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Old 04-20-2009, 11:29 PM   #1
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Default Road Speed calibration

Today I tried calibrating the Speed Sensing and Gear Options on the Road Speed tab. I had the car up on jack stands at the time, so I thought it would be easy to do. Put the car in 1st, hit the 'Learn 1st Gear', then repeat with second, third, etc...

The problem is, every time I hit the 'Learn' button I got wildly varying numbers to the point that it could not be calibrated correctly. It was acting as if there was a lot of noise in the signal.

Anyone else tried this? I could have had some back lash issues from having the car up on stands (no load), but the speed was pretty steady and I did not hear any lashing noises.
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Old 04-20-2009, 11:52 PM   #2
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I looked at the log data from a drive (not on the jack stands) and there is definitely some noise in the speed signal. Here is an example. The x-axis is time (seconds) and the y-axis is the speed signal (MVSS).
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Old 04-21-2009, 01:13 AM   #3
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I was meaning to do this the past weekend, but didn't get to do it as I was alone. I would guess it's a two person job. Supposed to be nice tomorrow, so maybe I can get my wife to drive for me while I try it.
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Old 04-21-2009, 11:27 AM   #4
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OK I'll be interested to hear how it goes.

There is a tolerance setting in there. I had to adjust it to ~100 before it would even read a value IIRC. I suppose the thing to do would be to look at the relative ratios between the gears and set the tolerance to somewhere just below that? But then again if you look at those noise spikes there is a big jump from the nominal value.
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