RE: Hot turning in a quattro - T*rsen content warning

[QSHIPQ@aol.com]

After reading through the archives, both Jeff G and Brendan R comments 
regarding corner entry and skid correction really gets interesting when you 
read it wrt torsen center diff.  For discussion let's look at an "overcooked" 
torsen turn on water/snow/ice (read: low cf).

Power up after corner entry, Torsen shifts power to the rear, overloading the 
rears ability to grip, car is now at 90 degrees to the apex, what to do?

Scenario 1)  add opposite lock, throttle on (not wot).  Interesting problem.  
One can presume you weren't at full lock going into the turn, so in order for 
*more* Tshift rear to NOT occur, your opposite lock would have to be *less 
than or equal to the steering angle going into the turn to begin with*.  
Remember, if a torsen is fooled by slip angle differences, that also applies 
to the equal opposite lock slide.  So one could conclude that the same 
relative slip angle <torsen fooled> applies to both turn in slip angle and 
it's corresponding opposite lock during a slide.   Don't forget too, that as 
you start to add opposite lock, you go from O, then U - wheels straight 
ahead, then O wheels opposite lock.  Get it exactly right, the second O is 
the same Bias Ratio as your turn in.

 I argue that dance is almost impossible to do (read:  more luck than skill). 
 I also argue that opposite lock during a slide varies with the slide (armco, 
ditch, turn out, etc.).   So, on top of the oh sh*t factor, you have a device 
that is constantly varying torque based on your relative slip angle, and the 
device could care less that you are sliding 90 degrees to the apex.  An 
absolute traction device isn't what you need here.

Scenario 2)  accelerate, both wheels ahead.  BTST (x a dozen or so, thanks 
valerie:) at Steamboat, maximum traction, no slip angle differences, car 
ditches into the apex.  (Graydon Stuckey gets credit for this summary, a 
hummv doesn't care what's at the apex).  Fine for Steamboat and for forgiving 
tracks.  However, a A4t at Road America found little protection on the walls 
in this manuever.  Few tracks figure on scenario 2, pea gravel on the apex?

Scenario 3)  Lift.  Nope, don't do it, spin guaranteed (Dave has a white 
paper that spells this out).  Remember, you have a rear bias oversteer on 
throttle slide, a rwd biased oversteer.  Problem, as soon as you lift, torque 
decreases toward zero, car goes back to Understeering fwd chassis. 1 of 2 
things happen:  LTO = spin or LTU = more slide.  Which dictates one or the 
other?  Depends on what kind of steering input you give and how much front 
end loading occurs.  No countersteer and/or  with front weight shift, gives 
LTO, countersteer gives you LTU.  My personal experience is extensively with 
the latter.  My summation is:  LTU off throttle during a slide gives little 
control, and time/distance becomes your biggest enemy to staying "passive".

Racer rule of thumb while turning:  If you are steering only, you are really 
only praying, too true.

Scenario 4)  WOT, with steering.  Result:  with luck and enough room you 
might be able to pull it out.  However, opposite lock skidding technique 
would dictate, that you are in a delicate dance.  Too much opposite lock 
(more than your initial turn in steering) gives *more* torque rear (which 
means that the throttle needs to come up a bit with "increased" opposite 
lock).  Remember too, that when wheels are spinning on the same cf, the 
torsen is confused, and immediately sends the torque transfer into an 
infinite loop (slip angle differences have less effect on the torque 
transfer, cuz a torsen, being a 'traction' device, the traction issue is 
simpler for the torsen.  Or put another way, traction with four wheels on the 
same cf gives bigger and maximum Tshift, slip angle differences can make the 
torsen Tshift max, but won't necessarily).  Watching this at RA was kinda 
cool, fronts spin then backs then fronts, all in 5-7seconds of a turn.

Bottom Line:  None of the above give you that "quattro advantage" feeling.   

Neat toy.

Scott Justusson