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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1569 Registered: Jan-08 | My buddy owns a machine shop and agreed to help me make a dual alt mounting bracket. Do the alts have to be the exact same to run duals? I was planning on using my stock alt and my ho alt so i dont have to buy a new one. What kind of electrical stuff do I need to do? What is the difference between a multi alt set up and a regular single alt setup? (other than the obvious second alternator) Thanks |
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Platinum Member Username: Nd4spd18Philadelphia, PA Post Number: 11744 Registered: Jul-06 | Depends on the vehicle. Wiring is going to be a big problem if the voltage is PCM regulated. In an old 1 wire alternator setup you get just put 2 alternators in a run a positive wire to each and thats it. |
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Silver Member Username: ThelonewolfNew Ipswich, NH USA Post Number: 304 Registered: Jul-05 | could just run the HO for the audio gear... power to batt(s) in the rear. Just a thought. |
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Gold Member Username: TejcurrentPost Number: 2713 Registered: Apr-07 | The pulleys should be the same- not necessarily the diameter but the groove etc. Having similar alts helps your voltage be the same on them both, you want them to be similar. The vehicle will determine how you have to wire the alts up. If you're adding an older chevy or Ford alternator you can throw those on just about anything. For instance I'm making a dual kit for the Dodge 1500 that uses a GM AD 244 with 7 groove dodge belt. For the idler pulley I normally use Gates 38006 as it's a good size and well made, and costs <$20 at most stores. The hard part is getting the spacer (bushing) for the pulley, though you can pull one off any 90's full size chevy. I also have bushings I've designed that fit the 38006 perfectly, I could sell them really cheap if you have trouble finding one. Before buying fasteners you should get that spacer though, because depending on which vehicle you pull from you'll get a 10mm or 12mm ID (Inner Diameter). Mine are 10mm ID. What year vehicle and which alts are you considering using? |
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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1571 Registered: Jan-08 | 99 alero 3.4L v6 How do I plug both alternators in since there is only one plug? I know this is pretty vague, but I dont know what to call the plug. I want to use the alternator that came on my car (delphi automotive) and my ho 200amp alt from motorcity reman. diameters on the pulleys are different, but they have the same groove patterns. I currently have the HO alt on my car, but i need moar power (especially at idle). I'm trying to get this done tomorrow, so quick responses would be awesome. Thanks so far guys, keep the knowledge flowing. |
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Gold Member Username: TejcurrentPost Number: 2714 Registered: Apr-07 | If your 2nd alt is a late 90s early 00s replacement the wiring harness you need should look like this: http://www.aspwholesale.com/index.php?act=viewProd&productId=2125 You can even chop one off of any vehicle. Do you have 2 wires going to the harness on your factory alt? Basically you either splice into your factory wiring, or use 1 wire (I can tell you which one if need be) and hook it to a switched power source. Also, just throwing this out because the new pulleys I had machined are 44mm where most places use 48 or even a factory pulley. You could get 2 of them and that would get you a nice bit more idling output, especially replacing the factory pulley which is 52-58mm. |
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Gold Member Username: TejcurrentPost Number: 2715 Registered: Apr-07 | ^ Also, I know you already have an alt but why not check into a large case? If you're building the bracket anyway you obviously need more power- and to go through the effort making a bracket I'd bet even a junk yard 150 amp AD 244 would have more output than the 200a MCR at idle (assuming it's a small case). |
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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1572 Registered: Jan-08 | Yeah, troy can you go into more detail about what to do with the wiring harness? I already have a couple smaller pulleys, but thanks My friend just wants a six pack in exchange for the work to build the bracket so I'm not really putting any money or effort into this. It was just something I realized I could do for next to no cost. |
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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1573 Registered: Jan-08 | So I went to my friend's shop and he drew up some plans for the bracket and where to mount everything. All I need to know now is how to wire both of them up. So any help there would be great. From searching around online i found this: "Splice into the brown wire on the primary alt (connector on the side) and run it to the same terminal on the secondary alt. Both come on at the same time, all is well." I think I understand this, but could someone please go into more detail? I want to make sure i do this right. and also i connect the power from my alt to my batt(+) with a fuse in between right? just like a big 3? Also I'm pretty sure the answer is yes, but can an alternator be run in reverse? |
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Gold Member Username: TejcurrentPost Number: 2716 Registered: Apr-07 | Post a pic of your alt wiring harness and I can give you directions in detail. Unplugging it first would be nice. If its just one wire going to the plug just splice into that and your done. Run a fuse from the alt to battery, but run a solid piece to connect the output of both alts. As long as an alt is spinning it will make power, it doesn't matter which direction. |
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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1574 Registered: Jan-08 | That link you posted earlier is the same harness as mine.
you mean like run a wire between the power outputs of both alts right? is it really necessary to do that? They will both be running to the same battery. |
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Gold Member Username: TejcurrentPost Number: 2717 Registered: Apr-07 | I didn't know if you had a 2nd harness, or if you were picking one from a 'yard, but that's a good price if you need one and want to buy new. Some cars have 1, 2, 3 wires etc using that same 4-pin harness. If you have just 1 or 2 wires in the center of the plug, splice into them and you're done. It's a good thing to run a connecting wire, it helps even out the voltage. With 2 different alts you could see a nice voltage difference, having similar alts helps, but one may be running at 14.1 and the other 14.2 etc. It's your setup so you determine if it's worth it, but it sure doesn't hurt. |
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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1575 Registered: Jan-08 | Alright, thanks for all the help Troy! I'll throw up some pics when its all done. |
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Gold Member Username: TejcurrentPost Number: 2718 Registered: Apr-07 | Good luck, I always love to see pics of dual setups. |
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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1576 Registered: Jan-08 | Well, I doubt mine will be too pretty, but it should get the job done. I got another question though. What gauge wire should i use to connect the two alts? I was thinking about doing 2 runs of 8gauge since I have it on hand and the alts wont be too far apart. one does 200amps peak the other does 105 peak. the 200a alt has 1/0 connecting it to the batt. I was also going to do 2 runs of 8 gauge between the 105a alt and the batt. I know i'm being skimpy, but money is tight and if i can safely get away with a couple runs of 8ga that would be free compared to going out and buying 8ft of 1/0. 4ga is safe to run up to 4' of 250amp current right? |
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Gold Member Username: TejcurrentPost Number: 2720 Registered: Apr-07 | The more wire the better, it's really up to you man. Better than nothing, and with as short a distance as it should be a few small runs will do OK. A tip to make things easier is to use cardboard to lay things out, transfer that to wood, then use metal. You'll save a lot of metal and cost since this is just for you, and the first try may not work. Make sure you keep an eye on bolt locations as it's easy to lose track and realize a bolt is blocking the belts path. Ugly pictures will do |
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Gold Member Username: DuckaShelby Twp., MI United States Post Number: 1577 Registered: Jan-08 | cool, thanks again troy. |