grounding ideas

[BOOTLEG]

Installing my Advance Autowire Harness and thinking about grounding.  Considering 3 bus bars, 1 in engine bay, another in cabin and another in trunk.  Would appreciate ideas from others

[BlownMGB-V8]

You're on the right track, it's hard to have too many grounding locations. If you run efi it gets even more interesting.

I have the following: Heavy ground cable (00) from the battery to the transmission tailshaft housing. #6 or 8 cable from the battery to the body. #6 or 8 cable (and power) from the battery into the trunk to 3/8" terminals. Separate  #10 stud for ground terminations in the trunk including lights. Two #10 studs under the dashboard. At least two #10 studs under the hood plus an additional #10 stud with a ground lead that runs directly to the battery ground post for sensor grounds.

It isn't too many.

Jim

[ruben]

Your not grounding you are bonding the car body parts together. If the engin is effectively bonded to the body the resistence between any point not inhibited by corrosion or paint and the negative battery post should be zero. I don't see how a ground buss can offer less than zero resistence. It is how the connections are made to the body and paint does cause resistence to current flow. And induced voltages in the sub mA range that may effect electronic will not be drained off by a ground buss. An insulated positive connection in the engine commpartment is useful so all the positive wires don't
have to connect at the starter or alternator. Good Luck

[Jim Stabe]

Actually, steel has far greater resistance than copper, certainly not even close to zero. At least ground the high current devices (starter, fans, etc) with copper of the same gauge as the feed wire back to the battery.

[Charles]

My 2 cents. Like the two Jims said.
The material used in the body construction of our old British Cars was at best very poor then, when it comes to the conduction of electrical current. Now some 50 or more years later and with the added rust it has gotten no better.

With the electrical currents demands we are placing on the materials used when constructed is only asking for electrical issues.

I personally do not use any part of the car body for grounds. I only use the body material as a tie point.

Of course my working back ground in the medical field, my have something to do with my lack of acceptance of a voltage drop across any tie points.

charles

[BlownMGB-V8]

Yeah, what those guys say. You can look up the conduction capabilities of metals and here is a chart that is rather illuminating:

http://en.coppercanada.ca/videos-publications/publications/pub21/images/05.jpg

If you look at it you'll see copper referenced at 100%, silver at 106% and gold at 72%. (Silver is best but tarnishes while gold does not.) Iron is at 17% of the conductivity of copper. Now that seems extreme but I believe if you look at the actual resistances you will find it correct. As the following table shows, iron has nearly seven times the resistance of copper:

http://www.teach21.org/wp-content/uploads/2016/07/fig10-41.jpg

So that's what you are using for your grounds. Why? Because early days, currents were gross and components inefficient and it just didn't matter. Things have changed a bit.

Jim