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Gen4 Haldex on the facelift S3

Discussion in 'A3/S3/Sportback (8P Chassis)' started by sakkie69, Aug 15, 2008.

  1. sakkie69
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    sakkie69 2008 Audi S3

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    According to Haldex the new facelift S3 will have the newest generation Haldex on it (generation 4). Does anyone know what difference this makes, as the current S has gen2 in it? (gen3 was used in I think the VW Tiguan)
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  2. Dandle
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    Dandle Member

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    Looks like gen 4 doesnt need a difference in axle speeds to vary the amount of torque its transfering and can vary it on its own. It would be unusual for the latest version of haldex to be fitted to a current platform(8P) but maybe they could do it, I didnt see anything on haldex traction about the new system being fitted to the S3.
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  3. sakkie69
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    sakkie69 2008 Audi S3

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    I got the email from Haldex themselves, I emailed them about joining the AWD club they have on their website. I asked them about any differences between the current S3 and the facelift one and I got
    "They have changed to Generation 4 during early spring 2008 according to info from Audi. Meaning that the year model 2009 should contain Generation 4."
    #3
  4. liam
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    liam waiting, waiting, waiting

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    According to the clips available on the "Technical" tab (HERE) as much as 90% of power can be sent to the rear wheels.

    Am I right in thinking the Gen2 Haldex could only send a maximum of 50% to the rear wheels?
    #4
  5. Dandle
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    Dandle Member

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    No both can send up to 100% of all torque transfer to the rear wheels but only if the fronts have zero grip. If all wheels have good grip and arent loosing traction then the maximum is 50/50 transfer, as the power for the rear diff/haldex unit is tapped directly of the front diff feeding power to the front wheels. The only way the rear can have more power is if the front is loosing traction/not able to make use of the power available.
    #5
  6. liam
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    liam waiting, waiting, waiting

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    Thanks for that. :thumbsup:
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  7. Dadracer
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    Dadracer New Member

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    If as seems likely it is the Gen 4 system on the S3 now, does that mean the eLSD that is fitted to the Saab XWD and new Insignia can be retro fitted to the S3? :think:
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  8. liam
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    liam waiting, waiting, waiting

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    Yeah, in addition to sakkie69 above I sent the following to the Haldex AWDclub folks...

    Q: Can you please advise which Haldex system is used on the latest "facelift" Audi S3.
    A: Audi S3 has a Haldex Gen IV coupling.

    I'm just trying to find some decent documentation that lists the difference between Gen II and Gen IV Haldex.

    :detective2:
    #8
  9. Dandle
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    Dandle Member

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    It looks to me like the difference between gen 3 and gen 4 is the eLSD and the fact that it doesnt any longer rely on a difference in speed across the input and output of the haldex unit to regulate the amount of pressure on the clutch pack(this difference in speed used to run a pump that closed the clutch pack, the more difference the greater the pressure the more the pack closed so the more power was transferred). Now it still has the pump but it also has an accumulator to hold a store pressure for when greater pressure then the mechanical pump can deliver is needed. It also has an electric pump to charge the system when the car hasnt moved(gen 3 which is also known as gen2 with pre-x before haldex renamed it had an electric pump but it was to only help instant torque transfer when moving off from stationary).
    #9
  10. Dandle
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    Dandle Member

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    I don't know but I wouldnt think it would be that easy. The main thing would be if all the inputs into the later haldex ECU are the same as the earlier versions(or available) if not then the car would need a new ecu too.
    #10
  11. larksoft
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    larksoft Larksoft

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    This Gen IV info conflicts with what the folks at hpamotorsport.com told me, but those guys may be wrong.

    I have a 2009 "Facelift" S3. If looking under the bonnet helps, let me know where to look and I'll tell you what I see :).

    Short of hunting down a workshop manual for this model S3 (does one even exist yet?), it'd be good to get an authoritative answer from Audi or Haldex (that looks like one above?).

