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Understanding Star Point Earthing on a Z32

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Hi everyone,

I am about to undertake the construction of my first wiring harness. After taking the wiring fundamentals course, clubsport course, and the motorsport course, I still have a difficult time understanding star point earthing. I have dissected my OEM harness in the name of science, and the ground layout in this harness doesn't seem to follow the laws of star point earthing, and maybe this is the cause of my confusion.

Attached is a diagram I've drawn of the ground layout, where you'll notice the ECU and coil packs ground to both the intake manifold and the chassis. Does this not violate the star point earthing methodology?

As I understand it, I can ground the coil packs (R35 coils in this case) directly to the intake manifold, and also eliminate the smaller chassis ground wire since the system should ground through the large 2 gauge battery ground attached to the block and chassis?

Attached Files

The way I understand the star point earthing course, the system should be configured as in the attached image below, eliminating several splices and a bit of wire. But if this is the correct way, why would Nissan create such a complicated ground layout with more failure points, and likely at higher cost to manufacture?

Attached Files

Hello Clay,

Yeah the engineer at Nissan who is in charge of grounding schemes is actually a toddler with a black crayon. They give him a picture of the car with all the electronic components mapped out and he just goes to town... or so I have heard... The Z32 is not an isolated case from Nissan either. They also have a habit of grounding their knock sensors through the sensor body (the sensor signal & shield being the two sensor pins), as well as some of their speed sensors, which can catch you out if you're not aware of it.

Attached is the design I would use, with the engine as your star point earth. The chassis can still be used for your fuel pump & body harness, just make sure that none of those items also ground to your engine.

Attached Files

Thanks, Callum.

I was pulling out my hair trying to understand why Nissan did it the way they did. Looks like I have a chance to simplify some things, which is always welcome on a Z32.