Hatzenbach

After reading the book "making sense of Squiggly lines" I am starting to understand the data from my AIM SOLO much more.
But I am still on a steep learning curve.

Could one of the experts on the forum confirm what I think I see here:

Picture 1:
Braking for turn 2 in Laguna.
Am I correct that the spikes in wheelspeed for the left wheels are ABS kicking in? (as a reminder turn 2 is a left turn)

Picture 2:
Braking for and through turn 8 (corkscrew)
Is it safe to assume that the difference in wheelspeed (specifically when I am off the brake through turn 8b) for the rear wheels means that my limited slip diff is shot?

Thanks

tedean

I would agree with the ABS kicking in on the first trace. I am not sure I would agree the second pic trace shows a weak diff.

Tom W

I really doubt it's ABS as the wheel speed is only a couple of mph different, I see that all the time (and I don't have ABS). It's just due to the difference in grip and weighting of the corner. There also isn't a corresponding pulse in the brake pressure data, but I don't know if your sensor is positioned in a way that it would even see the ABS.

A puzzling difference in wheel speed at the end of the trace where front right is faster than front left. Is the car a C4? The only thing I can think of is wheel lift in a C4 and one of the fronts is in the air a bit so it goes a bit faster. The negative (slower) spikes are the same as in T2 - different weighting leading to different grip and wheel speed.

I'd pay more attention to the overall brake profile at T2. You came off the brakes completely? Is it just a very bad heal/toe or did you do it on purpose? Same issue at the corkscrew - what is it biphasic? I would normally brake at the top (and trail brake a bit) into the initial left hand/downhill turn, but no brakes after that, just throttle modulation as you go through 8a and into T9. It looks like you are braking before the little hill and then doing more on the back side but not breaking at the hill. The hill really helps slow the car, you just need a little modulation as you crest it and get the weight back down on the backside before turn-in.

Tom W

For comparison, here's a lap at LS showing the wheel speed and brakes:

Matt Romanowski

I'm not sure either is correct. The first shows some speed difference, but it could be stability control. What do you feel there?

I also wouldn't agree on the diff. You need to look at throttle position, brake pressure, and then each wheel speed. Depending on the diff setup, you would see some lockup under braking, but then as it free wheels you'll see a delta on the wheel speeds, and then as the tps comes back up, you'll see diff lock up.

Tom W

I never considered stability control (not used to looking at it as my car obviously doesn't have it).

Hatzenbach

Bingo, it's a C4S, you really know your stuff

Bingo again, bad habits are like a comfortable bed.
I guess I picked that up a long time ago, when I was worried that the tires would be blocking when the car gets light, but honestly never questioned myself ever again if this makes sense, so it became a habit.

Thinking about which, I do the same on the crest before turn 6 in SEARS point :-(

Hatzenbach

Oh boy, much more difficult than I thought ....

Hatzenbach

Thanks guys,

as I said, I am just starting to understand the squiggly lines, and currently I mostly focus on speed, throttle position and brake pressure to find the places where I am coasting or hesitating.
However, I am amazed how much you can learn by just looking at the various data you collect.

Matt Romanowski

You're doing it right. Use Chris' book and look at speed traces, brake graphs, and throttle pickup. Those will get you 90%. Once you realize that much of analyzing the data is pattern recognition, it gets easier. Then choose three or fewer things to work on each session and drive with a focus.

Tom W

If you are around, stop by at Sears Point this weekend. I'll be there racing in the wet (if not too wet).

Hatzenbach

Would love to but have prior conflict, otherwise I would have signed up

ir_fuel

That's what my "abs has just kicked in yo" lines also look like