Autocross data

Any discussion on using LapTimer. Please use this forum in case you need guidance on how to use LapTimer or perform a certain operation
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Bobl36
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Autocross data

Post by Bobl36 » Tue May 03, 2016 5:23 pm

Hi everyone, I have a couple of questions for the group, please bear with me as I am not very computer literate. I recognize that Lap Timer is generally oriented to the road racer, but as an autocrosser I feel I could use some advice in some areas. I use Gran Prix Edition on an Android, and I have an OBD2-LX (which I can't seem to connect properly), and I will soon add an external GoPro.

First, I have seen references to the "autocross assistant", I can't seem to find it in the documentation. Also I need some help interpreting some of the logs, graphs and general information captured in the "Analysis" section. I imagine not all the graphs are as beneficial to A-X'ers as to Road Racers, and therefor not as significant for us.

This one may be pretty simple for most, but I really don't understand the graph displaying the green, red & yellow course sections, I know they refer to braking and acceleration, but the results from run to run show very different results and graphics. I would imagine understanding this graph would help me the most to improve my line and braking points.

Finally, most of the autocross tips & info are from old versions of Laptimer... can anyone help me to discover new or update features for the most recent version of Laptimer? I know Harry is pretty busy maintaining a great product, so perhaps a successful user can take some time to share his experience and tips...I'm sure a number of us Android users would appreciate the information

Thanks,

BobL36
gplracerx
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Re: Autocross data

Post by gplracerx » Tue May 03, 2016 8:54 pm

The autocross assistant or wizard is found on the 'Prepare Race screen. It's the middle button in the left column for iOS. Touching that button brings up an overlay to set start and finish positions. You need to walk directly from the starting line to the finish line, preferably without changing the device orientation, to avoid timing out. I also turn autolock off.

You should buy a GPS before you buy a camera or an OBDII dongle either for that matter. Android gives you more options for GPS. You want at least a 10Hz update rate.

The colors on the map are for lateral acceleration only. They have nothing to do with lineal acceleration or braking. You can adjust the setpoints for the different colors as well as how the colors are displayed by touching the map preview and then touching the wrench icon in the upper left corner of the map. I have the switch from green to yellow set at 0.8g and from yellow to red at 1.10g. I want to see a lot of yellow and red. The default setting is for the width of the color band to be proportional to the magnitude of the acceleration. There are other display options as well.

GPS, even greater than 10Hz is not precise and accurate enough to analyze your line. As for brake points, the total g time series will tell you where you're coasting. You want as few dips as possible. You especially don't want a dip between braking and turning in. You can also see that on either the lateral or lineal acceleration chart. Both are displayed, but the other is a dotted line. You want to see lateral acceleration increase while the lineal acceleration is increasing from the maximum negative reading for braking for corner entry. You also want to see acceleration increasing as lateral acceleration is decreasing on corner exit.

If you set two cursors on the total g time series, you'll see the path between the points on the g-g plot for that section of the course. You want the path to be mainly on the outer edge of the circle. The points should be concentrated towards the outside too. It won't be a circle because you can usually brake harder than you can accelerate unless you have all wheel drive.

Also, I recommend going to settings/expert settings and setting the detection corridor width to 5m for all. You should also set directions for start, finish and any split point you set. That will help with false trips if you get too close to another trigger. You can get to the settings for each trigger by opening the track set by touching that line in the Lap List screen. You'll see a list of triggers that you can open by touching. Scroll down to the bottom of each trigger and there's a line for direction. Android will give you a compass for the start (and finish when Harry fixes the bug) in the AX assistant. Point your device in the direction of travel and set.
Bobl36
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Re: Autocross data

Post by Bobl36 » Wed May 04, 2016 9:36 pm

Good information, thank you....keep the tips rolling!
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