Guys, I used to frequent here a quite a bit, but I've been on hiatus. Planning return.

I've got a '68 restomod street car that's heavily modified under the skin (SRIII with C4 stuff). As many projects go, I got to a point where I realized the electrical system needed serious attention. Using these links from a related thread I've crafted the plan below:
www,madelectrical,com
https://moretraction.com

Hoping to hear from the electrically savvy.

In general, I'm trying to isolate power devices from control devices. Currently power and ground for head unit is off the fuse panel and amp direct to battery (both fused). Amperage listed is for relay ratings except of 1 or 2 devices and there's a typo on Relay M (it should be O for the stand alone fuel pump and 20-30A. As you can see Dirty Bus 2 is the main distribution and voltage sensed bus. I did not depict fusible links or fuses on the 4 AWG bus inter-connect wire, but this was just oversight. Note that the chassis and birdcage are a ground plane and the clean bus will be grounded direct to battery. Here logic said it was good to leave my 1/0 battery to starter ground in place as opposed to a direct battery to chassis cable.

Criticism appreciated and thanks in advance,
Rob

 

Bump

 

I'll try this again. I realized that my first post and diagram are a bit impossible to offer good advice. Hopefully better format and explanation will help to understand what I'm working towards. I assume any major resto-mod effort will pose similar requirements and considerations.

Since wiring is so tedious and so critical, I'm looking for a sanity check. Just about everything is done as illustrated here with the exception of the 4 gauge wiring connecting Alt to Buses and Starter Solenoid. Basic theory was to:
-- isolate the EFI system as much as possible from remaining electrical system
-- make best use of 1 wire alternator by connecting it directly to highest possible total system load. I'm trying to make this custom alt work because of front drive system (crank trigger and dry sump)
-- provide robust ground path, but rely on chassis for motors, pumps, etc and rely on battery for EFI specifics. I was also trying to avoid loops and separate dirty and clean ground paths as much as possible.

Holley's main power harness is 40A; this includes a 20A harness to power injectors and power fuel pump (recommend relay if > 10-12A pump draw). I'm running 8 injectors and pump relay. The harness is also designed to power various ignition options up to OEM CNP. When using IGN-1A coils, setting high dwell times or running batch fire, they instruct to modify CNP harness power source (40A relay for 8 coils) and ground wire size/path (10-12 wire direct to Batt-). I'm using a 75A Bosch relay with #8 power wire and #12 fusable link to main bus.

For the fuse panel load:
-- the light switch is now used to activate headlight relays
-- ignition powered at main bus
-- no blower motor; Vintage A/C powered at main bus
-- interior lights are now LED
-- fuse panel still powers OE wiper motor.

Thanks in advance, see below. Main electrical system diagram and EFI specific diagram make it easiest for me to see what I'm trying to accomplish.

 

I did a complete rewire for my custom 1978 c3. I used Ron Francis 24/7 kit and never looked back. It had more circuits than you could possibly need…24. Instructions and schematic made it easy even for me. I added one more thing that they sell, an isolated ground system for the whole car. Check them out and the info they have on the site is really helpful. Lots of tips and optional stuff available.

 

Some thoughts- I look at how new cars handle the power distribution- as ECUs and electronics like nice clean power.
I cleaned yous up a bit

Every time you have a junction of power wires- if you drop the size - you need to drop the fuse size. Fuses are just suppose to protect the wire from melting due to an over current situation
See chart and a new cars wiring layout ( BMW)

 

Thanks for this. I've searched the site and looked at harness options, and something like this probably would have been the way to go. At the least, it would provide an upgraded backbone to install the holley system. One issue I have is that I'm so far off the reservation with component placement it'd be a challenge to order a perfectly fit chassis harness.

I see that their site offers reference material for sale. Does it also list them online? I looked but couldn't find any.

Thanks again,
Rob

 

I have been looking at the American Autowire update harness but it doesn’t relocate the fuses. If they relocated the fuse box, I would have pulled the trigger a while ago.

 

With Ron Francis you can put the fuse box anywhere you want, mine is in the glovebox so I don't have to get upside down anymore ( an advantage of a '78). I probably went overboard with my project but I was putting an L98 computer controlled engine into the car. SO I had to install a custom engine harness along with everything else so I just started from scratch. Also dual elec fans from a C5, elec headlight motors ( nod to Richard454), relays for my halogen headlights, elec parking brake etc.. Here is the first catalog I got from them a long time ago, maybe callthem up and see if you can get a copy. It really helped me a lot from the theory to the execution. Also here is a page that they had in that catalog explaining grounds, which are a big deal in our plastic cars. Glad to share whatever I learned so far.



Zoom in on this and you can see how easy there descriptions are to understand

 

Richard,

Thanks for your response and for putting thought to this. The theories on this topic are exactly what I was hoping to discuss. Comparing my original power distribution to your alteration I can see how it's now mimicking the BMW system. A few observations.

Similarities:

• What I listed as Bus 1 is the same basic function as BMW's "High Amp Fused Distribution Center." Each is the main power distribution hub.

