[torsen] More Rallycross and e-brake turns

QSHIPQ at aol.com QSHIPQ at aol.com
Fri Dec 15 14:38:20 EST 2006

Ok some more time to work this thru last night Roy....
3:1 x 0 torque = 0 torque to other axle.  If you use the throttle to  steer 
and apply the ebrake, you have TBR of engine torque and a slower spinning  axle 
(the one you applied the ebrake to), so you have torque to both axles, 25%  
to the front/75 rear.  But since the rear wheels are spinning slower to the  
front (you are absorbing rear axle engine torque with the rear discs - macguyver 
 traction control at the rear axle), I would expect understeer to rule from 
25%  of engine torque being too much torque to the front in low cf conditions.
When you lift throttle and apply the ebrake, you still have 75r/25  front 
torque allocation, but in terms of overall engine torque, it's really low,  and 
almost none to the front axle at a 3:1 TBR, hence the rear  skidding tires 
creates oversteer.
As a rule, rally drivers get bad looks and helmet whacks from  navigators 
with handbrake turns, it screws up the computer mileage.  I  would encourage you 
to use LFB technique to work the torsen around to your best  advantage.  The 
longer you can have torque applied and get the car around  the course, the 
faster you will be.  Lift throttle and skidding tires can  help in car placement 
on a tight course, but given the two scenarios, LFB  will yield the faster 
All that said, most torsen quattro drivers at Steamboat use the LTO/ebrake  
technique with good success.  I might also suggest you consider snipping  the 
blue white wire at the rear locker, and using the locked rear diff to help  
swing the back end out.
It's quite possible to not use the ebrake and be really fast.  I used  a 
borrowed 5ktq to an overall win at an SCCA Rallycross at Steamboat (1997)  never 
touching the ebrake.  LFB and mid apex locking of the rear diff (blip  throttle 
unlock just before turn in).    BTW, there is  conflicting documentation on 
engine overrun or decel TBR during braking.   My claim is that if the helix 
gears are symetrical, so is the TBR on and off  throttle.  Engine overrun torque 
is just so much less than braking  force (and it goes to the rear axle, which 
is doing almost none of the  braking) the TBR becomes a negligible factor.
If you need more practice, or want to experience a lot of spiders, sign up  
for some track time at Steamboat, we have a few spots still open ( 
_www.gruppe-q.com_ (http://www.gruppe-q.com)  ).
Scott 'torsen boy' Justusson
In a message dated 12/15/2006 7:16:40 A.M. Central Standard Time,  
erwendell at mac.com writes:

The  difference in my technique was more than just the amount of force   
and the length of time I was using the e-brake. When I started going   
for broke I was also off the throttle all the way which would put  the  
torsen in the mode which allows for proper operation of ABS.  Not  
"unlocked" necessarily but if I recall correctly the bias ratio  on  
overrun is lower. On my initial runs I was trying to use the  throttle  
to steer and playing with the e-brake only mildly. On the  later runs  
I was determined to get the thing sideways no matter what  and was  
only thinking about pulling the spin handle and catching up  on the  
steering hence the throttle foot was off the  floor.

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