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89 mazda rx7 alternator modification


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rhythmicnoise 
Member - Posts: 19
Member spacespace
Joined: July 13, 2007
Location: Indiana, United States
Posted: February 22, 2008 at 5:18 AM / IP Logged  
As the title says, I'm looking to modify my 89 rx7 alternator for a higher output. From the factory they came with Mitsubishi alternator part # A2T18874, or N370-18-300, N370-18-300A, N370-18-300B. I believe they were rated at 90 amps.
I'm running a JL Slash 300/2, Zapco Studio150, and an Alpine V12 that came with the car. It's a 4 channel and I think it does around 30 watts/channel. Soon I will be adding a Ford Taurus electric fan. I believe it draws around 30 amps at startup and 8-10 during operation. I'm not sure how relevant this is, but I've got an aftermarket turbo boost gauge, and will be adding a wideband A/F system with gauge. I don't know if those 2 gauges pull enough power to matter. With lights on, and a/c or heat blowing and stereo playing my volt meter will barely top 12volts. And that's without the e-fan or O2 system wired in.
I'd love to find a source for alternator parts and rebuild mine into higher output. I'm not sure what I should shoot for in terms of output in amps. And I haven't been able to find any online sources for parts. I've found direct replacement parts for my model Mitsu alternator, but no info or parts on upgrading/modifying.
Any help would be greatly apreciated
n2audio 
Copper - Posts: 95
Copper spacespace
Joined: March 02, 2005
Location: United States
Posted: February 22, 2008 at 1:42 PM / IP Logged  

I had an '88 in college - cool little car.  One day on my way to class it just died.  4 shops later (one guy called his shop "Rotary Dr.") it still wasn't running and my dad ended up selling it for almost nothing.

flip through your local yellow pages for auto electric - make some calls.  A lot of shops can rewind an alt.

However they can't just build it to whatever current you want.  There's only so much room in there.  I was told by a shop a few years ago 20-40% is about all you're going to get depending, of course, on what alt they're working with.

A lot of cars use mitsu alts.  You might be able to find a bigger replacement that will bolt right in.

I know a lot of older Fords did - I'm not sure if the new ones do.

I had an '88 tbird with a 75A alt and was able to bolt a 110A out of a '90 Super Coupe right in  (yes, they're both thunderbirds but the engines and electrical systems had VERY little in common)

rhythmicnoise 
Member - Posts: 19
Member spacespace
Joined: July 13, 2007
Location: Indiana, United States
Posted: February 22, 2008 at 2:44 PM / IP Logged  
RX-7s are definitely fun, I've got a convertible which I imported and swapped a JDM turbo into.
I can swap a 3rd gen RX7 alternator that is rated at 100 amps with minor modifications. I'd need to have my pulley bored and have a spacer welded on.
I'd really just like to crack open my extra alternator and see what I can do with it. I've found a local shop but I need to find out what kind of output I'm looking to get out of the alternator. I need to do some reading about the calculators that are available on this site. I've got 3 amps that push a total of about 600 watts (one of the amps came with the car so I'm not sure what specs it has...I'm guessing high). Right now the factory gauge reads just over 12 at night with lights on, stereo on and heat or a/c blowing.
I've got one aftermarket boost gauge and will be adding up to 2 possibly 3 more gauges. I doubt they put much strain on the electrical system though. I'm going to be adding a ford taurus electric fan which will put a decent strain on the electrical system. I think 30 amps or so at turn on and 8 amps or so constant.
n2audio 
Copper - Posts: 95
Copper spacespace
Joined: March 02, 2005
Location: United States
Posted: February 22, 2008 at 3:44 PM / IP Logged  

For comparison --

In my '88 Tbird (turbo coupe) I originally had a 75A alt.  In turbo coupe circles it was well known that alt was undersized WITHOUT any add-ons.  The car had pwr seats/windows, fog lights, dual elec radiator fans etc.

In my broke days I ran various different budget amps at 300-600w rms - never any signs of much stress on the electrical system.  I slowly built up to about 1000w rms from a pair of high quality amps.  At idle with one of the fans on it wouldn't maintain 12v w/the system playing loud, but at 2K or so it would maintain about 13v.

I ran it like that for two years before the alt finally died - it had 226k on it.

That's when I opted for the SC 110A.  With all accessories on and playing Techmaster very loud it maintained 14v.  35A made a WORLD of difference.  It ran that way for close to 2 years with the same old Wal-mart battery that had had been run dead probably 10 times.  I eventually put the car out of its misery during some "spirited" driving late last summer at 283k and about 14 psi :)

rhythmicnoise 
Member - Posts: 19
Member spacespace
Joined: July 13, 2007
Location: Indiana, United States
Posted: February 23, 2008 at 12:36 AM / IP Logged  
From the RX7 forum I'm learning that the most I can expect to increase the alternator is to 120A..at the most. Oh and the alternator I have is 80A. But if I can do the work myself, I'm out only parts. Now for finding those damn parts.....
atsronnyats 
Member - Posts: 2
Member spacespace
Joined: October 29, 2005
Location: United States
Posted: February 23, 2008 at 8:35 PM / IP Logged  
weird i have and fc3s too also looking to upgrade and this post happens to be on the first page luck. dude i called i guy from ohio generators (a renound highamp alternator company look them up) and he comfirms it the misubishi case is only big enough for 120 rewound and yes the stock fd has 100 amp i have a 88 vert with 70 amp stock. im a member to rx7club.com forum (atsronnyats screen name hit me up) lots of info their not only on what you have but what you may want to do. me personally i took advice from both the guy from ohio gens and the guys the forums advise and have decided to put a gm alternator (decided to go with one from 95 chevey caprice police package 140amp the case is just like if not a cs130 fyi) with some mods to wiring it is very possible and easy at that using alternator wiring plugs from your local napa (they kepp them on hand) here is some help links on this topic as a whole....
---the first are very helpful diagrams about our alternator btw 89-92 is a series 5 which you have so and fd alt. isnt much trouble
---the third is probably the most helpful that is if you'd to switch to a gm and dude it is the way to go their availibility makes them the cheap and obvious answer for nething above 120 amp on a budget
---the last link is just a random link for an fd alt i thought i throw in for doodies and giggles
http://www.rx7club.com/attachment.php?attachmentid=199213
http://www.rx7club.com/attachment.php?attachmentid=170065
http://www.rx7club.com/showthread.php?t=504471&highlight=alternator+swap
https://00dfde1.netsolstores.com/index.asp?PageAction=VIEWCATS&Category=859
newho let me know what you think after you give it a good evaluation and btw us Rotary/rx7 must stick together man remember pistons suck neway

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