Targa Miata
March 8, 2009 - At the last track day, I entered the 21st century.
Traqmate sent along a loaner data acquisition system, so I stuck it into the car when we headed to the track on Friday. It's a small box with accelerometers and a high-precision GPS unit in it and a display unit that can be mounted in the driver's line of sight.
On the track, the display unit can be set up to display a timer along with a predicted lap time - whether the box figures you're ahead or behind of your current best time. It's great immediate feedback, try a slightly different line and see if the computer says you're going faster or slower than your best. Make a mistake and it immediately tells you how much your screwup cost you. Hanging the tail out on turn 4? Not the fast way around this track! It can also show you instantaneous g loadings but not in the easiest-to-read format.
Once you come in, plug the display unit into a computer and it'll spit out every dirty little secret from the entire session. Your lines, exactly when you braked, how early you lifted off the gas, friction circles - everything. You can isolate one or two laps and see how they differ, or overlay a whole bunch and see how consistent you are. Get a datalog from another driver and you can compare lines, braking points and the like.
Data porn: the Targa car can corner at over 1g, sustained. I see peaks as high as 1.3g. I can brake at 1g as well. Meanwhile, acceleration peaks at about 0.5g. As I expected, I can't accelerate as hard in a right turn as I can in a left (there's that inside wheel spin) as there's a little dent in the friction circle, but looking at other cars it might be how the track works - a couple of the left handers have downhill exits, so you get get more acceleration out of them.
I pulled up the new lap record put down by a turbo Westfield. The big difference? Max acceleration of 0.9g. Holy cow. Slightly different lines (ie, he can't straight line the chicane like certain cars with rally suspension can) - but it's interesting to see where I'm actually carrying a little bit more speed or braking more agressively. Also, minimum speeds in the really tight corners aren't much different, and you can see how I'm keeping the throttle pinned all the way down the back "straight" while he has to feather it much earlier as he hits his peak cornering speed about 400 feet sooner. It's fascinating stuff, and with Janel's cool little netbook we can do analysis while the brakes are still cooling.
I was helping evaluate to see if Flyin' Miata should carry this doodad. And after this, I'm a big believer. Now I just have to see if I can use it to peel some time off my laps. The real advantage will be getting a datalog of a fast driver in a slow car.
The container of home made cookies is optional.
entry 661 - tags: datalogging
August 9, 2009 - I didn't spend a whole lot of time on the track last weekend.
I was spending more time than usual organizing for some reason. I did take the Targa car out a few times, and also went out to play in Elvis the V8 Miata.
Tom Heath from Grassroots Motorsports was there, and he took the Targa car out for his first session. He really enjoyed it. And it is a fun car, I'm not going to argue. It was set up with a bit of oversteer and the softer springs (as used in the race) and I think it was faster with the stiffer setup, but it was still very entertaining and Tom seemed to enjoy himself quite a bit.
I did a bit of data acquisition with a Traqmate during my few laps. I was having trouble with my line on the fastest part of the track, and this is pretty clear from the data. At least, I think it is. I'm not accelerating as hard as I should down the straight, and I'm not at my maximum cornering speed until right near the end. There, it peaks at over a g and then is followed by about .75g braking while still cornering at 0.5g.
I also compared it to a log from our previous datalogging session, a lap that was 1.2 seconds faster. I have a lot more analysis to do, but this is going to make for some really interesting reading.
Not a terribly coherent report, I know. It's been a long weekend. The Targa car acquitted itself well, and after talking to a number of people about the race and watching the videos, I have the itch to go back again very badly.
entry 690 - tags: datalog