S3 awd system

Benjamin Weste Pearre bwpearre at alumni.princeton.edu
Thu Apr 24 19:24:31 EDT 2003

Please help!  Here's my current misunderstanding:

Haldex: basically an improvement on the viscous coupling.  You have to
break traction on some wheels before other wheels get more torque.
Yes, it's only for a few milliseconds, but it still doesn't appeal to
my aesthetic sensibilities ;)

Torsen: you're 4wd by default---power is routed to all wheels, so you
don't have to skid before those other wheels start helping.  In this
way like a locked center diff, but slip is allowed if the torque ratio
exceeds some threshold (4:1 or so) as it would when turning, using
ABS, towing, etc?  I've seen diagrams and read explanations, but I'm
not convinced that I grok it.  I think I'd need to play with one.
What's the going rate for the diff out of a dead car?

Aesthetic sensibilities aside, does anyone who's spent lots of snow or
track time on both systems have any comments?  I've heard rumours that
supposedly "unbiased" (whatever that means) people have said things
like "power delivery seems more even with a torsen" and such like, but
I'm not quite sure what that means - it could be consistent with what
I said above :)

Ben Pearre          1990 200TQA          http://hebb.mit.edu/~ben

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