Alternator Options?
 

So I think it may be time to put a new alternator on my car, that or just do it now before the current one I have on goes bad as it sounds like one of the bearings may be going bad. I was wondering what my options were on alternators as I would like to get one that puts out a decent amount of juice. Anyone out there have any sudgestions?

FD alternator is probably the easiest. 100amp I believe?

Is there any mods that need to be made or is it something that will bolt right on?

That's correct - FD alternator is rated at 100A. For a swap into an S5, the wiring is plug & play. Wiring into an S4 requires some mods, and I've seen that discussed on the other forum.

What I don't know and would like to find out for myself is can you swap the FC alternator pulley over to an FD alternator without any machine shop work? FC's are v-belt, FDs have serpentine belt pulleys. I *think* the FD alt has a larger diameter shaft, which would mean the FC pulley would need to be bored out to fit.

Most use a pulley designed for the FD alternator to be used in FC applications. It properly spaces belt grooves to align with the water pump and crank pulley.

I got mine from japan2la, a forum member on 7club that made pulleys specifically for this application, and even made them in many colors. I am not sure he is around any more. Occasionally they pop up used.

https://lh6.googleusercontent.com/-z...313_175507.jpg


http://www.rx7club.com/attachments/2...altinstall-jpg

Brian/japan2la is still around and doing just fine. He unfortunately got himself in a pickle playing a middle man for some JSpec engines where his supplier basically f'd him royally and left him holding the bag. I personally bought two TII engines from Brian 5+ years ago that I dropped straight in and not a problem to date. Daily drive both of them. So from personal experience the infamous engine situation was an exception from the norm, but the 7club bull dog couldn't see past that.

I'm using his pulley on FD alternators I put in both those swaps. In one I didn't use any Loctite, the nut came loose, and the pulley got damaged. To make the offset correct, the full thread isn't available for the mounting nut as you can see in FerociousP's picture above. So Loctite is a must. But Brian replaced and shipped it for free despite my operator error.

Anyway, I'd bet he is the manufacturer for the ones Mazdatrix is selling as I've never seen as good a plug and play FD v-belt dual pulley from anyone else. He makes great stuff and is/was a great supplier of all things RX7 for years, but bad luck threw a wet blanket on that.

I'd spend the extra money and order his Titanium one via Mazdatrix. About double the price, but worth it IMO.

Try and find this eBay seller: "ace_alternators"
http://www.ebay.com/sch/ace_alternat...p2047675.l2562

I have not bought one of their upgrade alternators, but I've just bought a starter for my 1987 Turbo II.
These guys are one of the CHEAPEST on eBay.
My alternator came out to just $49.00 + $15.00 shipping, USPS Priority 3-day.
Other sellers were asking $70+!
I just installed it, and that thing zings!

These guys sell:
S4 alternators: 70A (stock?), 110A
S5 alternators: 80A (stock?), 110A, 140A
FD alternators: 100A (stock), 110A, 140A, 150A
(This is what is currently listed on their eBay items for sale listings.
I dunno if they offer an S4 / 140A...
These things are priced UNDER $200 EACH.

I'm going to buy one of these - probably FD / 150A - soon.
I currently run a stock FD rated at 100A.
I run a stock sized alternator pulley, so the system is not underdriven.

I'm telling you now, my car barely keeps up the voltage at night, idling, with headlights.
When my electric fan goes on, system voltage goes under 12.0VDC.
I haven't tested the actual current on the alternator, but it does have a problem dropping it's current field when I kill the engine in it's current configuration (i.e. field lead +12VDC all the time) - "S" or "R" terminal labeled in above diagram.
I have a circuit breaker inside the car, so I reset this to drop the active field on the alternator, or else there's parasitic current draw.
If I remember the #'s, it was about 1.0A before reset, and 0.3A after reset.
Let me go check the #'s tonight just to make sure...

I'm starting to put in a stereo system, so I want big amps.
Since I had a good experience with their starters, I'm willing to try their upgrade alternators...

If I had the BUCKS, I would go for a MechMan alternator for $549!
240A!!!
http://store.mechmanhighoutputaltern...rs/mazda/rx-7/


-Ted

I have the mechman 240 amp alternator. I bought mine about 10 years ago for my racecar . The original owner of mechman was Dennis Moore . A great family friend.. This is by far the best alternator money can by !!!!!

I've always wondered what the actual output of a FD alternator on a S4/S5 setup is. Is the main pulley/alternator pulley diameter ratio on the FD maintained with the adapter pulleys on the FC?

I'm seriously considering the 140A S5 alternator on eBay due to my e-fan and fuel pump even though I've deleted a whole bunch of circuits (A/C, stereo, defroster, etc.)

The FD alternator has a bigger output shaft. So you have to enlarge the S5 pulley to get it to fit. (yes start the BAW jokes now) Otherwise it should output the same voltage regardless of what car it is in.

Unless it's severely underdriven, output won't change much, idle is a different situation though which is why I prefer to NOT underdrive alternators. I also think that people that remove airpumps without a solution are asking for problems, but that's just me.

Also.... I don't know which one it is, that diagram MAY be it..... double check the wiring diagrams with the FSM. I have had sooooooo many problems with alternators in the past because someone posted up a diagram like that on TeamFC3S back in the day that I printed out and it was WRONG!!!!! What I'm going to do now is find an FD or S5 connector and wire it up ONE TIME and mark everything..... I don't know how many alternators I've blown because the INTERWEBZ WERE WRONG!!!!!

It would be nice if there were a smaller alternator pulley available to offset any underdrive caused by a reduced main pulley diameter. I'm underdriving my water pump to avoid issues at engine speeds over 8000 RPM. In order to increase the water pump pulley diameter you have to reduce the main pulley diameter so even though my alternator pulley is the stock diameter the alternator is still underdriven.

Based on MY understanding of the S4 and S5 wiring diagrams it looks right. It has the field signals (L terminal) coming from the dash (idiot cluster in S5 and CPU in S4) and the sense signals (S on S5 and R on S4) coming from 12V sources (constant on S5 and switched on S4).