Anyone know where the factory battery-to-body earth point is, and if running an additional earth cable is warranted when using amps?

Anyone know where the factory battery-to-body earth point is, and if running an additional earth cable is warranted when using amps?

It runs from the negative terminal to the top edge of the firewall.

Haha thanks, saw that and assumed it wasnt the 'main'earth as I was imagining something heavier.

Its always been a good idea to fit another earth earth from the battery negative to the chassis, the same size and the earth strap for the amp....

I thought the same that a heavier 'main earth' exists somewhere, so I looked in the maintenance book (CD) and found this..

https://lh5.googleusercontent.com/-LSNcqodRtp4/U8YG2FzMhgI/AAAAAAAAAag/oK7Uk66wHJs/w376-h368-no/380-ground.jpg

apparently there are 15 ground point through out the whole car all connected to the battery negative (some how)

Its always been a good idea to fit another earth earth from the battery negative to the chassis, the same size and the earth strap for the amp....

So replace the factory one with a larger item with the same size cable to the amps?

In addition to...
The car operates on its own positive and negative system, if adding additional power wire, additional earthing should be done as well...
Kind of like a water flow, if you add extra piping to a point/water feature/wheel you need to allow for the extra return current as well..
On a 2 x 50watt Amp, or something tiny, its not all that necessary, they did design the car to have accessories fitted..
But when you are adding an Amp/s that might have 100 Amp fusing or more, then I'd recommend it for sure... Keep in mind that an 100 Amp fused Amplifier, might only draw 20-50 Amps when playing music as the output is not constantly using 100% of the power, but Bass guys will find this figure rising fairly quickly....