# Haldex (Quattro), how does it work?



## Shox Boy (Jun 25, 2003)

I search on the A3 forum and I found this post about FrontTrak vs. Quattro (Haldex). http://forums.vwvortex.com/zerothread?id=1959176
After reading it, it seems like the A3 3.2Q is FWD based. The thing I don't get is that if it is FWD based, and Quattro only kicks in when the need for traction. Then what's the difference between a Limited Slip or Traction Control compared to Haldex Quattro system?
Why I am asking is that after hearing that the 3.2 has quattro, I can't decide to get a 2.0T or a 3.2Q. The only reason I would get a 3.2 is cuz it is Quattro, but if it the 3.2 is FWD based, then why not just a get 2.0T, if the 3.2 is not full-time AWD?
I still don't get it, after reading the mentioned post and explaination from my friend.







Hope other Audi enthusiasts can help me out.


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## TheBigYahi (Mar 28, 2005)

*Re: Haldex (Quattro), how does it work? (Shox Boy)*

the rear wheels don't ever get power with FrontTrak because there's no axle to the rear or any mechanism to send power there. quattro, whether haldex or torsen has a power delivery method to the rear wheels. haldex works by having an electronically activated clutch that sends power to the rear wheels when it detects slip.
traction control simply applies brakes in a calculated manner when you begin skidding or sliding to try to get you back on track.


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## Nuvolari (Jun 22, 2004)

*Re: Haldex (TheBigYahi)*


_Quote, originally posted by *TheBigYahi* »_traction control simply applies brakes in a calculated manner when you begin skidding or sliding to try to get you back on track.

What you are describing above is ESP (Electronic Stabilization Program). It works to prevent you from going into a skid where you might lose control over your car. It controls the stability of the car by applying brakes on one or two wheels--the ones necessary in the individual dynamic situation.
Traction control does only that: control _traction_. If your powered wheels lose traction (because they are overpowered for that dynamic situation), traction control reduces power to these wheels (by either applying brakes, or reducing engine power, or both). It slows you down.


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## TheBigYahi (Mar 28, 2005)

*Re: Haldex (Nuvolari)*

ah right, VAG calls traction control ASR right?


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## Shox Boy (Jun 25, 2003)

*Re: Haldex (Nuvolari)*

So traction control REDUCES power on only the powered wheels (i.e. front wheels for fwd). 
But Haldex sends power to all wheels to match power for equal stability and traction? Am I correct along those lines?


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## dandle (Sep 14, 2005)

*Re: Haldex (Shox Boy)*


_Quote, originally posted by *Shox Boy* »_So traction control REDUCES power on only the powered wheels (i.e. front wheels for fwd). 
But Haldex sends power to all wheels to match power for equal stability and traction? Am I correct along those lines?

Kind of. Traction control on the A3 will start to brake the wheel that is about to spin(starting to slip) this will transfer some of the power to the wheel the other side(due to the action of the diff) You only have to worry about powered wheels for traction control as the others are only being pushed or pulled along. If both wheels are about to slip then it will retard the engine power until it is under control and no wheels are slipping. Haldex senses the wheel slip and engages the back wheels, by doing that your now stealing power from the front to power the rear this reduced power on the front can no longer cause the fronts to slip(in most situations). If you end up with all wheels spinning then the engine will again retard the power output. 


_Modified by dandle at 9:08 AM 12-20-2005_


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## ylwghost (Sep 30, 2004)

*Re: Haldex (Quattro), how does it work? (Shox Boy)*


_Quote, originally posted by *Shox Boy* »_Then what's the difference between a Limited Slip or Traction Control compared to Haldex Quattro system?


