[torsen] Re: torsen digest, Vol 1 #28 - 4 msgs *diffs*understeer*

J123fs at aol.com J123fs at aol.com
Fri Jan 26 00:05:03 EST 2001

My. 02. or maybe is this $20.00? :-)
As a racer (cars and bikes that is) I find the some of the discussion 
regarding torque bias/ handling in the AWD Audis kinda fascinating, but 
incorrect in it's logic. 
I do believe from a standpoint of affecting handling that changing the torque 
split will of course affect the maximum grip on one end of the car or 
another, but only under acceleration or deceleration while turning, not 
steady state cornering. 
Why: As the car is turning wheels spin at a different rates, and any attempt 
to change bias relative to weight distribution will effect the Max traction 
the tires can produce as they will be fighting each other, not working 
together. This cannot be an efficient process (extra heat as diff overworks, 
and extra tire scrub). 
I do believe from my past reading that the torque split was chosen (making 
most type 44s AWDs understeer) to make sure that massive oversteer would not 
happen with the center diffs locked and because of the designed weight 
The rear diff locked is a whole other ball of wax. 
Frankly, as a purely academic excersise it might be fun to see what would 
happen if that was done, but practically speaking it is completely nonsense 
to change max slip angles doing it that way ( changing torque bias). The 
point regarding overheating the diff and tranny is not to be taken lightly, 
as you be forcing the diff to work overtime. 
The correct way to change handling most chassis tuners use is to correct for 
in-equal weight distribution through changing springs, roll rates ( rollbars 
are springs too), maybe roll centers to achieve maximum tire contact while 
Not by forcing less adhesion at one end or another. The key is to optimize 
the contact patch, not to force one end to do more work.
As all AWD type 44s ( 2wd too) have massive forward weight bias, conventional 
wisdom would have you change rear roll rates or centers, which in effect will 
give the front more traction. This will effect the car during all stages of 
cornering, not just steady state. Nuetral bias is what you are looking for, 
where traction at steady state is good, and transient maneuvers will not 
force the car to rotate, or push (understeer) quickly. (but now we are into 
polar moments.....not good to muddy the waters more)
So if you really want your type 44s to stop pushing get a big rear anti- roll 
bar, as it will not effect ride quality too much ; as compared to stiffer 
springs, and will eliminate some push in the cars. 
Don't waste your time worrying about torque splits, as it's almost not 
relevant to reducing understeer in Audi's.
See ya

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