innertwist

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Whether or not you still have the thermal reactor, if you've blocked off your air control valve (perhaps to eliminate backfire) there's no longer any point to the part time trailing ignition of SA's. Here's how to disable it on an 1980 for full time ignition without changing the distributor. This is only for RX7s that have an 80' style electronic distributor. 79's are covered elsewhere.


Option 1 - The easy way
Locate the ignitor box on the drivers side strut tower. It looks like a tin box with two large power transistors bolted to it. There are four harnesses coming off of it. One is a large harness with a 6 pin connector that goes to the distributor. Another has four wires and connects to the ignition coils. Another one is simply a ground wire. The last one is a two pin connector off the ignitor box that goes to the emissions circuitry. You guessed it, unplug that one. DONE! Well, almost...

To confirm that everything is in order, and to let you know if you're ever having a trailing ignition problem, connect the tach wire to the trailing coil. Since this wire is a little short, I suggest that rather than building an extension or, god forbid, splice the wire, that you merely swap around the function of the coils. So we want the coil towards the front of the car to be our leading and the one in the rear to be our trailing. Remember that harness going from the ignitor box to to coils? Well, disreguarding the positive leads, there are two wires that control the spark. The black connector which has a yellow wire with a green stripe is for the leading coil. The blue connector which has a blue wire with a yellow stripe is for the trailing coil. Reverse the connection of the two. The trailing coil should now be the one that has the tach connected to it (there should be two spades connected to it). Be sure to reverse the ignition wires too.

Start her up and hit the throttle. The tach should rise smoothly. If you were to reconnect the wire it would show idle very well but would get highly erratic the higher your rpms get.


Option 2 - The adventurous way
The first way was way too easy, and now you have this clunky box with all this useless circuity wasting space. It also makes too tempting a candididate for wiring up a a coil pack ignition. So, remove the box from the car. Pry open the lips of the box cover to remove it. Unscrew the circuit board from it and cut every wire as close to the board as you can get. Toss (or better yet, recycle) the board, but keep the standoffs for it. While you're at it you can yank out the two wire connector - it's not going to be spliced to anything. Assuming that you're not doing any fancy ignitions at this time, make the following splices:Bolt the internal ground spade connector down and put the standoffs and their screws back on. It should look like the picture below. If you chose to leave the emissions connector in place, there will be a black/red wire and a green/orange dangling about, so don't be concered. At this point you could very well put the box cover back on, mount it, move over the tach signal as described in option one and be done with it.

If you wish to make a DLIDFIS or 2GCDFIS w/ TT ignition, you now have a nice empty wiring box to assemble it in. I haven't yet done this myself, so I can only offer ideas.

If you're doing DLIDFIS, you could sink the third ignitor to either a plate cut to mount where the circuit board used to be, or mount it to the box cover. If you do sink it to the cover, be sure it has a clean contact patch. The wires that you'd be splicing are the red (splice #4) and black wires going to the leading ignitor. Also, it's probably safest to use another 80' ignitor (J105) rather than the J109s found on FBs. I say this having examined the magnetic pickups in both 80' style dizzys and FBs. In FBs, as the induced magnet is spinning it first ramps toward the pickup coil (to charge the ignition coil) and then it quickly drops away for the spark. In an 80' it's just the opposite. It quickly rises toward the pickup coil for spark and then it slowly ramps away for charging. My guess for why this was changed is this: in the 80' style, the ignition coil has time to bleed off charge before it fires, leading to weaker spark and hence greater emissions than the FB style at low rpms. Of course if this were true, then the 80' style would also have a stronger signal at high rpms . I vaguely remember hearing that you could use an FB ignitor with an 80' style dizzy provided you reversed the +/- connections, but I can't substantiate this.

With the transistor trick, you can have the wires of the leading ignitor feed back into the box and have your circuit mounted where the old circuit board used to be. The output of the circuit would then have to be fed back out of the box to the FC coil/ignitor. If you're doing basic 2GCDFIS then there's no point to even gutting the box! (unless you don't trust that pesky bit of circuity - I don't either); You just have to connect the leading ignitor to your FC coil; it's the one on the right when the box is properly mounted, with the B/W and Y/G wires).

