MSD 8973 tech question

Discussion in 'PSI Superchargers Tech Questions' started by Will Hanna, Oct 1, 2008.

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  1. dandimand

    dandimand New Member

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    Hi not sure if this applies to you guys with this box or not but if your running one of the big relays for your wiring they can clip trust us it happend to us with the bickel solenoids . these are the heavy duty solenoids that look like ford starter solenoids . we found it by bypassing our solenoid and just turning the power off with the master cut off switch .
     
    #21
    dandimand, Oct 2, 2008
  2. pentastarrail

    pentastarrail Top Dragster

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    8973 question.

    I'm glad Will brought this up as I just put an 8973 in my car this past weekend.
    I'm new to the digital stuff so I may have missed something.

    My issue is that the engine spikes from 3000 rpm to 4000 back to 3000 when the 2 step (which is set at 4000) is activated. I have the trans brake wire going to the blue wire to activate the launch retard so while on the 2 step my ignition is retarded.

    My computer showed that the 1.5 seconds that I was on the 2 step this was happening (which I heard and was freaking me out). It spiked 4 times.
    My combo is a 526 hemi, TD with a PG, a 4600 stall converter with a MAG 44 with NO crank trigger.
    Also when I put it back to the old way (just using the MAG and a regular 2 step box) there was no problem.

    What am I missing?
    Is there a setting in the 8973 for this?
    Electronic interference?
    Too low of a 2 step RPM?

    Thank you in advance for the help, this site and you people are great.

    Frank
     
    #22
    pentastarrail, Oct 7, 2008
  3. Mike Canter

    Mike Canter Top Dragster
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    I believe this is all just a setup problem or wiring problem since it was just installed

    I don't believe the ignition retards on the Launch Retard until the 12 volts is removed from the blue wire which is when the transbrake button is released.

    Hook a laptop up to the 8973 and have somebody watch it while you start and have the motor running. Watch the screen in the upper left corner under Monitors. This will tell you what retards are on and when. Also watch the two gauges down in the lower left corner. Record where everything is when motor is started and running then hit the Two Step button and see what changes.

    Again, one thing to remember is that the 8973 starts in the Run Retard Curve which is whatever the timing curve is in the bottom timing graph. When you hit your transbrake button an apply 12 volts to that blue wire the 8973 switches to the Launch Retard Curve which is the top graph. If the Launch Retard Curve and the Run Retard Curve have different timing curves in them then the timing will change. Always set the timing on the car after you have pushed the Transbrake button once to put the 8973 into the Launch Retard Curve or your timing maybe wrong.

    Do you have any of the three Step Retard wires (pink, tan, dark brown wires) hooked up to anything?
     
    #23
    Mike Canter, Oct 7, 2008
  4. pentastarrail

    pentastarrail Top Dragster

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    8973 question

    Thanks for the info Mike.
    No, nothing else is connected at this time. I wanted to keep it simple.
    I did put a timing light on it.
    As soon as the transbrake is activated it retards the correct amount, which I "THINK" is correct.
    It stays there until the transbrake releases and then ramps in as it should.
    It's just weird that when I'm actually against the transbrake at launch rpm it starts to spike.
    It actually seems like a convetional 2 step EXCEPT that the amount of rpm is about 1000 rpm variance vs the regular 2 step rpm.

    I'll do as you say and connect it to my laptop and fire it up.
    There has to be something else activated.
    I just need to find a helper.
    Thanks again.
     
    #24
    pentastarrail, Oct 7, 2008
  5. Mike Canter

    Mike Canter Top Dragster
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    Let me know what you find out.
     
    #25
    Mike Canter, Oct 7, 2008
  6. WJ Birmingham

    WJ Birmingham New Member

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    How far is the 8973 mounted from the mag?

    MSD told me to put the points box no closer than 1 foot to the mag, and keep the 8973 two feet from the mag and one foot from the points box.

    Maybe it's picking up some RFI causing the issue?
     
    #26
    WJ Birmingham, Oct 7, 2008
  7. Will Hanna

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

    pentastar..

    we went through this on the lencodrive fc i drove. the problem is voltage bleeding from the transbrake solenoid through the transbrake switch to the violet or light blue (i don't remember which color)..the activation wire...to the 8973 box. this will make the 2 step release after the launch.

    i agree wholeheartedly with the door stop remedy, but if you want to use the box, call shogun industries, they make a kit for this problem with some diodes to wire into the circuit.

    as far as launch retard goes, it's not that hard to rig the six shooter to do that. not to mention you can richen the barrel valve, lower launch rpm, take static out.....

    i really like this leahy box six shooter set up i'm playing with now.
     
    #27
    Will Hanna, Oct 7, 2008
  8. BUTCH

    BUTCH Member

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    6 Shooter

    Will, Are you using one of Leahy's 8 channel programable timmers to control the 6 shooter ? do they work well? I was thinking of one for my set up? 1 to 5 for the timing and 3 for fuel ? great web site.
    thanks Butch
     
    #28
    BUTCH, Oct 7, 2008
  9. Bottlefed

    Bottlefed New to Blowers

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    Unless I read this wrong pentastarrail said that his RPM and timing are fluctuating while his transbrake is applied. I think the shogun product is meant to supress the flyback voltage that is the result of the coil being deenergized. Still a good idea though, since when it is released it will cause a spike then who knows what will happen, also MSD won't tell ya to put that sucka in a grounded metal box unless you sit between the motor and the box but I will:D

    Will,
    Maybe you could you start a separate 8973 column? :rolleyes:
     
    #29
    Bottlefed, Oct 7, 2008
  10. pete9857

    pete9857 Member

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    8973

    We have our boxes mounted next to each other on frame rail below mag.(dragster) Hemi-Lencodrive. No extension cables, metal boxes, diodes. Just old fashioned grounds everywhere. Never had an issue in over 3 years.
    Glenn Sheppard, TD 3131
     
    #30
    Last edited: Oct 8, 2008
    pete9857, Oct 8, 2008
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