Has anybody had issues with engine noise coming through the speakers when using an additional amplifier in the trunk ?

I have tried a few different and very expensive RCA cables, and the problem has not gone away. I have the RCA cables running up the driver side and the amp power cable running up the passenger side. I have even tried running the RCA cables directly from the HU to the amp free-air through the car and the noise still exists.

I tried grounding the shielding around the RCA cable connected to the amp to a ground in the trunk, and the noise got much much louder. It makes me think that I might have grounding issues ?

I am grounded to the bolt under the passenger-side plastic tray. Perhaps this ground point is not very good ?

I have also upgraded the ground from my battery to the chassis but using self tapping screws from the battery ground terminate to the existing OEM ground point below the battery.

Any help or experience would be appreciated.

 

It doesn't sound like you did much of an upgrade from the battery to the chassis. Revert that back to stock. If you're going to upgrade grounds in the engine bay, upgrade the big 3

Also, try changing where you grounded the amp in the trunk. Try where the back seat bolts down on the floor of the trunk.

 

Same things I thought. I will do this and post an update.

 

How long is your ground cable for amp? Try to keep it under 16 inches, also what brand of amp are you running?

 

A great ground is the loop that is on the side. Its not clean but it is convenient and another great spot is on a seat bolt, but you may want to sand off some of the paint if you do that so you get a good connection.