Tach

Discussion in 'New Hemi Engine Swaps' started by Mopar Sam, Jul 12, 2018 at 6:53 AM.

  1. Mopar Sam

    Mopar Sam Well-Known Member

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    I put a stroked 5.7 in my wife's satellite [sorry,not an a body]. I used the tach signal from the MSD Hemi6 to trigger the FAST EZEFI. How do I hook up the tach? Can I trigger it from the same wire without affecting the efi?
     
  2. Steven190

    Steven190 FABO Gold Member FABO Gold Member

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    I am not familiar with this box. I hope that someone can help. Just my thought is that there maybe interference if you connect the two wires. The only thing I have is I used a 6 AL with the Fast and used different wires for the ECU and the tach.
    Good luck on your project.
     
  3. General Disarray

    General Disarray Well-Known Member

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    Why don't you call the FAST or MSD tech support?
     
  4. billccm

    billccm Active Member

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    I would assume both inputs are high impedance, so yes both inputs can share the same signal wire.
     
  5. Mopar Sam

    Mopar Sam Well-Known Member

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    Yeah, I guess that is what I will do.
     
  6. Mopar Sam

    Mopar Sam Well-Known Member

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    I hope you are right. I know the EZEFI is sensitive to electronic noise. I was hoping some one on here had already one this. When I find out for sure I will post.
     
  7. billccm

    billccm Active Member

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    I recently used a oscilloscope to measure the msd tach signal. It's a clean, stable 24% duty cycle square wave. Voltage peak to peak is right with the battery.

    If the signal gets loaded down you could add a 10K pull up resistor, but I doubt you will need it.
     
  8. billccm

    billccm Active Member

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  9. Map63Vette

    Map63Vette Well-Known Member

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    I'm splitting the tach signal to run my Megasquirt and my column mounted tach and haven't had any issue so far. I had originally tried to use the ignition output of my Megasquirt to run it, but it was easier to just use the signal straight from the MSD box.
     
  10. Mopar Sam

    Mopar Sam Well-Known Member

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    Thanks! I think I will try it.