What's the skinny on Haldex?
11-12-2005, 09:56 PM
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What's the skinny on Haldex?
If I understand correctly, the Haldex multi-plate clutch is the next-gen Quattro. Torsen has pretty much gone the way of the doo doo. Audi.co.uk spec sheet for a A3 3.2Q say it's permanent 4WD (should I assume 50:50 under normal driving conditions?) but all the stuff I'm reading tells me Haldex is not permanent 4WD, rather it's FWD under normal driving conditions and then distributes torque to the rear from a 100:0 ratio. Where am I off? How does it really work?
I've also heard lots of people say Haldex isn't all that it's cracked up to be. Why is that? Is the drive still limited by engine torque because of the size/number of clutch plates?
I've also heard lots of people say Haldex isn't all that it's cracked up to be. Why is that? Is the drive still limited by engine torque because of the size/number of clutch plates?
11-12-2005, 11:11 PM
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You can read about Haldex at haldex.com
Haldex is front wheel drive until the front wheel(s) slip. The Haldex equipped cars are practically FWD cars except when the front wheels slip.
The amount of torque that is transferred to the rear is up to 30%, at least on my 2000 Haldex TT, and if I remember the figure correctly.
I've driven my TT in autocross for a year; I am probabyl still a novice. I've experienced what I had read before: Haldex has snap oversteer. After driving it in autocross and thinking that it happened, I now think that it's true.
From an understeer condition, because of having slipped the front wheels, suddenly (and proudly) the power is pushed to the rear. That change in balance turns the car rather successfully.
But again, I am still a novice; don't trust me much
More experienced drivers would probably take advantage of that; I don't know...
Having said that; I remember that I also had nice sweepers (long drifting turns) in my car. Really, maybe it was me, not Haldex...
Ali
The amount of torque that is transferred to the rear is up to 30%, at least on my 2000 Haldex TT, and if I remember the figure correctly.
I've driven my TT in autocross for a year; I am probabyl still a novice. I've experienced what I had read before: Haldex has snap oversteer. After driving it in autocross and thinking that it happened, I now think that it's true.
From an understeer condition, because of having slipped the front wheels, suddenly (and proudly) the power is pushed to the rear. That change in balance turns the car rather successfully.
But again, I am still a novice; don't trust me much
More experienced drivers would probably take advantage of that; I don't know...Having said that; I remember that I also had nice sweepers (long drifting turns) in my car. Really, maybe it was me, not Haldex...
Ali
11-13-2005, 05:19 AM
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Re: What's the skinny on Haldex?
the 2nd link is preety clear
http://www.difflock.com/offroad/4wdawd.shtml<ul><li><a href="http://www.geocities.com/gkurka2001/CarTech/tech_traction_4wd_2.htm#Torsen">http://www.geocities.com/gkurka2001/CarTech/tech_traction_4wd_2.htm#Torsen</a</li></ul>
http://www.difflock.com/offroad/4wdawd.shtml<ul><li><a href="http://www.geocities.com/gkurka2001/CarTech/tech_traction_4wd_2.htm#Torsen">http://www.geocities.com/gkurka2001/CarTech/tech_traction_4wd_2.htm#Torsen</a</li></ul>
11-13-2005, 06:17 AM
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So '06 A3 3.2 Quattro is Haldex based on 4Motion?
I'm confused. 2nd last paragraph of http://www.geocities.com/gkurka2001/CarTech/tech_traction_4wd_2.htm#4motion says Haldex can't handle high torque. It can handle the 206lbft from the TT. Can it handle 250lbft from the V6 without modifications?
It is actually normally 50:50 split?
It is actually normally 50:50 split?
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11-13-2005, 07:19 AM
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Re: What's the skinny on Haldex?
To paraphrase about a million threads on this out there,
Haldex is basically FWD until a small bit of wheelspin occurs or until the system detects certain parameters have been met to engage the system (throttle position, brake usage, engine spped, etc -- consult the mulitudes of doco out there for everthing).
Haldex can transfer up to 100% of available torque to the rear, torsen systems can't do this. Don't confuse this with 100% of POWER to the rear. Once the maximum amount of torque that the system can send to rear is reached the rest is distributed to the fronts. That's why haldex can still work fine with some of the super and turbo charger systems out there that provide more power, the remaining power that the system can't handle goes to to the front wheels, it isn't lost (i'm not talking about super power like the HPA TT here).
Haldex has much less drivetrain loss than a torsen system does. IIRC my S4 has about 28% loss while my R32 has about 18 - 20%.
I wrongfully believed (when I just owned my S4) that haldex systems are inferior. Then I bought my R32 and have since spent much time reading through many, many threads on this on the vortex. Both kinds of systems have their disadvantages and advantages. Haldex is extremely capable, and with the HPP upgrades out there (which essentially transfers power much quicker to the rear in certain driving conditions) you really can't tell the difference between the systems.
Now all of this is from my memory (which isn't the best at times so I may have left someting out) and based off Gen1 haldex, all new golf based platfoms (A3, TT, and of course the golf) now use gen2 haldex.
Haldex is basically FWD until a small bit of wheelspin occurs or until the system detects certain parameters have been met to engage the system (throttle position, brake usage, engine spped, etc -- consult the mulitudes of doco out there for everthing).
Haldex can transfer up to 100% of available torque to the rear, torsen systems can't do this. Don't confuse this with 100% of POWER to the rear. Once the maximum amount of torque that the system can send to rear is reached the rest is distributed to the fronts. That's why haldex can still work fine with some of the super and turbo charger systems out there that provide more power, the remaining power that the system can't handle goes to to the front wheels, it isn't lost (i'm not talking about super power like the HPA TT here).
Haldex has much less drivetrain loss than a torsen system does. IIRC my S4 has about 28% loss while my R32 has about 18 - 20%.
I wrongfully believed (when I just owned my S4) that haldex systems are inferior. Then I bought my R32 and have since spent much time reading through many, many threads on this on the vortex. Both kinds of systems have their disadvantages and advantages. Haldex is extremely capable, and with the HPP upgrades out there (which essentially transfers power much quicker to the rear in certain driving conditions) you really can't tell the difference between the systems.
Now all of this is from my memory (which isn't the best at times so I may have left someting out) and based off Gen1 haldex, all new golf based platfoms (A3, TT, and of course the golf) now use gen2 haldex.