on the frame? Supposed to improve spark or something like that?

My brother was telling me someone he works with did this on his 350Z. Sounded kinda hokey to me. (No offense Hokey_90) :-)

Our grounding wires for every plane I worked on was no larger than 10 gauge. It wouldn't really hurt anything, but why? There may be more to it, like if he's running a hellish sound system. Even then most people that use that large of a wire don't need it; it's more of the bling bling factor in car audio.

There are some other cars with poor ground connections between chassis parts and unit body.

this is where voltage circulates between the ground connections.

<a href="http://www.epanorama.net/documents/groundloop/index.html">http://www.epanorama.net/documents/groundloop/index.html</a> says:

"Ground loop is a condition where an unintended connection to ground is made through an interfering electrical conductor. Generally ground loop connection exists when an electrical system is connected through more than one way to the electrical ground."

You'll see it mostly in audio systems, where you get a "hum." There are things you can do to prevent it. Read, read, read.