Improving overall body grounding - weld in studs?

[bergie33]

So I was thinking about future planning for possible amp under the rear seat and possible battery under rear seat and started thinking overall about good body grounding.  Most grounds in the car are through-the-body sheet metal screws that need to be properly prepped to prevent rust.  There seems to be a tough balance between getting good bare metal contact and preventing rust.  I am doing full body restoration/paint/etc, would it make sense to put in some weld-in studs in the typical ground locations to get better grounding without having to worry about future body rust (under dash, under rear seat, trunk for tail lights, under hood)?  Would it make sense or is it overkill?  Newer BMW's use welded on studs for ground posts and it seems like a good idea.  What are your thoughts?  Here are a few examples...

 

    

Edited November 9, 2022 by bergie33

[John76]

If you are doing a complete paint/restoration the I would say weld-on ground studs would be an improvement.

The wire gauge, terminal and fastener for the ground wire is equally important.

I agree...some of those factory ground points on our cars are hideous!

 

John

[tzei]

I’m a big fan of welded ground points. I use just regular bolts. Welded all the way around.

 

New (uh?) BMW’s like E85 has tabs spot welded  (edges, 3 small dots) to chassis. Not much mm^2 to go with and rust can lure under.

[TobyB]

BMW obviously thought it was a good idea.

 

I'd suggest, though, looking at the TIS on more recent cars-

there is a pretty carefully- thought out plan for what grounds where.

www.bmwteka.com

 

So a dirty high- current ground (the fan motor, say) won't use the same stud as 

lower- current sensitive electronics, and sensing connections (like for burned- out taillights)

will return to their own stud.  Then the paths through the body sheet metal won't converge

until they hit the central point (star grounding) as the steel body's actually not a fabulous conductor...

And truly sensitive sensors like the engine temp for the DME will have the ground sourced

FROM the DME so that it's known to the microvolt.

 

t

induced voltage by excessive current.

[jimk]

I know the E30s used SS for the stud material.

[tzei]

Beware of galvanic corrosion and protect contact (ground) point after connections are fastened. Something to keep moisture out of it.

[bergie33]

I also think a couple of these could be useful for ground points with multiple connections...

 

 

[NickVyse]

Good chance you already have welded in seat belt mounting points under the rear seat, job done

[calw]

On a related topic, for ground connections anywhere, anytime, External tooth lock washers are your friend:

Install between the (cleaned of corrosion first) car's body and the wire lug.  In commercial and residential wiring, they're required to be included in the package of many devices for UL approval to ensure safe grounds, and are used thoughtfully in the electromagnetic compatibility (elimination of RF interference) world. 

[Dudeland]

15 hours ago, TobyB said:

 

And truly sensitive sensors like the engine temp for the DME will have the ground sourced

FROM the DME so that it's known to the microvolt.

 

Ditto.... especially for the sensors.  I was a big car stereo guy back in the day, and the common response about running grounding cables was that it was unnecessary because nothing would conduct more than the chassis itself.  Pumpin those 18" pizza pies in the back of the "Bitchin Camaro" was a ton of fun, and about 100A draw. 

 

Now with EFI and other sensors, having them all grounded to the same point is the gospel, which means running ground and power to each device to a common central point, otherwise you can't trust the readings.   

[jimk]

Haltech uses a sensor ground system and has a dedicated port where all sensors are grounded.  In addition the ECU has a general ground to the chassis.  No sensors are grounded directly to the chassis.