Monday, July 23, 2012

NASA Heat Wave at VIR

I find myself in a relatively unique position. I just had what I should call a very bad weekend at the track, but I came away with so many ideas swirling around in my head.

After finishing a very close 3rd on Saturday (by less than .2 seconds), I came a very distant 3rd on Sunday--1.5 seconds out of contention for 2nd. Both cars that finished ahead of me were running with significant advantages: new rubber and superchargers. My car, meanwhile, was running on tires that were first mounted in February, and dealing with residual high-idle and overheating issues and a suspension setup that's always just been guessed at--never properly calibrated.

I knew going into the weekend that a win was out of reach, and that 2nd place may not happen either, but still, it was a shock to be beaten so soundly on Sunday.

But I learned a lot. And I mean a whole lot.

I learned that ballast cannot go behind the rear axle. I didn't think it was a good idea when I did it, but I really didn't want to risk interrupting fuel and brake lines to mount it in the driver's compartment. I will fix that for the next event. At one point a car braked quite early and off-line in front of me, causing me to swing right to avoid his bumper. When I turned the car back to the left for the corner, the back end washed out. Not cool. I removed the ballast and ran with extra fuel to prevent that happening again.

I learned that my wing does, indeed, cause significant understeer at corner-entry. It was nigh impossible to get the car to the apex of T1, though I was able to carry more speed than ever before into South Bend (95mph), and brake even later for T14.

I learned that urethane bushings don't make a car faster, they just reveal inefficiencies in your suspension setup. I had an off-line entry into T4 that, when I corrected with a touch of oversteer, caused the car to skitter across the track in a very unsettling series of bounces. At one point the horizon began to rotate and I had to do some very creative steering to get it back under control. The lower esses are just an exercise in bouncing, though it doesn't seem to affect top speed. I may need stiffer springs & shocks in the rear, though experiments with tire-pressure should help resolve that question.

I learned that I'm running too much negative camber. I've had a tire pyrometer for years and have never used it. This time I had K pull temps, and inners were 10 - 20 degrees higher than the rest of the tire surface.

The most important thing I learned, though, is that my car simply isn't competitive for VIR in its current configuration. And that's got me thinking about my plans for the other car.  Bridget (orange) is very close to lap-record time at Summit Point, a track with significant time spent in corners. Aero is important at Summit Point, because without it, I cannot carry speed through Turns 3, 4, and 10, and braking into 1 and 5 are weak.  But at VIR, with a 4000' straight-away and a whole lot of time spent going straight-ish, the aero just holds the car back.

Last year I was just under 2:20 and seeing 118mph on the back straight, and 117 on the front straight.  This year I'm seeing 116 on the back and 114 on the front. My competitors are seeing 120+ on both. The wing is slowing the car down.  Worse yet, I had one of the supercharged Miatas behind me on the back straight, and he sucked up under my wing and passed me like I was tied to a tree. So not only does it slow my car down, but it speeds my competitors up. Decidedly not awesome.

So what to do?  Do I run a supercharger at both tracks? The Chute (T4) at Summit Point is scary, and I do not really want to run that track without aero. But I'm not really interested in doing full motor-swaps between events.

The solution may be Stacey (the new car I bought last November). Stacey is currently getting a roll cage, and her development track had been to run in Chump then TTD/PTD. But nobody's racing PTD, and the registrations for TTD are consistently slim.  So what if I built a Spec Vinny car out of her?  Supercharger, TTE* with shocks, springs, LSD, and Hoosiers.  One car for VIR, one car for Summit Point. One with power, one with aero.

In any other situation it would be a profound absurdity to consider, but I have two cars to run. And running the power car at VIR would save me from having to get dyno-ed for every single event, since temperature variations make a dramatic impact to horsepower.

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