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Anyone using a lightweight alternator?

 
Old 01-07-2015, 12:38 AM
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Around 10.5 pounds.

Originally Posted by zossy1 View Post
I have one at home, will put it on the scales when I get home from work.
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Old 01-08-2015, 03:47 PM
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Does anyone know if the alternator Leafy mentioned could be wired to run on a NB2?

My fourth alternator has been acting funny. I have had 3 failed autozone/oreilly/pepboys alternators, I found a used stock one and it has been good for about a year or so, but now it's giving me a battery light over 5000 RPM, not that I go there very often(street car), but still annoying.
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Old 01-08-2015, 03:51 PM
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Originally Posted by Dustin1824 View Post
Does anyone know if the alternator Leafy mentioned could be wired to run on a NB2?

My fourth alternator has been acting funny. I have had 3 failed autozone/oreilly/pepboys alternators, I found a used stock one and it has been good for about a year or so, but now it's giving me a battery light over 5000 RPM, not that I go there very often(street car), but still annoying.
You would wire it up the same way you would if you were to convert your NB2 to use a 94-97 alternator.
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Old 01-08-2015, 06:05 PM
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From the wiring diagram Leafy linked earlier, an additional wire (switchable ignition) would also be required...
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Old 01-08-2015, 06:13 PM
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Originally Posted by zossy1 View Post
From the wiring diagram Leafy linked earlier, an additional wire (switchable ignition) would also be required...
Internet seems to say conclusively, that it might be required, maybe.
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Old 01-08-2015, 06:27 PM
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Originally Posted by Leafy View Post
Internet seems to say conclusively, that it might be required, maybe.
I rewired mine on an NA. I can't remember exactly how right now. Stock Miata alternator is powered all the time through one of the little wires. The 60amp Swift one is not and uses a keyed power source for that otherwise I can confirm it drains the battery very slowly when the car is off. I spliced in some wires near the fuse box with male and female spade connectors and it is setup so I can quickly switch how it’s wired ether keyed or not keyed just by changing how I have the spade connectors plugged. The stock Miata one can be wired like the swift one with a keyed power and it works fine as well I think but I haven’t tried it to see if it will run the battery down without constant power. I am not an electrical guy. It’s all compressed smoke to me.
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Old 01-08-2015, 06:46 PM
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Originally Posted by concealer404 View Post
You would wire it up the same way you would if you were to convert your NB2 to use a 94-97 alternator.
I figured this would be the case. Whats involved in doing this?

I remember seeing a thread on this subject a long time ago, but can't find it like the noob I am.
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Old 01-09-2015, 10:05 AM
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Bob did you ever try it without the ing wire connected at all? Some people seem to think it works without it connected.
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Old 01-09-2015, 01:11 PM
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Originally Posted by Leafy View Post
Bob did you ever try it without the ing wire connected at all? Some people seem to think it works without it connected.
No I didn’t. But I will say anything that is advertised as a true 1 wire alternator seems to run the battery down when the car is off unless you disconnect the battery from it entirely with a cutoff switch.

Somehow the stock Miata electronics in the stock internal regulator switch something when the alternator is not spinning to keep the coils from slowly sucking the battery down. I think it needs a constant 12V on one of the two small wires to perform this function but I’m not sure.

The internal regulator on the Swift one I’m using the power on the IG termanal needs to be a switched voltage with the ignition switch otherwise it runs the battery down slowly when the car is not running. I found a wiring diagram for the swift to see how it was wired to figure this out.

I also tried the aftermarket style jumper wire 1 wire alternators which supposedly turn the alternator on only as it reaches a certain RPM. They also ran the battery down slowly with the car off no matter how I hooked them up unless you disconnected the battery entirely. If you let it sit for a week in-between events you had a dead battery.

I don’t have a clear understanding of how any of this works but that is what I have found.
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Old 01-09-2015, 01:26 PM
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Might give slightly more insight. From the sound of this, yes the ING for certain needs to get power for the alternator to charge. I'll probably grab mine off the switched power I had to use for the ABS pump.
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Old 01-10-2015, 02:31 PM
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So I pulled a chevy tracker alternator, didnt look right, too new. Then I saw the geo tracker that was all crunched up. After freezing my *** off my scale says its 8.5lbs and a stock 1.8 alt is 11.5. So not quite as light as advertised, maybe the 3 rib belt ones are lighter. This alt does use only 2 wires and its a smaller shaft diameter than the miata alt. So maybe the 3 rib early prizm one is even lighter and this pulley will work on it. The two wires it uses are the ING and L terminals.

So it doesnt quite fit directly. You need to drill two different holes out and tap one of them. You need to drill the tab with a steel sleeve out to 7/16s, 13/32 if you have one on hand would be better. The other tab thats in line with that hole you just drilled needs to be tapped to M10x1.25, no drilling required its already the right size. Then the remaining tab was already tapped, this needs to be drilled out with a 5/16th drill bit. Then it just drops right in and the pulley lines up. You end up putting the tensioner bracket in front of the tab rather than behind like the miata one. You also have to loosen the bolt on the block for the tensioner bracket and swing it down a bit. And from now on you will have to loosen this bolt in order to make any large tension changes since the alternator does not swing in the same arc as stock. I'd also recommend getting a shorter belt, it works fine with the stock one, but when I replace this belt it will be with a shorter one. Now that the tensioner is on the front of the alternator tab, replacing it with something lighter gets easier.

