RE: torsen naderism

[Eaton Dave <dave.eaton@minedu.govt.nz>]

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.

a couple of "nits" here jeff.:

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.

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.

now, lets look at the type 44.

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...

lets see what the road testers said:
1) on the type 44.

"there are no chassis changes of significance...wheels and tyres remain
the same...so any change in the feel of the 200 quattro must be
attributable to the torsen transmission".

"a difference there certainly is. as before the big audi can be heaved
into and around a corner with that familiar on-rails feeling, only now
it is even more apparent.  seek out a patch of ice in the shadow of a
tree, and you discover just how quickly the torsen acts to send its
torqe output to the end where it will do the most good.  the effect is
almost uncanny, although you are always aware that the audi 200 is a big
and heavy car."

"there is a limit of course, and when it is reached, the 200 quattro
goes into terminal understeer just like its predecessors.  in the end
there is no disputing the effect of massive nose-heaviness.  however the
torsen makes it even easier to approach that limit with something like
blithe confidence.  over confidence is discouraged mainly by the
increasing heaviness of the steering...when cornering extremely hard.,
and also by the harsh juddery noises of the front tyres as they begin to
slither at truly tortured slip angles..."

2) on the ur-quattro

"the result [of torsen and engine mods] is a car transformed: a big
advance on its predecessor and light years beyond that mould-breaking
original.  still essentially the same in character, however; a machine
that can be driven fast and far..."

"power and grip that quattro has always had them in abundance...
driven, as any sane driver would drive it - at 8 10ths, these virtues
have made the quattro one of the true supercars of its generation.  but
its mighty abilities have all too often tempted its driver to find those
last 2 10ths.  and here, in the past, the quattro has revealed its
weaknesses, sometimes even biting back." [reference to the open centre
diff bite]

"the 1988 model has not pushed the limit any further - power is
unchanged and ultimately so too is grip from the massive 215/50 15 tyres
- but those last 2 10ths have become easier to explore."

"the marked gain is however, in the handling.  the torsen diff's ability
to vary torque to match traction has put an end to the nose-heavy feel
that couldn't help but mar the old quattro's high speed handling.  it
now feels a much more neutral machine....

"the understeer is stil there to a degree however.  driven hard into
bends the quattro wil run markedly wide of the line."



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.  

is a torsen chassis, a torsen chassis is a torsen cahssis?  nope.

dave
'95 rs2
'90 ur-q

On Thursday, June 18, 1998 10:50 PM, audidudi@mindspring.com
[SMTP:audidudi@mindspring.com] wrote:

[snip]
> 
> >but what beggars belief is that you then state that this proves that
the
> >"bite" *must* happen on all chassis, because of it's alleged
occurance
> >on a type 44 chassis.
> 
> If you accept the basic principle of operation, then it's a given.
Like I
> said, what happens to the car AS A RESULT OF THE TORSEN's operation is
> another matter altogether.  Some cars may handle this better than
others;
> some cars may not be affected at all.
> 
> >so, you assert that the the following have *no* influence on the
> >torsen's input parameters:
> >
> >1) the ability of the chassis to put power to the ground (and keep it
> >there).
> >2) the ability of the chassis to provide good levels of steering
> >response when cornering
> >3) the roll stiffness of the chassis (keeping tyre contact patches on
> >the ground)
> >4) the type and quality of tyre used
> >5) the fundamental dimensions of the chassis (wheelbase, track etc).
> >6) the torque characteristics of the engine
> 
> All of the above parameters may indeed affect the INPUT signals from
which
> the Torsen takes its lead; however, NONE of them will alter how THE
TORSEN
> ITSELF operates.  Give it the same set of input signals (as modified
by the
> above factors in whatever combination you prefer) and it'll allocate
torque
> exactly the same way ... every time, without exception.  Like I've
said,
> there's no way that it CAN'T do this.  It's just a simple mechanical
device
> -- dumb, even -- that's remarkably complicated to design.
> 
> 
> >for all we know, it's the *inability* of the type 44 chassis to do
some
> >of the above things "consistently" which produces the bite, where it
is
> >simply non-existant on other, better balanced, chassis.
> 
> Quite possibly ... but it's also possible that the Type 44 is a
superior
> chassis design and thereby responds more immediately to any changes in
> torque distribution.  At this point, though, I can't tell you which
and I
> have never claimed anything other than that the Type 44 and Torsen
> combination isn't a particularly good one ... it's entirely possible
that
> the RS2 and Ur-Q chassis cope with a Torsen doing its thing much
better than
> any of Audi's other chassis.  Personally, I think this rather unlikely
in
> the case of the Ur-Q -- after all, its chassis was designed well
before Audi
> ever considered using a Torsen whereas the Type 44 was very likely
designed
> with the Torsen in mind from the outset -- but I acknowledge that it's
possible.

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.

> Reality check.  What do you all understand by 'bite'.  Seems to me
> that Scott and Jeff have been defining it as an inappropriate
> distribution of torque, regardless of whether it has any adverse
> effects on the handling of the car whereas Dave and Phil are requiring
> something nasty to happen, regardless of what the torque distribution
is.
> 
> Orin.