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MaxxECU can-bus via OBDLink MX+ equations

hasolehasole
in RaceChrono for Android
Hi

I can connect to my MaxxECU via CAN bus using my OBDLink MX+. I'm trying to use the help from MaxxECU, but I'm lost as to how to find out what equation I need to get the correct values.

https://www.maxxecu.com/webhelp/can-default_maxxecu_protocol.html

I currently have configured rpm, tps, map, intake temp, coolant temp.

It is connected and when I run the CAN test I get the raw values.

When I start a session, I can see it connected by CAN bus. Should it show the frequency of the values (Hz) like it does when connected via OBD?

Any help would be much appreciated.

Comments

  • aol_of_RaceChronoaol_of_RaceChrono
    edited July 2022
    I'm not sure what you're seeing? Did you configure those CAN-Bus channels in your vehicle profile in RaceChrono?

    Adding the following CAN-Bus channel should give you RPM:

    Channel: RPM, PID: 0x520, Equation: bytesToUint(raw, 0, 2)

    Notice the PID is in hexadecimal, so enter it like 0x520, and I think RaceChrono will convert it.
  • hasolehasole
    Thanks I tried this, my coolant temp shows up as 168242526305280 deg C, where the ecu reads it as 11.9 deg C. intake temp was 2567177220 deg C where it was 6.0 deg C.

    Just need to work out the equation to get the value.

    This is using the hex which RaceChrono converts and using bytesToUint(raw, 0, 6) (coolant) and bytesToUint(raw, 0, 4) (intake), based off the MaxxECU help.
  • aol_of_RaceChronoaol_of_RaceChrono
    From your list, the coolant temperature is PID 0x530, offset 6 bytes, length 16 bits ( == 2 bytes), factor 0.1.

    So the equation should be bytesToInt(raw, 6, 2) * 0.1

  • hasolehasole
    Thank you for that. I just tried that and the result is in this screen shot.

    https://imgur.com/a/vZmlV9R
  • aol_of_RaceChronoaol_of_RaceChrono
    edited July 2022
    Right. I missed an important part of your linked document: "Little endian (least significant byte first)".

    So the equation needs to be adjusted to little endian: bytesToIntLe(raw, 6, 2) * 0.1

    I think it will come as 13.7 celsius

  • aol_of_RaceChronoaol_of_RaceChrono
    edited July 2022
    Rest of the data on your screenshot resolved according your linked documentation: Intake air temp seem to be 6.8 .c, barometric pressure 103.1 kPa (sounds about right), and battery voltage 11.82 V (remember to charge your battery).
  • hasolehasole

    Thanks again. That did the trick. I really apprecaite the fast help.

    The car wasn't started for the low battery voltage and my ecu reads about 1.0 V lower than the battery which is apparently normal.

  • aol_of_RaceChronoaol_of_RaceChrono
    Great to hear you got it sorted :)
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