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star point wiring - ign1A coils

Practical Motorsport Wiring - Club Level

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I think this is a popular earthing question and understanding as of late.

star point says to earth at one location, most likely engine block. my cars factory design goes from factory negative to firewall to engine block all on one cable (nissan z32). sufficient ground obviously manufacturer designed. in this case i would presume the star point is the engine block.

my ecu grounds to the upper intake manifold which obviously is connected to engine block hence i would presume thats part of the star point where ever a battery ground is called upon the engine block (in this case upper intake manifold) would suffice as that battery ground?

now for a ign1A coil which is super popular nowadays, would that mean when it calls for battery ground you would ground it to the engine as well? but the ign1a also calls for a cylinder head ground. this is the confusion for me, would both the cylinder head and engine block (star point) be the same ground in essence? or in this case since this calls for both cylinder head and battery negative, should the ign1A be directly grounded to battery negative?

Hello i would recommend grounding to the head with these coils not the battery

Regards Ross

Hello i would recommend grounding to the head with these coils not the battery

Regards Ross

Yes but the coils call for grounding to the head on pin c and grounding to battery in pin D, so in that case would it be recommended to ground both pins to the head? Just to seperate locations on the head?

Good question, I'm in for an answer to this too. I have these coils currently wired as haltech recommended.. Ground pins c to engine, pins d to the battery but I plan on redoing my wiring. Works fine connected this way but would be tidier grouping the 2 pins together, pretty sure I've seen it suggested on here that it's fine to do.

Since these coils have the primary, secondary and logic grounds all isolated from each other, the most appropriate way to ground them is exactly how everyone that sells them tells you to.

Pin D is the primary winding ground (coil negative in old fashion terms) so to keep the return path as short as possible it should be grounded to the same power source that supplies the primary positive (Pin E, i.e. the battery).

Pin C is the secondary winding ground. So to keep this circuit as short as possible this needs to be connected as close to the spark plug as possible (i.e cyl head).

Pin B is the logic ground for the trigger circuit so needs to reference the same ground as the ecu ignition output, usually ECU sensor ground is the most appropriate.

Just for absolute clarification, Pin D (primary coil ground) is grounded to the block or the chassis correct? That would keep it within start point grounding as I understand, avoiding an alternate ground path.

I see so many diagrams and other posts on forums stating "connect it straight to the battery negative" but I think that violates star point grounding. Not sure if the diagrams produced are not being clear enough and we have a classic case of forums spreading misinformation...

Planning to use these on a 13B if that makes any difference to where the primary coil ground goes.

No, although in real life it will probably be fine grounded anywhere, the most correct point to ground pin D is the battery negative. Star point grounding doesnt matter with these coils because the 3 grounds are all isolated from each other, they are effectively 3 separate circuits.

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