13 Mar Course Analysis

[Richard Watson]

This was a great course and difficult (for me) to figure out. Gerno beat me in C-mod because he figured it out faster. I beat Art by cheating - I rode with him and "copied off his paper". [}}:-|>>]

So now that it is all said and done here is my analysis.

see these two pictures for what I am talking about
http://www.pbase.com/dr47watson/image/40822474  map
http://www.pbase.com/dr47watson/image/40822477  graph of my and arts speed through the course

The start was a drag race to the lefthand offset (Art won this part).
At the offset I tapped the brake, turned left hard, and jumped back on the gas to approach turn 1a.
1a got another tap, steer, and gas to 1b.
Through 1b I was harder on the brake while looking out the passenger window for my throttle point.
As the car finshed the turn I was hard on the gas to critical turn 2.
At this point I have made up most of the lead Art pulled with his launch, but am still slightly behind.
Turn 2 gets a brake stab and steer jerk that rotates the car around the apex and onto the slalom straight. (not ideal but it worked)
Hard on the gas until the very end of the slalom.
You can see on the speed chart that Art backed off a little more than I did towards the end of the slalom.
Art had a nice entry to turn 3 where mine was a dirty mess, but I still got more speed on the following straight.
I finally pass Art coming out of turn 3.
Turn 4 is fun, heavy braking with the rear end hung out trying to rotate right at the end for the next straight.
Turn 5 is critical to get right so that you enter the box correctly and dont lose time. I use the tail out braking approach again here.
The box is not fun, and Art does it better (less turning), but I still lead
The last turn (6) is a classic "wait for it" 95 degree sweep.
Art waits a little longer and does it the right way, but it is still not enough.
We hit the lights and I win by .220 s.

Richard

[Ed Harloe]

Great analysis Richard.  I also loved this course.  (Thanks Ricky)

I did my usual, lazy, "seat of the pants" drive during the first heat and
was way way behind my benchmark driver.  So I set and watched
a bit while looking at a map and realized that this course really did
take some figuring out.

I would LOVE to see a side by side analysis like this of two good
SASCA drivers, in the same car, but where one of the drivers
was a left foot braker and the other was a right foot braker.  I
wonder just how different it would be in the plots.  

Were your brake taps left footed??? I was just using a partial throttle
lift to slightly pivot the car at 2 and 5.  I wasn't pivoting at turn 4, but
I probably should have been. The straight after 4 was the place I lost
the most time. (I think.)

Hopefully, posts like yours will let some of the newer drivers know
that its not all car and reflexes that make for low times.  There really
are things to learn about how to drive an autocross course.

[Richard Watson]

All of my braking is right foot. The only time LFB is an advantage for me is if the car is set up for it. Last month Phil and I both drove my Miata and I assume that he LFB'd it. He was noticably harder on the brakes for a shorter time everywhere. The biggest gains he had on me in braking were at the ends of straights in to semi fast sweepers. He messed up last months turn 5 (exactly where this months turn 5 was) which was a fast straight into a slow 90 degree turn. I got him by ~.02 s

[:-bonc01]

Richard

[JohnB]

Can you overlay a rich VS an art track map and post it?

[Richard Watson]

Art vs Rich map. Reasonably accurate, but expect some error. Art is black, Richard red.

http://www.pbase.com/dr47watson/image/40843400

Richard

[JohnB]

What GPS card dare you using?  What is the maximum update rate, do you know?  What other hardware are you using.  It looks interesting.  I might want to do something like that with my pocket pc.

[Richard Watson]

I am using the Race Technology DL-1

www.race-technology.com

GPS update is 5Hz, this is combined with 100Hz accelerometer data via a kalman filter.

[JohnB]

Why the accelerometer?  Does not the GPS provide enough resolution to calculate speed and distance vectors, and derive acceleration?

[Richard Watson]

My assumption is that because accelerometers are cheap, you get the benefit of both ends of the posistion - acceleration integration/differentiation - slightly better accuracy. You also have a backup for when one of your sattillites is obsured by a tree, bridge, ect.