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Re: Haldex Research results II

In a message dated 9/9/99 7:04:40 PM Central Daylight Time, 
Dave.Eaton@clear.net.nz writes:

> 1) deactivation (perhaps unlocking is a better term) of awd systems on abs
>  activation (note this is not the same as *braking*) is de rigeur in order 
>  allow abs to do it's thing.  not required with the torsen due to it's
>  design, but required with a vc, a centre locker or a haldex.  the haldex
>  does this via computer, the vc via a lock-out, and the centre locker by 
>  fingers.

Let's be clear, the haldex and the VC are the same in terms of ABS function, 
both need to be unlocked for ABS function to work, both hence create an 
interesting LFQB problem.  Unfortunately for everyone owning an audi since 
1992, the switch for ABS delete is no longer available.  Which CAN tuner is 
taking on the ABS delete liability?  Which CAN tuner will take on the 
clutchpack wear of a true full time awd Haldex?  

>  2) you're not correct about this 50% maximum torque transfer thing.  there
>  is nothing which i see in the design which limits torque transfer (unlike
>  the torsen).  as far as i know, based on the haldex literature i have, the
>  coupling will transfer 100% torque either way.  just like the generation 1
>  quattro system.  when the coupling is locked (joined, whatever) you have
>  100-0-100 torque transfer possibilities by definition.

How is that possible Dave?  If the primary drive axles is fwd, then you have 
lock, if the front slips EDL kicks in,  Trg reduces.  Hardly just like the 
gen I system, in fact it's not at all like it.  My understanding of the 
Haldex system is you either have all fwd or 50% rwd.  For it to be more, you 
would need to have different FD ratios to the rear axle, in the front 
transmission.  Claiming it has more than 50% capability, means that the 
Haldex is capable of massive understeer and massive oversteer coupling and 
uncoupling the rear axle.  Not the case here.  If EDL is used on the front 
axles, the transfer of torque can not exceed the highest Trg of the highest 
traction front wheel, by definition.  EDL is a potential mess here.

>  3) agree about the fwd/rwd haldex thing.  perfectly possible to have a
>  rwd-biased haldex system, although doing that with a transverse front 
>  would be difficult.  with a longitudinal engine, no big deal - the audi 
>  tranny is almost exactly what you'd want - simply replace the torsen box
>  with a haldex and you're there.  the audi manual tranny would be more
>  difficult.

I'm thinking about the Stealth/mitsu3k tt here.  Transverse motor, rwd and 
VC.  What's the difference.  Difficult?  It's been done for many years, 10 in 

>  4) the haldex white paper i circulated a while ago shows actual printout of
>  the torque transfers through the system, wheel speeds etc while taking off
>  on ice.  this shows that the torque distributed to the rear occurs 100ms
>  after the front, that the axle velocities front and rear are the same, and
>  that there is a small but noticeable "cycle" of rear axle velocities that
>  the front doesn't have (very similar, but much smaller/faster than the
>  characteristic vc cycle).  also diagrams showing the pressure drop when the
>  abs systems kicks in.  also comparisons with the haldex vs a vc-equipped
>  vehicle starting off from sand (the vc got stuck apparently).  interesting
>  reading.

Again, looking at the comparo, I'm convinced that Haldex should take on the 
gen I locker locked in position 2.  I'm not enamored with the Haldex, sorry.  
It's a step from the torsen, but 180 degrees from the norm.  One major flaw 
in the logistics, IMO.  Audi hasn't had big gains in proving btdt wrong in 
the torsen arena.  Better luck here?  I'm not as optimistic as you.  Another 
6 years of "proving" everyone wrong, that makes a total of 16.  Even if they 
prove to be batting 1000 with the Haldex, that's still less than a .500 
batting average.  Quattro advantage indeed.  

My .02 thru the peso, losing money fast, but we don't need no stinkin badges 

Scott Justusson