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Engine Electrical Grounding

in 912 / 914 Technical Questions 10 years ago
I am starting to do the wiring on a new 912ULS installation in a kit plane.

The kit manufacturer shows the connection from the battery negative terminal going to a tapped hole on the cylinder head of the engine. However there are two machined bosses with holes on the end of the HD starter that look like the perfect ground connection point.
What have others done for the engine ground point and does anyone know of a reason why the starter wouldn't be an excellent ground connection point?

I couldn't find anything in the Rotax installation manual that specifies the recommended ground connection.

  • Re: Engine Electrical Grounding

    by » 10 years ago

    Hi John,
    I have my engine off for a mount problem and can show you some pictures of my 912 F series 80 HP on a Model IV.
    This picture is the ground wire from the cyl head to the engine mount. Behind the mount are several grounds and i didn't chase them but I can if you wish. I suspect (but don't know) that one of them goes to the battery negative.
    Does that help.
    Secondarily, the CDI ground is very important and I lost partial power in flight from a broken ground strap at the CDI. The single point ground for that item has been addressed and I believe your new engine has a completely different and fool proof system for it. check this forum for info on ground strap CDI issues.
    Good luck.
    DSC_0142.JPG (You do not have access to download this file.)
    DSC_0154.JPG (You do not have access to download this file.)
      
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  • Re: Engine Electrical Grounding

    by » 10 years ago

    Thanks Jay,
    That's exactly how the build manual shows the ground connection to the engine.

    I just thought that since the starter is the largest consumer of electrical power that it might make sense to attach the ground to it instead. And it has that big nice lug on the end that is just begging for a wire to be connected.

    I'm new to this forum but i'm kind of surprised that someone from Rotax hasn't replied to this. Or is that normal here?

    I did check the CDI ground and it looks much more robust than the strap that you described.
      
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  • Re: Engine Electrical Grounding

    by » 10 years ago

    The rv12 has the ground cable attached to the lug on the starter frame and it has been good for so far 137hrs
      
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  • Re: Engine Electrical Grounding

    by » 10 years ago

    Thanks Andre, That's how I will do mine also.
      
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  • Re: Engine Electrical Grounding

    by » 10 years ago

    On therv12,The negatif from the battery is connected to the battery box for the frame ground the from there it goes to the stater frame for the engine ground
      
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