by geolemon » Tue Jan 24, 2006 7:21 am
TechSys wrote:So you have a 8gauge and 4gauge wire running from the battery to your amps? Or am I just reading that wrong?
You are reading that wrong - but this is a good opportunity to clarify what really matters, so that you can have a good solid understanding to do your own system.
I have two vehicles...
Let's walk through the Civic, it's the smaller system (at least wiring-wise).
I originally only had a 400w amp, for my sub... and then later added a small 50x2 (or something like that, it's been a long time
) amp for my components.
So, my total current draw was just small enough that I could get away with 4 gauge comfortably.
First thing I added (as with everyone
) was my main power wire... you can buy these as a "wiring kit" these days, incuding your underhood fusing, distribution block, RCA cables, turn-on wire, etc. for cheap.
I used 4 gauge wire...
From the battery (I'd suggest a replacement battery terminal, but you can often get away with a ring terminal on the end of the 4 gauge), less than 16" down the wire from the battery, you want your main fuse installed.
(It should be at least as large as the sum of all the fusing for everything in your trunk. This fuse doesnt' protect that equipment, it protects the wire (and really the car) from fire, should something happen to the wire, causing a short. You don't want this fuse popping under daily operation, obviously. ]
From the main fuse, the long, long 4 gauge wire travels back to the trunk.
(run it through an empty grommet, or an oversized grommet with room next to it, in the firewall - 95% of the time at least, there is one you can poke through, no drilling through the firewall required. If you do drill, use a grommet in the hole, or that sharp metal will potentially cut the power wire, quickly teaching you a lesson on why that main fuse exists! 
)
It usually is connected to a terminal block.
Now is a good time to point out again that it isn't just wire GAUGE that matters - length factors in as well. Ultimately, what you care about is "how much resistance is in this length of wire".
You can lower the resistance of a wire by making it shorter, and you can lower the resistance of a wire by making it larger in diameter.
I point this out because the "main power wire" is very long (between the battery and the distribution block in the trunk).
And generally the short links of power wire from the distribution block and the amps are very short.
...which means that not only can you "get away with" using 8 gauge wire for the short power wire between the amp and the distribution block - but actually that short wire might ultimately have less resistance than the long run of 4 gauge!
I have two runs of 8 gauge wire going from my distribution block to my amp - each of them less than 4 feet long.
I also upgraded the power wires underhood - and again, because these were so short, I used 8 gauge for all of them.
I replaced the factory battery ground - and made sure the contact was bare metal-on-metal (paint is an insulator!).
I replaced the factory engine ground (think of this as your alternator's ground).
I replaced the positive power link from the battery to the alternator. Even being a longer than the other two of the "magic 3", this wire was less than 4 feet long. 
Now - if I had bigger amps, say... an 800w amp and a 100x2 amp or something... upgrading to a larger wire - maybe 2 gauge would be wise. 8 gauge on the short links might still be OK...
2 gauge is hard to find though, and 1/0 is common and has become cheap.
I generally skip right to this option. :happy055:
and if you were running something larger... over 1000w... I'd go right to this anyway.
Again, factor in length...
1/0 on the main power wire. Maybe 4 gauge to an amp that draws a ton of power (ie. big sub amp). 8 gauge is probably fine for a stereo amp.
The engine and battery ground underhood, if they are less than a foot - probably 8 gauge is fine, for the main power wire I might step up to 4 gauge, because it's longer and we're talking about drawing more current.
Or, you could go 4 gauge for everything that's not the main wire - no harm in that either.
Hopefully that's helpful and not confusing.
It's always safer to run a larger wire than you need, when in doubt.
That's the bottom line.[quote="TechSys"]So you have a 8gauge and 4gauge wire running from the battery to your amps? Or am I just reading that wrong?[/quote]
You are reading that wrong - but this is a good opportunity to clarify what really matters, so that you can have a good solid understanding to do your own system. :fing02:
I have two vehicles...
Let's walk through the Civic, it's the smaller system (at least wiring-wise).
I originally only had a 400w amp, for my sub... and then later added a small 50x2 (or something like that, it's been a long time :p ) amp for my components.
So, my total current draw was just small enough that I could get away with 4 gauge comfortably.
First thing I added (as with everyone :D ) was my main power wire... you can buy these as a "wiring kit" these days, incuding your underhood fusing, distribution block, RCA cables, turn-on wire, etc. for cheap.
I used 4 gauge wire...
From the battery (I'd suggest a replacement battery terminal, but you can often get away with a ring terminal on the end of the 4 gauge), less than 16" down the wire from the battery, you want your main fuse installed.
[i](It should be at least as large as the sum of all the fusing for everything in your trunk. This fuse doesnt' protect that equipment, it protects the wire (and really the car) from fire, should something happen to the wire, causing a short. You don't want this fuse popping under daily operation, obviously. ]
From the main fuse, the long, long 4 gauge wire travels back to the trunk.
[i](run it through an empty grommet, or an oversized grommet with room next to it, in the firewall - 95% of the time at least, there is one you can poke through, no drilling through the firewall required. If you do drill, use a grommet in the hole, or that sharp metal will potentially cut the power wire, quickly teaching you a lesson on why that main fuse exists! :sad017: )[/i]
It usually is connected to a terminal block.
Now is a good time to point out again that it isn't just wire GAUGE that matters - length factors in as well. Ultimately, what you care about is "how much resistance is in this length of wire".
You can lower the resistance of a wire by making it shorter, and you can lower the resistance of a wire by making it larger in diameter.
I point this out because the "main power wire" is very long (between the battery and the distribution block in the trunk).
And generally the short links of power wire from the distribution block and the amps are very short.
...which means that not only can you "get away with" using 8 gauge wire for the short power wire between the amp and the distribution block - but actually that short wire might ultimately have [i]less[/i] resistance than the long run of 4 gauge! :fing02:
I have two runs of 8 gauge wire going from my distribution block to my amp - each of them less than 4 feet long.
I also upgraded the power wires underhood - and again, because these were so short, I used 8 gauge for all of them.
I replaced the factory battery ground - and made sure the contact was bare metal-on-metal (paint is an insulator!).
I replaced the factory engine ground (think of this as your [i]alternator's[/i] ground).
I replaced the positive power link from the battery to the alternator. Even being a longer than the other two of the "magic 3", this wire was less than 4 feet long. ;)
Now - if I had bigger amps, say... an 800w amp and a 100x2 amp or something... upgrading to a larger wire - maybe 2 gauge would be wise. 8 gauge on the short links might still be OK...
2 gauge is hard to find though, and 1/0 is common and has become cheap.
I generally skip right to this option. :happy055:
and if you were running something larger... over 1000w... I'd go right to this anyway.
Again, factor in length...
1/0 on the main power wire. Maybe 4 gauge to an amp that draws a ton of power (ie. big sub amp). 8 gauge is probably fine for a stereo amp.
The engine and battery ground underhood, if they are less than a foot - probably 8 gauge is fine, for the main power wire I might step up to 4 gauge, because it's longer and we're talking about drawing more current.
Or, you could go 4 gauge for everything that's not the main wire - no harm in that either.
Hopefully that's helpful and not confusing.
It's always safer to run a larger wire than you need, when in doubt.
That's the bottom line.