[msendit]

Tracks are still closed, so let's do some bench racing. Might be more productive than arguing which drivetrain's better...

Here's very simple example to start with (have a lot more if there's interest). There's a lot you can see from just a speed trace. And in this case, there's a massive setup change (285 square vs 245/265 tires, same conmpound), so it's pretty obvious even with an uncalibrated driver. Red is the wide tire setup, blue is the narrow, from two days about a year apart. Video below is from the red line, so you can get an idea what the track looks like.

What are the specifics you can spot?

[lufsig]

This is very nice!

Are you able to get the CAN connection working? I assume this is the only way to get brake data on AiMSolo..

[msendit]

Originally Posted by lufsig

Are you able to get the CAN connection working? I assume this is the only way to get brake data on AiMSolo..

Yes, you only get the brake channels through CAN, not OBDII. I've written how I connected it here. Ironically, I did that one week after the traces in the first post, so no brake data in this dataset.

[msendit]

Originally Posted by msendit

What are the specifics you can spot?

Ok, I'll start with the most obvious ones:
- Generally higher corner min speeds, which is expected.
- Although the driver does some "paint by number" and just uses the cues he remembers for the previous setup, instead of looking for max grip. Most obvious in the corner before the "8" section (that's actually T9), but also in the botched up braking into T3.
- Better stability in the high speeds parts -- T1 and T8 (labelled "7" on the screen). There's about a full second gained from that.

Anyone else?

[MassNerd]

Looks like you lost some top speed. The slope of acceleration on the straights is clearly slower than with the 245/265 setup. Possible due to the extra drag of the tires, or was there some other factor that day?

[msendit]

Originally Posted by MassNerd

Looks like you lost some top speed. The slope of acceleration on the straights is clearly slower than with the 245/265 setup. Possible due to the extra drag of the tires, or was there some other factor that day?

Yup, good catch. I think it's a combination of a few things:
- strong winds that day. You can see it's mostly happening on just two of the full throttle sections -- looking at the track layout these straights are both in the same direction. The main straight (end of the lap) points the opposite way and it's not a problem there.
- warmer day -- higher IAT.
- some other mystery "engine's down on power".

I only mention the last one -- which is the oldest excuse in the book -- because it's shown up a couple of times soon after this, when there wasn't any apparent difference in conditions. Still looking for the root cause.

[msendit]

Hah, I was planning to post a chart a week, but that didn't happen... Oh well...

Let's look at braking today. This is a neat type of chart I read about in Making Sense of Squiggly Lines. You basically overlay all the individual wheel speeds on top of each other. They should be pretty close (less so with aftermarket wheels/tires, but you can correct for that in a math channel, in my case the difference was small enough I didn't care to do that).

Now under braking, you look for these tiny micro-lockups where one wheel (front inside in that corner when trailbraking) starts sliding a small bit -- its speed is lower than the others by just a few mph. That's a sign the driver's using the available braking grip, but modulating enough so it doesn't develop into a full lockup.

These are the red circles in this screenshot -- the one with the cursor is a full 7 mph off, so that might be overdoing it and more of full lockup. Not seeing these is a good sign the driver can brake harder and get away with it -- like in T1 here.