I have a MINI Cooper Cabrio (Non-S) that I intend to install an Alpine MRP-M450 amp up to my stock HK Amp (using line level) to install an 8" sub in the trunk, but I need to figure out the best way to run my 4 gauge power wire from the battery under the hood to the amp in the boot. If need be I can use 8 gauge instead but I'd prefer to use 4 gauge as it leaves me with upgrade options and it's what I already have from my previous car.

The other thing I was considering was simply finding a power source in the trunk that would be sufficient for the amp as it would make the install a lot simpler. The amp is quite efficient and wouldn't require a significant amount of power.

I've only had the car a few months so I haven't taken much apart so any advice from the many seasoned owners on this side would be very much appreciated. I intend to do the install on Tuesday.

 

I don't know of an unswitched power source in the boot area. There is switched power (ignition key position 1), going to the cigarette lighter outlet in the boot. To run power from the battery to boot, run the wire along the side of the car under the door sill cover. There are numerous harnesses that are bundled together and routed on that path. You'll see what I mean when you run signals from the HK amp (under the passenger's seat) to your amp in the boot.

For your amp, you'll be using speaker level (not line level) inputs. There are no line level signals available. The HK amp uses speaker level outputs from the headunit.

 

Oops, i meant to say that the amp has speaker level inputs. What's the best way to run a wire through the firewall?

 

There are two rubber grommets in the firewall that pass wires through. Punch an additional hole through one of the grommets for your wire.

One of the grommets is visible under the drivers side cowl when you open the hood. There is a picture and description in this thread. On the other side of the firewall it is up high under the dash in a tight location and not so easy to see.

The other grommet is easier to find under the dash, but not as easy to see on the engine compartment side. In your case this is the grommet I would use because of the more direct wire run. Look under the dash near the steering column and you'll see the grommet with wire harnesses running through it. Use a skewer or sharpened wire hanger to poke a hole and see where it comes out on the other side, and use it as a tool to fish the wire through.

 

Thank you very much RKW. I will post how it goes when I get it done.