[logician]

Here's what I wrote recently to a friend that asked about data logging. My experience is with the Mychron XG-Log system, which I have installed in both my GTS and SM race cars.

1) I like programmable shift lights on the Mychron. Those are helpful for optimizing your shifting. But they can also be used to give feedback on performance. For example, you can set one to light up at the target RPM for T2 at TH (a sweeper). No light in the turn means go faster.

2) I like the lap time display, which in addition to displaying your last lap time, will also display your best time for the session. Best time is especially helpful for qualifying.

3) The MXL has predictive lap timing, which tells your relative time vs. your best lap as you go. It''s kind of like the ghost car in Grand Turismo. So for example, on a particular lap, you know that going into T9, you are behind by 0.1 seconds. This is a good coaching tool to help you pick up the pace.

4) When I analyze the data on my laptop, I compare a known good lap vs. my current lap. I usually focus on speed traces and compare performance in different segments. It is helpful to look at the maximum speed before braking, and the minimum speeds in a turn. The max speed tells you how well you exited the last turn. The min speed tells you whether you are over-braking. Relative segment times are also helpful. After looking at a trace, it's pretty clear what you need to improve.

5) Related to point 4, it is really really really helpful to exchange data with other drivers. Thus you can see where each driver is quicker and why. This can help give you some confidence that more speed possible in certain turns. Unfortunately, the software will generally not allow you to share data between systems. So you are limited to exchanging data with drivers that are using the same system as you. Consider which drivers you might want to exchange data with when you select a system.

6) Studying RPMs can be helpful to analyze shift points, and predict better gear choices. You can also drive turns in different gears, and then look at the data to compare the results (exit speed and segment times) and objectively decide which approach is better. Another example is analyzing optimal gear choices in a start, where you might not be fully up to speed.

7) On systems that have wheel speed sensors, you can see lockup in the traces, since the wheel speed glitches to zero. You can also compare the longitudinal G's with lateral G's to analyze the degree of trail braking.

8) Because the system monitors RPM, it will log mechanical over-rev conditions. This is helpful to understand the degree to which an engine might have been stressed.

9) Logging temperature and oil pressure can be really helpful to monitor critical engine issues. Oil starvation can be seen in the logs, where you might not notice it otherwise. Same with temps. You can program four alarm lights on the Mychron to come on under critical conditions. Maybe this will save your engine.

There's a lot more that you can do with the system. But those are the basics, and mostly how I use it.

-Juan