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Thread: Will the Dominator work with my Mercedes-Benz coil packs?

  1. #1
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    Default Will the Dominator work with my Mercedes-Benz coil packs?

    I'm trying to figure out if the Holley Dominator is going to play well with my Mercedes-Benz V8. I'll have lots of questions, but let's start with the coil packs.
    This engine has a set of 8 coil packs; each pack has two coils that fire a pair of spark plugs per cylinder:
    Click image for larger version. 

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    Here's a picture of the underside, for good measure:
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    Here's the schematic of the coil pack:
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    The center pin goes to a common +12v source and each of the outside pins is fired by the ECU.
    I haven't had a chance to scope the ignition signals yet, but I assume both coils fire at the same time.

    Should I wire the Dominator ignition output to both of the outside pins?
    That should work as long as the combined current draw isn't too much for the Dominator's output,
    but I can't find any published numbers showing how many mA each ignition output can handle. Any thoughts or suggestions?

    UPDATE: I changed "common ground" to "common +12v source"
    Last edited by JoeJErnst; 11-27-2018 at 04:55 PM. Reason: I changed "common ground" to "common +12v source"
    - Joe Since 1970
    Follow me on StumptownBenz.com

  2. #2
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    Default

    After more research, I think I might need a couple of the "Four Channel Coil Driver Modules" (P/N 554-112: Instructions) Would it make sense to wire one of the +12V leads from the driver module to BOTH power terminals (pins 1 & 3) on the coil pack, and then wire the center pin to one of the Y/O/B/P wires from the driver module? I think this would work if the driver module's circuitry is completing the ground path to fire the coil. I would love to hear what the experts have to say.
    - Joe Since 1970
    Follow me on StumptownBenz.com

  3. #3

    Default

    It does look like there is no internal igniter in the coils, which would mean that you would need two four channel coil drivers. The way the schematic looks it might be setup that way so that each coil can be fired separately (staged sparks or multi-spark at high RPM?). Does the factory ECU have a separate control box for the ignition or does it go straight to the ECU?

    With the Dominator you would probably end up having to wire the coils like you said using the center pin as the trigger, which would fire both plugs at the same time. I'm not sure if wiring the coils in that manner would affect the operation at all. Maybe having the center pin grounded provides a better path for the electrical current after going through the gap in the spark plug, which is why Mercedes chose to use the positive side to trigger the coil.

    I would also take a look at the later Gen III HEMI coils that have three pins and see if you can find any internal schematics (I couldn't) to compare to the Mercedes coils. I'm not sure how similar the coils are, but they do fire two plugs per cylinder, and Holley's wiring harness seems to use only two pins on each coil.

  4. #4
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    The wiring schematic shows pins 1 & 3 going straight to the ECU. I haven't traced the wires to confirm yet. There is speculation that the two coils fire at slightly different times. I plan on putting a scope on the car soon to verify. In either case, I don't see a problem with just firing them at the same time from the Holley. My buddy who has the oscilloscope also knows the new Mopars quite well, so I'll ask him what he knows about the Gen III Hemi coils. Thanks for the info, I'll report my findings back here when I get more info.
    - Joe Since 1970
    Follow me on StumptownBenz.com

  5. #5
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    Default Updated with more info.

    First of all, I corrected my mistake above. The center pin on the Mercedes coils is NOT ground, it's +12V power sourced from a common power feed circuit. I guess the ECU fires the coils by connecting the outside pins to ground. This means I would still need the Holley coil modules, but I would wire the red +12V to the center pin and wire the two outer pins together into the appropriate cylinder's wire on the module. Also, I got my Mopar guy to confirm that the third pin on the Hemi coils is unused by the factory, not just by Holley.
    - Joe Since 1970
    Follow me on StumptownBenz.com

  6. #6
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    Default

    I'm closing the loop on this thread, just in case any Mercedes guys stumble across it in the future.

    The car is running now, and I can confirm that it needed a pair of the Holley coil driver modules. The center pins on the coils get +12V, and the outer pins get tied together and fired by the coil drivers.
    - Joe Since 1970
    Follow me on StumptownBenz.com

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