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RX-7 2nd Gen Specific (1986-92) RX-7 1986-92 Discussion including performance modifications and technical support sections.

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Old 07-27-2014, 09:23 PM   #1
2gslse
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Pete, I would just run a stock FD alternator on your car and get the correct pulley to run the v-belt. I am running a FD alt on my FB and have 2 044 bosch pumps, 17" electric fan, electric PS pump and all the other power goodies and it keeps up fine so far.
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Old 07-28-2014, 04:38 AM   #2
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Quote:
Originally Posted by 2gslse View Post
Pete, I would just run a stock FD alternator on your car and get the correct pulley to run the v-belt. I am running a FD alt on my FB and have 2 044 bosch pumps, 17" electric fan, electric PS pump and all the other power goodies and it keeps up fine so far.
A stock FD alternator should have enough juice for anything I'm running now, plus whatever I might add down the road (e.g., stereo upgrade/e-fan).

Quote:
Originally Posted by RETed View Post
I'm going through a bunch right now...

I already run an FD alternator on my FC 13BT.

I've got a "160A" FD unit off of eBay for like ~$160.
It's a disappointment.
The damn thing barely idles @ ~13.0VDC.
Loaded down at idle, it runs about 12.0VDC.
The seller was named "HighAmpSpecialist" or something like that.

One of my previous posts talks about having good experience (rebuilt starter for my FC) from an eBay seller "AceAlternators" (or something like that), but they don't offer an FD unit anything over 130A now...
They used to have a 160A, but I haven't seen that unit for sale for a few months now.

There's another eBay seller called B&R or something, and they offer FD alternators in the 160A range for about $200?

Check the feedback. and there's negative comments of the upgrade alternators being bullsh*t.

I would highly recommend to go with a MechMan unit if you got the bucks...
Last time I checked, it was about $330?
Yes, it's a little pricey, but these things are rated like 250A...
http://www.mechman.com/

-Ted
Yup, I recall you mentioned AceAlternators on ebay, and took a look there. They have S5 drop-ins for about $140 that are rated 110A, which is roughly the same as a stock FD alternator. They didn't show anything in stock above 110A. One year warrantee on it FWIW. I might give them a shot as it's enough juice for my current & future needs, and I can reuse the dual belt pulley I already have.

Also heard good things about the Mechman alternators, but that is overkill & too much coin for my needs.

Quote:
Originally Posted by TitaniumTT View Post
I'm not sure these really hi Amp alts are all that necessary unless you're running one or a few accessories that pull some serious Amps...
I run a stock FD alt and I seem to not have voltage issues. Although I've rewired the car and the charging and the main distribution wires so voltage loss isn't a concern to me.
That being said I don't get a full 14.4volts, it's usually around 14.1-14.2 but I'm still playing around with resistance values on the excite wire.
Stock S5 alternator is about 70~80A at most; I'm just looking for a better reliability margin to ensure the fuel pump gets enough juice when I'm running all the stock electrical loads, and any future changes (big stereo, e-fan, etc.). So something in the stock FD range (100~110A) should be fine.
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Old 07-28-2014, 11:40 AM   #3
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Just for reference...

1987 Turbo II
13BT
Haltech E8
Electric fan - measured @ 17A of steady-state current pull
HID's - "35W", 4300K
Stereo:
Alpine 7618
Rockford Fosgate PA-1HD
Rockford Fosgate EPX2
Currently running an Adcom GFA-5275, but have also ran Harman Kardon CA260, Precision Power 2075AM, Adcom GFA-4403 (bridged)
Only running a pair of separates at the moment: originally a Diamond Audio D3 D351, but tweeters were bad, so replaced them with some Polk DB1001's

Everything on (at night), the HKS voltmeter will dip under 12.0VDC.
My original silverrotor FD alternator was able to hold 13.0VDC, but it had a problem with shutting off the exciter field in the alternator when keying off.
I am more comfortable having everything over 13.5VDC at idle with it loaded down, and ideally 14.5VDC...
I am eyeing the Mechman alternator, cause it claims it'll pump out 100A of current @ idle!


-Ted
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because you're only as good as your backup
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Old 08-01-2014, 01:12 PM   #4
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FWIW, I ended up picking up that 110A alternator from AceAlternators on ebay. I have no means of measuring current draw to verify the 110A upgrade, but here's the voltages I'm seeing with it:

@ 750 RPM idle, low beams on + fog lights on + A/C fan on max = 12.6V. Nudge the idle up to 850 RPMs or higher, and it goes up to ~13.6V.

With same loads switched off, from low idle and up nets between 13.6~14.5V.

Also I have an alternator installation tip that might be useful if anyone runs into the problem I had. This particular alternator didn't want to slip over the water pump housing at the pivot point - it was maybe a few thousands of an inch too tight, and there was no persuading it to fit. After much cursing, and considering shipping it back, I had a brilliant idea... Just loosen the 4 bolts that hold the alternator halves together about a 1/4~1/2 turn each; that "spreads" the alternator half's just enough to get it to slip over the water pump housing pivot point. Once the pivot bolt was in, I just tightened the 4 alternator bolts back down and everything was fine.
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Old 08-01-2014, 02:32 PM   #5
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Quote:
Originally Posted by Pete_89T2 View Post
FWIW, I ended up picking up that 110A alternator from AceAlternators on ebay. I have no means of measuring current draw to verify the 110A upgrade, but here's the voltages I'm seeing with it:
I picked up a Mastech MS2108A as a cheapie option for now.
You can get them for under $50 shipped - check eBay and Amazon.
Until I can scrape up the skrillah to get a Fluke for several hundred $, the Mastech is "close enough" - who cares if it's off by 20%?


Quote:
@ 750 RPM idle, low beams on + fog lights on + A/C fan on max = 12.6V. Nudge the idle up to 850 RPMs or higher, and it goes up to ~13.6V.

With same loads switched off, from low idle and up nets between 13.6~14.5V.
It sounds like you got a better unit than I did.
I've never seen mines go over 13.9VDC, and it's an FD unit rated to 150A... :P


-Ted
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because you're only as good as your backup
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