They will swap easily.  One is probably an E12-80 and the other an E12-92 (or is it 93?).  The E12-80 is the simple one.  The extra plug on the other one is a different way to advance the timing for emissions purposes, replacing the extra pickup coil method.

bty both modules work the same. If you use the extra connector on the turbo unit,, you get less advance when activating it. If you do not use it then no worries.

I've read of erratic timing with one of the odd modules, -92 or -93.  Fixed by adding a power line to it.  Just saying, somehow,there's a way to have a problem, if it's not the E12-80.  But you can change them with the distributor installed so not a big deal if you start with one, then switch.

 

Found one thread (nasty people...).  classiczcars even got a reference for a picture. http://community.ratsun.net/topic/56630-e12-92-retard-or-no-retard/

Edited March 3, 201510 yr by Zed Head

Color this one solved! Just got back from driving my 77 after bypassing TIU,and installing ZX dizzy.My favorite Z doesnt have to live in garage for a couple of weeks.I went ahead and just switched modules so I didnt have to deal with any unknowns. You were right Zed.the right one was an E12-80. Thank you for all the help and hopefully in future Ican help some of you out.Karma is a wonderful ideal!

I have one more question regarding the 280z to 280zx dizzy swap to bypass TIU. Should I switch to a zx coil or does it matter? It ran good,but I dont want to run chance of prematurly burning up 280z coil if I can help it,especially since it was new yesterday. Ithink I remember reading a thread that said you should run 280z and 280zx dizzys with thier respective coils.Does anyone know the truth behind this?

That's a good question.  I think that the ZX module's have current-limiting technology like the HEI modules, which should work with any coil of higher resistance than stock.  But I can't find any documentation, and the ZX coils are 0.84 - 1.02 ohms, higher than the HEI's ~0.5 - 0.7 ohms, and higher than the early 280Z's ~ 0.5 ohms.  .  You might measure yours, since aftermarket parts tend to vary.  If you're around 1 ohm, you're probably fine.

 

Note also that the manufacturer's spec their parts to last 10's of thousands of miles.  If your coil's not getting hot it's probably not a problem.  It's the heat over time that bakes them.

Thanks Zed Head. I will measure coil tomorrow and make decision from there. Todays been a pretty long one for me. Thanx for the help,and I will give back whenever I can.

I looked up that link you posted on the modules Zed Head...yeah-nasty,but the info was golden.thanks again.

Well, after performing 280zx ignition upgrade on my 77 Z,I had thought problem was solved except for tach issue. Today I drove it for about 2 hours straight then parked it with no problems. I took it out half hour later ,and she began having same symptoms as before upgrade. I do have good spark coming from coil right after it dies and it will start after 1 or 2 minutes, but die again after 20 or 30 seconds. Tach also immediatly drops to 0 RPM like it has rock tied to end of tach needle. Could I have burned out module [new],allready,or could this indicate a different problem.I love these cars, but they sure suffer from some uncommon malfuncti

The ECU's pin #1 is on the same wire as the tach signal.  I wonder if a bad tach could cause the ECU to stop working right.  Or if a bad ECU could cause the tach to stop working even though there's spark.  Yes, sometimes you can stuck in a weird place.

 

Have you tried tapping/beating on the side of the ECU when it dies?  Others have reported that that has temporarily fixed bad ECU connections.  The solder joints crack and lose their connection at the main connector.

 

I know a trick you could try to take the tachometer out of the picture but it might make you uncomfortable. 

So here's a possibility - your tachometer might be losing ground, or failing, causing a loss of ground on that wire.  From my own experience, the EFI system's will not work if the tachometer is disconnected.  So the "trick" i mentioned would be to find the resistor under the dash, disconnect the side that goes to the tach, and connect it directly to ground.  I ran an engine in my garage like this with no problems.  The resistor is very high resistance so no chance of burning wires.

 

superlen or Captain Obvious or SteveJ might have some thoughts on why the computer needs the tach to work.  All I know is that they need it.

 

You might also check the tach's ground.  The wiring diagram shows a dedicated ground wire through C1 for 1977.  Page BE-31.

Edited March 7, 201510 yr by Zed Head

I will try you tips tomorrow. Thanks Zed Head!!!