Re: torsen tech iv

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

scott et. al.,

given traction to both driveshafts on a torsen, there is *no* transfer of
torque which you describe.  by definition....

what you are describing will ******only****** occur with the *****complete****
loss of traction on one [virtual] axle (we're talking wheel lift folks).  in
this case, i'll take all the torque to whichever axle has traction thanks very
much.  in normal traction situations (ie dry road cornering), you scenario will
not happen.

ok, lets look at the math some more (i'm using a maximum 70:30% torsen split
which i think is correct)...

vehicle with 200 lb ft available torque, cornering too hard, inside wheel lift
(worst case scenario)...

open centre diff:
normal operation: 100 lb ft to each [virtual] axle.
inside front wheel lift, 0% torque swing to rear axle, 100% (200 lb ft) torque
to front axle (specifically through the lifted wheel).  vehicle is now
unpowered and about to oversteer.  significantly. attitude is restored when
wheel contact is re-established...

torsen centre diff:
normal operation: 100 lb ft to each [virtual] axle.
inside front wheel lift, torque to back axle of 140 lb ft, front of 60 lb ft. 
torque difference is 80 lb ft.  vehicle has responded to the wheel lift by
transferring power to the axle which has traction.  vehicle *may* now be more
likely to oversteer due to the additional torque to the rear.  however, this
'attitude' (whether oversteer or not) will stay *constant* until the front
inside wheel drops and contact is re-established, whereupon 40 lb ft of torque
is sent back to the front axle, which will correct the oversteer and bring the
car back to neutral.  ***this is exactly the behaviour you want!***.  the hunt
which you speak about will not occur because the torsen will distribute torque
to the driveshaft with the *greatest* torque reaction.  which in this cae will
always be the rear (oversteer or not).  this explains my (and phil's i guess),
history of satisfactory power-on oversteer with these cars...

locked centre diff:
normal operation: 100 lb ft to each [virtual] axle.
inside front wheel lift, torque to back axle of 100 lb ft, front of 100 lb ft.
the vehicle is less likely to oversteer than in the torsen scenario because of
it's inability to provide additonal torque to the rear (could still happen). 
this attitude will stay the same until front inside wheel contact is
re-established, when 100 lb ft of torque is sent back to the front axle.  less
torque makes it to the ground here, means car goes slower through the turn.

which car would i rather drive?  the one which puts the most power to the gound
and makes most of the avilable torque.

hth,
dave
'95 rs2
'90 ur-q

>
>Date: Sun, 1 Mar 1998 16:38:27 EST
>From: QSHIPQ <QSHIPQ@aol.com>
>Subject: TSD's, what's with Trg
>
>If you look on Page 7 of the technical paper found at:
>
>http://www.mindspring.com/~audidudi/Torsen.htm
>
>Assuming dry road, full contact, slip angle only Trg for a 160 ft/lb car vs a
>300 ft/lb car.  
>
>160 ft/lb, 75/25/25/75 torsen Center
>
>T1/T2 = 3:1
>T1 = 120
>T2 = 40
>or
>T1 = 40
>T2 = 120
>Tshift = 80 lb/ft
>
>What does that mean here.  Well that means up to 3 times the torque of the
>faster Driveshaft can be generated in the slower one.  Assuming a dry track
>that is a "transfer" of 80lb/ft of torque to the opposite driveshaft.  Not
>astounding.  KISS, means that 120 ft/lbs can be at the front or the rear, 40
>will always be generated to the opposing driveshaft.
>
>So, given a set torsen (all gen II and gen II audis are 75/25/25/75) split,
>the T-shift is insignificant as the traction cf is high and the HP low.  But
>start messing with the higher HP/torque cars, "a handful" would be an
>understatement.  However, the spider can bite just as hard if you take the cf
>(page 3) and lower it.  Then even that insignificant 80lb/ft becomes a whole
>lot.  Don't think so?  Think of this a little further.
>