Niaxe

Hello!

I made a post recently about my alternator issues on my 2002 NB miata with haltech. After long 22 years of service, the alternator decided to commit seppuku and stopped charging my battery. I installed FD RX7 Alternator on my NB and everything seems to work great for now, so I will write some tips for future people who want to do this mod. This will not be an instructional post, but just gathers information that can be found from other many posts.

Why FD RX7 Alternator?

Unlike NAs, NBs' alternators are controlled by ECU. It's a pain in the *** if you want to go standalone route because you would have to make standalone ECU control the alternator. The general consensus of the community seems to be that standalones don't do a very good job controlling NB alternators. If you swap self-regulating alternator it's one less thing worry about and you don't need to tinker with ECU.

This article on revlimiter is pretty good and gives some good info on available options. I decided to go with the FD alt because NA8 alternators with 65-70 amps might be too low for my needs (SPAL fans, stereo, bigger pump, etc), while KIA alternators might be new but some people have issues with them. 100 amps on FD seems pretty good and it's not too much more so you shouldn't need to get thicker wiring.

Tips

1. Remanufactured FD alternator can be bought on rockauto
2. You don't actually need to grind this alternator. This step can be avoided by using a slightly larger belt. I used Bando USA 4PK890, I believe the stock belt if 4PK885 (so it's a tiny bit bigger). The benefit of going this route is less work, plus can still use warranty.
3. You will also need to buy M10-1.25 X 110mm bolt with a thick washer (or two thin ones), the bolt on the stock alternator is too short for this one.
4. There are other instructional posts how to do this swap, and some of them tell to get a pig tail connector from NA8 Miata. I did not have to do this step, I still ordered it, but my stock pig tail connected beautifully without any modifications.
5. I also suggest to swap pulley from NB's alternator on FD alternator (FD alt has more grooves), but I am not sure if this step is necessary.
6. You need to do some wiring changes to basically disconnect ECU control of the alternator and let it self regulate. There are instructions how to do it, I suggest this
   video
   and this
   one
   (the second video will also teach you how to check for electric continuity to make sure you have correct wires). My haltech was installed at the shop so I had no insight into how wiring was done. I found these wires on pins directly plugged in to Haltech
7. I did not have to use car jacks and my car is lowered too! I lifted it up just a bit, but most of the work was done through the top of the engine bay.
8. Dont forget to disconnect your battery lol

Issues

I did run into some issues but sorted it out. Once everything was installed and we started the car, we heard a very loud pig squeal like noise. We thought the culprit was orginal FD alternator pulley with more grooves, so at first we tried to place the belt on inside grooves and then on the outside grooves but none of that helped. The belt was also slightly shredded near pulley and lots of that rubber flew in into alternator. So we swapped in NB pulley. Even after that It still squealed and even slightly smoked. Turns out that the belt was tensioned too high and the smoke was due to rubber parts getting into alternator. After we played with the tensioner and cleaned alternator, everything ran greatly and battery was charging at 14.18 volts. So I am not sure if Tip #5 is necessary, some people did not do that step and had success, but I would probably recommend to do it just in case.

Hope this helps to all future people who ran into the same issue!