Hello everyone, sorry i haven't really been around the past couple days, as many of you know my house is on the market and the other day somebody made an offer so I have been scrambling to make it slightly more presentable, in regards to my graveyard of bimmers. Anyway I thought that i would post this article for the benefit of many of you with older cars, as well as those with electrical upgrades, audio and otherwise. What the Big 3 upgrade is, essentially, is to replace your cars positive leads and grounds with thicker wire such as higher end audio power cable or welding cable. Stock BMW wiring is generally sufficient when a car is new, but over time wire can become brittle and corrode internally, and your alternators output can decrease over time and also when it is hot. I have also noticed that BMW ground straps tend to become worn out to the point of non-existence after about 10 years of foul weather here in the northeast. So to do this upgrade you will need about 10 to 25 feet of high quality cable (length depends on model) as well as about a dozen quality terminals suitable for that size cable. I recommend 1/0 gauge, but for most of you 2 gauge will be sufficient. Make sure you get a different color to differentiate between negative and positive. Now get to work on the following:

1- Alternator + to Battery, if you have an upgraded audio system and are driving at night, in the winter, with your lights, heated seats, defroster, etc. all on, this can make a huge difference. Since your alternator produces nowhere near rated power under most conditons, chances are that at certain points your electrical system is running at a defecit. Thicker wire = Less resistance, therefore more current that is being produced is making it to your battery, where it can be stored, as well as the rest of your electrical system.
On my M20 powered 525i, this was easy as the battery is right under the hood, but on other models like my 535i, with the battery mounted in the rear, it takes a little more work to drag that thick cable through.

2- Engine block to Chassis ground, anytime there is increased current on the positive side you want to make sure that the ground is AT LEAST equivilent in size to the power wire. Luckily this is a short run of cable so it is pretty easy, and resistance is at a minimum. Still, make sure you match the positve lead and grounds in thickness and make sure you clean the metal on the chassis before bolting on the new ring terminal

3- Battery to chassis ground, another easy one, pretty much common sense,
Make sure you clean the metal on the chassis before bolting on the new ring terminal also

You may find that you need to grind down the ring terminals to fit on the alternator. I use a dremel or a bench grinder depending upon where i am.

I also recommend replacing the battery terminals with a quality aftermarket terminal available at the car audio store, rather than using the crappy lead bmw terminals.

I will post pics as soon as i get a digital camera to show you the process step by step. You will be suprised at the result. Many people have noticed that their lights are brighter, and that the A/C runs better in the summer, though i have no hard evidence of this. I am currently running 1/0 Gauge throughout my car, but this may be overkill for most of you as my audio system can draw up to 250 amps, and i have a second dry cell Stinger battery in the back. I have also made additional grounds throughout the vehicle.

Anyways, i have to get back to cleaning the basement. It's 2AM, and i am exhausted and overbooked with work, but that's life. Hopefully some of you can try this and benefit from it. If you need help i would be more than happy to precut the wire and crimp the terminals for thos of you who don't have something capable of crimping 1/0. A bench vise works ok in a pinch, too