[urq] So, How good is Haldex?

[Wylie Bean]

Date: Thu, 20 Oct 2005 08:15:59 -0400
From: "j.koenig" <j.koenig at adelphia.net>
>Subject: Re: [urq] awd
>To: "Schaible, David" <David.Schaible at jrspharma.com>, "Urq List"
<urq at audifans.com>
>Message-ID: <002801c5d570$07fa8840$905c3018 at TopGearhome>
>Content-Type: text/plain; charset="iso-8859-1"
>
>The ur-quattro *was* an unbelievable start (no transfer case, etc.),
with a handful of
>world rally championships to show for it, but certainly 25 years,
electronically
>controlled diffs, etc., have moved the goal posts.  Audi's pretty
well drifted away from
>serious, competition-oriented development.  Does anyone know what the
late-'90s A4 Touring >cars or Champion's RS6s were running for diffs?
...or of any world-class competition uses
>of the Haldex system (Skoda?)?
>
>Oh, and just 'cause I haven't seen it here yet... some also refer to
them as *vicious*
>couplings...
>
>John

For someone that's driven traditional quattro (that'd be most of us
here) for a while, the Haldex action is definitely perceivable,
although IMHO miniscule and not necessarily intrusive in a negative
way.  For a newbie to AWD, or to someone that comes from Volvo AWD or
Subie AWD (Viscous couplings for example) it may not be evident right
off the bat since they're most likely used to a front-drive feel with
impending transfer upon wheel speed differential F/R and the delay
involved with the fluid warmup in the VC to transfer power.  Haldex is
a multi-plate clutch setup, with a pump (active vs passive) that
pressurizes fluid in the coupling to cause the plates to engage
gradually, in order to drive the rear wheels at up to a 90/10 R/F
bias.  Otherwise it's 90/10 F/R if my Audi-trained memory serves.
ESP on or off didn't seem to affect the way the AWD operated to my
recollection with regard to straight line driving; only to cornering,
as it brakes one wheel at a time to 'pull' the car around corners.

Wylie Bean
TheRingmeister at triad.rr.com
90 Cq
99.5 A4 Avant 1.8Tq
Ex (thank goodness) Audi Brand Specialist