[torsen] RE: Torsen differential

Keith Maddock Keith.Maddock at trw.com
Wed Nov 20 04:30:05 EST 2002

I never said it "isn't AWD" :)  Please don't twist my words.  I would describe the Jeep and Audi units the same in terms of current functionality as follows:

Pure Technical:  "Part time AWD"
Functionality:  "Full time AWD"
Marketing:  "Full time AWD"

Sure, there is no actual coupling force until slip occurs, hence the pure technical description as "part time AWD", but since the driver can't ever disable the AWD feature (at least as delivered from the factory..), it is functionally and commercially "Full time AWD".

WRT to Haldex, I think the ABS de-clutch is purely acheived with the throttle valve.  To declutch you have to reduce hydraulic pressure, and the feeder pump generates hydraulic pressure.  Im curious to hear how the literature you have describes a de-clutch event being enabled by the feeder-pump.


Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> "Dave.Eaton" <Dave.Eaton at clear.net.nz> 09:59:01 20.11.2002 >>>
ok, good - you agree that the jeep haldex-lsc transfer case (nvg 247) isn't
"awd" as scott asserts.  my posting was prompted by scott's statement that
the jeep was full-time awd using a haldex lsc, and that the audi wasn't
because the audi engineers had turned that capability off.  we agree that
the jeep is a part-time, progressive system, as nvg describe it, as is the
audi unit.

however, i think that we are talking at cross-purposes with regards to the
haldex generation 1 unit.  there is a feeder pump in the lsc, but this is to
allow the clutch to be controlled either during abs braking, or when there
is a full throttle start.  in these cases the clutch is opened and closed
respectively.  this is a normal function of the generation 1 lsc, as fitted
to the audi from day 1.  it is not a full-time awd system, although there
are clearly some aspects of that to it.  nor is this what haldex are
currently working on which is, as i understand it, more of a true "active"
clutch using a similar operating principle.

so, maybe we are in agreement.  i agree that there is a "feeder pump" as
part of the lsc, but the function is as i described - at least according to
the literature that haldex sent me.

'95 rs2
'90 ur-q

-----Original Message-----
From: Keith Maddock [mailto:Keith.Maddock at trw.com] 
Sent: Tuesday, 19 November 2002 10:11 p.m.
To: 'QSHIPQ at aol.com'; 'quattro at audifans.com'; deaton at tranzrail.co.nz 
Cc: 'torsen at audifans.com' 
Subject: RE: [torsen] RE: Torsen differential


Sorry, you're missing a major difference between the NVG/Jeep and Haldex/VAG
LSC systems.

The NVG/Jeep system is purely mechanical.  I agree that it is not "full
time" by the engineering definition, as there is no coupling force without
slip.  But the marketing types will refer to this as "full time"

However the Haldex/VAG unit  has more features than that.  It has electronic
control of the maximum hydraulic pressure *AND* a small electric motor to
maintain a small amount of hydraulic pressure without slip.  Its already
there, since 98. The current implementation has a small motor, and open-loop
pressure control.


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