I'm working on how and where to ground electrical components to the chassis. I'm trying to avoid problems, but this is my first, from-scratch, vehicle and I doubt I have it all correct. So, I'm going to expose my current thinking and see "what the smart kids think" as JD likes to say.
My 1994 Mustang donor is your standard issue 12V, negative ground system. Off the battery are two positive connections, one to the starter motor and one to the "Power Supply Module" mounted nearby. The ground from the battery goes to the chassis directly. The Power Supply Module appears to provide power directly, or indirectly, to all other components in the vehicle. Here's a mini-view of the situation in the donor:
Attachment:
Power-Dist-Module.jpg
My battery will be mounted at the right, rear of the vehicle. A positive cable runs from there through the transmission tunnel, and will terminate on the passenger side firewall. A stand-in for the positive cable appears in subsequent photos as the orange extension cord. To ground my electrical system in the Locost chassis, I've chosen the location shown in the photo below as a black rectangle. I've selected this particular member because it is welded directly to all the other members shown with a green check mark. The horizontal members run all the way to the opposite side of the chassis and really connect up well to a majority of the chassis tubes.
I'm not sure what kind of ready-made part is available to anchor the ground cable, but I was thinking a piece of 1/8" plate with a threaded stud welded to it, and it in turn welded to the chassis would do.
Attachment:
Main Chassis Ground.JPG
The starter motor (huge consumer of power when engaged) is located on the passenger side, just below where the cable from the battery will emerge. It's indicated by the blue rectangle shown in the photo below. I'm told it's best if the starter is grounded directly to the chassis rather than through the engine block ground. So, I've picked an area of the chassis adjacent to the started to put another grounding connection. It may be the stud/plate component described above for the battery cable ground at rear.
My understanding is that grounding the starter motor by itself, away from other grounding points, helps avoid problems due to the high current load of the starter when engaged, which reacts through the chassis locally.
I'm thinking that to have a situation similar to the donor setup, I'll need to feed the battery cable into some kind of mounting lug, and then have two cables running from that. One will go to the starter, and the other to the Power Supply Module, mounted up above on the firewall shelf.
Attachment:
Starter Grounding Point.JPG
I'm understanding all the major loads like the alternator, engine wiring harness, sensors, etc., are grounded to the engine block. The engine block is then grounded to the chassis. In my original donor setup, some components on the engine, and the starter motor itself, were grounded using a common cable. The engine block itself had a second ground which connected on the drivers side through a braided cable. That braided cable ran from one bolt on the engine block side of the motor mount around the rubber vibration damper to another motor mount bolt on the chassis side. I'm thinking I'll go directly from the bolt on the block to a grounding point on the chassis as indicated below.
Attachment:
Engine Grounding Point.JPG
Lastly, all the other things like the instruments, accessories, ECU computer, radio, etc., also need a ground. I'm understanding that the chassis can act as a sort of "filter" on the big activity of the starter, and having a ground for the above components somewhat removed from the starter motor ground area is a good thing. So, I'm thinking a ground on the member indicated below, but on, or close to, the driver's side of the car is a good location.
Attachment:
Instrument-Acc-Dash Ground.JPG
So, "smart kids" how did I do with the basic plan? Does it look fairly decent? Where should I look for some ready-mades for the chassis grounding parts and the distribution lug for the positive battery cable?
Thanks in advance,
Lonnie