Guess your question is.. swap in an LSD on the 2.0; or fork over $4k for the V6+Haldex
-Haldex has a 'type' of LSD which has already been described (EDL braking slows the spining tire and sends that power to the other wheel with more traction) EDL is a compromised LSD (but efficent for street use)
-Question: do frontracs have EDL braking? (want to see if you are starting with the same equipment)
So Haldex is going to be more dynamic than FWD because it can distrubute power to all 4 wheels.. but it is a compromised AWD system.
-it doesn't have a center differential.. so you can expect to feel the weight transfer which may be unsettling to some at high speeds. 
The Viscous coupling devise that is used is not compatible with ABS/EDL.. so it will disengage when you hit the brakes (100% FWD)
I enjoy the feeling of being surrounded by torque.. but ~$40k for a non-transparent AWD system?
-give it to me as an only option on a MK5 GTI; I'll jump all over it
But if you are talking track purposes; you are arguably better off with FWD and a real LSD
-However, If I was planning on getting the same options on a 2.0 that are standard on the 3.2.. $4k for having a cosworth tunned V6 infront of me + being surrounded by Torque (most of the time); would be still well worth it (if I had the money)


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## yam (Jul 18, 2005)

Using the search button...
http://forums.fourtitude.com/zerothread?id=2302076
http://www.difflock.com/offroad/4x4explained.shtml
Have fun with the new info.


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## jakbeatz (Nov 26, 2005)

*Re: Haldex (dandle)*

This is all assuming you have ESP enabled, correct? If you have ESP disabled, you will not experience lack of power due to the engine retarding the power, nor will you experience slipping wheels braking?


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## montrala (Oct 24, 2005)

*Re: Haldex (jakbeatz)*

With ESP disabled, EDL is still working and it will work until rear brakes (EDL is realised by means of applying power to rear brakes to limit slip on diff) will overheat. This can happen for eg. if you are doing donuts on snow, ice or mud for extended period.


_Modified by montrala at 6:23 AM 12-21-2005_


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## DBLFRVGNGN (Sep 24, 2000)

*Re: Haldex (Quattro), how does it work? (Shox Boy)*

Just go drive it in the snow! Its an excellent and quite seemless style of AWD. While its different from 'regular' quattro- it works very well.
RB


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## montrala (Oct 24, 2005)

*Re: Haldex (DBLFRVGNGN)*

Definitelly lots of fun in snow. Lancer Evo or Delta Integrale it's not... but defintelly more fun that A4 Quattro








ESP mandatory disabled and DSG in S or +/-


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## ylwghost (Sep 30, 2004)

*Re: Haldex (montrala)*


_Quote, originally posted by *montrala* »_Definitelly lots of fun in snow. Lancer Evo or Delta Integrale it's not... but defintelly more fun that A4 Quattro 

Comparing the A4q to A3q in terms of fun is like comparing a Jetta to a Passat. (its more in terms of wheel-base than AWD)
-but I agree that Haldex offers its unique degree of fun in the right conditions. (I have seen drivers use Haldex's sudden weight transfer to an advantage in the snow.. breaking the rear loose and using that momentum to get the fulcrum-type drift simular to a RWD car)(The fronts of an A4 and its 2:1 Torsen differential will always be clawing its way out of the drift) 
The most fun ideally would be a B5 with a Stasis 4:1 Torsen differential.. along with a FSI2.0T swap (someday)
-but that should give you a static rear bias on an Audi of simular size to the current A3 (when your talking fun you can do away with the new A3's luxuries)


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## DemianSP (Dec 27, 2005)

