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Re: GEEZ!, Equal cars and Drivers

To: Todd Green <tag@cs.utah.edu>
Subject: Re: GEEZ!, Equal cars and Drivers
From: Byron Short <bshort@AFSinc.com>
Date: Mon, 08 May 2000 09:51:17 -0700
Notes about your notes...  ;-)

> >The dip in the lateral chart at 11.4 is caused mostly by
> >over braking at 10.6.  This results in the small foot fake
> >at 11.2.
> 
> Bingo.  Traditionally as I go into my later runs and carry more speed, I
> forget to move my braking point earlier to compensate for the speed, and
> overcook the corner.  So rather than overcooking the difficult corners,
> I mentally tried to brake a bit early.  Clearly I was too early here.
> Also by this time in the event, I knew that I wasn't going to catch Bob,
> but if I just put in solid runs, 2nd place would be mine.  (I was
> currently in 3rd due to cone damage, but had 2nd by ~.5 on scratch.)  So
> I was shooting for 9.8/10ths to make sure I didn't cone, yet put in the
> times that I needed to have an M3 1-2 finish ;)

Trying to "conserve your way to a position" instead of
"attacking your way to a win", eh?  ;-)  BTDT.  I hate
driving in that mode.  But clearly there are times that
discretion is the better part of valor.

If you are going to brake early, a practice I wholeheartedly
endorse btw, use the extra stability to accelerate earlier,
even if very slightly.  Most cars handle better at 1/3
throttle than they do under braking.  Under braking and
turning you saturate the outside front tire while the
outside rear tire is underutilized.  If you brake early
enough to allow time for the chassis to settle and pickup
maybe 1/3 throttle you can transition the weight to the rear
more gently and earlier, and that way maybe (just maybe) you
can apply more significant power earlier, making your
handling limit come when both left-front and left-rear tire
are saturated, rather than only the left-front.  I'm no M3
expert, and YMMV, but the
1/3-throttle-to-balance-the-weight-trick works because it
allows both outside tires (front & rear) to take on
significant lateral force, rather than simply saturating the
front.  This kind of "gentleness" is hard to do in the
violence of a fast run like yours, but you already exhibit
some fabulous examples of this kind of control and
gentleness.

For instance...the perfect, classic, braking to accelerating
trace is a steep drop into braking, followed by a slow
continuous climb back to full throttle.  Drawn sideways this
is a sudden drop, followed by a much longer ramp up to full
throttle.  This formation happens when the driver combines
hands and feet, and blends his lateral g's with his
accelerative g's, and when we look at Todd's run, this is
exactly what he has done.  This takes real calmness and
smoothness and outstanding skill...in the middle of all of
that violence that's happening out there.  (See examples at
5.4, 16.8, 25.0, and 28.1.)  If you look at the Total G's
chart after these points you'll see some real calmness in
the face of fury, as Todd maintains a very high and very
consistent g level during the blend from feet to hands to
feet, braking to lateral to gas.

> (On this particular run I understeered at 17.4 and wasn't able to take
> that turn as tightly as I had wanted, and thus struggled to straighten
> the car for the whole return trip until ~23.4)

You hit on a biggie here--the push at 17.4 probably took you
outside your perfect line.  So you get a double whammy.  You
are traveling a greater distance, and the front wheels are
plowing which greatly inhibits acceleration. 

> On a side note, I've always measured "shifting time" from the point when
> the acceleration starts to drop (i.e. off the gas) until the
> accel curve's slope becomes positive (i.e. on the gas) no?  The .7 that
> you have noted seems to be from when the accel starts to dip, until when
> it is maxed again.  If I understand this correctly, the .7 would
> represent the total accel time lost due to shifting, but not the
> physical time it actually took to shift, no?

I agree completely, but I prefer to measure the full dip
length...guys that really shift quickly, (Brian Priebe comes
to mind here) can greatly minimize that time over my typical
effort.  Either way is valid, of course, just be consistent
with how you make comparisons.

--Byron

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