3G alternator swap

Topic: 3G alternator swap (Read 2908 times) previous topic - next topic

3G alternator swap

June 08, 2009, 03:42:22 PM

I'm lookin at doing one of these, but the 3g install thread is missing the core info at posts 49 and 50. Would anybody like to either link to some info or explain the process? Thanks.

3G alternator swap

Reply #1 – June 08, 2009, 04:57:02 PM

http://www.corral.net/tech/maintenance/130a-tech.html

3G alternator swap

Reply #2 – June 08, 2009, 05:00:47 PM

Well worth it,and doesn't take much time or money.I got my 3G from a 3.0 Taurus for cheap,polished it,and after 3 years,still going strong.

3G alternator swap

Reply #3 – June 08, 2009, 05:31:27 PM

Doesn't everyone go 6G now? Better idle power output with the same bolt pattern and wires.

3G alternator swap

Reply #4 – June 08, 2009, 05:33:35 PM

Quote

1. Locate the point where the pair of MAIN wires (black/orange) join and become one.
2. Cut at intersection., leaving one MAIN wire.
3. Splice in new piece of 10 Gauge wire, solder, and use heat shrink tubing to insulate.

10 gauge will suffice? I was under the impression the stock wire was larger. My car is 15 miles away and I can't really check right now...

3G alternator swap

Reply #5 – June 08, 2009, 08:36:15 PM

Isn't that to wire it up alongside the stock wiring? Even then, it isn't the best (voltage drop!). Either way, I wouldn't go less than 6 gauge with 4 or larger preferable. 4 gauge is good for a maximum of ~150A. 10 gauge is good for a whopping 60. Two 10 gauge runs will effectively get you up close to what 130's can put out. The wires WILL heat up though.

3G alternator swap

Reply #6 – June 08, 2009, 10:41:04 PM

Sounds good, thanks for the info guys. I have a lil' somethin cookin up while the 306 is gone :) .

3G alternator swap

Reply #7 – June 09, 2009, 02:06:31 AM

Quote from: Seek;276560

Isn't that to wire it up alongside the stock wiring? Even then, it isn't the best (voltage drop!). Either way, I wouldn't go less than 6 gauge with 4 or larger preferable. 4 gauge is good for a maximum of ~150A. 10 gauge is good for a whopping 60. Two 10 gauge runs will effectively get you up close to what 130's can put out. The wires WILL heat up though.

nope.........to part of what you are saying although you are so close to being right, its arguable nonetheless.

two considerations before selecting wire.

1- Will the wire be in a "free air" rating
or
2- will the wire be in "raceway or cable tray" , ie- enclosed or surrounded by a covering

The two situations above drasitcally change the ampacity of a conductor as well as its allowable voltage drop. The NEC is just now catching up to the world of DC power as in ref to the nec 2002 on back there was little data. The only place a man could find DC wire rating would be in teh Telcordia or GR1275 standards.

Of your above two criteria,, the temperature rating must be selected.

Lets use the 10awg as an example

In raceway or cable tray rating of #10 at the three temp catagories as ref by the nec...
at 60deg C its good to 30A
at 75deg C its good to 35A
at 90deg C its good to 40A

Free air rating of #10 at the three temp catagories as ref by the nec...
at 60deg C its good to 40A
at 75deg C its good to 50A
at 90deg C its good to 55A

In conservative cerspoogestances, we use the middle temp range as our guide for both free air and raceway/cable tray options.
If your wire is going to be enclosed, its heat buildup is greater so follows the voltage lost across the length of wire. Lenght of wire is critical in DC power.

Now, in an automobile engine bay, you have a power plant producing watts of heat dispation directly effecting the surrounding wiring. IN this instance, it is far better for you to use the 60deg C "in raceway or cable tray" column in the nec. However, better isnt always practical or cost effective as you will see in the conclusion to this post.

Why? Not only is the wire going to produce its own heat by way of current draw and the natural characteristics of copper (K factor) but the insulation around it also plays a heat holding roll. In addition, the engine running offers radiant heat to the wiring and thus forces you into a more conservative wire size scheme.

Take a look at some of your wiring inside the car and read off the fine print stamped along the conductor insulation.

You cant just size wire by its ampacity predictability in DC power, thats just totally retarded.

So, your ampacity goal is 130A lets say.

6awg at 90deg C free air rating is 105A
4awg at 90deg C free air rating is 140A
2awg at 90deg C free air rating is 190A

If your wire will dangle in the wind so to speak with no covering on it,then the free air rating applies.

