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Old 08-17-2010, 02:10 PM   #1
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Default Alternator upgrade?

The stock 70 amp (or whatever it is) alternator isn't cutting it anymore. I'm running 3 fans, not including the blower with the a/c on, and add headlights to the mix and I'm getting about 11.9 volts at idle. Are Miata alternators pretty much the same as other Mazda alternators? I remember from when I had my FE3 powered 626, the alternator interchanged with one from an FD RX7 (100 amp), and even later model Subaru's (the legacy GT turbo has a 130amp unit!). Only a pulley swap is necessary. I'm hoping the same holds true for the Miata's as well.
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Old 08-17-2010, 02:29 PM   #2
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Not 2 minutes after I posted this did I get the bright idea of looking at pictures of them on rockauto.com. Well looks like it will fit.

Miata alternator


RX7 100amp Alternator


2005 Legacy GT 110 amp Alternator


The legacy unit looks tricky since the terminal is on the other side, and the connector is probably different. Looks like the RX-7 alternator might be the way to go here.
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Old 08-17-2010, 02:45 PM   #3
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signal source for the RX7 alternator?
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Old 08-17-2010, 05:45 PM   #4
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How much would it cost to get a miata alternator re-wound?
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Old 08-17-2010, 06:10 PM   #5
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How much would it cost to get a miata alternator re-wound?
http://www.yellowpages.com/brooklyn-...g=Brooklyn,+NY
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Old 08-18-2010, 12:24 AM   #6
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I think Reverant and Ben both use FD RX-7 alternators, maybe drop them a line regarding fitment.
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Old 08-18-2010, 12:52 AM   #7
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f more power, where can i find a lighter one for my track car that will run 2 fans and ignition?
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Old 08-18-2010, 08:10 AM   #8
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f more power, where can i find a lighter one for my track car that will run 2 fans and ignition?
Bill Schenker runs a very light alternator on his CSP Miata, but I cannot find any details about it.
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Old 08-18-2010, 10:05 AM   #9
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I had my 97 alternator rebuilt with a 100amp core. Cost me 120 for everything. I have it running in my Hydra ecu'd MSM and its been working great since. Pulls about 80 amps when hot which is still great. I have a write up on Clubroadster.net somewhere on how to do it.
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Old 08-18-2010, 02:24 PM   #10
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I'm using an RX-7 FD alternator. Its pretty much a bolt-on, minus the battery light (leave the plug unconnected). It charges at about 14.3V when cold, but it drops as low as 13.5V when it gets hot (ie after several miles in stop and go traffic in 100*F weather). I'm going back to the stock NB alternator now that I have built my own alternator controller circuit.

Dimitris
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Old 08-18-2010, 05:41 PM   #11
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Originally Posted by CoralDoc View Post
Bill Schenker runs a very light alternator on his CSP Miata, but I cannot find any details about it.

+1
I noticed Scott Frasier/Tom Kubo had a tiny light looking alternator on their CSP car as well. What is it. I want one.

FWIW the 323 GTX guys running stage rally with all the extra lights run the 100 amp RX7 units. It is pretty much a bolt on.

Bob
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Old 08-18-2010, 06:57 PM   #12
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Quote:
Originally Posted by Reverant View Post
I'm using an RX-7 FD alternator. Its pretty much a bolt-on, minus the battery light (leave the plug unconnected). It charges at about 14.3V when cold, but it drops as low as 13.5V when it gets hot (ie after several miles in stop and go traffic in 100*F weather).
Dimitris, does your FD alternator still have the FD pulley on it or did you retrofit the pulley from the Miata alternator?
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Old 08-18-2010, 10:00 PM   #13
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Quote:
Originally Posted by Reverant View Post
I'm using an RX-7 FD alternator. Its pretty much a bolt-on, minus the battery light (leave the plug unconnected). It charges at about 14.3V when cold, but it drops as low as 13.5V when it gets hot (ie after several miles in stop and go traffic in 100*F weather). I'm going back to the stock NB alternator now that I have built my own alternator controller circuit.

Dimitris
What's the deal with leaving it unplugged? Is the wiring that much different? I'd rather have the indicator light functioning.
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Old 08-19-2010, 04:55 AM   #14
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Originally Posted by JKav View Post
Dimitris, does your FD alternator still have the FD pulley on it or did you retrofit the pulley from the Miata alternator?
I used the RX-7's pulley, which is a 5-rib Vs the 4-rib on the miata alternator. The belt has no problem and hasn't jumped once - and I'm punishing the engine pretty hard on a daily basis.

Dimitris
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Old 08-19-2010, 04:57 AM   #15
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Originally Posted by anarchyx34 View Post
What's the deal with leaving it unplugged? Is the wiring that much different? I'd rather have the indicator light functioning.
One of the two wires needs to be connected to a 10A fused, +12V feed (switched) and the other is supposed to connect to the battery light. It never worked for me, so I made a circuit that monitors the overall system voltage and blinks the battery light if the voltage is below 13V when the engine is running.

Dimitris
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Old 08-19-2010, 04:44 PM   #16
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Quote:
Originally Posted by Reverant View Post
I used the RX-7's pulley, which is a 5-rib Vs the 4-rib on the miata alternator. The belt has no problem and hasn't jumped once - and I'm punishing the engine pretty hard on a daily basis.

Dimitris
Is the FD's alt pulley diameter larger than the Miata's? If so then it would spin slower at idle/low speed, which might explain the voltage drop you're seeing in those conditions.
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