Help on alternator upgrade

Standard alternator is 80 amp on the 3.4. Not sure what the 2.7 is but its certainly not more than 80 amps. I didn't go nearly as large as you with the alternator, but I'd sugguest keeping your existing wiring in place. Just run an additional miniumum 4g line with an inline fuse from your alternator to you battery (not your fuse box). I used a 100 AMP AGU fuse, but then again my alternator is only 170 amps. Biggest AGU fuse you can get is 100 amp so you'd have to step up to ANL fuses for your application.

The wires from your battery to your fuse box should be sufficient. You're powering amps so the assumption is you'll be running dedicated lines to your amps and not tapping off of anything already ran through your truck. As such there's no reason to upgrade the wire from battery to fuse box.

If you run 1/0 gauge to your amps, you should be running 1/0 from your alternator to your battery. If you're running 4 gauge, you might be able to get away with a 4g line from your alt to your battery but it depends on how much current your amps will be pulling.

Too thin of wire and the wire heats up...and quick. Thinner wire has more resistance and during high loads if the resistance is too great the wire gets hot. To thick of wire doesn't really "hurt" anything as long as your alt can dish out what's needed (which a 250 surely will) but it's extra weight and a PITA to run.

 

Not knocking that thead as it's a great writeup, but not for me. When it comes to pulleys and anything belt driven I like things that fit OEM and fit as they are supposed too. I don't really want a GM alternator with a 6 rib pulley (OEM has 4) held together with washers as spacers and a butt-conected wiring harness. I drive the piss out of my truck and there are certain parts of my vehicle I want to be sure hold together, the alternator being one of them. Missaligned pulleys can fray a belt quick. More importantly for me, the alternator belt also runs the TRD supercharger. For me...no fucking around, OEM fit only.

I picked up my 170 AMP (corrected...its 170 not 180) HO alternator for less than $200. Certainly more than the GM, but it's piece of mind more than anything for me.

 

Again I'm speaking from 3.4 motor and not the 2.7, but it should be the same. Stock there's a single line that runs from the alternator to the battery. The alternator's job is to push as much current as needed to the BATTERY. Your fuse box should have a separate (and thinner) gauge wire that runs from the battery to the fuse box. This drives all your powered accessories on your truck.

Keep all your wires as they are, and just run an additional line from the alternator to the battery (so you'll have two strands, factory and aftermarket 4 gauge or better) from alt to battery.

The way current works is it always takes the path of least resistance. Remember thinner wire = higher resistance. In high load (high current draw) situations, your thin wire won't matter because the majority of the load is going to be flowing through your thicker aftermarket wire. Also keep in mind with amplifiers, they are not pulling continuous 400 amps. That would be peak current draw (deep bass notes and such). Add a decent stiffening cap close to your amps and it will will also help out considerably with possible overdraw.

 

Gotcha. Still makes no difference. You'll still run the 4g+ extra line from your alternator to your battery. You're amps are going to be direct connected to your battery (not your fuse box) and that's what is going to require the majory of the power. No need to mess with the factory wiring. Good luck bro.

 

Dude seriously, kinda threadjack...but...no misunderstandings at all. You said it exaclty right, on a budget. I didn't belittled your writeup so dont take offense. I merely gave MY reasoning as to why I wouldn't do it. I'm all for innovation and doing things on your own. In this situation it's just not my cup of tea considering I have the s/c on the same belt.

Nod. You're dead on bout that. Went out and re-gandered at mine after OP mentioned his was set up this way. For his purposes, he still needs a separate run from alternator to battery.

 

Your supposed to pick your fuse based on your wire. 4 AWG is good for up to ~125 amps and 1/0 AWG is good up to ~300. I always started smaller and only fuse up to what I needed. I think 270 might be overkill, but it depends on what your amps are going to draw at full load. Quick and easy, sum up the total amount of fuses in your amps and use that as a starting point for your main fuse.