], [[Audi S4]], [[Audi RS4]]
** [[Audi A5|Audi A5 & S5]]
** [[Audi A6]], [[Audi S6]], [[Audi RS6]]
** [[Audi A8]], [[Audi S8]]
** [[Audi allroad quattro|A6 allroad quattro]]
** [[Audi Q7]]
** [[Audi R8]]
** [[Audi V8 manual]]
* [[Chevrolet TrailBlazer|Chevrolet TrailBlazer SS]]
* [[Lexus|Lexus]] [[Lexus GX|GX 470]], [[Lexus_ls#LS_600h_.2F_LS_600h_L|LS 600h / LS 600h L]]
* [[Range Rover]] L322
* [[Toyota]]: [[Toyota 4runner|4runner]], [[Toyota FJ Cruiser|FJ Cruiser]] (only manual models)
* [[Volkswagen Passat]] (badged as [[4motion]]) (B5 platform)
===Center and rear===
* [[Audi V8 with manual transmission]]
===Front and rear axles===
* [[High Mobility Multipurpose Wheeled Vehicle|HMMWV or Humvee]]
* [[Subaru Impreza|Subaru Impreza STI]]
===Front axle only===
* [[Honda Integra|Honda/Acura Integra]] [[Honda Type R|Type R]]
* [[Alfa Romeo]]: [[Alfa Romeo GT|GT]], [[Alfa Romeo 147|147 Q2]]
* [[Honda Civic Si]] (06-current)
* [[Honda Civic vti 1.8]]
* [[Nissan Sentra]] SE-R Spec-V
* [[Oldsmobile Cutlass Calais|Oldsmobile Calais W41]] (7 cars equipped from the factory, C41 option code)
* [[Oldsmobile Achieva|Oldsmobile Achieva W41]] (7-10 cars equipped from the factory, C41 option code)
* [[Rover 200 Coupe]] Turbo, 220 Turbo , 420 Turbo , 620 Ti , 820 Vitesse (200PS version only)
* [[Mazdaspeed 3]]
* [[Honda Accord]] [[Honda Type R|Type R]]
===Rear axle only===
* [[Audi V8 with automatic transmission]]
* [[Alfa Romeo]]: [[Alfa Romeo 155|155 Q4]], [[Alfa Romeo 164|164 Q4]]
* [[Citroen BX 4x4 with ABS]]
* [[Ford F-Series|Ford FX4]]
* [[Honda S2000]]
* [[Lancia Delta Integrale]]
* [[Lexus IS300]]
* [[Mazda]]: [[Mazda MX-5|Miata/MX-5]] ('94+ manual models), [[Mazda RX-7|RX-7]], [[Mazda RX-8|RX-8]]
* [[Peugeot 405 4x4 with ABS (same as Citroen BX 4x4)]]
* [[Subaru Impreza WRX STI]] (2007)
* [[Toyota Supra]]
==See also==
* [[Limited slip differential]]
* [[Haldex Traction]]
== References ==
{{reflist}}
==External links==
*[http://www.torsen.com Torsen Traction official site]
**[http://www.torsen.com/files/Traction_Control_Article.pdf Torsen traction control article] (PDF)
*[http://torvec.com/products_isotorque.html Torvec IsoTorque]
*[http://members.rennlist.org/951_racerx/PS84Gleason.html Popular Science article]
*[http://individual.utoronto.ca/stehlik/torsen.html Torsen in LEGO]
<br>
[[Category:Automotive transmission technologies]]
[[Category:Automotive technology tradenames]]
[[Category:Audi]]
[[de:Torsen-Ausgleichsgetriebe]]
[[es:Torsen]]
[[it:Torsen]]
[[no:Torsen]]
[[pl:TorSen]]
[[sv:Torsendifferential]]