High output alternator (where can I get a good one, and how good are they?) - Miata Turbo Forum - Boost cars, acquire cats.

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Old 01-31-2008, 04:27 PM   #1
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Default High output alternator (where can I get a good one, and how good are they?)

I have been doing some current measurements (DC clamp-on ammeter at the alternator and see a large draw when everything is on - spal's, blower, lights - I'll post the component draw numbers below if anyone is interested). I am first trying to track down if I should be drawing this much current but assuming I need more steady state juice does anyone have direct experience with high output alternators, how much current can I get from a good one and where might I source it)? Knowing how much current I can get will inform how I modify the current system once I confirm that everything is working properly).

Here are the numbers:
I used a clamp-on DC ammeter and measured at the alternator and turned on one component at a time and recorded the reading (rechecking the base current each time too). Listed is the excess current above the baseline when that component is turned on (I also continually checked the logged voltage which stayed at 14V during the measurements).
All measurements are done at idle and there is no fan in front of the car (no airflow into the radiator).
The car is a 91 with a turbo, MSPNP, big injectors, FM radiator and IC and other stuff...


Baseline current: 13A
Fans (FM dual Spal package) 27.6A (18A for the big fan, 9.6A for the small fan)
PIAA Headlights (Xtreme white) 18.6A
Blower 15.9A
PIAA Foglights 11.4A
Aftermarket sound system on full 7.4A
Radar 0.3A

Last edited by aseer; 01-31-2008 at 04:38 PM.
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Old 01-31-2008, 07:17 PM   #2
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i think FFS sells one thats controlled by a pcpro and not only does it out put 15X the ampage but it also spins with zero friction and emmits sub-freezing temps instead of heat while under full load....sorry for the BS newb but i had to, been reading too much QUACK lately

to answer your question, you can get an alternator out of an automatic and it should out-put a little more juice (55a vs. 65a i believe)
other than that, you may have to find one of those old little shops where the owner knows what he is doing and have him re-coil(?) yours to put out more juice
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Old 01-31-2008, 07:17 PM   #3
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also try to search, im sure this has been discussed
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Old 01-31-2008, 07:55 PM   #4
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I'm sure Dan is right and I should make a search but I'm interested in this topic too and at least would like to be pointed by someone about some good thread on the subject. :gay:

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Old 01-31-2008, 09:33 PM   #5
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https://www.miataturbo.net/forum/sho...lternator+high

good thread to read...if your alternator dies might as well get one for an auto, or do what Ben says, im sure those kinds of shops are much easier found in the dominican republic than here
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Old 01-31-2008, 09:39 PM   #6
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Quote:
Originally Posted by whaaamx5 View Post
https://www.miataturbo.net/forum/sho...lternator+high

good thread to read...if your alternator dies might as well get one for an auto, or do what Ben says, im sure those kinds of shops are much easier found in the dominican republic than here
Thanks for the response. I had seen that thread and I was hoping for more juice than a 1.8 auto can provide (or I start pulling stuff off the car; my numbers add up to a ~100A alternator unless I have a bad part which is drawing too much).
The alternator is new as is the battery, I swapped them before I thought to take current draw measurements (I did not own a DC clamp on ammeter until yesterday).
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Old 01-31-2008, 10:09 PM   #7
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Quote:
Originally Posted by whaaamx5 View Post
https://www.miataturbo.net/forum/sho...lternator+high

good thread to read...if your alternator dies might as well get one for an auto, or do what Ben says, im sure those kinds of shops are much easier found in the dominican republic than here
Thanks Dan; I'll read some and ask some dumb questions later! :gay:

FWIW, my son's Opel Corsa is going around with an alternator adapted from a Skoda! and no, it does not work well! lol.
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Old 02-01-2008, 06:12 AM   #8
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You have a basic flaw in your test that you checked at idle. Current demands at idle are going to be higher because voltage output is a bit lower.

94-97 auto alternator is going to be your best bet. IIRC the difference is 10A. After that, you'll need to get an alternator rewound. There's a place local to me that does it... I'm sure there are others.
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Old 02-01-2008, 12:57 PM   #9
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Thanks for the input.

I was also worried about the voltage drop and its effect on the current draw but I checked the voltage during every test and it stayed around 14V as long as long as I did not turn on more than one component at a time. 14V is the most my alternator seems to put out (I checked this by rev'ing above 3k rpm). In the real case situation where multiple components are running the voltage does drop and I can make it up with RPM's to a point but I run out of capacity after the fans kick in.

Do you know how much extra current capacity a good rewind can provide?
I also understand that not all shops that do performance rewinds are equal, have you used the one you mentioned.

Quote:
Originally Posted by Ben View Post
You have a basic flaw in your test that you checked at idle. Current demands at idle are going to be higher because voltage output is a bit lower.

94-97 auto alternator is going to be your best bet. IIRC the difference is 10A. After that, you'll need to get an alternator rewound. There's a place local to me that does it... I'm sure there are others.
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