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Thread: Installing P-Mags

  1. #1

    Installing P-Mags

    I have updated my ignition systems to two P-mags and have a question about how to attach the sensor for the tach to my 5400.
    Is the voltage from the 5400 12 volts or do I need to use the diode that comes with the P-mag system to go down to 5.4 volts?
    Is the correct pin for the ignition input pin 33? I am removing the three-wire connection from the previous magneto.
    Thank you.
    Paul Collins

  2. #2
    Paul do you have the AFS internal engine monitor or the SkyView EMS-220?

  3. #3
    Assuming you have the internal EMS, since you have our RPM sensor. Yes, remove the old 5V rpm sensor wiring from the plug, run from the Emag tach output to pin 33 on the EMS plug, and leave the diode out of the emag so the emag stays in default 12V signal mode.

  4. #4
    Yes, I do have the internal EMS. I very much appreciate your making sure I am doing the right thing!
    So, just run the wire from pin 33 to the Emag tach output. Sounds good.
    Paul Collins

  5. #5
    Well, I ran the engine for the first time to day and the tach was significantly incorrect with wildly varying numbers and extreme speeds shown. What did I get wrong? Please feel free to call me to discuss if you can. I did leave a phone message.
    Paul Collins

  6. #6
    Pulses per 2 revolutions in the SET --> MORE --> CAL --> Prop RPM menu should be changed to 4 pulses per 2 revolutions, per the EMAG tach output default of 2 pulses per revolution. Leaving the default setting of 2 pulses per 2 revolutions will result in the RPM displaying as 2x the actual reading.

  7. #7
    Thank you Jonathon! This was just what the box wanted!!
    Paul Collins

  8. #8
    Got your VM but you didn't leave a callback number and there was nothing on the caller ID records. It sounds like your RPM signal is being polluted by an EMI source of some sort, most likely a power wire whose output is proportional to engine power, so alternator b lead, the power going in to your emags, etc.. A few things to try:

    - where is the shield for your tach wire being drained? You might try an alternate location
    - reroute the tach wire, especially if it's bundled with anything carrying power for any length
    - try swapping the tach wire to your other emag
    - try installing the diode to put the emag in 5V mode, and then move the tach wire from pin 33 back to pin 32 on the engine sensor 37 pin connector. If that fixes the problem, make sure the diode is very well secured against loosening and against vibration. If it falls out and reverts back to 12V signal, it will burn up the engine monitor tach pickup.

  9. #9
    Thanks and I am sorry I did not give my call back number. It is 208-861-8257. So here are my answers;
    1. The shield wire is grounded at the P-mag. I will move this if you feel that might help.
    2. The wire is not bundled with any other wires.
    3. I can try to re-route the wire to the other emag
    4. If all this fails I can then try to change the engine sensor to pin 37 and implant the diode to go to the 5V mode.
    On we go and thanks.
    Paul C

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