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And THIS is what it looks like when you overdrive the car (GEEZ! Plots)

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And THIS is what it looks like when you overdrive the car (GEEZ! Plots)

Old 09-27-04, 03:22 PM
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And THIS is what it looks like when you overdrive the car (GEEZ! Plots)

Well, we had another autocross yesterday and I was once again humbled by my stupidity. Amazing how a 3200lb, 400 HP car has a tendency to that, eh?

This was a pretty fast course which was not very technically challenging at all. In fact, I made it too difficult during my course walks which was just plain dumb and ruined my first three runs (we get six).
After three runs I was forced to completely re-analyze what I was doing because it obviously wasn't working. I came to the sad conclusion that I was just plain overdriving the car. I wasn't smooth and I was taking the wrong line around a pair of linked corners. Because I was taking a different line, I was off in the debris instead of on the clean asphalt. I really don't know if the line I wanted was better, but in the case it didn't matter because I was forced to run where everyone else was running.
So I decided to start over. Pretend I didn't know the course and drive like a geriatric. And it worked. Took a full second off and I KNOW I left a lot ot there.
Run #5 was more of the same- took ANOTHER full second off (that's two seconds for those pf you playing at home). Sheesh. Who new I was driving THAT poorly in the morning?
Run #6 hacked ANOTHER half a second off and gave me FTD for the street legal cars. (I don't compare myself to those silly carts or anything that arrived on a trailor without plates. Those guys are cheating. )

Hmmm, so what was I doing wrong, exactly? Lucky for me, I have GEEZ! telemetry of the races.

I attached the plots of run 1 next to run 6. Start on the lower right, two loops, the exit lower left. The colors are utilization: Red is less than 70%, pink is 70-80, blue is 80-90, light blue is 90-100, and white is above 100%
The first thing you'll notice is the sixth run is much smoother. Fewer spikes in the throttle and steering input and a much more CONSISTENT run. Keep in mind the right run is 2.5 seconds FASTER.

Some more analysis:

The cursor on the track shows the second cone in the slolom. The red line corresponds to the spot on the lateral forces at that time. I overcooked the first cone in run 1 and it shows: I have huge lateral G's while I'm braking to make the cone, despite the slower speed. Run six is much better- I'm going 7 MPH faster with less utilization because I actually had the car positioned properly. Granted, it looks like I could have gone even faster, but it's a huge improvement over the first run.
The green line and orange circle on the first run is where I thought I was going to have to brake heavily in order to make the left hand corner coming out of the off-camber sweeper. However, the plot of run #6 shows that I can make the corner with just a slight left foot brake to rotate the car before standing on the brakes at the green line. Also, notice the on run six I did my braking in a straight line (green line) versus the first run where I was trying to "do too much" and brake and turn at the same time. Stupid, stupid.

Purple circle:
Notice how much smoother I was on the corner on run six.... On the first run the car pushed out at the end of the corner which is why the G's went to hell. Just plain going too fast.

Red Circle:
Same thing as above. Overcooked the corner and paid for it. You can see the G's fall off on the first run as the front end washes out.

So what can YOU learn from this?

Well, for starters:
Learn when you're overdriving the car. Novices especially have a tendency to do this. I'm proof that this doesn't just happen to novices, though.

Try to take the SMOOTHEST route around the course. Jerky wheel and pedal inputs unsettles the car and hurts you a lot more than you realize.

Follow the line that everyone else is taking. Even if it's the "wrong" line in your eyes, it will quickly become the faster line when all the debris ends up in in YOUR line.

I apologize for the fuzzy picture.... The screen cap didn't work out too well.
Attached Thumbnails And THIS is what it looks like when you overdrive the car (GEEZ! Plots)-geez_run1.jpg  

Last edited by Umrswimr; 09-27-04 at 03:50 PM.
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Old 09-27-04, 03:45 PM
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Run 6

Run 6 image:
Attached Thumbnails And THIS is what it looks like when you overdrive the car (GEEZ! Plots)-geez_run6.jpg  
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Old 09-27-04, 03:47 PM
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Utilization Percentage

Here's the overall Utilization percentage:

This shows how poorly I did and how much room for improvement there is....
Attached Thumbnails And THIS is what it looks like when you overdrive the car (GEEZ! Plots)-geez_utilization.jpg  
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Old 09-27-04, 04:49 PM
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The instances where you're under driving the car look to be exactly the same places I was when I first started using Geez: everything just before and just after mid corner. Geez helped me figure out quickly how much blending of braking/turning/acceleration I could really sustain.

I should have plots from the TMS bus lot up tonight. That lot is sealed asphalt and is by far the slipperiest course I ever run on. My first run was absolutely miserable as the car pushed like a pig. After taking nearly all the shock out of the front end and dropping the tire pressures at all four corners about 3 pounds I got the car to work. The fast way around was to let the rear drift just enough to point the car through the turns. Not so much to require counter steering but enough to turn the car. I'm interested to see what that did to the numbers.
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Old 09-27-04, 05:01 PM
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Yeah, I have a ways to go in the mid-corner range.

The two LARGE red areas I attribute to a few things:

1) The big sweeper was off-camber on the upper left side so the numbers are ambiguously low here. Traction was lower than the rest of the course as a result. Additionally, at the end of the off-camber corner was a curb that I did not want to hit. One car came close.
2) The red area at the bottom sweeper and between the red and purple circles is engine bog. On run 6, I'm only going about 30-35 MPH here on lap 1 which is pretty low for second gear, comparitively. Since it's almost perfectly straight here, I was at the mercy of the engine. The second lap I'm going closer to 45MPH which is a MUCH better spot for power and the utilization shows it. I can only imagine trying to deal with turbo lag on top of it.

So much room for improvement on the slolom, though.
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Old 09-27-04, 05:09 PM
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Originally Posted by Umrswimr
So much room for improvement on the slolom, though.
My other big buga-boo. You absolutely can't get the slalom perfect though without being ungodly smooth. I didn't appreciate that enough before and didn't realize how much faster that last little bit of smoothness will let you go. I still have a tendency to get behind if the slalom is 5 cones or more.

We had an event recently where each of us in SS were going slower each consecutive run. We all just figured we were being bone heads and making mistakes. After most of us were done we compared notes and decided we must be over driving the course; there was no other explanation. We were trying too hard to do what couldn't be done. With that in mind there was one SS competitor left to make his final run of the day. That last run was about half a second quicker than the rest of us and about a full second quicker than his next best run. When he got back he said he just did what we all discussed: he drove "easy". Didn't push hard and just kept the car in tight; said he didn't feel he drove spectacularly at all. That's only the second course I've ever seen that did that: the harder you try the slower you go. I wish I could but my finger on what made that course so different as I really can't point to anything in particular.

Last edited by DamonB; 09-27-04 at 05:18 PM.
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Old 09-29-04, 02:26 AM
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The old solo mantra:

Slow down, go fast.
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