    There is quite a good description of the different versions at http://en.wikipedia.org/wiki/Haldex . That last note on Gen IV was put there by me on the basis of this thread :-/.
    #11
  12. MACCAA
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    MACCAA New Member

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    Timbo and I ran our cars at Wakefield Race Track last week.Both are 2008 S3's,so presumably run Gen 2 Haldex.
    Cars are completely stock apart from reflash[mine APR,Timbo GIAC]
    Handling is very good,on stock Bridgestone 050A rubber.
    If the facelift model has a better Haldex,you should be pretty pleased with the handling,as we have no complaints at all about it.
    Cheers
    Len
    #12
  13. Lima
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    Lima AUSmotive.com

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    I'm sure MACCAA won't mind me posting this email exchange between him and Haldex, which he sent to me last week. The reply showing the part numbers will be of interest to a few here I'm sure...

    #13
  14. BoufisG
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    BoufisG New Member

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    Hello all,

    I recently scanned my car with Vag-Com and this is what I came across

    Address 22: AWD Labels: None
    Part No SW: 0BR 907 554 A HW: 0BR 907 554 A
    Component: Haldex 4Motion 3016
    Coding: 0000005
    Shop #: WSC 00000

    No fault code found.

    So in other words, it should be equiped with Gen4 haldex ECU. Btw the car is an S3 Sportback late 2008 production. To be honest at first when I pushed in into a few corners it did give me a feeling that the back end was a bit lets say more... "alive and eager to pop out" something that the 07' test drive car did not do for me. Oh well, dunno, i guess the newer the better :racer:

    cheers!
    #14
  15. Dandle
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    Dandle Member

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    You would need to go on the HW version to find out if it is gen4. I dont think Haldex 4motion means its gen 4 necessarily(maybe someone else with vagcom can compare a known earlier car). Haldex may well call all the couplings 4 motion after all thats what VW have used to signify awd on cars for years including haldex equiped ones.
    #15
  16. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    :whistle2:
    Part No SW: 0BR 907 554 A HW: 0BR 907 554 A
    #16
  17. Dandle
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    Dandle Member

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    Thanks but what does it mean then, what version is it?
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  18. Rabbit222
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    Rabbit222 Member

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    OAR = Gen II
    OBR = Gen IV
    #18
  19. Dandle
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    Dandle Member

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    What was gen 3 then?
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  20. Lima
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    Lima AUSmotive.com

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    Gen III is also known as Saab's XWD system.

    AFAIK they're the only company to use the Gen III spec.
    #20
  21. S3 Big Andy
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    S3 Big Andy Stealth Beast Baby Yay

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    Might get one!
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  22. boggysv
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    boggysv Member

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    My vag-com is neither?

    #22
  23. Rabbit222
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    Rabbit222 Member

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    Do it! My car when used in Race mode launches like a bat out of hell!
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  24. BoufisG
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    BoufisG New Member

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    duh! the H/W version is stated right above, compare it to what the lady from haldex said and u have a match!
    #24
  25. Lima
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    Lima AUSmotive.com

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    The press blurb from the Golf R has a bit more of an explanation about Gen IV (rememering the R32 they refer to ran Gen II and the new Golf R runs Gen IV Haldex, same as facelifted S3s).

    #25
  26. LWNY
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    LWNY Member

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    The VW quote is not accurate, since the Gen II did not require slip in order for it to operate. In most types of driving where the front wheel is not pointing dead straight ahead, there is a difference in wheel rotation between the front and rear wheel, which is enough to operate the differential pump for the clutch pack. It is the Gen II standard module that does not have a sport mode, thereby, keeping the clutchpack disengaged until slip occurs. With the Gen II performance module, if the throttle is utilized aggressively, the pump will in fact be ready and clutch engagement would occur even before any notice of slippage.

