Pro Mag 20 to 8973 w/o crank trigger connection...

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by WJ Birmingham, May 19, 2008.

  1. WJ Birmingham

    WJ Birmingham New Member

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    http://www.msdpromag.com/pdf/8973_frm25079.pdf

    There's the wiring diagram.

    I just called MSD, and they confused me as much as their diagram. Not sure why they can't post up a diagram for those of us without crank triggers.

    Anyhow... Violet/Green from the 8973 to the same on the mag?

    What of the Brown/White wire from the 8973 that shows as going to the input lead on the mag?

    Mr. Canter, are you out there?
     
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  2. pete9857

    pete9857 Member

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    mag 20

    ours hooks up just like the diagram. The pick-up in the mag is essentialy the same as a crank trigger for electrical connections.
     
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  3. WJ Birmingham

    WJ Birmingham New Member

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    Sorry, not to be insulting, but that's about as clear as mud. The diagram shows a crank trigger. I do NOT have a crank trigger.
     
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  4. Flyboy68

    Flyboy68 Member

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    The diagram shows the mag violet/green wire being disconnected from the "do not use" wire. Just plug those wires (violet/green to the "do not use") back in and use the mag (by turning just like a distributor) to adjust timing. Your 8973 should have a cam syn to use on cyl #1 or a cam syn for timing curves, etc. So you shouldn't need the 8164 harness shown at all.
     
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    Last edited: May 19, 2008
  5. WJ Birmingham

    WJ Birmingham New Member

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    Ok, that's clearing it up. Violet/Green from 8973 to the same on the mag. That's what I suspected, but I didn't want to hook up something wrong and bang the blower on startup or something stupid.
     
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  6. Mike Canter

    Mike Canter Top Dragster

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    Forget that 8164 harness and hook the violet/green from the 8973 to the violet/green on the mag. Then hook up the yellow/yellow from the 8973 to the Electronic Points Box. Make sure you do not use the start retard feature in the 8973 while cranking the car. It will not start.
     
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  7. WJ Birmingham

    WJ Birmingham New Member

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    Thanks guys...
     
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  8. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    8973

    The best way to hook the 8973 to any mag is not to...

    There's a lot of smart racers that have hurt motors out of nowhere, unplug the box and quit killing motors. When that box goes skitzo for whatever reason, it will tear up parts. Unfortunately when you approach MSD about the problem, they look at you like you're the stupidest person to ever walk into their trailer, and the problem is definitely not with any of their components.

    I know there are people that have run the 8973 with no problems. We never hurt a motor with it (3 races) on the FC I drove, but it did some weird shit on the jackstands that really scared us. When these things go south, it costs you a motor.

    If you think I'm wrong, ask Mick Snyder, Marty Thacker, Ken Perry, Mike Manners among others about their experiences with the box.

    If they would address the fact there is a problem with the box, it has the potential to be a neat unit. I did like the features wrapped into the box. The interface isn't very user friendly, and I work on a computer all day. That aside, it has potential, but if MSD doesn't want to correct the problem, I would highly recommend anyone to NOT run the box.

    That's my .02
     
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  9. fastavenger 588

    fastavenger 588 New Member

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    hay mike why wont it start if you use the retard we had the same prob and could no figureout why it would not start:confused:
     
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  10. Mike Canter

    Mike Canter Top Dragster

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    A ProMag doesn't produce much spark when the motor is turned over slowly by the starter. When using start retard the Promag fires the ignition at a point where the rotor is too far from the distributor terminal (retarded) for this low power spark to jump. The 8973 used to come from MSD with start retard set as default and racers couldn't get their newly converted cars to start:confused::mad:. Now the come defaulted with start retard turned off.
     
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  11. Bottlefed

    Bottlefed New to Blowers

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    Fastavenger,

    Why don't you ask the experts at MSD about it:eek:...

    This got me thinking too, I wonder if with the difficulty the ProMag has firing at cranking speed if creating a little additional load on the primary coil winding due to the change in rotor phase or a slight change in the signal due to the 8973 causing distortion during cranking is all it takes to keep it from firing. It would be interesting to look at the signal on a scope and see how accuratly reproduced it is (if it exists at all) during the delay function.

    PS Mike, does anyone use the 8973s rev burn feature in addition to the throttle cable clip to control the burn out RPMs?
     