*Re: Haldex (Quattro), how does it work? (Shox Boy)*

Sorry for the German Text, i cant translate it. But perhaps is anybody here who speakes German. It shows you how the Haldex in the A3 works
Auf der Suche nach einem intelligenten Allradantrieb, der vor allem regelbar ist, stießen die Antriebstechniker von Volkswagen im Jahre 1995 auf eine neue Kupplungsart. Dabei handelt es sich um das Antriebskonzept der schwedischen Firma Haldex, für das die Allrad-Spezialisten von Steyr-Daimler-Puch in Österreich die Funktions-Software entwickelt haben. Kernstück ist eine im Ölbad laufende Lamellenkupplung, die axial zusammengedrückt wird. Mit der Höhe des ausgeübten Drucks lässt sich das übertragbare Drehmoment variieren und damit die Kraftübertragung auf die Hinterräder regeln. Der Druck wird nach allen Regeln der Programmier-Kunst so gesteuert, dass der "4MOTION" getaufte, neue High-Tech-Allradantrieb alles das kann, was dem bisherigen Syncro-Antrieb fehlte
Ihr elektronisches Steuergerät erhält Informationen über den Hauptweg aller elektronischen Informationen, den CAN-Bus. Dieser überträgt vom ABS- und Motorsteuergerät: Signale von den Radsensoren, Signale der Schlupf-Regelsysteme und Bremsen, Motorsignale wie Gaspedalstellung, Motordrehzahl u.a. Abhängig davon regelt sie Höhe und Verlauf des hydraulischen Drucks, der auf die Kupplungslamellen ausgeübt wird. Den Druck erzeugen zwei kupplungsinterne Ringkolbenpumpen. Sie werden nur dann wirksam, wenn Ein- und Ausgangswelle nicht mit gleicher Drehzahl laufen. Denn nur dann ist eine Drehmomenten-Aufteilung erforderlich
Ein wesentlicher Vorzug der Haldex-Kupplung ist ihre außerordentlich kurze Reaktionszeit: Schon nach einem Drehwinkel von nur 45 Grad - also am Anfang der ersten Umdrehung nach "Befehlsempfang" durch elektronisches Signal - liegt der Druck vollständig an und erzeugt das entsprechende Hinterachs-Drehmoment. Die Kupplung regelt das Moment stufenlos von Null bis zur vollen Übertragung hoch, was einer Aufteilung des Antriebs von 50:50 zwischen Vorder- und Hinterrädern entspricht, je nach Reibwertverhältnis sind sogar bis zu 100 Prozent des Antriebsmoments an der Hinterachse möglich
Sie ist sehr robust ausgelegt und kann maximale Momente bis 3200 Newtonmeter an die Hinterachse übertragen. Das ist mehr als das Doppelte gegenüber der bisherigen Visco-Kupplung.
Vorteile: 
Sie verwirklicht den permanenten Allradantrieb, sobald der Motor gestartet wird und ist regelbar. 
Sie garantiert spurstabiles Beschleunigen 
sowie neutrales bis leicht untersteuerndes Fahrverhalten im Normalbetrieb und 
sogar übersteuerndes Fahrverhalten bei Leistungsüberschuss. 
Sie führt zu einem gutmütigen Fahrverhalten im Schubbetrieb, 
verspannt sich beim Rangieren nicht, 
verkraftet unterschiedliche Reifenumfänge (Notrad) und 
gestattet das Abschleppen mit angehobener Achse. 
Vor allem aber harmoniert sie mit allen Schlupf-Regelsystemen von der Antiblockierbremse (ABS) über Antriebsschlupf-Regelung (ASR) und elektronischer Differentialsperre (EDS) bis hin zum Fahrstabilitätsprogramm (ESP).
Das Motordrehmoment wird über das Schaltgetriebe, das Vorderachsdifferenzial und den Vorderachsantrieb auf die Kardanwelle übertragen. Die Kardanwelle ist mit der Eingangswelle der Haldex-Kupplung verbunden. In der Haldex-Kupplung ist die Eingangswelle von der Ausgangswelle zum Hinterachsdifferenzial getrennt. Eine Drehmomentübertragung auf das Hinterachsdifferenzial kann nur über das geschlossene Lamellenpaket der Haldex-Kupplung erfolgen.
Funktion der Mechanik
Im Moment des Beschleunigens dreht die Eingangswelle mit dem Rollenlager des Hubkolbens um die noch stehende Hubscheibe der Ausgangswelle. Dabei läuft das Rollenlager des Hubkolbens über eine Berg- und Talbahn der Hubscheibe. Diese Auf- und Abbewegungen gibt die Rolle weiter auf den Hubkolben. Der Hubkolben wird dadurch in Hubbewegung versetzt und baut einen Öldruck auf. Dieser Öldruck wird über einen Ölkanal an den Arbeitskolben gelenkt. Der Arbeitskolben wird durch den Öldruck nach links gegen die Lagerrolle und Druckplatte des Lamellenpaketes gedrückt. Das Lamellenpaket wird zusammengepresst. Die Verbindung der Eingangswelle zur Ausgangswelle der Kupplung ist hergestellt, und damit der Allradantrieb.
Bei Drehzahldifferenz zwischen der Vorder- und der Hinterachse dreht das Außenlamellengehäuse mit den Rollenlagern um die Ausgangswelle, so dass die Rollenlager des Hubkolbens auf der Hubscheibe abrollen. Durch die Form der Hubscheibe durchlaufen die Rollenlager des Hubkolbens eine Berg- und Talbahn und geben diese Hubbewegung auf den im Gehäuse liegenden Hubkolben weiter. 
Die Ausgangswelle mit der Längsverzahnung für die Innenlamellen bildet mit der Hubscheibe und dem Trieblingskopf eine Einheit. Das Außenlamellengehäuse mit der Längsverzahnung für die Außenlamellen und den Rollenlagern bilden eine Einheit mit der Eingangswelle.
Durch die Hubbewegung des Hubkolbens wird ein Öldruck erzeugt, der sich über den Ölkanal auf den Arbeitskolben auswirkt und diesen nach links treibt.
Über die Rollenlager des Arbeitskolbens wird der Druck über eine Druckplatte auf das Lamellenpaket übertragen. Die Kupplung schließt und stellt so eine Verbindung zwischen der Vorder- und der Hinterachse her.


