Question for those with LM-1, PLX and Various Data-loggers

fastsc92

Registered User
I have a PLX M-500 wideband/wireless data logger. I've been trying to datalog the MPH signal and I can't seem to get a good reading. I've been tapping into pin #3 on the EEC connector which is the speed signal from the tranny sensor into the computer(DrkGrn/Wht).

Currently I just get a signal that is jumpy and makes no sense. I'm wondering where everone else has been tapping into this signal. Would I have better luck at the sensor itself? Should I tap into it behind the cluster?
 
I don't track speedo. Don't care. I track RPM.

If you want speed, your software will need to be able to do a calculation based on pulses over time. Speedo signals are pulses of on and off. So many pulses per second translate to a given MPH based on the ratio of trans gears and the gear on the end of the speedo drive.

For example, the Innovate equipments typically have at least one channel that can be set to monitor Frequency. A VSS Input on that channel can then be configured to provide a MPH or KPH.
 
My logger can capture 2 speed or pulse signals and 4 additional voltage signals(0-5vdc). One of my speed inputs is measuring RPM, the other I'm trying to get it to read MPH. The company claims it can be logged and I'm sure it can, I'm just getting a weird signal from it. The value can be adjusted in the software to get the correct frequency and display the desired value.

When I contacted the company they mentioned in an email that the diode needs to be up-voltage. I've never heard that term before. I was assuming that the wire from the sensor goes dirrectly to the computer, branches off somewhere and also goes to the cluster but I thought it contains no diode.

Unless the signal goes into the computer and then is converted into another form which is then sent to the cluster...I'm not sure. I guess I'll try to tap into it from the cluster and see what happens.

The reason I'm interested in logging the MPH mainly just for kicks. I have a 2-axis g-sensor that measures acceleration/braking/corning dirrectly in G's. Therefore, with all the info I logg, I can calculate instantanious realtime horsepower and torque as a function of time.

This can be done by measuring MPH, RPM, and the g-sensor, with the weight of the car inputed as a scalar. The formula should be:

HP= (Weight X MPH X G's)/806.4
Tq=(HPx5252)/RPM
 
I'm not sure what they are talking about. A diode basically allows electricity to flow just one direction, not the other. Typically you might use that to keep a voltage surge from traveling back along the source wire. I'd ask them to get specific. If they sell it to work, they should help you get it working.

Note that you can calculate MPH from Gear and RPM.
 
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