[torsen] RE: Torsen differential

Dave.Eaton Dave.Eaton at clear.net.nz
Tue Nov 19 03:30:03 EST 2002

nope sorry.  you have the physics wrong (deja vu).  if the haldex lsc is
locked, then there is by definition 100% torque available to the rear end,
not 50% as you assert.  for example, if the front end is in the air, then
the lsc will lock and all available torque will go to the rear end.  think
it through more clearly, and you'll get the picture.

once again, despite your assertions, the jeep unit is the same haldex
technology as the audi one.  see
http://waw.wardsauto.com/ar/auto_allwheel_drive_revolution/ for details of
nvg's implementation of a hang-on clutch.

the key phrase is "NVG engineers say the most critical improvement is in
response time. Ronald Frawley, chief engineer- transfer cases, says, "It's
all in response time. The new unit essentially works in two-wheel drive
until wheel-slippage is detected; then reaction time (to send drive to the
other axle) is about 40 milliseconds. A viscous coupling can take two or
three seconds to do the same thing."

enough said?

happy to send anyone the technical description of the haldex lsc where the
theory of operation is explained in some detail...

there is nothing wrong with a hang-on clutch - they have been used
successfully in the highest forms of motorsportfor year - the toyota wrc
team usedd them for theier wrc car in it's 1st iteration, when carlos sainz
came within 500m of winning the wrc.

'95 r2
'90 ur-q

-----Original Message-----
From: QSHIPQ at aol.com
Date: Mon, 18 Nov 2002 20:00:20 EST
Subject:  RE: Torsen differential
To: Keith.Maddock at trw.com, quattro at audifans.com
Cc: torsen at audifans.com

[ Picked text/plain from multipart/alternative ]
This statement is not correct wrt the audi haldex type, this is only true of
a passive (mechanical) haldex type coupling.  Since lockup is electronic, it
doesn't at all need slip to be locked.  In fact, audi (or a good hacker)
could lock it based on factors completely unrelated to slip at all.  This
would include the electronic NVG models you refrerence in your site.

A haldex LSC as installed in the audi TT should be considered as an "active"
lockup rear axle, and as such can be controlled or biased in it's current
design at any point (any time) from 5% rear to 50 rear torque (100%lockup).
"Hang-on" really describes the lack of center diff, not the actions of the

As such, the haldex TT can be a "full time awd" system, OR a synchro system.
The unit itself is designed to be either in the TT, audi electronically
it to be synchro (part time 4wd) that's all.  In fact, the engineers at
Haldex actually indicated that a good hacker could change that retroactively
without undue stress on the unit as designed.


Scott Justusson

In a message dated 11/18/02 6:28:27 PM Central Standard Time,
deaton at tranzrail.co.nz writes:

thanks for all the explanation keith.  i am quite familiar with the haldex,
and the way that it operates.  it is, by definition, a "hang-on" clutch.  it
can be nothing else as the pressure needed to operate the clutch is
generated by slip in the 1st place.  this is the same whether the
application is jeep or audi.


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