My car is a '98 BMW 318 (e36). The battery is mounted in the trunk and the negative terminal is grounded to the chassie in the trunk. The positive terminal has a nicely sized wiring running up into the engine bay.

For the head unit there is structural chassie frame around the steering column that I previously used as a grounding point. Should I stick with this or run a #10 wire back to the battery Neg. terminal in the trunk (about 10 or 12ft of wire).

And for the 2 amps and capacitor that will be mounted in the trunk should I ground these directly to the battery neg terminal too? If so I would pobably use some copper grounding lugs with self tapping screws connected to the chassie to connect to HU, amps and cap then one good size wire from the lugs back to the battery neg terminal.

 

Your a lucky man to have your battery in the rear.

I'd keep the HU ground near the HU. Then everything else can be connected directly to the battery. NIIICE!!! The only thing is you might eventually want to upgrade the wire to the alternator. How big is "nicely sized wiring" for the positive that runs to the alt? How big are your amps?

 

I just spoke to the BMW dealer and he couldn't find the wire gauge (his info is just a part number for the cable itself). He figures a number #2 or #4 wire. I'm an electrician and quite familiar with AWG sizes. I'll have a look to confirm later this evening. The amps are;
400w rms x 1 - MTX (RT2200X) for the sub
85w rms x 4 - US Acuostics (USX 4085) for 5 1/4 Components & 6x9's
1 farrad capacitor (I've been told 1 ferrad for every 1000w rms)

About 740w rms total, give or take a bit of power.

By the way the infinity reference speakers that I'm using claim to be a 2ohm design to
draw all the power from the amp. And sure enough when I put an ohm meter on the speaker leads before connecting to the amp it read a little over 2ohms - speakers were paralled on a two channel amp for my previous setup, reading about 1.5ohms per channel if I remember correctly. I've never put an ohm meter to other speakers before so I don't know if there really is a differance and of course this doesn't acount for any inductance once the speaker is powered.

 

If i were you, before I ground everything to the negative batt terminal, I would add an extra ground to chassis in 1/0awg on top of the existing ground.

 

Ya, if it's 2 or even 4ga wire, you should be good. Like Jalat said, upgrading the batt neg to ground always helps.

 

ps.

take me as an electrical apprentise please

 

I'm surprised no one has commented that hes using a cap when the battery is located in the rear of the car.

Anyways, if you don't already have it, I say its a waste of money.

 

Hell, if your willing to relocate to BC, I think I can still get you a job in Calgary.

 

Hey Njord, I already have the cap. Is it not so usefull in this application? If not I'm sure it won't harm anything and It's aesthetically pleaseing if mounted nicely, especially with the digital voltage reading. The terminals also doubles as a distrution block (maybe an expensive one though).

Jalat, be carefull coming out here. You might not want to go back........well at least untill you see the realestate prices and all of the f***** rain.

 

A 1 farad cap is only good for like .?? of a second until it discharges then it's only a draw on your system. I use to swear by them, now running almost 3000rms and I don't use one at all. You can use it if you'd like. Like you said, they do look cool. lol