To correctly calculate the actual KCMIL (circulair milimeters of copper) required to carry the hypothetical 130A,

Kcmil= Kfactor x wire loop lenth x ampacity / voltage drop
Kcmil= 11.1x 2 x 130 A / .10 VD

11.1 is my k factor constant for copper (in dc power only)
2 is my wire distance (there is only one hot feed, no return on the alt as its bolted to its own ground source assuming your plant is grounded.
130a is my full duty on the alternator
.10 is the voltage drop loss across that 2' distance of wire that i am going to engineer and allow for.

now i can calculate the above and i come up with ........
28860 circulair mills of copper required to carry a 130A load across 2' of distance.
28860 cmil converts to NEC chapter 9 table 8 wire size as closer to 6awg than 4awg. Since the Kcmil wire size is greater than 6awg, we default to the next higher size which is 4awg.

so,,,,,,,
4awg not only meets the DC power current carrying conductor properties of the application, it also fits the ampacity requirement of a "free air rated" wire at 90deg C.

In reality, all of these 3g's running parallel with a smaller guage wire seems odd to me. I would want to replace those black/brown wires with a single conducter fitted with a fuse rated at 80 or 90% the value of max ampacity of the alternator.

In short, a DC power conductor must meet two criteria to qualify for the job.
IT must be the correct circulair mils of copper and be the correct size for the amperage it will carry.

Seek's example of laying another run of #10 in parallel with the existing harness does /does not add to the total copper required, you just have to understand that the two blk/brn wires splice forward to one black brown and then into one single yellow wire. Those splices get corrosion over time so its best to eliminate them all together. The 5.0 final alt landing on the starter relay is configured a little different than the 3.8 but they are close enough.

Just my 2cents worth.

3G alternator swap

Reply #8 – June 09, 2009, 07:57:52 AM

Holy , now that is a response!

4 gauge it is then.

3G alternator swap

Reply #9 – June 09, 2009, 09:07:48 AM

when i did mine, it was a lot of trial and error, i guess i'm lucky i didn't fry my wiring or the alt.

my alt puts out 191 amps at 2k rpms though (according to autozones tester)......i have no clue what it came off of because i found it under about an inch of dust in the shop i work in. Reg was bad, so i went to the junkyard and pulled one off a junk alt that had been laying in the mud for years.....came off of something with a 10 rib belt.

3G alternator swap

Reply #10 – June 09, 2009, 09:51:49 AM

my gut would say a 10rib alt would be off a diesel.

3G alternator swap

Reply #11 – June 09, 2009, 09:02:41 PM

Quote from: jcassity;276625

snip

Overachiever :p

Anyways, yes there are more variables but most people don't care about anything but solid numbers. I am confused about the 30A ratings of the 10awg. Perhaps I was thinking 8awg as I use 10 for all my main wire lines, 8 for heavier duty systems (headlights and so on), and 1/0 for the backbone. Either way, the largest thing that most people run into is that not all 10awg or 4awg is the same (or any other sizes, but these are common) - strand count doesn't do a whole lot of anything besides flexibility with small differences in the way AC and DC travel. "10 gauge" is completely different from one manufacturer and another though. Most "4 gauge" I've found at shops other than stereo have been closer to 6awg. You can basically guarantee you will get what you want with the big welding wire though - not very flexible but it's a solid, cheap choice.

Know what you're getting by looking at the wire diameter itself. Wikipedia's got a pretty good chart covering this: http://en.wikipedia.org/wiki/American_wire_gauge

3G alternator swap

Reply #12 – June 09, 2009, 11:15:03 PM

seek
you know what I am waiting for,,

Im waiting for the NEC to catch up to "FLEX" wire ampacity ratings. the more strands the higher current carrying characteristics it has.

A 1/0 STR vs FLEX is very different. I will put 125 loop feet of 1/0 flex up against a 250A DC breaker any day at -48VDC.

That welding cable your talking about,,,,,,I have only had dealings with DLO cable (diesel locomotive) cable. If it is CT rated cable (ct-cable tray) then DLO CT wire is very flexible and exceeds the charts for ampacity.

That stranded stuff you talk about has solid but mulitple large strands. The air in between them offers a place to hide and effect its resistivity. The more smaller stands (ie- hairs) the better wire because it has less odds of corrosion and more conductors to dispate heat and conduct.

I stil think your example is better though, simpler and to the point.

3G alternator swap

Reply #13 – June 10, 2009, 12:32:42 AM

I think people go with some insane thing like 200-300 strands in the car audio field. I like my 4704 strand "1/0" (it has a diameter of just under 3/0). Got the 50ft roll for $75 2-3 years ago. Flexible but not very friendly at the battery/starter relay/fuse block.

I had voltage drop with 4awg auto part store wire (.2v at the battery) with the 3G alternator with the Mark VIII fan. There is nothing with the larger wire. All grounds were upgraded to 1/0 also though. For the serious enthusiast, I tell them to go 2awg - welding wire if they want "cheap". Copper got expensive the last few years.

3G alternator swap

Reply #14 – June 10, 2009, 03:22:38 AM

I find that the best place for 2awg wire or some cool stereo wiring for the cheap is at the JY. Do you have any idea how many people install a system in their car and junk the wiring when they are finished. I always snag the Amp wiring kits with the large wire when I see 'em. They work great for the 3G alt wiring.