[torsen] Rallycross and e-brake turns

E. Roy Wendell IV erwendell at mac.com
Thu Dec 14 22:15:02 EST 2006

Thanks Steve,

We agree on the overrun theory. After I wrote that message and it  
came back from the list I read it and all the sudden the light bulb  
went on. Seeing it laid out in print suddenly made things clear. When  
I was writing I guess I was concentrating too hard on making the  
message read properly as opposed to analyzing the situation.

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.

I can't wait to try it again next month.

I am rather happy with the torsen at this point precisely because I  
can use the e-brake. All the Subaru drivers that showed up were  
happily abusing their viscous locking center diffs in the manner  
expressly warned against in their owner's manual. Judging by the  
behavior of some of their cars their viscous units were already shot.

As a side note, it's a shame that the whole torsen subject got such a  
bad reputation. Thanks to the torsen flame war on the main list I  
know way way too much about differential theory. It's turning out to  
be quite useful when I have discussions with all the Subaru punks who  
think they've got the cat's meow and own the bragging rights on AWD.  
Most of them are absolutely clueless.

Roy Wendell
erwendell at mac.com
Too many type 44 tq
A pair of MR2s

On Dec 10, 2006, at 11:01 PM, urq wrote:

> Congrats!  I've wanted to do the same thing with the V8 some day ...
> I was hoping folks with BTDT might respond ... but since they  
> haven't I
> thought I'd lend my tuppence ... mostly in a likely vain attempt to  
> get more
> activity on this list!  :-)
> From my understanding the whole idea of a handbrake turn is to do it
> abruptly.  By slowly applying the brake it would indeed just be  
> slowing down
> the car.  If you do an abrupt, hard pull on the handbrake it should  
> lock up
> one or both rear tires and giving the opportunity for oversteer.   
> Of course
> you will also need to be using the steering wheel correctly to  
> complete the
> oversteer.
> I really don't think the Torsen enters into this one much at  
> all ... you
> should be in an "overrun" (engine braking) situation, where the  
> Torsen is
> not doing much.
> Steve B
> San Jose, CA (USA)
>> I did my first rallycross today with my 200tq.
>> I needed oversteer, and lots of it at the right time. The tried and
>> true solution is a quick yank of the e-brake.
>> At first I tried applying it lightly and over a relatively long
>> period of time, kind of like I used to do when left foot braking a
>> fwd car I used to ice race in. This resulted only in a slowing of the
>> whole car and no oversteer. In desperation, I tried hard, quick
>> application of the e-brake. Voila! It worked and my times came down a
>> lot.
>> What I want to know is why I can get away with doing this. I know,
>> from theory, that trying to stop the rear wheels from rotating causes
>> the torsen to lock, which is why I end up slowing the whole car and
>> still understeering. But why does the quick application and release
>> work? Is there a certain amount of differential rotation allowed
>> before the torsen really starts locking? I would have thought not but
>> reality and theory have a way of diverging.

More information about the torsen mailing list