Of course, for any of the ignition options, you don't have to disable the part time trailing. You could keep the circuitry intactly connected and work with it that way. You will have to find other locations to mount your supporting circuits, which is no big deal. Although, an upgraded ignition does rather defeat the purpose of the part time trailing ignition system: to get gas into the exhaust manifold.

Jeff20B

iTrader: (13)

Good job.

t_g_farrell

iTrader: (1)

I just came across this post in a search for something about coils. I guess i missed it the other day. This is an excellent mod for 80 SA. I've been meaning to disable that crap but haven't done the homework to figure it out. Thanks for saving me the time.

The bit in there about the distributor mag pickup is interesting. I wonder if that means 80 distributors are marginally better to use than FB ones for higher rpm applications? Also, how does this play to the way the TT would work? Does it affect the TT positively or negatively? I'd like to see gsl-addict chime in on the merits for starters.

Archive this thread. Great write up.

innertwist

iTrader: (3)

From the ignition specialist himself, wow! Thank you!

I sincerely doubt there's any difference performance wise caused by the pickups. That portion is really just wishful thinking on my part.. We're never really know though unless there was hard data on the subject, Any takers?

Seeing as FBs and 80's have the same exact coils (Diamond LB-84) and they're listed the same, they must take the same input signal. Therefore, the output of the ignitors should be the same and you should be able to use the same transistor circuit. There is a catch: a generic coil can be fired on either a positive or negative swing and I don't know if the 80 does this the opposite way. The tt circuit, being a ttl not gate, would fire at the wrong time if it were the opposite. I doubt it though as the coil is probably polarized and would fry if fired at the opposite pulse. Wire it up and see, it'll most likely work. Post your results

Thank you also for the promo. Maybe you could post that on the "what's archivable" thread?


I have found this thread on the forum where someone did use J109s on a 1980 dizzy to good effect. Sadly the pictures are long gone and I can't find it mentioned anywhere if they're wired up the same. For a DLIFDIS setup this would make it alot easier, not just for availability but also because it's very cramped mounting the larger J105 inside that box.

There's also one mistake to note. Don't throw away the circuit board right away if you're planning to make a plate/pcb that will mount inside the ignitor box. Use it as a template.

I've started making a DLIDFIS setup using a plate. I've got the plate already cut and the J105 ignitor mounted, but I'm still looking for a good place to mount the coil. My car still has A/C, the hot start assist, the ignitor box (of course), and I'd like to leave room for a strut bar in the future. This makes for a very crowded arrangment, So far I'm leaning towards mounting it on the A/C compressor. I'll post pics once I have daylight to work with and get it all sorted out. Any suggestions on where to mount the coil with these prerequisites? FC coil mounting suggestions would be good to have here too.

7aull

iTrader: (2)

Thanks! Don't get much 80-specific tutorials so this is GOLD! - thank you Innertwist
Stu Aull
80GS
Alaska

t_g_farrell

iTrader: (1)

I mounted my 2G coil on the drivers side fender side wall (I want to keep my AC as well) where 3 relays are mounted (hot start assist, ac relay and the automatic kickdown relay). I only need to keep intact the AC relay so I can keep my AC going. They mount on a small rail that is attached to the side wall inner fender. You take the relays and turn them around and mount them under/behind this rail and then you can bolt up the 2G coil by the two of the bolt holes with it on its side with the plug wire attachments facing forward. It rests on the inner fender on the other side which I placed a piece of fuel line slit in half over to cushion it and prevent rattles. Its a great location. The stock wires reach and I can keep my AC as well. Plus I don't have to cut or mangle anything to put it in. I'll get a picture and update the board on it later in the spring when I have it out and about.

innertwist

iTrader: (3)

Having been called not to come into work for the past couple days, I finished my DLIDFIS setup. The first thing I made was the plate to mount the ignitor on the inside of the ignitor box. I used a drill and jewelers saw to cut some 14 gauge steel. I then used a dremel diamond wheel to finish off the edges. I sized up the ignitor and then cut wholes for it as well. I used the screws for the ignitor to thread the holes in the plate.. This is what it looked liked when it was fininshed:



Being so large, once the J105 is mounted there's no longer any room for the stock connector or even spade connectors. Wanting a clean installation, I cut down a connector as short as I could without breaking the retainer clips for the spades. This not being short enough to feed the wires out and around it, I also cut slots into the side of it for them to feed through.