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## jakbeatz (Nov 26, 2005)

*Google's translation:*

The search for an intelligent all-wheel drive, which is above all adjustable, the drive technicians of Volkswagens encountered in the year 1995 on a new kind of clutch. It concerns the propulsion principle of the Swedish company Haldex, for whom specialists of Steyr Daimler Puch developed the all wheel in Austria the function often commodity. Principal item is a multiple disk clutch running in the oil bath, which is axially squeezed together. With the height of the exercised pressure the transferable torque can be varied and to be regulated thus the power transmission to the rear wheels. The pressure is steered in such a way according to all rules of the programming art that the "4MOTION" knows baptized, new High Tech all-wheel drive of everything that, which was missing to the past Syncro drive your electronic controller receives information about the artery of all electronic information, the CAN bus. This transfers from the abs and engine expensive equipment: Signals of the wheel sensors, signals of the slip monitoring systems and brakes, engine signals such as position of the gas pedal, engine speed among other things. Dependent on it it height regulates and process of the hydraulic pressure, which is exerted on the clutch lamellas. Two clutch-internal annular piston pumps produce the pressure. They become effective only if in and output wave do not run with same number of revolutions. Because only then an allocation of torque is necessarily a substantial preference/advantage of the Haldex clutch is their extraordinarily short response time: Already after an angle of rotation of only 45 degrees - thus at the beginning of the first revolution after "command receipt" by electronic signal - the pressure fits completely and produces the appropriate rear axle torque. The clutch regulates the moment steplessly from zero to the full transmission high, which corresponds to an allocation of the drive of 50:50 between front and rear wheels, depending upon friction value relationship is even up to 100 per cent of the drive moment at the rear axle possible you is very durably laid out and can maximum moments to 3200 Newtonmeters to the rear axle transfer. That is more than the double opposite the past Visco clutch. Advantages: It carries out the permanent all-wheel drive, as soon as the engine is started and is adjustably. It guarantees trace-stable accelerating as well as neutral to easily untersteuerndes handling in the normal operation and handling even overriding with energy surplus. It leads to a good-natured handling in the thrust enterprise, does not strut themselves when ranking not, bears different tire extent (emergency wheel) and permits a towing with raised axle. Above all however it harmoniert with all slip monitoring systems of the anti-blocking brake (ABS) over drive slip regulation (ASR) and electronic differential lock (EDS) up to the driving stability program (ESP). The engine torque becomes over the transmission, which Vorderachsdifferenzial and the front wheel drive transfer to the cardan shaft. The cardan shaft is connected with the entrance wave of the Haldex clutch. In the Haldex clutch the entrance wave is separate from the output wave to the Hinterachsdifferenzial. A torque transmission to the Hinterachsdifferenzial can be made only by the closed lamella package of the Haldex clutch. Function of the mechanics for the moment accelerating turns the entrance wave with the roller bearing of the lifting cylinder around the still standing stroke disk of the output wave. The roller bearing of the lifting cylinder runs over a mountain and a valley course of the stroke disk. These up and Abbewegungen continues to give the role on the lifting cylinders. The lifting cylinder is shifted thereby in stroke and develops an oil pressure. This oil pressure is directed over a oelkanal at the working pistons. The working piston is pressed to the left by the oil pressure against the camp role and pressure plate of the lamella package. The lamella package is pressed together. The connection of the entrance wave to the output wave of the clutch is manufactured, and thus the all-wheel drive. With number of revolutions difference between the front and the rear axle turns the external lamella housing with the roller bearings around the output wave, so that the roller bearings of the lifting cylinder unreel on the stroke disk. By the form of the stroke disk the roller bearings of the lifting cylinder go through a mountain and a valley course and pass this stroke on on the lifting cylinders lying in the housing. The output wave with longitudinal teeth for the interior lamellas forms a unit with the stroke disk and the Trieblingskopf. The external lamella housing with longitudinal teeth for the external lamellas and the roller bearings form a unit with the entrance wave. An oil pressure is produced by the stroke of the lifting cylinder, which affects over the oelkanal the working pistons and drives this to the left. Over the roller bearings of the working piston the pressure will transfer over a pressure plate to the lamella package. The clutch closes and makes so a connection between the front and the rear axle.


