Grounding Question

It's ok if I use the engine block as the star point and do the following:

- Coil ground to the engine block.

-Battery negative to the engine block

-ECU to de engine block.

-Chassis to the engine Block.

And the big question:

Can I connect ground from any device to the Chassis even when I am using the engine block as a star point?

I dont claim to be an EE or expert, but i have successfully wired some very nice LS/Milspec harnesses. My understanding is that you should really take all grounds to a star point/home run near the battery in general where possible. In most cars, you will also want a ground bus and chassis/block ground to go there as well. I understand that, for instance, LS coils want a ground at the cylinder head, and apparently RATHER than going to home run. I dont understand that and would like to know more.

for instance, with 8 LS3 coils, can you combine their harness pins into one ground wire which Y's to each cylinder head? Or is there some reason why 1-7 should ground only to that head, and 2-8 only to the other?

Why is that?

Professional electrical engineer here and I can shed some light on these two subjects. A big consideration for any signal (I.e. voltage) is whether the signal is switching or not. If the signal is a DC voltage or switching at low frequency, say less than a few kilohertz, the wiring path is going to be a lot less critical. If the signal is switching and ESPECIALLY if there is appreciable current switching along with the voltage, then wiring is a lot more critical. For the DC or low frequency case we are only concerned with the resistance of the wiring path. If the switching is higher speed we have to be concerned with the inductance of the wiring path as well. The switching interacting with the inductance raises the impedance (AC resistance) so the dynamic voltage drop will increase. So for switching signals you want to keep both the resistance AND the inductance as low as practicle. On to the specific questions.

First, star grounding for DC and low frequency. I would say yes, you can use the frame rail as a grounding point instead of pulling a ground wire back to the engine block, BUT you gotta make sure the engine block has a very low resistance, high current capacity connection from the engine block to the frame rail. Like a braided strap or 4awg wire with crimped copper lugs (I’m not a professional automotive wiring person, so someone that knows more please weigh in).

Second, why should LS coils have their own ground at the cylinder head? You can guess from the above discussion that it is because the LS coils are switching at high frequency and they are switching a lot of current. So you want the inductance to be as low as practical. In professional EE, for high current switching, we call the path from the voltage source, through the load (the coils), and back through ground, back to the voltage source, the hot loop (Google “Hot Loop SMPS”). The figure of merit for the hot loop is the loop inductance. You want the loop inductance to be as low as practical. As an example, look at a PC (computer) power supply. All computer power supplies are switching supplies. You’ll notice that the capacitors and inductors are jammed right next to each other. It does save space and thereby cost, but the primary reason is to get the loop inductance as low as possible.

Hope that helps!

very much appreciated and a lot to chew on. I'll study and come back with findings as i go. Thanks.