Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

How to plan accommodate grounds in concentric twist design for chassis harness

EFI Wiring Fundamentals

Forum Posts



Tech Articles

Discussion and questions related to the course Motorsport Wiring Fundamentals

= Resolved threads



I just recently purchased the Motorsports level of video guides, and I'm trying to absorb all of this information as fast as I can. Unfortunately, I'm delving into this arena of car modification only after I spent thousands purchasing a custom motorsport-quality engine harness from someone else. So, I'm in a unique position compared to most beginners using these message boards. I want to learn so that I can build for myself, but I already have a decent portion of the work taken care of.

This has led me to largely focus on tackling the chassis portion of the harness. The front end beyond the bulkhead, to be specific. I'm finding that the harness design philosophy is very different in that I don't have pre-determined cabling to be my core, and must instead designate another cabling bunch to handle that task in accordance with some other logical path. I think I've done that by choosing the device with the longest lead length away from the bulkhead connector-in this case the windshield washer pump-as that will allow me to have a somewhat higher amperage cabling requirement consistently throughout the harness. Assuming that's the correct logic, then my main hold-up is the ground design.

From the factory, few grounds pass through the firewall from the respective fuse/relays in the cabin. Most of the grounds are terminated via ring terminals on the chassis. This is all well and good, as the factory does not have the consideration of concentric twisting to design around. So when the loom is designed based on the arrangement of the circular connector, and the grounds do not pass through the connector, how do most of you plan for the grounds?

If you don't have the need to remove (and thus flex) your harness, there is very little advantage to going to the extra trouble of concentric wiring. In order to keep that flexibility, you will find that high-current devices often use multiple smaller-gauge wires.

Regarding grounds, you need to remember that you need to carry the same amount of current through a ground as the power supply wires. For things like fans, headlights, electric pumps that need substantial current, there is nothing wrong with continuing to use convenient chassis grounds, just make sure that what you are attaching to, is free of paint, and has a good solid connection to the battery ground.

What is your project? -- carbonfiber chassis prototype or tube-frame GT for endurance racing, or a modified production car for track day or club racing, or something else?