Data Logging - Speed (MPH)

[steve]

Is it possible to get MMCd to show vehicle speed on a log? I thought this would be a very basic thing but its not one of the parameters.

 

[14u2nV]

Even if it could, by changing tire/wheel size, or if the factory one had mech problems, the speed would still be inacurate, thus making it no more useful than the factory speedo.

 

Tell it to log address C6, the speed sensor. Its not very accurate though, as it jumps around alot.

 

[steve]

OK cool thanks!

 

[jepherz]

Quote:
Tell it to log address C6, the speed sensor. Its not very accurate though, as it jumps around alot.



How do you tell it to log a specific address?

 

[steve]

In MMCd you'd go to Options>Preferences and then change the address for one of the "custom sensors" like so:

 

The reading you get from C6 doesn't make much sense, mph-wise. The reed switch in the speedometer pulses to ground 4 times per revolution of the cable. The speedo input on the ECU is normally biased to +5 volts, so you will get a high reading, like 228 IIRC, when the car isn't moving. As you start moving, the voltage drops very quickly. It's resolution is really only useful for seeing things at low speed, which is why the ECU only uses it up to ~35mph I believe.
This is probably why Mitsu went to a better transmission mounted unit, maybe hall-effect, for the 2G's, since they instituted a speed limiter at 130 mph for FWD's.

 

+1 I was getting 228 in neutral. Then like 65 when I was going 25MPH /ubbthreads/images/graemlins/crazy.gif

At-least I know it's not just me

 

[steve]

/ubbthreads/images/graemlins/idea.gif I had turned this on before in the past, but figured something was wrong because the #s were all over the place. Thanks /ubbthreads/images/graemlins/worthy.gif Jeff.

 

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