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need help with 12a ignition wiering

Old 08-09-10, 05:03 AM
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Question need help with 12a ignition wiering

i bought an early 12a from an rx7 a while ago for my 929/rx4 wagon project,
the thing is, i dont know how to wire it upp.
im going to run an msd direct foire hybrid wastespark system.
so i partially know how to connect the leading coils.
what i need help with is how im supposed to connect the trailing. i have the distributor with separate mounted igniters and the gray 6wire cable.
how do i connect everything up? and are the wire colors the same on that distributor as the newer one with the internal igniters?

all this retro stuff makes me miss my Fd (in storage)
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Old 08-09-10, 09:58 AM
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2 things; if your running a DFIS or wasted spark then trailing isn't really needed.
Its your call but it simplifies things a lot.

If you using an SA 80 distributor, your going to get a poor signal for the igniter
(MSD in this case). I discovered that the 81-85 12A dizzys have a better inductor
wheel designand work better than the first electronic dizzy mazda used in the 80
SA 12a application. See the link in my sig for TFIDFIS for details on what I found.

Hope this helps you some, theres also wiring diagrams in my thread for hooking up
my HEI modules but it should be straight forward to throw an MSD in there.
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Old 08-09-10, 06:34 PM
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Question

Originally Posted by t_g_farrell View Post
2 things; if your running a DFIS or wasted spark then trailing isn't really needed.
Its your call but it simplifies things a lot.

If you using an SA 80 distributor, your going to get a poor signal for the igniter
(MSD in this case). I discovered that the 81-85 12A dizzys have a better inductor
wheel designand work better than the first electronic dizzy mazda used in the 80
SA 12a application. See the link in my sig for TFIDFIS for details on what I found.

Hope this helps you some, theres also wiring diagrams in my thread for hooking up
my HEI modules but it should be straight forward to throw an MSD in there.
ok. i think i can use you diagrams.
im going to use the 80 distributor for now since i have nothing else available.
but as soon as a good cheap 81+ appears, i will try to get one
as for the trailing, im going to use that, if for nothing else, the economy reason
by the way. how do i connect the 80 trailing wires to the igniter(the j-105 one)
and what about the external transistor on the distributor(the cylindrical shaped thing on the outside of the distributor with the short black cable,) what does that connect to?
(im new to this old stuff, im used to the FD and all its computer stuff )
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Old 08-11-10, 10:08 AM
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The external "transister" you refer to is just a capacitor to reduce ignition noise
which can interfere with some radios. I think I left mine disconnected for now.
My radio sounds fine.

You really won't get very great results using that 80 dizzy. Trust me on that. You
can pick used ones all day long on here for ~$15 or so.

I'm note sure about the j105 wiring. I'd look to the FSM to figure it out. The
wiring diagrams but also the testing igniter section as well.
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