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IGN1A Grounding Question

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Working on building a MaxxECU harness for a friend on a 6-700 hp turbocharged Race harley with IGN1A coils.

Typically I would terminate the IGN1A coil grounds as such

PIN B : Logic Ground; Sensor 0v from ECU, or IGN coil specific ecu ground

PIN C: Cylinder Head Ground, as close to plugs as possible

PIN D: Battery Ground or wherever the power source for coils is, in this case MAXX PDM, the maxx pdm grounds to engine so I figured it would be okay to ground to engine

However, maxx calls for the coils to be wired like this

So I cross as to whether to follow the ecu documentation or to use my better judgment and follow what ive learned from experience.


It seems like the MaxECU is telling you they want to use Engine Ground for everything related to ignition. I would do that.

I think that this is the ongoing issue of folks not understanding that all 3 grounds on an IGN1A are isolated, combined with poor understanding/implementation of different types of grounding by the end user causing folks like Maxx to suggest a best practice that may not actually be 'best'.

Personally (and for builds I support) I ground per the original design of the IGN1A. Since Maxx is specifying - and if you want to be under warranty/supported by someone - I'd agree with David and ground per Maxx in your case however.

Thank you for your answer M:EP I will ground how I have always done it. This isnt the first harness ive built from scratch or even the first set of IGN1A coils of done however it is the first MAXXecu I have done and the first ecu that has recommended to ground all 3 grounds to the cylinder head. Which is why I was overthinking it and wanted to confirm with people who know more than I do

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