Major Differences:

• The BMW can remote sense voltage and regulate alternator output. My 1 wire cannot remote sense voltage output.
• My Bus 1 receives all power from Batt + when not running and primary power from Alternator when running. BMW main power source is Batt + in all cases; at least as shown in diagram.
• When running, my Alternator to Batt + path is via main hub. BMW Alternator to Batt + is direct and uninterrupted
• My diagram has ECU and some EFI specific power/ground wiring direct to battery. In your diagram, ECU power is from main hub and ECU ground is effectively direct to Batt - but physically closer to other chassis grounds.

Aside from good overall ground path, it seems there are two focus areas:
1) effective power distribution and battery charging
2) proper EFI function

My understanding and concern due to 1 wire alternator -- I assume the BMW will sense voltage at the main hub and regulate alternator output so the main hub(s) maintains ~14.2V. My 1 wire will sense voltage at alternator output terminal and voltage at main hub will be subject to effective line loss/voltage drop; downstream buses and battery will be subject to line loss/voltage drop. For this reason, I was attempting to power as much as possible from main hub and minimize line loss between alternator and hub. In my original diagram, my hope was that I could do this and maintain >12V to Batt+. Would my original diagram, as depicted, benefit from an added wire from alternator to solenoid (batt charging wire that bypasses main hub)?

For ECU/EFI wiring, Holley is adamant about what to wire direct to battery and what not do wire direct to battery.
Specifically to battery -- ECU power, ECU ground, 12V loose wire for injectors/fuel pump control and CNP harness ground
Specifically not to battery -- CNP harness relay power source

I believe this is guidance, but although literal language, the instructions fail to elaborate. My understanding is that direct to battery is used where the need is stable, noise-free on positive power, and on the grounds, it's the need to smooth and absorb path to ground. Is it likely, the example BMW ECU and sensitive electronics use isolated power and ground paths to battery? I'd think this would be necessary.

Hoping this is useful stuff guys. Thanks again.
Rob

 

Kanvasman,

Thanks for posting that article. In second column above engine pic does it say, "to the same stud if possible?" I've either read this before or something similar. What he lays out is fundamentally what I'm trying to accomplish. There are some questions though.

Steel is ~12-15% as effective as copper wire. Is a 2" steel frame tube less effective than a 10 or 4 gauge copper wire?

They state you can never have too many grounds. I'd think it should say you can never have too robust of a ground. On ground loops, admittedly, I don't understand how to avoid this in all but the most basic electrical circuit. To simplify it in my mind, I equate ground paths in a vehicle system to an idiot in an argument. High power systems, like the idiot, are random, loud and overbearing. They defy logic, but they're effective at disruption.

Example, at the rear of my car I've got a ground bus. Grounded here are vaccum pump relay, main fuel pump relay and electro-hydraulic P/S pump relay; with 15, 30 and 80A wires/fuses. I've got this bus grounded to chassis with 4 gauge cable. I can easily add 4 gauge cable from Batt - to bus, but should I? If the bus to chassis is adequate, great. If it's not adequate, and I attach an added cable from Batt- to bus, am I adding potential for ground loops or adding surge path that might affect EFI? If I remove the bus to chassis cable and attach bus to Batt - am I risking EFI function as the high-load motors cycle?

Thanks again,
Rob

 

With three of these sockets- and three relays- you can easily replace the function of the OEM fusebox plus up- grade it with relays
I moved my fusebox to the kickpanel-
Then use LED fuses for really easy confirmation if one is blown or not..
Oh-love this labeler- makes troubleshooting way easier

 

So I made a call to one of the links in my first post and was extremely fortunate to speak with the main author. Extremely knowledgeable and eager pass things on.

Specific to my setup, this was my takeaway:

-1 wire alternator vs the ability to remote voltage sense is a game changer. 1 wire requires short, heavy gauge cable from alternator to main bus to so bus equals voltage output.
-He said my forward bus, by design, will be fine and my rear bus should be fine; depends on heat/resistance in bus to bus cable. He cautioned workmanship issues can aggravate problems in high amp systems
-Wire efi and delicate electronics to battery. Direct is not technically necessary, but it is necessary to avoid connections on buses or splices with motors, lights, a/c etc.
-Treat engine block at primary negative bus. He recommended 2 heavy gauge block to chassis cables, block to interior ground bus cable. I asked about alternator case to block cable and he stated "it can prevent problems."
-He's not a fan of fuses, breakers or fusable links on battery to starter cable. He is a fan of remote solenoid so cable is only hot during cranking; and using separate fusable linked charge wire. Rationale is that it's impossible to reliably fuse protect this cable and dead cable is safer than high amp protective device. Bus wires and accessory wires can be fused to be reliable and safe.

In general:
-He cited many examples of great OEM design and a few horrible OEM designs. He cautioned that many OEM systems are fine as is, many work fine with added accessories on relays, but cautioned about high output alternators and especially high output 1 wire alternators on most OEM harnesses; not just sizing, but routing.
-Build it like you plan to crash it
-Be wary of workmanship and wire condition; think ohm's law for performance and joules law for protection

I feel like I should have paid tuition. Most of the tech articles are 2002-2003. I wonder if advancements in battery fuses would sway his opinion on the main battery cable. His logic makes perfect sense though.

Hope this helps,
Rob