Msd 8973 issues

Discussion in 'PSI Superchargers Tech Questions' started by letitrip, Feb 7, 2008.

  1. letitrip

    letitrip New Member

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    Is it possible for the msd 8973 box have the timing come in and out as you were going down track when you are pulling it out by rpm at launch and ramping it back in,,i dont have any way to monitor the timing as far as a racepak,dont know if it its the timing related or something else,just seems like thats the way its acting,i havent tried to zero out the box or unplug it ,just looking to see if anybody has ran into a running problem like this!
     
    #1
    letitrip, Feb 7, 2008
  2. Mike Canter

    Mike Canter Top Dragster
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    Are you using a crank trigger with it?
     
    #2
    Mike Canter, Feb 7, 2008
  3. letitrip

    letitrip New Member

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    no crank trigger is being used
     
    #3
    letitrip, Feb 8, 2008
  4. Mike Canter

    Mike Canter Top Dragster
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    The only real problems that have occured on the 8379 is when used with a crank trigger with and unshielded cable or somebody has moved the 8379 a long distance from the mag and made an unshielded extension cable.

    No their is no way possible for the 8973 to get a mind of its own and start doing stuff like that. The software is basically the same that is used in the Digital 7 and has been working OK for years. I would look elsewhere.

    One of the biggest offenders of causing ignition problems in a Promag is the coil and plug wires or not having the heads grounded together and grounded to the ground of the coil.
     
    #4
    Mike Canter, Feb 8, 2008
  5. letitrip

    letitrip New Member

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    Thanks for the tip!
     
    #5
    letitrip, Feb 8, 2008
  6. dcwinters

    dcwinters New Member

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    I just hooked our 8973 up this weekend. Started the car up and the timing droped 4 degress to 22 degress. Then I took the 8973 back out of the loop (crank trigger straight to the Mag) timing went back up to 26 degress. I doubled checked all my 8973 setting, making sure I had not program something wrong, put the 8973 back in the loop and again it dropped the timing 4 degress. I left the laptop connected to the 8973 while it was running and the "dials" view on the MSD program showed 0 degress retard???

    I had programed a Timing retard cruve, so I depressed and release the clutch to activate the timing cruve and it worked, it brought down the timing and then went back up (still 4 degress overall down). So the box is working. But I can't figure out why it is dropping the timing 4 degress without a retard programed...

    Anyone seen this? I know I could just move the crank trigger to compenstate, but I should not have to. We lined the crank trigger up with one of the flying magnets with the engine off and the timing mark at 26. So it should be 26.. This box is retarding 4 degress all the time???

    Help?

    Doug
     
    #6
    dcwinters, Feb 9, 2008
  7. aj481x

    aj481x Member

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    Most electronic controls have a built in delay for "processing". You could check with MSD but we saw the same thing with our first 8973, although it seems to me it may have only been 2-3 degrees. Watch all the settings on the "tree". For some reason + means off and - means on. Seems backward to me.
     
    #7
    aj481x, Feb 9, 2008
  8. Mike Canter

    Mike Canter Top Dragster
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    Actually what is happening is normal. When you start the car the MSD 8973 starts in what is called the Run Retard Curve (the timing graph at the bottom right of the computer screen). If you have the blue wire to the MSD wired to the clutch switch and you push the clutch in and send 12 volts to the blue wire on the 8973 it resets the 8973 into what I call the "Ready to Go Mode" and switches the shift lights so you start in first gear and ALSO switches the timing to the Launch Retard Curve (the upper graph on the computer screen. If the timing degrees are the same in the Launch Retard Curve as it is in the Run Retard Curve then no change will happen to the timing. If they are different then you will see a change from when the car was started to when you apply 12 volts to the MSD 8973 blue wire.

    The 8973 only changes the timing to what you have set in it. The trick is as you found out is to reset the MSD with 12 volts to the blue wire after it starts.
     
    #8
    Mike Canter, Feb 9, 2008
  9. Mike Canter

    Mike Canter Top Dragster
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    Forgot....yes if you do a side by side comparison with the car without the MSD 8973 to with the 8973 then you will see a slight difference in timing as aj481x stated. You really don't care because you are going to reset the timing with the 8973 in the circuit and it will be timed as to what you see with a timing light. It is not something to worry about.
     
    #9
    Mike Canter, Feb 9, 2008
  10. dcwinters

    dcwinters New Member

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    Thanks, I did find on the "tree" part of the program there is a MagComp setting. It says when set to AUTO there is a 4 degree delay between input and output. So that explains it. Thanks. I will need to move the crank trigger advance 4 degrees to compensate.

    However, what I am worried about is what happens if the 8973 loses it's 12V input for some reason (blown fuse, wire falls off, etc..) what happens to the timing? And for that matter the engine. Does it shut off? Or does it just deactivate the box? If it deactivates the box would not the timing go back up 4 degrees. Now what was set at 26 will jump to 30...

    Any idea?
     
    #10
    dcwinters, Feb 9, 2008
  11. Mike Canter

    Mike Canter Top Dragster
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    The the 8973 loses 12 volts the car shuts off due to no spark so it will not see any timing changes. It is highly recommended to get that large MSD capacitor part # 8830. This can supply emergency power for a few seconds.
     
    #11
    Mike Canter, Feb 9, 2008
  12. Eric David Bru

    Eric David Bru Member

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    Agreed, and to protect the sensitive electronics.

    EDB
     
    #12
    Eric David Bru, Feb 9, 2008
  13. dcwinters

    dcwinters New Member

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    Got it, thanks. I have installed the capacitor. Lets go testing!

    Doug
     
    #13
    dcwinters, Feb 10, 2008

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