    BTW, It was Land Rover's LR2 that had the Haldex Gen III, not Saab, which has the Gen IV.
    #26
  27. Dandle
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    Dandle Member

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    That's not right. "In most types of driving where the front wheel is not pointing dead straight ahead, there is a difference in wheel rotation between the front and rear wheel, which is enough to operate the differential pump for the clutch pack." This is what the mean by slip not wheel spin as some people believe and the difference is there the whole time the car is being powered fwd not just on corners. The Gen II does require an amount of slip(don't forget its not wheel spin but a slight difference in axle speeds) to control the clutch pack otherwise the mechanical pump wouldn't supply any pressure to the clutch pack. Gen II pre-x(only used by Volvo) used an electric motor to supply power to the clutch pack when the car was stationary so it could close the clutch and engage all four wheels with no movement , once moving the mechanical pump took over.

    The Gen 2 HPP upgrade works exactly the same as the original module but it acts faster and more aggesively to transfer more power faster.
    Last edited: Nov 3, 2009
    #27
  28. LWNY
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    LWNY Member

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    You are saying what I am saying, which is the rotational difference btw the front and rear wheel, when driving into a turn, etc, is enough to operate the pump. But the stock Gen II controller does not take advantage of that pressure and only engages when there is actual wheelslip (you almost don't feel it unless you have no pressure in the pump, as when starting from a dead stop).

    The Gen 2 HPP module, doesn't just transfer power faster (with a different valve unit, I presume), also reads the accelerator pedal movement via the CAN bus and could estimate how aggressive you are driving and engage the clutch pack if possible.
    #28
  29. tcardio
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    tcardio Active Member

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    x2

    I have the GEN IV HPA module in my car!
    #29
  30. Dandle
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    Dandle Member

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    No i am not saying what you are saying because you are saying "the stock Gen II controller does not take advantage of that pressure and only engages when there is actual wheelslip (you almost don't feel it unless you have no pressure in the pump, as when starting from a dead stop)." This is wrong. The system is acting all the time the reason the wheels will spin from a stop is because the pump has no pressure to close the clutch pack(gen 2 with pre-x addressed this).

    If engine power is being used to move the car then the clutch pack will be engaged and transferring power all the time. The rotational difference even when driving in a straight line is enough to operated the pump and cause the clutch pack to be engaged somewhat. It doesn't require a change in direction or wheel spin to operate, just the fact the front wheels are being powered and the rears in effect drag on the system is enough slip for it to operate most of the time and be transferring power to the rear wheels. The more aggressively the accelerator pedal is used the more the difference in slip and more power is transferred. There are times when the clutch pack will disengage such as braking, or no throttle input but if the car is being powered forward then power will be going to the rear wheels all the time.

    The HPP module works of the same inputs as the standard controller including the throttle position, brake inputs, steering position etc. It does have a different valve built into the control module and just acts more aggressively transferring power aft at a greater rate then the standard controller, the rate and speed depending what mode is selected.
    #30
  31. tcardio
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    tcardio Active Member

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    I think this may be helpful but not sure:

