Torsen vs. Haldex and Question
#1
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Torsen vs. Haldex and Question
The TT and A4 brochures show illustrations of the transfer of power to wheels under certain situations.
On Torsen and Haldex, if 2 front wheels lose traction, power is transferred to the 2 rear wheels.
On Torsen and Haldex if 2 rear wheels lose traction, all power is on the front wheels. In Haldex, all power is on the front wheels to begin with.
On Torsen and Haldex, if 2 rear wheels and 1 front wheel lose traction, power is transferred to the remaining front wheel that does have traction.
On Torsen only, if front and rear on one side of the car loses traction, power is transferred to the other side front and rear. Question...what happens in this case under Haldex? Power goes only to one front wheel and NO rear wheels?
On Torsen and Haldex, if 2 front wheels lose traction, power is transferred to the 2 rear wheels.
On Torsen and Haldex if 2 rear wheels lose traction, all power is on the front wheels. In Haldex, all power is on the front wheels to begin with.
On Torsen and Haldex, if 2 rear wheels and 1 front wheel lose traction, power is transferred to the remaining front wheel that does have traction.
On Torsen only, if front and rear on one side of the car loses traction, power is transferred to the other side front and rear. Question...what happens in this case under Haldex? Power goes only to one front wheel and NO rear wheels?
#2
Yeah... you'd spin the rear wheel, unless the rear has EDL like the front.
(edited... added this text...)
What I mean to say is that one front wheel would have traction, because EDL would brake the free-spinning one.
Power WOULD be transferred to the rear via the haldex coupling, but the rear is an open diff without EDL (I think), so you'd just spin the tractionless rear wheel while the other sat still.
1WD!
What I mean to say is that one front wheel would have traction, because EDL would brake the free-spinning one.
Power WOULD be transferred to the rear via the haldex coupling, but the rear is an open diff without EDL (I think), so you'd just spin the tractionless rear wheel while the other sat still.
1WD!
#3
Which activates first, EDL or Haldex?
IIRC, one of the main advantages of Torsen was that it engaged (so to speak) before EDL, reducing brake wear substantially.
Curious if the Haldex design preserves that feature.
-Jon
Curious if the Haldex design preserves that feature.
-Jon
#4
EDL and Haldex cover different territory... it doesn't matter which engages first...
EDL is for the front (open) diff. If the left wheel has no traction and is spinning, EDL will brake that wheel so that the right one can have some power.
Haldex couples the always-on power of the front wheels to the rear (open) diff. It doesn't matter if EDL is activating on the front wheels or not... power to the front wheels equates to rotation of the driveshaft feeding the haldex. If the rear wheels are not rotating at a speed commensurate with the input shaft, the coupling activates and applies some proportion of the power to the rear wheels.
AFAIK, the rear wheels have no EDL.
Haldex couples the always-on power of the front wheels to the rear (open) diff. It doesn't matter if EDL is activating on the front wheels or not... power to the front wheels equates to rotation of the driveshaft feeding the haldex. If the rear wheels are not rotating at a speed commensurate with the input shaft, the coupling activates and applies some proportion of the power to the rear wheels.
AFAIK, the rear wheels have no EDL.
#5
I was under the impression that.......
the Haldex system was able to send 100% power to any given wheel and also split that power as it deemed necessary. What I mean by this is, it can send 40% power to the right rear and 60% power to the right front if the left sides are slipping and the front has more traction than the rear. I might be thinking of something else but this is what came to mind......
#7
Nope...
At full haldex lock, you're at 50/50 front and rear. At zero haldex lock, you're at 100/0.
The front and rear diffs are open, which allows 100% of the power at that axle to go to either the right or left wheel. However, all power is actually sent to the wheel that has _no_ traction! That's why the front diff has "EDL" to brake the spinning wheel so that power can be sent to the wheel with traction.
I don't believe the rear has EDL.
The front and rear diffs are open, which allows 100% of the power at that axle to go to either the right or left wheel. However, all power is actually sent to the wheel that has _no_ traction! That's why the front diff has "EDL" to brake the spinning wheel so that power can be sent to the wheel with traction.
I don't believe the rear has EDL.
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#8
I didn't say it wasn't true AWD! It certainly IS true AWD, but yes... the rear diff is open.
I'm not 100% certain, but I believe that the rear diff is actually part of the haldex coupling unit itself, so you cannot replace the rear diff alone.
The rear diff being open and having no EDL doesn't matter much in the real world. The rear wheels would be difficult to overpower. It might be a concern if you were drag racing in the snow.
The rear diff being open and having no EDL doesn't matter much in the real world. The rear wheels would be difficult to overpower. It might be a concern if you were drag racing in the snow.
#9
Partially agree (more) ...
I agree with everything you've said, but up to a point, *either* EDL and Haldex can keep a front wheel from spinning.
EDL can brake the spinning wheel, or Haldex can simply reduce the power to the front axle by shifting it to the rear axle. Either way could work.
Of course, once both front wheels are spinning, there's no good choice but to use both Haldex and EDL.
I was just curious which order the technologies were applied; in the real world, it's not a huge issue either way (aside from wear-and-tear).
-Jon
EDL can brake the spinning wheel, or Haldex can simply reduce the power to the front axle by shifting it to the rear axle. Either way could work.
Of course, once both front wheels are spinning, there's no good choice but to use both Haldex and EDL.
I was just curious which order the technologies were applied; in the real world, it's not a huge issue either way (aside from wear-and-tear).
-Jon