For those of you who did this, how did you do it? Did you use one of the two bolts on each end of the bar? Did you put your ground cable under the bolt, or under the bar. If the latter, did you have to remove the bar in order to get under it and sand the paint off?

thanks,
gil

 

i did this. i have photos at home and will try to post them later.

i used the lower of the two bolts at the end of the bar. i placed a crimp on ring on my ground wire, then placed the ring between the bolt and the bar. you do not necessarily have to sand any paint off.. the bolt itself is unfinished and the threads it contacts in the bar and frame are unfinished - therefore you have a good ground path through the bolt. you can check this path by using a volt meter to measure the voltage between your + amp lead and the bolt itself.

 

What you really want to do is pick a good ground (the negative battery cable, or wherever it is bolted) and measure the resistance between that and your prospective site, preferrably with your connector tightly fastened in place. Any appreciable resistance between the two points would tell you that it is not a good ground. Any voltage differences between your + amp lead and different ground locations may be more difficult to read and would depend on all the variables that may make the voltage fluctuate.

 

[QUOTE]Originally posted by fmah
[B]What you really want to do is pick a good ground (the negative battery cable, or wherever it is bolted) and measure the resistance between that and your prospective site, preferrably with your connector tightly fastened in place.

 

Thanks, guys. I've never liked the whole "sand the paint off" idea, anyway. And I've noticed that the factory ground locations aren't sanded down. Their threads are unfinished, though.

I never thought about using my multimeter (I'm always learning new uses for it). Tell me if I did this correctly. I measured the voltage between the two leads on my battery. The car was off, if that makes a difference. I got about 13.21V. Then I tested the voltage between the + battery lead and the bolt holding the short ground cable that connects the - battery lead to the chassis. Same reading. Then I went to the trunk. I tested the voltage between one of the open spots on my power distribution block and a factory ground bolt. I got about 13.19V. If I moved the black probe on my multimeter to a painted chassis location right next to the ground bolt, my reading dropped into the mV range. I guess paint does make a difference! And it was much thinner than the exterior paint. Anyway, when I tested one of the rear strut bar bolts, I got the same 13.19V. So, it's just as good as a factory ground location, right? BTW, I assume the 0.02V difference between the battery test and the trunk test had to do with the difference between touching the + battery lead vs the power distribution block, which is at the end of an 18 ft run of 4 AWG cable. I'll shorten it when I decide where everything is going to go.

So, is this testing good enough, fmah? I'm not sure how to do your method, i.e., measuring resistance. Would the leads on my multimeter have to be long enough to go from the battery to the prospective ground location in the trunk? Also, regarding the method I used, what sort of variables might make the voltage fluctuate?

Always learning,
gil

 

Yes its a good place to ground. 12mm bolt. I WOULD use a metal file and scrape deep lines then sand off the paint. I want to see shiny metal before I replace the bolt. This way I have NO doubt how good my ground.

If you run multiple amps ground seperately. Ground your caps seperately too.

 

So, did you remove the rear strut bar to do your sanding, Lucid?

Regarding your last remarks, are you saying that I shouldn't distribute one ground cable into three amps (say, one 4 AWG into three 8 AWG via a distribution block)? Because that's what I was JUST thinking about doing. What are the negatives (no pun intended) in doing that?

thanks,
gil

 

Lucid,

What about all three ground cables going to the same spot on the chassis? Is that the same thing, i.e., are you against that, too?

thanks,
gil

 

[QUOTE]Originally posted by lucid
[B]
If you run multiple amps ground seperately.

 

Grounding the amps seperately prevents high currents drawn by an amp from modulating the ground voltage of any of the other components.