Last edited by Leafy; 01-10-2015 at 04:43 PM.
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Old 01-12-2015, 10:58 AM
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Originally Posted by Leafy View Post
So I pulled a chevy tracker alternator, didnt look right, too new. Then I saw the geo tracker that was all crunched up. After freezing my *** off my scale says its 8.5lbs and a stock 1.8 alt is 11.5. So not quite as light as advertised, maybe the 3 rib belt ones are lighter. This alt does use only 2 wires and its a smaller shaft diameter than the miata alt. So maybe the 3 rib early prizm one is even lighter and this pulley will work on it. The two wires it uses are the ING and L terminals.

So it doesnt quite fit directly. You need to drill two different holes out and tap one of them. You need to drill the tab with a steel sleeve out to 7/16s, 13/32 if you have one on hand would be better. The other tab thats in line with that hole you just drilled needs to be tapped to M10x1.25, no drilling required its already the right size. Then the remaining tab was already tapped, this needs to be drilled out with a 5/16th drill bit. Then it just drops right in and the pulley lines up. You end up putting the tensioner bracket in front of the tab rather than behind like the miata one. You also have to loosen the bolt on the block for the tensioner bracket and swing it down a bit. And from now on you will have to loosen this bolt in order to make any large tension changes since the alternator does not swing in the same arc as stock. I'd also recommend getting a shorter belt, it works fine with the stock one, but when I replace this belt it will be with a shorter one. Now that the tensioner is on the front of the alternator tab, replacing it with something lighter gets easier.
What do you think about just running the 3 rib belt on the four rib crank pulley? Do you think it would have any chance of jumping around if it is tight? I have a 91 altenator with the three rib, it is currently being tested (came out the junk yard) I will weigh it when i get it back, I feel like it is a bit lighter than 8.5 lbs. My guess is around 6 lbs.
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Old 01-12-2015, 11:14 AM
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I wouldnt do it. The tracker alternator uses a smaller diameter shaft than the miata alt, and so do the rest of the denso alts. It seems reasonable that the pulleys would swap.
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Old 01-12-2015, 11:48 AM
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Default Zero pound alternator

With all the trouble some of you have had, perhaps some of you are candidates for a 16V total loss system like I have on my CP Mustang. Perfect for autox, but you'd have to run some numbers to see if it would work for a track car.
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Old 01-12-2015, 01:02 PM
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Originally Posted by Leafy View Post
I wouldnt do it. The tracker alternator uses a smaller diameter shaft than the miata alt, and so do the rest of the denso alts. It seems reasonable that the pulleys would swap.
Some of the early 1.6l alternators used smaller shafts as well. I have run for years with just putting electrical tape around the shaft to center the pulley before tightening it down without issue before. Currently though I have an Unorthodox Alternator pulley that I found on EBay for $50. Its lightweight aluminum has the correct small shaft diameter hole to fit the Suzuki alternataor and correct Miata compatible multi rib pulley and offset. I think the pulley that worked best was for a Mitsubishi eclipse.
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Old 01-31-2017, 01:20 AM
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I've been running a Suzuki alternator for a season now. I picked it up for $30 from a wrecker and it already had a 4 rib pulley that was slightly larger which helps slow down the spin rate a bit.

I moved the alternator to the exhaust side of the engine so that I have more room to access the oil filter and underneath of the intake manifold. It's mounted by a small waterjet cut bracket that is mounted off the block.





This verson has a T plug for ignition trigger and doesn't seem to draw down the battery.

I made a billet tension bracket... but accidently made it flipped. Still works though but just looks wrong. It mounts off my EWP water pump delete plate.

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Old 02-02-2017, 10:42 PM
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Nice bracket!

My experience with a couple of alternators is similar to Bob's. A true "1 wire" creates dark current; the battery will drain.

All of my dead battery problems were solved when I took a closer look at the wiring diagram and realized there are a couple of diodes and resistors inside of the gauge cluster, between the +12v power supply, the alternator/charge/battery warning light, and the white/black wire that goes to the alternator. I've since gone back to stock.
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Old 02-18-2017, 11:46 AM
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Originally Posted by Leafy View Post
Back from the dead. Thanks to one of out mazda sedan based cousins I found the secret sauce. 5.7lb alternator that bolts right in and just needs a simple re-wire of a plug avalaible on ebay. 95-97 geo metro 3 cylinder or 89-97 geo tracker 1.6. You want the denso one not the mitsu one because the mitsu one sucks. Stock its 55 amp, there's a company that sells them rebuilt to 75amps though. The 89-94 metro 3 cylinder alternator uses a 3 rib pulley so it wont work. Oh yeah the electrical connector. And the wiring diagram.
I know this was stated two years ago, but figured it certainly wasn't worth starting a new thread over. Is there any reason this wouldn't work under an NB1 harness? I know the ECU regulates the voltage in the NB, whereas the NA is internally regulated. Would this alternator have the regulator on it? If I read correctly from other sources and this thread, I would only have to wire the charge lamp for the cluster? Thanks!

I did see where Leafy stated on M.net in June of 2015 (5 months after his last input on the topic here) that his Geo alternator was working quite well.

https://forum.miata.net/vb/showpost.php?p=7532566&postcount=11
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Old 02-19-2017, 07:45 AM
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Yup worked better than the stock one. It'll work just like an na alternator swap if you put it in an NB. I've got the one I was using with some wiring harness for sale now that I'm running a Mazda 2 alternator on the mzr swap.
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Old 02-19-2017, 09:00 AM
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Originally Posted by WAM View Post
With all the trouble some of you have had, perhaps some of you are candidates for a 16V total loss system like I have on my CP Mustang. Perfect for autox, but you'd have to run some numbers to see if it would work for a track car.
i think I am going to try this.
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