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## Nuvolari (Jun 22, 2004)

No matter how it works, it works! I sell those, and I've driven both the 2.0T and the 3.2 quattro. Believe me, it wasn't easy for me to dish out $4000 more for the 3.2. If there were no difference, I would have saved that money, as the 2.0T is a great engine. But when you want to apply its power, the driven wheels tend to lose grip, particularly the way I drive. That has never happened with the much more powerful 3.2. So, there's your answer. It works.


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## DemianSP (Dec 27, 2005)

*Re: Google's translation: (jakbeatz)*

Thankx for translating


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## ylwghost (Sep 30, 2004)

*Re: Google's translation: (jakbeatz)*

thanks for the translation..

_Quote, originally posted by *jakbeatz* »_The clutch regulates the moment steplessly from zero to the full transmission high, which corresponds to an allocation of the drive of 50:50 between front and rear wheels,* depending upon friction value relationship is even up to 100 per cent of the drive moment at the rear axle possible... *

Which explains RWD-type drifts in the snow..
(common misconception is that Haldex *can not* ever transfer more than 50% to the rear)(only this happens with certain conditions)


_Quote, originally posted by *jakbeatz* »_depending upon friction value relationship is even up to 100 per cent of the drive moment at the rear axle possible* you is very durably laid out and can maximum moments to 3200 Newtonmeters to the rear axle transfer.*

what is the 3200 Newtonmeters refering to?


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## gizmopop (Feb 6, 2000)

*Re: Google's translation: (ylwghost)*


_Quote, originally posted by *ylwghost* »_thanks for the translation..
Which explains RWD-type drifts in the snow..
(common misconception is that Haldex *can not* ever transfer more than 50% to the rear)(only this happens with certain conditions)

what is the 3200 Newtonmeters refering to?

Torque...they use Newtonmeters (NM) vs ft/lb (or lb/ft, I always screw up the order...







)
as an R32 owner, with ESP on, it will intervene diminishing the power if it thinks your going to fast for the steering angle (often times killing the fun as well) with ESP off, it will let you apply the power, the AWD will usually get you going in the pointed direction anyway...


_Modified by gizmopop at 6:10 PM 12-28-2005_


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## aussie audi guy (Jan 28, 2003)

*Re: Google's translation: (gizmopop)*

http://www.haldex-traction.com
All the info & tech info is on this site in German


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## yam (Jul 18, 2005)

*Re: Google's translation: (gizmopop)*


_Quote, originally posted by *gizmopop* »_
Torque...they use Newtonmeters (NM) vs ft/lb (or lb/ft, I always screw up the order...







)
_Modified by gizmopop at 6:10 PM 12-28-2005_

Actually its Newton*meters, as in Newtons multiplied by meters. No "/" or division. Sames goes with ft*lb or lb*ft.


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