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How to do the BIG 3 upgrade (electrical system)

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How to do the BIG 3 upgrade (electrical system)

Postby el_jelly » Fri Oct 09, 2009 11:11 pm

How to do the BIG 3 upgrade

In the car audio community the Big 3 is one of the most important mods you have to do to your car to improve the electrical system of your car and maintain good power to your audio system. Although this mod is more related and useful to cars with audio systems considering the 4g is in her twenties and most of the wires on the car people leave them stock, doing this upgrade can be beneficial.

In stock form our alt supply a crappy 70 amps, enough for the stock electrical accessories, too weak if you add aftermarket stuff like amps, computers, dc/ac converters, lightning kits, etc. And the amp rating is in stock form, as time passes and with older alternators the output is even lower (the car audio community always hates hondas for this). It's common for people to see their lights dimming at night when amps hit hard or when turning on some additional accessory. Adding a second battery, a capacitor or replacing the alternator for a higher output one can solve this, but still the wires in the "big 3" are the weakest link.
But this is not only for car audio or accessories, as you can see on the site is common for people to have problems starting their cars, erratic idle, low power and other problems that can't seem to be resolved with tune-ups or replacing parts. While upgrading the big 3 is not guaranteed to solve this problems it may be a way to improve them. The following procedure was gathered from several car audio websites, the most important and valuable being (for the audio and electronics enthusiast that place has loads of info).

NOTE: Upgrading the big 3 is not the same as putting ground kits, replacing all your grounds or unifying them. The upgrade is similar but the scope is different.

What is the big 3 upgrade?

The purpose of this upgrade is to improve the capacity of three wires:

1. Battery negative to chassis (gnd).
2. Engine/tranny ground to chassis.
3. Alternator positive to battery positive.

Some people leave the stock wire and simply add the new wires around or over the existing ones. Current always goes the path of less resistance so the stock wires in that situation will be useless. It is then recommended that the stock wires should be eliminated (less clutter and easier to work with).

Tools and stuff needed:

- High strand power cable.
Low strand cable is less flexible and solid core wire is not recommended for cars, it can break.
The length of the cable you get should be enough to cover the 3 positions you can measure it to the exact point or use the stock ones as reference for length.
Gauge of the wire: it depends on your application and plans. If you have or will have an audio setup in your car match the gauge of the wires to the power needs of your car. The cable has to be equal or BIGGER than the power cable of your amps, the alternator wire and the stock wires. The smallest gauge recommended for this upgrade is 4 awg, 2 awg (or bigger) is recommended. There are online charts and calculators that can help you choose the minimum size of the cable according to the amps. If you don't have an audio setup simply use wires bigger than stock ones.
- Ring terminals.Try to get copper ones, not "gold plated". They should fit the cable you selected.
- Soldering iron and core to solder the terminals to the cable.
- Heat shrinking tube for covering the soldered connection, it should fit over the cable-ring terminal end. Don't use tape
- Something to heat it.
- A blade or crimping tool to strip wires
- Wire cutter, pliers, cable ties, wrenches, screwdrivers, new bolts, etc.


1. A cooled engine is better to work with in this. Disconnect the battery and other charged stuff you may have (2nd battery, capacitors). Remove the battery and the tray. Identify the cables to be replaced:
Battery negative to chassis: it goes from the battery negative terminal to a bolt below the battery tray.

Engine/tranny ground to chassis: the engine ground wire goes from the valve cover to a bolt near the right side radiator support bracket (standing in front of the car). In this procedure we are upgrading only the engine ground, however, the tranny ground can be also upgraded if you have enough power cable and terminals (and it's recommended). It goes from a bracket over the tranny to the same point where the battery negative cable is connected. It's a flat braided cable, usually corroded.

Alternator positive to battery positive: it goes from the alternator (a single wire over it), throught the harness and into the main fuse box. It is fused (#31 60A) then the other side goes to the battery. You can go two ways: use one wire from the alt to the fuse box then another from the fuse box to the battery so you use the stock fuse. Or get an online fuse holder with a 60A fuse and you can eliminate the connection to the box (still two wires are needed).

2. After measuring up the wires (leave some slack on them so they can move), cut them and strip the ends so they fit inside the ring terminals. Again measure them so they are not too tight between the points of connection.

3. Insert one end on the ring terminal, crimp the connector to hold the wire (not too strong or it can break strands). Get the soldering iron and solder the wire.

4. If the shrink tubing doesn't fit over the ring terminal then now is the time to insert two cut pieces before you solder the other end ring terminal. It should cover the ring terminal and soldered wire plus 1 cm over the cable insulation. Use a heat gun or something like to heat the tubing and fit it.
Do the same to the other wires, if using a online fuse holder for the alt to bat cable then secure the cable on it as the fuse holder allows.

5. Battery neg to chassis: remove the stock battery negative wire and its terminal. If the grounding point in the chassis is very corroded or in bad form you may decide on making a new point or sand it down, either way be sure the metal surface is in good condition. Attach the terminal to the other end.
Engine gnd to chassis: remove the stock one and place the new one using the same bolts. You may also choose another location on the chassis to mount it.
Alt pos to bat pos: this could be the hardest to change since the stock wire is inside wire loom with the harness behind the block. If you decide on not remove all the wire loom and mess with it then simply disconnect the stock wire over the alt (10mm nut), attach the new wire with its ring terminal and then work from there.If you decided to eliminate the stock fuse and use and online fuse holder remember to place it more close to the battery than the alt and away from heat sources. If you decide to route it through the stock fuse box then connect it to the terminal in the box (if the wire gauge is too big it will be a tight fit) and another wire to the other terminal that goes to the battery. Don't connect it to the battery yet.

6. If you are changing the tranny ground then do it now. Check that all the connections you made are fine, no wires should be near heat sources or too tight between the points. It's a good idea to check the connections with a multimeter that reads resistance. Place one end on the battery negative terminal new wire, the other side to ground. The reading should be less than one. Also check the wire end that goes to the alternator and the other side that goes to the battery. Again if the reading is not less than one and is high then something is bad with the connections or wires, check again.

7. If everything is fine put the battery again in the car, connect the battery positive wire first, then the negative. Start the car and see if there's smoke or any problem with the wires. If you have a voltmeter hooked to the car check the voltage and compare it to previous readings.
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Re: How to do the BIG 3 upgrade (electrical system)

Postby Tuboflard » Wed Apr 13, 2011 2:47 pm

Very good write up. thumbs up. maybe some pics? =)
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Re: How to do the BIG 3 upgrade (electrical system)

Postby TechGuy8 » Thu Jun 21, 2012 9:43 pm

Is the tranny ground located just below the battery?
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Re: How to do the BIG 3 upgrade (electrical system)

Postby el_jelly » Fri Jun 22, 2012 5:09 am

IHeartMySTD wrote: We all know we like our women and cars with D's, not B's!!!! ;)

Where most of the questions are already answered > Engine swap guide, FAQs and Index thread
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