[torsen] RE: 15mph diff lock off - torsen content

QSHIPQ at aol.com QSHIPQ at aol.com
Sat Feb 10 12:56:02 EST 2001


In a message dated 2/9/01 2:54:46 PM Central Standard Time, 
Dave.Eaton at clear.net.nz writes:

> scott,  the original post was asking about the effect of maintaining the
>  rear diff lock on a torsen car above the cut-off speed.  the audi paper
>  addresses this.
>  
>  ego to one side, this is a safety issue - not a (torsen) pissing contest.

Not at all meant to be, I just think you presented a problem that isn't 
relevent to the reason folks want to cut the BL/WHT wire, nor really is the 
concept a differential locking problem.  Think of all the Gen 1 lockers that 
*haven't* gone flying off out of control while braking, makes you think that 
the test needs some scrutiny, and your warning somewhat more limited in scope 
than you presented.
  
>  if you want to tell people that it's ok to lock the rear diff under the
>  conditions where, according to audi's engineers: "the driver is forced to
>  correct the steering quickly and accurately.  during the first second, the
>  rate of increase of the steering angle exceeds the limit of
>  controllability", then i would assume that you are not giving this advice
>  "professionally"?  if so, then i hope that you have liability insurance.  
if
>  you're not, then i will categorise this in the usual file...

Dave, please correct your *claim* here to only address *1* scenario wrt 
steering input and angles.  The results in fig 12 are for split u conditions 
of exactly of .25 left side, .8 right side (.9 considered dry pavement, .1 
solid ice).  It would have been nice to see a few more results, like what is 
the highest split u contrast that can be handled in fig 12.  Right now, I can 
share that anyone wanting to do this diff lock mod for the conditions at 
Steamboat (~.1-.3) are going to find better results with rear diff locked.  
HOW do I know that?  Well after 7 years of watching cars come down the 
straightaway at over 80mph and braking in the mixed u at the end of the 
straight, I haven't seen anyone spin or lose steering input for the 90 
right/left (CW/CCW respectively) with diffs unlocked or locked (I discounted 
those that just went straight, a different cf problem;).  

The danger of high split u exists in any car without abs engaged, and even 
engaged on a 3channel abs car.  Using that as a all inclusive warning call 
indicates to me, that you could benefit highly from a steamboat experience.  

All that said, you have laid a blanket out there that really may not apply to 
many, reading this quote on page 39:  "The extent to which this condition can 
be controlled will of coruse depend a great deal on vehicle parameters such 
as the wheelbase, track, and the height of the center of gravity, etc."  So, 
1 split u, 1 chassis, 1 set of results

Dave, a better report would be for you to do some of your own testing and put 
forth some conclusions as to your experience in split u conditions, to help 
determine what is significant to either your RS2 or your Urq.  All it would 
require for you to do is put a switch on the Bl/WHT wire on each car and go 
test.  You might find your results surprising.

Right now everyone that's been to Steamboat is smiling at this "warning" vs a 
whole bunch of btdt.

Thanks for your posts.

SJ



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