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

[QSHIPQ@aol.com]

Dave E writes:
>the questions were simply to see what you understood at a basic level.  it
>is one thing to observe, and another to understand.  and to help any other
>poor sods still attempting to get information from this thread.  bear with
>me.  some more questions.

I'm happy to answer yours, maybe then, you can answer mine.  Your paper can 
help you.

>1) what is the difference between a locked centre and a torsen in your
>scenario if the torsen is not at the bias ratio?

How can a torsen NOT be at some bias ratio other than 50/50 front/rear while 
turning at all.  It's in your reference paper.  You turn, the torsen 
allocates torque.  PERIOD.

>2) as above, but with an open centre?
Lets do something smarter, since we have talked all along (3years almost) 
about a locked center v torsen, let's keep it there.  For infomation about 
the open, we could regurgitate your referenced paper.  

>3) what do you mean by the comment "Any speed axle difference would result
>in a front to rear alternate spin, it's in the presentation".  

What happens if either driveshaft loses traction (as apposed to torsen 
allocating torque due to slip angle differences).  That is in your paper.

>if there is
>no axle speed difference during a normal turn with the torsen, how does the
>torsen handle front/rear slip?

There IS an axle speed difference during a normal turn, and the torsen 
appropriates torque because it doesn't know or care that you are turning.  
Your paper says how much for a bunch of "givens".  The paper grandly states 
how dumb the torsen is.  The authors try to say that rear torque split favors 
turn in on an understeering chassis.  Maybe true for the "givens" they used.  
Not "necessarily" true when those "given" variables change.

>btw, some things you should understand....
>1) a spinning tyre does not make the torsen shift torque.  torque is
>shifting well before that point by definition.

Not completely true.  Read the section of you paper about when "the wheels of 
one axle reach the limit of adhesion...  Independent of the forced slip...".  
How exactly do you interpret that phrase?

>2) a spinning tyre continues to support torque (i.e. supplies tractiveforce).

More specifically, look at it this way dave.  In a hot turn (same cf), the 
conditions could be right for the tires to spin equally front and rear.  So 
all tires could be spinning at the same rate, the torsen assumes all is well. 
 Only when some condition happens that changes the front or rear tractive 
ability (or relative slip angle), does the torsen shift torque.  Remember, a 
torsen wants to see 50f/50r all the time.  If you accelerate up the front and 
the back of the car at the same time (spinning away the tires) the torsens' 
happy.  That only lasts for a little while, then it starts to hunt, then the 
torsen shifts torque overloading the fronts which then shifts torque again, 
overloading the rear, then shifts torque again.... Been there watched that at 
Road America behind an S6 in the rain. The key to all this, is what that does 
to the chassis dynamics while turning.   

Looking forward to your open book test answers.

HTH

Scott Justusson