Re: Marketing 101

[Brett Dikeman <brett@pdikeman.ne.medaone.net>]

So, basically, is consensus that a q-car with torsens handles corners like
crap?

I found the torsen diff in our Volvo to be a royal PITA.  Whilst trying to
get out of the driveway, both rear wheels break free instead of just one,
causing the car to slip uncontrollably sideways...very scary...

Brett
(aquiring a torsen-equipped Quattro in a day or two :|  )


>Jim Simone writes
>>Being a new owner of an A4 1.8T qms and  not an engineer (immunologist), I am
>>trying to understand your arguments for VC and against Torsen.
>>But, if I may ask an ingenuous question, what are the "advantages" of a
>Torsen
>>diff and why does Audi use them if viscous diffs appear to be the better
>choice?
>>Is this a question of racing versus street? Or, is it just good marketing?
>>Thanks,
>Not sure, maybe the idea that in a straight line, the torsen wins.  Darn
>turns.  The biggest issue against the torsen is predictability (and you can do
>an archive thread, or post me privately for the book version).  It assumes all
>inputs to the device to be traction inputs.  Even when they aren't (slip angle
>f&r and relative f&r slip angles) traction inputs.
>
>AND, ABS works (this is in deference to the old lockers, which disabled the
>abs).  To jump and say that ABS works 'better' in a torsen than in a VC needs
>a lot more data than has been published.  Given Trg at a minimum, I don't
>think either claims a win, both are 'linked' to some extent (in techno terms,
>both have a decel Bias Ratio).  Racing, the Torsen was not used to any great
>extent (singular exceptions so noted) in the audis.
>
>What the torsen EXACTLY lacks, that a VC doesn't, is that you can get U-O-U
>(understeer = u, oversteer = o) in the same turn with no 'traction' reasons
>for Tshift.  A torsen audi then exactly doesn't maintain chassis character
>thru a turn, since at 50/50 static distribution it understeers, at 78r/22f it
>oversteers, and at 22r/78f it understeers.  A VC (3kgtVr4 for instance) has a
>primary set of drive wheels, and the lock is at a specific ratio, that can be
>made to keep the inherent chassis dynamics, here O-O-O.  Even with slip angle
>variables, the chassis dynamics doesn't change, it's still oversteer.  Just as
>predictable as a locked 50/50 audi diff at U-U-U, only better (racers tend to
>use a 65r/35f split as preferred, btw)
>
>The argument FOR torsens is in terms of absolute traction devices.  In a
>straight line, they can't be beat.  Darn turns.  Good marketing, and the
>beaners were happy to.  A torsen center, with open front and rear is cheaper
>than a locker and all it's hardware.  The customer is happy, cuz 'ABS OFF'
>doesn't appear when they fear in need of it the most in a locker.  Sounds like
>a win win.  Yup, until you go to steamboat, or drive with Jeff and I at a
>track, or step out a little in the rain or snow.  Then spiders land in your
>lap.  An absolute traction device fooled, has some (upside-)downsides
>associated with it, when turning.
>
>Not a single other manufacturer uses torsen centers.  I argue for good reason.
>And believe the audi racers knew it too.  Too bad they didn't take those
>marketing boys for a ride.....
>
>HTH
>
>Scott Justusson


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Brett Dikeman
brett@pdikeman.ne.mediaone.net
~)-|
Hostes alienigeni me abduxerunt.  Qui annus est?
Te audire non possum.  Musa sapientum fixa est in aure.
Ita, scio hunc 'sig file' veterem fieri.
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