RE: Can someone give me some info to refute this?

[Fringe Ryder <fringe@fringeweb.com>]

DasErde2@aol.com wrote... a bunch of anti-Torsen stuff.

Rehashing your same objections to torsen centre-diffs, basically that they
may behave oddly at the extreme envelopes of handling for ANY car and are
not used in racing.  Also you claim that they are used only by Audi, not by
others, so the others must know something more, and that even Audi is
phasing Torsen out for EDL.

I'm not sure if your point was that Torsen sucks, or just that it isn't the
ideal extreme-performance-machine centre diff.  If the latter, please
forgive this message; I got lost in your message.

In defense of Torsen for street cars, though, allow me to point out that...

1) Racing conditions and street conditions merit entirely different
equipment.  Racing slicks would handle extremely poorly in Seattle (wet,
muddy, sometimes snowy, etc...)  The best street tires won't survive long
on the race track.  

2) Similarly, the engines need different characteristics.  The start/stop
of street driving isn't very typical to the Indy 500.  Ditto a saleable
suspension. 

3) Audi has an exclusive license to Torsen as a centre diff.  The fact that
BMW didn't use it is not because they didn't want to - they may have wanted
to; they just didn't have the choice.  (BTW, the ix sucked pretty badly.)

4) Audi does not seem to be phasing out Torsen for EDL.  My car has two of
the latter and one of the former.  It's fairly new ('97).

5) I don't race, so I can't speak for race conditions.  I have driven a lot
of AWD and 4WD cars.  The only two systems I like AT ALL are the Audi
Torsen and the Subaru planetary-gear.  I do NOT like the Subaru
viscous-coupling, or Volvo's viscous coupling, or the 4WD of any of the
various cars I've tried with that.  My normal route includes several rather
torn-up reverse-banked corners that are often wet and muddy, sometimes icy,
and never smooth.  It's a good test for a car; enormous fun in my FWD Ford
Escort.  Of all the AWD/4WD systems I've mentioned above except the BMW,
only two handle it smoothly, the two I mentioned.  However, I like
stick-shift, and the Subaru planetary-gear centre-diff is only available on
their automatic tranny.  So we have one of each: I drive a '97 A4Q 2.8L
stick, and my SO (who hates stick) drives a '96 Subaru Impreza 2.2L coupe.
(And I still have the '87 Escort, bought new for less than $4K, for the
heck of it.)


You rely on what the Torsen inventor states.  I suspect there's some bad
blood there, and he may not be in the loop on current advances.  However,
I'm willing to believe that a Torsen centre-diff will screw up at the
extremes you described.  I also suspect you can MOVE the point at which it
screws up, as high or low as is essential, so you could probably build a
Torsen that even a performance car wouldn't max out..  Either way I just
don't think it's relevant - I'll never get anywhere near those extremes,
and would have reached complete uncontrollability far sooner in either the
Subaru (which is a great car) or the Escort.  

I challenge you to bring a stock Audi A4Q (1.8T or 2.8L, your choice) to
Seattle.  I will lend you an '87 Ford Escort with substantial upgrades from
stock, including greatly improved tires, wheels, and suspension.  I'll pick
the course.  You get your stock Audi up to the speed that it takes to
evidence the behavior you're describing... on a course of my choosing,
driving normally-but-quickly.  (I'll be right-seat verifying the behavior.)
 You then have but one challenge... get my Ford Escort (which you can
verify the condition of first, if you wish) to with-in 5mph of the Audi
speed and not wipe out.  (I won't be right-seat for this one.)

If you succeed, I'll write you a check for $250 (and post the video on my
web site, for all to see.)  If you fail, you pay for the repairs to the
Escort, assuming you survive.  (I won't post that video - I'm not morbid.
If I sell it, I'll give your relatives 50% of the take.)

Again, to readers, I hasten to point out that I may be misinterpreting his
position; he may have been simply stating that Torsen differentials do not
work ideally in high-speed racers that spend most of their time at the
extremes.  That I can't address.  Probably 95% of S4's never are in track
races, so I don't consider it relevant.  However, I do believe that you
could BUILD a Torsen that would meet most race conditions.  It just may not
be profitable.  After all, you -could- build a racing diesel, but again,
R&D would exceed payback.