    The main components of the new Haldex system are the Power Take-Off Unit (PTU), Limited Slip Coupling (LSC) and eLSD (Electronic Limited Slip Differential). The PTU is the final drive unit at the front of the vehicle that transmits power to the front wheels and sends power down the driveshaft to the rear wheels. It is not a Haldex design, but is required to adapt the system to a front-wheel drive vehicle. The LSC sits at the rear of the vehicle in-line with the driveshaft. It controls the torque split between the front and rear wheels of the vehicle. The LSC sends torque to the eLSD that sits between the rear wheels. The eLSD transfers torque to the two rear wheels. Like with XWD, previous generation Haldex systems also included an LSC and an LSD. However, with the new system Haldex significantly redesigned the workings of their LSC. The LSC is still a clutch pack that adjusts torque split depending on hydraulic pressure. It is the method of fluid flow through the device that has changed.
    A large complaint about the old system was its lagging response time. LSC versions 3.0 and earlier used a built-in pump to create hydraulic pressure on the clutch pack to increase the torque drive to the rear wheels. While efforts were made on Haldex's part to create pre-emptive torque by adding a check valve and feeder pump to provide some instant pressure when triggered by wheel slippage, it was still limited in capacity. That is why for version 4.0 Haldex made an effort to improve response time by eliminating the hydraulic pump built in to the LSC, which also reduced its overall packaging size. Instead they have added a proportional pressure release valve with an accumulator that is kept filled by a detached feeder pump. This provides more instant response by holding the valve open to limit the torque drive to the rear wheels and keeping the hydraulic fluid flowing through the system. That way when rear torque is demanded, the valve closes and hydraulic pressure is already there.
    The LSD used by Haldex 4.0 is also not the mechanical limited-slip differential of old. They swapped the old system LSD for an electronic unit. The eLSD works in much the same way as the LSC, a feeder pump and pressure relief valve are used to control hydraulic pressure on the differential clutch pack. This allows for complete control of the rear differential lock-up without the need to wait for wheel slippage to occur. The system has its own control unit contained in the LSC. This control unit communicates between the vehicle systems to get sensor input for data such as wheel speed, rpms, throttle position, steering wheel input, etc. It also works with anti-lock brake and traction control systems.
    The XWD system can transmit 100 percent of available torque to either the front or rear wheels. However, for those conditions to occur one end of the vehicle would have to lose all traction, like driving on ice for instance. During a standing start the rear wheels are put to use, without the need for any slip to occur. Then under straight-line cruising conditions, to conserve fuel and driveline wear, the torque split to the rear wheels is reduced to a level between 5 and 10 percent. Also up to 85 percent of torque can be transferred by the eLSD between to any single rear wheel if necessary. The system can adjust torque splits based on calculated conditions, such as those that indicate an aggressive lane change manoeuvre, to effectively reduce oversteer or understeer without any wheel slip occurring. In the event that some wheel slip does actually get to occur, the system can react more timely and efficiently than in the past.
    #31
  32. LWNY
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    LWNY Member

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    Isn't eLSD obsoleted by torque vectoring rear differential?

    Or was torque vectoring ever really needed, given the fact that in almost all types of cornering, the front wheel takes a longer path than the rear, so when the haldex is in full lock, the rear wheels are in effect being overdriven, causing it to increase its slip angle in order for it to follow the longer path of the front wheel. This would give it a feel of the rear in balance with the front, as opposed to the rear following the front.
    #32
  33. tcardio
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    tcardio Active Member

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    Just may well be but doesn't TVD also adjust brake input?
    #33
  34. tos
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    tos New Member

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    Last edited: Sep 14, 2010
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  35. Dandle
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    Dandle Member

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    No way to swap it. The whole unit is different.
    #35
  36. tos
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    tos New Member

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    Damn...
    #36
  37. tos
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    tos New Member

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    So, what about this?
    Costs too much for nothing :w00t:
    #37
  38. LWNY
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    LWNY Member

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    That's what Electronic Torque vectoring does like on Porsches (can't believe they charge extra for that, especially when it already has traction/stability control)...inside wheel less grip and slipping....brake and slows down that wheel so the outside wheel turns more. The real ones overdrives the rear axle and either L/R clutchpack engages when overdriving of the one of the rear wheel is needed.
    #38
  39. A3SBQ
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    A3SBQ A3 SportBack 2TFSI quattro DSG

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    I like this idea. Have even sent a mail to Haldex in Sweeden. Did not get any reply thow.
    #39
  40. A3SBQ
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    A3SBQ A3 SportBack 2TFSI quattro DSG

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    Hi. Little late but got the info finally.

    The eLSD is exclusive for the SAAB lineup
    it is as I am told and read a Haldex Gen4 but with the extra eLSD

    I have talked with HPA witch are working close with Haldex and they
    confirmed this. (they thought it would be great to retro fit too)

    The only way for us to get more grip in the back is the performance controller
    and/or a new diff from Pelquin or other producer.

    Dose anyone have experience changing the diff?
    #40

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