EFI Harness vs. Auxiliary Harnesses

When designing a harness should I split the harness into two separate harnesses (1) for the EFI and Engine related components and (2) into the more auxiliary powered items in the car such as Cool Suit, Helmet Blower Fan, Rear View Camera, Go Pro power, Rain Light and Push to talk and Digital radio.

Furthering onto to this discussion, the car has the battery in the trunk, all the switches are located either on the wheel or the swith panel in the middle of the dash. Several of the items needing power are in the trunk next to the battery (rain Light, Cool Suit and Rear view camera) and the rest are closer to the drivers seat. Ideally where should I locate the fuse panels and relays, should they be closer to the battery side in the trunk or closer to all the switches in the trunk. It seems like I will have to run quite a bit of wire either way.

Thanks in advance for any design times to keep this clean and tidy

I definitely try to separate the engine harness from the rest of the chassis.

For the fuse and relay box placement, I try to put it as close as possible to the majority of accessories that are gonna be powered up. You usually want to have the shortest wires as possible, but sometimes you have to make compromise like if you use fuses and relay that could need to be replaced, then I would put it a bit more accessible than a solid state PDM.

I don’t think there are right or wrong answers as long as you use logic and put them away from big heat source and areas that could get wet or super dusty…

Much appreciated advice!