Oversteering AWD

[ptimmerm@mashtun.JPL.NASA.GOV]

Everyone on this list must be well aquainted with the thrill 8<0'
of understeering into a corner that was entered too hot.  Now, I 
am not a genius race car suspension guru, but I have to say I think
I really discovered some things recently.  I traded off my rather worn
323GTX rally car for a very nicely prepared car.  The last owner was
a automotive engineer and single seat racer who also dabbled in rallying.
His goal was to make the car understeer, and he succeeded.  I drove the
car at race pace for the first time this weekend, and it is a fantastic.

Some say that you shouldn't let out stuff like this that could help the
competition, but here goes.  The mazda is slightly better than the audi
in terms of weight distribution and polar moment due to it's transverse
engine mounting, but they both have basically the same problem.  Understeer
at initial turn-in.

Locking the center differential in low traction environments helped
drive the car at the limit.  The new car has a limited slip differential
in the back (some people weld up stock units), and this also helps.  

But the suspension also comes into play.  The car was set up with proport-
ionally stiffer springs in the rear.  Finnaly, the front anti-sway bar
has been removed, and the rear bar left on the car!

Sounds a little radical, but the strong rally springs give enough roll
stiffness that a front bar is not missed, even on the tightest onramps
with street tires.  (I tried it last night :-)  

So, should everyone run out and do this to their street car?  NO!
Welding up rear diffs for the street or track is a bad idea.
And these springs are much to stiff for everyday driving. But perhaps 
moving in these dirrections, less front bar, and more spring would
be a step in the right dirrection.  I can also see where a lsd upgrade
for these cars would be a big benefit for spirited driving.

Be good, or have fun.

Paul Timmerman