[torsen] RE: Haldex differential

QSHIPQ at aol.com QSHIPQ at aol.com
Sat Nov 23 10:30:02 EST 2002

In a message dated 11/23/02 1:46:02 AM Central Standard Time, 
Dave.Eaton at clear.net.nz writes:

>1) you're wrong, the haldex lsc in normal operation transfers no torque to
>the rear of the vehicle.  quoting directly from the haldex lsc article "the
>two shafts are connected via the wet multi-plate clutch, normally unloaded
>and thus transferring *no* torque between the shafts" (page 7, "basic
>function").  this is *not* a vc, scott, it is a clutch.  there is no
>residual shear, as you have in a vc.

Sure there is, just as there is preload in any clutchpack.  If you take a 
look at the Torque Transfer Characteristic graph, "The colored area indicates 
the area within which the characteristics of the coupling can be controlled." 
 That doesn't include 0 in either a front or rear application coupling.  
Which indicates to me, that once "active" as defined (car on), it is never 
decoupled completely.  Put differently, if you apply *any* TORQUE to the 
device it can no longer be "decoupled".

>2) is the haldex lsc an active clutch?  no - its a reactive one.  an active
>clutch uses an external pressure source to supply all the required operating
>pressure.  the haldex can't.  not even close.  another simple test.  can the
>lsc initiate full lockup without slip?  no, of course not.  therefore it is
>not active, because an active clutch can do that.

Think outside the box Dave.  It is "fully active" when the car engine is on 
the car is moving.  Does it have FULL lockup capability all the time when in 
that fully active state?  Nope, just as a turbo FV creates boost, it can't 
exceed 100% of existing boost pressure.  That doesn't at all mean that a WGFV 
is not active boost control.  The purely mecahical jeep Haldex type is a 
passive system.  Adding an ecu to control lockup, any percentage of it, moves 
that device into the active state.  Wanting infinite *capability* doesn't 
change the definition.  

>we're getting nowhere with this.  read the information on the web about the
>lsc, or if you'd like i'm happy to email you the information which haldex
>has sent me.

I'm always happy to learn more about this device Dave.  Right now, your 
thoughts and comments would put audis own "awd" claims in question, since by 
your definition, the TT is only part time 4wd, not even synchro.  I will 
disagree with that statement, since it IS the synchro part (that meaningless 
5%) that slips it under the awd category, and allows audi to claim awd, not 

I'd be more interested in your plots of locked and haldex couplings in the 
contexxt of fig 6 in chocholek's paper.  It might help me better understand 
your points.  

>i'm done with this.  over and out.

Thanks for your patience.

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