Of course, the wires for the connector had to be cut down too. Here's a picture of the shorter one after I soldered a lead to it.



In wiring the box, I tried to make use of as much existing wiring as possible. For the B terminal of the internal ignitor, I made a four wire splice using the existing Black/White and Red/White wires, along with the positive lead for the new leading coil. For the positive lead of the other leading coil, I soldered directly to the B spade of the existing ignitor's connector. I could have forgone that last splice and just used a bridge wire between the coils. The rest of it was fairly straighforward. The last thumbnail is of everything assembled inside the box. Note the two holes on the box cover, I'll get to that in a minute.

innertwist

iTrader: (3)

My mounting for the coils was a little less elegant. I ruled out mounting them on the A/C compressor since I didn't know if they could withstand the constant vibration. At first I was considering just using the stock location for two of them and only finding a place to mount one. This would have been clean; I could have made a mounting plate that bolted right to the strut tower, without moving a thing. Then I realized I would have to go out and buy new wires right away... I didn't want to do that just yet :-P Besides, everyone says it's better to have them closer to the plugs (I know, EXCUSES!)
So this is what I came up with. I took the bracket mounted on the strut tower



and welded the bottom part of one of the stock coil mounts to it (removing the plastic clip before welding of course). This is how it looked one after cutting the the bolt holes off the coil mount and cleaning up the weld:



The only thing that had to be moved was the power distibution block that used to be mounted on the bracket. This is why there were two holes on the ignitor box cover, so I could mount it there. This contraption had the added benefit of sticking out just enough for the coils to hang low over the brake line. If I were to ever to upgrade to the transistor trick, my thinking was, I would remove the bracket completely and mount the coil to a custom bracket in it's place. If anyone wants to repeat this, JB-Weld could probably be used in place of the actual weld. The last few thumbs show how it looked installed in my mis-colored engine bay. That extra wire hanging from the distributor doesn't go to anything, I just stuck it alongside the A/C compressor just in case.


t_g_farrell, that sounds like a very good mounting spot for the coilpack, especially if it just bolts up. I definately want to see that.

innertwist

iTrader: (3)

didn't notice but a couple of those were too large to upload, will resize later

Jeff20B

iTrader: (13)

You really went to town. Very cool setup.

I have two J-105s and a few '80 distributors. I discovered the S and G terminals seemed reversed in function when compared to J-109. Then upon seeing the reversed reluctor, it made sense.

innertwist

iTrader: (3)

Here're the last couple pictures.

Jeff, when you compared the pickup signals, did 'S' = '+' and 'G' = '-' for both test setups? i.e. the j105 expects the inverse of the signal the j109 expects on the same channels? I'd like to know to clear up this confusion about wiring a j109.

Jeff20B

iTrader: (13)

I don't remember the details. I bench tested a J-105 and J-109 with an '81-'85 distributor. The S and G terminals' function appeared reversed.

It would be best to test it in real life. Hook it all up and use a timing light. I recently had a chance to do this with some GM HEI ignitors. Compared to the J-109, G=G and W=S on an '81-'85 distributor. The timing was correct.

innertwist

iTrader: (3)

I did some tests on the oscilloscope and determined that J109s can be wired up the same way as J105s. The two should not be wired together on the same pickup, but if you use two of the same type for leading and a different one for trailing it should be fine. Furthermore, these tests confirm that the same transistor trick circuit can be used since the output of a J105 is the same as the output of a J109.