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Diffy - q's, some documentation for the archives
Some interesting documentation can be had regarding Center diff configs in the
Race and Rally cars thru the 80's. These quotes may prove enlightening:
* Audi Quattro - Rally Car AUTOSPORT April 2, 1981
On testing the "new" Audi (Ur-) Quattro Rally car
"The Quattro rally car is permently locked into four-wheel drive, with the
distribution differential providing power equally to the front and rear
wheels. At the rear of the car is a limited slip differential, set to operate
at 75 per cent power loading, while the front differential is free spinning,
thus have no effect on the steering reactions.
... "Despite the use of lightweight items, like carbon fibre sump shields,
it is an inescapeable fact that the quattro has one more cylinder and three
time as many differentials as the 'conventional" rally car."
<I read locked 50/50 f/r center diff, and LSD rear above>
* King of the Forests MOTOR July 3 1982
On testing Hannu Mikkola's Bristish Open Rall Champion (Ur-) Quattro at MIRA
"In normal use, the road car's three differentials ar "free" though there is
the facility(generally of little benefit on the road) to lock up the central
and rear diffs. In the rally car, the front diff is free, the central one
permanently locked (giving 50 per cent of the power to each axle) and rear
axle has a 75 percent limited slip."
<I read locked 50/50 center diff, LSD (not locker) in the rear.>
* Just for Sport Track Test Car & Conversions Nov '86
First factory Sport track test of the 'new' Racing Sport Q
"On the handling of the Sport, which was patently very difficult, whether
judged from the 1984 passenger seat, or simply spectating, Blomqvist offered
these illuminating insights: "It is much, much, much better on the S1 than it
was before. The car goes where you steer! No more understeer, oversteer,
understeer as you do just one corner!"
<HELLO, to help understand what he is talking about, read the next report from
C.S.A '87 report below folks - Sounds like Torsen didn't work to me>
Back to test above:
"At slow speed you notice the lack of a central differential in the hopping
and scrabbling of wheels attempting to follow the same path via routes of
varying distance. But as soon as you get on the loose, the competition
quattro system - solid shaft centre, front and rear diffs and a complete
absence os cockpit-operated diff locks (redundant) - makes good use of such
<I read the above to mean that this particular (early) SQ had torsen rear with
a locked split center with no diff>
"Handling? Here the car felt most recognisably like a road car, or the
previous competition series. I certainly slid a lot more readily into
oversteer that the LWB machines, but at the modest speeds we enjoyed, it was
possible to approach a corner conventionally, brake and apply increasing power
for a rewarding tail slide thereafter. In full-blooded rally use, however,
the drivers get to know quattros willful nature at its worst. Which means
heavy initial understeer that can really onlyb be countered by left foot
brakeing or just the sheer speed of 'bunging it" sideways."
* Audi Sport Quattro Road Test CAR SOUTH AFRICA Jan '87
Testing the Group A (outlawed "B" in europe, but not S.A.) Sport quattro
Safari Rally car.
- "Although a variable transmission torque split was introduced on the S1,
the car that Mortimer will use this year features the fixed 50-50 front/rear
torque split and full time four-wheel drive system that was used in the
<Which would mean Center diff locked at 50/50, and LSD rear, but read VTTS to
mean exactly Torsen>
What I find interersting here is the last two reports. If you reread those,
you can see that Torsen had it's debut in the S1 early on. If you look to the
Racing results of 1984, the first Sport Q's debuted in May, but only won Ivory
Coast (Blomqvist) and got second at RAC (Mikkola) both in November of '84.
They ran every race, as did the Ur-quattros (albeit with better success), the
most notable was Mouton "Went-off" DNF of 1000 lakes. Would the question,
"Was it the Torsen?" be relevent?
My belief is that the Torsen was used in 1984 SQ with basically no success,
certainly no backing from the drivers. It also appears that the drivers were
given the choice of Gen I racing diffs, or set lockers (no diff center) thru
the late 80's on the Sport Q. Given the comments above of the no diff locked
centers, one has to wonder what audi did in the 90's to make the system work
in the tarmac cars. More slip in the gears in the center, or more slip in the
gears in the f/r diffs. My guess is the latter.
So, my take on this center diff thing is as follows:
* Center diffs were run locked on all Rally Ur-q's, with LSD rears, not
* Torsens were used in 1984 debut of the Sport Q's, without success, then
went to either fixed f/r (no center) or Gen I center diff, LSD rears on all
* I believe to know (from a source) that the IMSA cars used torsens f/c/r
with some locking ability to them, rear drive character into the apex then
regular post apex
Sure would like to talk to some of those drivers after looking at the above.
Seems to me that the Torsen spider bit a couple of drivers in it's SQ debut.
HTH, please excuse spelling errors, very late night last...