Sunday, June 7, 2009

Testing 1 2 3

This Saturday was yet another first time experience. This time the event wasn't a school, and wasn't a timed competition. There was no organized runs with score sheets, and there were no instructors. It was a free form autocross... a veritable playground of cones. This was the Test 'n tune!

First I spent some time in the mini-course on the theory that seat time is always useful, and I wanted to practice pushing myself to higher speeds. I got some decent times, and had some spins, and noticed something odd in the 180 degree turns... sometimes I would get into a massive under steer condition. Frequently this was with the brakes ON. Everything I've read indicates that breaking while turning should cause over-steer. Even more odd, I noticed that the car tended to stick better when I let off the break... at first I thought I must be imagining things, but then at the end of the day I was talking to Russ about his Elise, and his track-bar/adjustable shocks. He made a comment about the car being "camber challenged" And suddenly other stuff I'd read about Elise's and about sway-bars all made sense.

Test 'n tune lesson 1: The Lotus Elise is different in turning. What happens is the camber (vertical tilt) of the wheel changes as you break, and the weight is transferred to the front. This is true on most cars, but in the case of the Elise, the tires are fat enough and the stock camber setting is such that the effect is enough to lessen the pressure on the outside of the tire. This means that less tire surface is actually working for you in the front outside tire (which is already smaller than the back) and so the front slides before the back does creating under steer. This means that to get a good turn out of the Elise, one needs to *not* break hard. This also leads me to suspect that trail breaking would therefore have to be done after the turn stabilized and the front-back loading was more equalized than it is when you are turning in.

I finished up at the mini-course around the time things shut down for lunch. After Lunch I borrowed Russ's pyrometer and headed over to the skid-pad. I had started off at 22.1 lbs in the front and 24.5 lbs in the back in the morning, just to see how a lower pressure felt. All in all it had felt pretty good but now I, and set about warming up my Kumho v710 tires with the idea that I would figure out what the best pressure... I took the readings, and it came out fairly linear outside to in. I went around the circle again the other way... same result.

I didn't want to go around the circle too many times in a row because long periods of sustained sideways G's can do funny things to oil flow in cars, so to get an even better warm up on the tires, I went around one way, then did a quick 180 and went the other-way around the same number of times.... Same result but not as drastic of a fade across the tire...

Test 'n Tune Lesson #2: Kumho v710's on a stock lotus Elise like to be a lot lower than the stock pressures. Stock pressures are 26 and 28 lbs front and back, but 22 and 24.5 seem to be fairly close to the right setting.

In all this I eased the speed up until I started having trouble holding to the line around the circle, and one thing I noticed was that I was holding a LOT more sideways force than I normally did in the sweepers on course.

Test 'n tune Lesson #3: I've been dogging it on sweepers. I need to break less and hang on more. If my guts aren't trying to climb out the window I'm not doing it right. This car TURNS.

So after that I went over to check out the offsets... I didn't like the setup. It seemed like the offsets were too easy. The entrances were to far apart and it was really easy to get a good late apex. Every offset/clam shell on courses I've been on has taken a lot of work to get yourself into the right position, including the one in the NER Novice/Intermediate school. I felt like I was practicing bad habits, and getting away with way too much. I left after two runs there.

The slalom was the next place I went and I had a lot of fun there. I really worked on getting the speed up on the slalom and began to regain some of the feel for correct slalom speed. Somehow I think I had lost the "feel" for it that I got on the first day of EVO school, and then in the NER school, the slalom session was a bit too short, and didn't provide me enough time for introspection about my own performance to quite find the groove. I knew the words they were telling me already, but what I needed was to develop the feel. I did the slalom about 10 times, and spent a good 30 min shagging cones for people too, but in the end I felt like I had begun to get a good feel for the difference between a 26 pace slalom (FAST) and a 22 pace slalom (slower, but with more aggressive early turn ins... )

After that I decided to finish out the day on the mini-course. I did 4 runs, and got the distinct impression that coming out of the 180 degree turns I was craving more power. Now that I had the line down and the feel of the car had been seeping into me all day, I found myself with the pedal to the floor and waiting impatiently for the car to get it's revs up, especially coming out of the first 180 degree turn. After a brief confirmation from Russ (I'm probably becoming a pest, but he knows sooooo much more about racing a lotus than I). I decided to try downshifting to first in the turn. Obviously heel-toeing it would be ideal, but I decided one thing at a time... we will work the heel toe some time later.

The result was that the first time I did it I got up so much speed coming out of the turn that I spun the car on the next turn :-). so control obviously was key. There followed several runs where I had difficulty getting it into gear smoothly (first one was a charm apparently) and then the last couple it seemed to work and I did get some improvement out of it. The conclusion however is that that will be something to try *after* have at least one decent (clean!) run laid in at an event.

So much fun, so much learned, and the next day... Dodging Orange, Points event #4!

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