So, I have a side biz building expensive fancy wiring harnesses for open wheel race cars.
Most of the cost is the environmental sleeving (fancy shrink tube and boots). Also spendy are a few of the connectors.
A couple tips I've learned that might apply well to your average rally car:
Tefzel mil spec wire is really nice and about the same cost as the SAE _XL stuff. just watch that the smaller diameter tefzel will seal in your connector system.
If you're gonna solder, add solder sparingly. this is where most DIY harnesses I deal with fail. The stuff I build for the formula cars does not use solder except a small data connector that you can't buy in a crimp version. I'd seriously avoid a solder splice in the middle of a harness somewhere, unless you're a good clean solder operator and sleeve it to support the wire beyond the solder.
Also a common failure- you need to sleeve this stuff. DR-25 is expensive and not repairable, but very good. also good and cheaper is the finger trap looking expanded nylon braid. you can get a big box of it pretty cheap and some is even split down the side if you think you'll add to it later. This stuff works very well but will look nasty after a while because dirt gets through.
Another common failure- You need to attach the wiring to the chassis every foot and a half or so, but don't strangle it with tight zip ties. A "snug" zip tie here and there is good. too tight and it makes a stress point in the wiring that will fatigue the strands.
Supporting the wire coming out of connectors will improve reliability a bunch. the shrink boots are really spendy, get some high shrink ratio stuff with adhesive lining from home depot (Raychem, sold in 6 inch pieces) and shrink an inch of it on the back side of connectors.
Deutsch connector systems use common crimp tools across wide ranges of connectors. other companies make clones of their stuff that use the same crimp tools and such. If you want decent stuff without needing $5000 in crimp tools (my collection is way past that already...) buy the field service Deutsch tools for the closed barrel mil type crimp terminals and use compatible connectors everywhere that you can.
Environmental sealing means water and dirt cannot enter inside the wiring insulation. you don't need a sealed sleeve system if the connectors seal to the insulation.
The only reason for MIL circular is that you take it apart several hundred times a race season. if you use it make sure it's "scoop proof" or you will regret it.
I could say more, but this post is too long already..
one last thing- Unless you have an old beetle like me, OEM is usually good stuff, don't cut it out and replace it unless you have a real good reason to.
Perry
Perry
FE570s course bike
KTM 950 ADV
74 Beetle turbo-efi etc..
72 Beetle stage rally project WRX powered
Attended about 15 rallies, usually a volunteer in a course car.
