I have a Alpine V12 MRV-T500 bridged to 1 chnl 200W 4ohms for Sub
and a Alpine V12 MRV-F250 4ohm 4chnls to rear & front components.
I am currently running 8 Gauge power and ground wires to the amps, directly from the battery. Im wondering is this enough or should I upgrade to 4 Gauge?, is it going to make a difference?

cheers,
JaBZ

It's common for stereo shops to over-sell you on wire gauge. Essentially, it's free profit for them. Who was putting the idea into your head that you needed a higher gauge?

Detailed charts and calculations to find the CORRECT gauge are here.

Hmmm yea, well it was when I was at a car stereo shop.
I was pondering whether to install a power fuse/distribution block since I now have three independent fused power feeds coming off my battery.

So the installer guy says to get a 4 way blade fuse holder distribution block which accepts a 2/4awg input to 4 fused 4awg outputs. Wasn't sure, it be a bit expensive tho....

JaBZ

It is definitely critical to get a proper fuse block as close to the battery as possible (unless you like seeing your car burn to the ground). Whether or not you need the 4AWG wire is where the debate lies.

But everything is fused, the three power feeds are fused close to the battery terminal with inline blade fuse holders, 1 is a 3AMP fuse for the Empeg power line, and the other 2 are 30AMP fused for both Alpine amplifiers.

The requirement of a Fuse block was to reduce the number of wires going to the battery.
I'll run 4AWG wire from the battery and then use my existing 8AWG from the fuse block to the amps, I'll leave the empeg power feed.
However should I use a fuse for the 4AWG power wire from the battery terminal to the fuse block? if so what rating?

JaBZ

Sorry. I meant any proper weatherproof fuse, not necessarily a distribution block. Sounds like you're covered.

"If it works, don't fix it."

That's quite interesting, when I installed my brothers car stereo I had a lot of trouble trying to get the local branch of Halfords (UK car shop) to order me some decent large-gauge cable as they felt it was unneccessary. The system in question consisted of a pair of Kicker ZR1000 amps running at 2 ohms into four 15inch Kicker SoloBaric subs in the back of a Vauxhall Nova. The amps come with 120 amp fuse holders and recommend cable capable of handling at least 100 amps. We could only run the system with the engine on and idling at 2500 RPM, very nice!

However should I use a fuse for the 4AWG power wire from the battery terminal to the fuse block? if so what rating?

It is only the most important fuse in your entire car, and the one most likely to be actually needed to prevent your car from catching fire.

The three smaller fuses on the power distribution block are mostly there to protect your amplifiers. The big fuse (I recommend 80 amp) that you need to put on the 4-gage wire running from your battery to the distribution block is there to protect your car.

That wire is the most likely one to be compromised, running through the firewall as it does and routed through improbable places to get to your distribution block. And even though that 4-gage wire can carry an impressive amount of current, your battery can deliver even more. If that wire were to short against your firewall, your battery can put out enough current to literally catch it (and anything else it is touching or even near) on fire in about five seconds or less. An 80-amp fuse in a short circuit will blow so fast that that wire won't even become warm to the touch, yet it will carry the 40 amp load that your amplifiers can draw forever.

You are correct that each device powered by the distribution block must have its own correctly sized fuse; but the distribution block itself must be fused as well, as close to the battery as possible.

tanstaafl.

What about grounding the head unit?
Should connect a wire from the sled itself to a grounding point behind the dash ??

Should connect a wire from the sled itself to a grounding point behind the dash ??

This is not necessary from the point of view of safety -- that is, keeping your stereo system from setting your car on fire.

However, it may prove beneficial in terms of audio signal -- it may alleviate a ground loop problem, for example. If you are not having signal noise problems, then you don't need any additional grounding. Since the sled is already grounded through the wire harness connected to it, any problems that go away when add an additional ground to it would indicate a problem in your wiring harness.

For a very definitive discussion of fuses (going back to the original topic), see here.

tanstaafl.