using the Fd alternator. Will this work?
 

If I buy an fd alternator for my 88t2, will my double pulley work on my s5 alternator? I have the rx7.com pulley. Thanks.

Why would you do this? Does the FDs have a higher amperage rating or something? I would contact RX7.com and ask them if I was you. In my experience they have been quite helpful with random stuff like this.

Both of you should utilize the search engine before asking questions or giving advice.

Of course the FD alternator is higher amperage. Why else would there be so much talk about this as an upgrade? I will give your referal to RX7.com is good advise. They know their stuff even if they are Dallas Cowboy fans.

To the OP:

1. The shaft on the FD alternator is larger than an FC's alternator. Use the search engine for this forum's classified for the double pully Japan2LA is selling. Trust me, it is the best alternative out there for the price. There are alternatives, but few if any provide the proper spacing built in so the pulley clears the alternator body and still lines up with the main pulley.

2. Putting a FD alternator in an S4 requires some minor re-wiring. An FD alternator is plug and play in an S5. Use the search engine and you'll find a number of threads that discuss how to do this minor re-wiring for your S4.

Know one thing that doesn't show up much in FD retrofit discussions. An FD alternator casing is simply larger.

If you're running a strut bar, that is an issue as you have a far narrower range for adjustment of belt tension. The fix to this problem is to use a slightly smaller alternator belt. Book calls for a 13320. I went with a 13315. More of a PITA to put on, but price to pay so you can put proper tension on the belt to avoid slippage. No strut bar, 13320 is probably still ok.

s5 pulley will not fit on an Fd alt.
S5 alt is either 70 or 80 amp where as an FD is supposedly 100.

It will if you bore out the hub center(s)...easily/quickly done on a lathe.

It's also worth noting that several other- more common- Mazdas use the same "frame" (alternator body) as the FD and they can be more easily found in junkyards (either for cores or usable parts).

If you have precision machine shop tools and machine shop skills, you're absolutely right.

If not, then not.

Japan2la's pulley is, as I recall, $44 shipped. Minimum shop rate to lathe it would probably be that much, but you still wouldn't have the incorporated spacing. Also, Japan2la's pulley designs around the spacing needed to clear the "lip" on the housing that you don't deal with on an S5 or S4 housing. Unless you grind away at the FD's housing, the "fix" is a larger spacer to move the pulley further away from the alternator housing. But then you have less threads for the pulley mounting nut to grab AND you have mis-alignment issues.

Technically correct answer vs. practical answer.

To be clear, I have no financial interest in what japan2la sells. I'm speaking from trying all sorts of pulleys from different sources. The only one i found that does't require some additional consideration when mounting is his.

+1

Thanks for the input, I might just have mine rebuilt to use my pulley. My friend does have a machine shop, i might just take it there.

Or just buy a good used S4 alternator for $50. I can help you there. I still have my S4 alternator from when I did my swap. I also have the tools to swap your pulley and I can show you real time what I'm talking about regarding the S4 re-wiring and FD belt and pulley situation with a strut bar.

On the pulley, if you go FD, trust me when I say boring out the center is only part of what you'll have to do to make it work. The pulley I referred you to, totally plug and play by comparison.