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FD Alternator Swap

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Old 01-15-08, 03:03 AM
  #26  
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Old 01-15-08, 03:05 AM
  #27  
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fd alt to fc i mean
Old 01-15-08, 07:10 AM
  #28  
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Originally Posted by mike_merryguy
i belive it may make a small difference, thinking more into it i don't know really, would have to do some tests and calculations, i would say maybe a smaller shaft on the same alternator would just make the shaft itself spin faster not nesasarilly the internals or the pully just the shaft, so maybe the larger shaft is just for strength since its a larger alt, who knows, it works lol
If it helps you, visualize the two pulleys (e-shaft and alternator) as direct coupled gears (since they are functionally identical).
Say the ratio is 5:1, the alt gear (pulley) makes 5 revolutions for each revolution of the drive gear/pulley.
Since the alt shaft is affixed to the alt pulley, it too will spin five times- no matter if the shaft is 2" diameter or 1/2" diameter.

Originally Posted by mike_merryguy
...and arn't we changing the pully OD when we go from FD to FC pully?
Maybe a little but what are you going to do?
Remember, the two pulleys use different belts, so the OD is not directly comparable anyway. I'm not sure how one computes the effective OD of a v-belt pulley but in practice I think they're pretty damn close.
The alternator doesn't seem to mind.
Old 01-15-08, 01:17 PM
  #29  
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Originally Posted by plainandsimpo
nope there is no negatives .....in swapping a fd alt into your fd i bought a dual v belt aluminum pulley with the rotor in the front from ebay....
hmm the only bad thing "i" have is that the belts sqeaks no matter much i try to adjust it ....it might be the pulley being new ???iono but this is the one i bought http://cgi.ebay.com/ebaymotors/RX-7-...spagenameZWDVW
not tyring to steal your thread but yea... any ideas guys/???
I bought a dual alternator pulley from Innovative for my FC alternator, soon it will be a real boy...er I mean an FD alternator swapped in.

I had trouble with belts also. The problem being it's hard to find similar length belts even in the same brand belt. There is some variance in their length. I ended up buying every Gates XL belt my local auto parts chain carried at all the different stores (4 total). What I found was that even within the same brand there was different construction. Two of my belts had an inner reinforced layer on the pulley side and 2 did not have that layer....all of them Gates XL belts though. 2 of each kind were similar in length to each other and I matched them up and returned the other 2.
Old 01-15-08, 03:07 PM
  #30  
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I got my fd alt with plug (i have s4) and the double pulley already mounted from silverrotor. Brand New!
Old 01-15-08, 03:40 PM
  #31  
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One negative I've found is, after installin an FD alt, my cheap eBay strut-bar no longer fit.
not that bit a deal though, since I just traded the bar away for some other parts.

So does anyone Have a Strut Tower Bar that will clear an FD Alt?
What kind ? & post pics please.
Old 01-15-08, 03:55 PM
  #32  
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My FD Alt swap is not going so good.

I have the new S5 plug and the double pulley from Banzai. I bought an FD alternator from Auto zone.

When I put the pulley on the FD Alt it binds on the housing. I need a shim or washer ( oddball size and hard to find ) or I need to grind/clearance the Alt housing. It has a small ridge, maybe 1/8 of an inch, that might allow the pulley to spin without a shim.

Still waiting to get the 100 amp project working.

Rob
Old 01-15-08, 05:19 PM
  #33  
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that shim is deffinatly needed, if you look at the stock pully you can get the dimensions of the spacer that is on the back of that pully and probably find something, somewhere, havn't started looking for that yet myself...

and i think the spacer would be required becuase without it the pully will not line up with the water pump and main pully, cuasing your belt to snap
Old 01-15-08, 05:35 PM
  #34  
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Originally Posted by 13angryB's
So does anyone Have a Strut Tower Bar that will clear an FD Alt?
What kind ? & post pics please.

Not a clue what brand this is, sorry.
Old 01-15-08, 05:36 PM
  #35  
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I couldn't find it doing a search, but I remember reading that someone used a spare crush washer from their oil cooler lines as a shim.
Old 01-15-08, 07:03 PM
  #36  
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Originally Posted by mike_merryguy
i belive it may make a small difference...
As has been stated by several people, it makes no difference. The outside diameter is all that matters.

and arn't we changing the pully OD when we go from FD to FC pully?
Only if you get a pulley that's a different outside diameter. The stock FC and FD pulleys are very close in size.

Originally Posted by 13angryB's
So does anyone Have a Strut Tower Bar that will clear an FD Alt?
What kind ? & post pics please.
Genuine Infini strut bar. See pic in sig.
Old 01-15-08, 07:11 PM
  #37  
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The bar in that pic is a corksport bar.
Old 01-15-08, 07:48 PM
  #38  
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I need to grind/clearance the Alt housing. It has a small ridge, maybe 1/8 of an inch, that might allow the pulley to spin without a shim.
The above is what I did and have been running strong for a week. Drove about 400 miles over the weekend as well.

GG
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