[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

RE: torsen naderism

>ok, now it seems that we have agreement (at least with jeff), that the
>chassis is a major component of the "input" factors" to the torsen.

Well, of course the chassis has an affect on the "input factors," as you
call them.  This goes without staying.

But the chassis characteristics do not -- CANNOT -- have any effect
whatsoever on the Torsen's operation other than by modifying the input
signals that are fed to it.  As I've explained before, the input signal
isn't very sophisticated and the Torsen isn't very smart.  It's entirely
possible for the Torsen to be fed the same input signal under widely varying
conditions and its pre-programmed response may or may not be appropriate.
In this instance, the chassis will naturally respond to the changing torque
distribution and an inappropriate response might very well make things
worse, not better.  Worst case, you end up with a dynamic feedback loop
that's not very stable and this gives rise to the (in)famous "Torsen bite."

Given the design of the Torsen, the potential for this to happen is inherent
in EVERY car where it's used in a center-diff application.  Like it or not
but it's simply the nature of the beast. 

>1) no-one knows the differences between the torsens used in the ur-q and
>the s2/rs2.  all we know is the bias ratio.

So?  If you noodle things over a bit, the bias-ratio can tell you an awful
lot about the other design choices that were made.  Certainly, the other
design factors are NOT significant enough to alter its basic character.  

>2) the type 44 (euro audi 200) was not designed with the torsen in mind.
>it was a facelifted 100.  as you know, the 100 came with the locker
generation 1 centre diff setup.

I beg to differ with you here.  The first Type 44 quattro appeared in 1985
and while parts of the chassis were common with the FWD 100 version, Audi
had been playing around with Torsens for a couple of years by then.  The
odds of them not having at least considered the possibility it might be used
in the future are pretty long and in my opinion, not very unlikely.  I can
cite references back to the 200q Grp. A rally car of '87 where it was
discussed in some detail (and not necessarily with postive conculsions,

>i've dug out a road test of the 200 which, co-incidently, is in the same
>issue of "performance car" (march 1988) as their first test of the
>ur-quattro with torsen.  btw, i don't think that i've ever read a road
>test of this car before...

Big deal ... it's a very brief, one-page review that might run 750 words.
Besides, you're skirting the issue by diverting attention from the operation
of the Torsen itself to the operation of the car as a whole. 

>so we have two different torsen chassis, one designed for the luxury
>market, and the other for the sports market.  we have two machines with
>markedly different handling [so attested].  and we have a quattro which,
>according to this road test [and the people who have driven the various
>models], is a markedly *better* handling machine with the addiiton of
>the torsen.
>it seems quite obvious to me that, if some untoward handling occurance
>on the torsen type 44 occurs [so attested], then this occurance could
>easily be the effect of a number of factors unique to that chassis and
>which do not occur on other chassis.  

And your point is?  Again, let's stay focused on the Torsen itself for a
while ... the "bite" is there even if it's not always obvious or painful.
Personally, I haven't experienced an innocous bite but I accept that they
can and probably do exist.

>to answer orin's question.  yes, i certainly take the bite to mean
>untoward behaviour leading to loss of control caused by the actions of
>the torsen diff.  scott's "brown stain" comments etc.

Frankly, all of the bites I've experienced have been of the painful variety
(or when I've been playing around, at least potentially painful).  Your
experience has obviously been different.

In conclusion, the existence of the bite phenomenon is non-negotiable once
you understand and accept the basis by which the Torsen operates.  Depending
upon a multiplicity of other factors, including chassis design and/or
suspension tuning, the severity of the bite may or may not be painful or
even noticed.  But it's always there, regardless.   

Now, are we finally done with this?
    _                _
   / |      _| o    | \       _| o  Jeffrey Goggin
  /__| | | / | | __ |  | | | / | |  audidudi@mindspring.com
 /   | |_| \_| |    |_/  |_| \_| |  http://www.mindspring.com/~audidudi/