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  12. Bottlefed

    Bottlefed New to Blowers

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    I think I need to learn to type faster:D this is the third time I have posted a response only to find Mike has typed and posted while I am still thinking....
     
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  13. WJ Birmingham

    WJ Birmingham New Member

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    Will;

    I don't doubt a bit that people were/are having issues with them. I've read about the failures of them since the day I joined the forum back in Oct, 2007.

    What has perplexed me is the fact that nobody published has any factual data of what actually occurred to their motor via the 8973 that caused the mechanical failure. Or, I should say, that I have not seen any published factual data.

    The cabling on the 8973 is not shielded, nor is the cabling from the mag to the points box. In the limited confines of dragster or funny car, I could definitely see RFI coming into play causing misfires, and catastrophic engine damage.

    With the GMC, however, we have plenty of room to separate components and critical wiring systems to keep them far enough apart to not cause issue.

    Right now, I'm not even looking to do more than use the 8973 as a rev limiter, air shifter controller (class legal for what I do), and tach output for the data logger.

    In the future, I may use the digital 2-step function for launching, as well as the timed timing retard to remove power at launch. That is down the road quite a ways though.

    So, sorry, but I will be using the 8973 as soon as I can get it wired up.

    Thanks again to Pete/Josh/Mike for the instructions on proper wiring.
     
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  14. Bottlefed

    Bottlefed New to Blowers

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    We have used both the digital 7 as well as the 8973 for the shift function and I can tell you that the first thing to fail on these boxs if they are hit with any kind of a voltage spike is the orange/yellow shift light wire. We have lost this function on both boxes by a single accidental use of the battery charger while the MSD was powered up to make changes. What happens is that the box will sporadically ground that circuit causing the car to leave in second, its been kinda hard on transmissions...

    We have since switched to using a shifter button since the driver is GunShy on letting the MSD have control of the shifter. However we are using the time/rpm (violet blue) circuit to run the shift light and it has worked flawlessly up to this point. We use it in the RPM mode of course and since you could use either to ground your shifter circuit I would recommend that you use this circuit since it seems to be more reliable than the shift light circuit.


    We also mount our box in the front of the car and if I had to mount one anywhere near the magneto I would shield the box as I am sure the components inside are no better at protection from emi than the power supply of the box is at protecting the circuits from voltage spikes.

    PS we do run the 8930 capacitor and I would highly recommend it to anyone who does not have it. I hope no one beat me to the board again:D I am typing as quick as I can....
     
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  15. WJ Birmingham

    WJ Birmingham New Member

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    Thanks BF...

    Yes, that was the plan... to use the violet/white trigger wire to fire a 30A relay, which would then in turn fire the shifter. I was then planning on checking the data logger to see what actual RPM the shift occurred at, and then compensate for any time delays as needed.

    The unit will be mounted under my driver's seat, which will still allow easy access to the programming serial port, as well as keeping it well away from the mag/points box and data logger.
     
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  16. Eric David Bru

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    Actually the PN is 8830 for the capacitor/filter.

    EDB
     
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  17. td314b

    td314b New Member

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    Six Shooter

    I agree with Will....I will never ever run an 8973 again! It cost me too much in parts and headaches!
    Troy

    P.S. Yes in a dragster you can not get it far enough away..and the 2 step function always went haywire to the point that we just used a normal 2 step box instead of the 8973.
     
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    Last edited: May 20, 2008
  18. pete9857

    pete9857 Member

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    8973

    Once again, we've run the 8973 for over 5 years without a problem on a Hemi. But, we run a Mag 20, no crank trigger. The box is mounted right next to the points box and in front of Mag on frame rail. We have the coil wire completely wrapped and insulated. Grounds are very important. I don't want to offend anyone, but possibly the programming on the 8973 is too complicated for alot of racers.
     
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  19. pete9857

    pete9857 Member

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    six shooter

    Hey TB314B, get a 8973 box! lol
     
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  20. WJ Birmingham

    WJ Birmingham New Member

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    I'm thinking the same thing. They're all trying to use too many retards at once, or they don't have all of the grounds in place.

    I just grounded mine from the frame to the 8106 to the driver's side cyl head, then over to the pass side head, all with 14 gauge high strand count wire.

    I'm happy to hear that you have yours mounted so close to the points box. MSD told me to keep the 8973 at least a foot from the 8106.

    Do you have any pictures on how you insulated your coil wire?
     
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