Fitting a HEI Module in Transistor Ignition Unit 1977 280Z

[Captain Obvious]

"doh!" Glad it was that simple!!

Don't remember if I was spinning this the correct direction or not, but here's what the reluctor pulses look like. Other direction would be mirror image about Y axis:

[TomoHawk]

I would bet the trace for a points ignition wouldn't be so nice

[Zed Head]

"doh!" Glad it was that simple!!

Don't remember if I was spinning this the correct direction or not, but here's what the reluctor pulses look like. Other direction would be mirror image about Y axis:

Pretty cool. I think that might be backward since the 4 pin module triggers "going positive" (according to the Megamanual - link below). You can see how timing gets all screwed up if the wires are backward. The zero-crossing is pretty broad.

You don't have a ZX distributor do you? It has a different-shaped rotor. I've read some things that imply the ZX distributor has better high RPM dwell. I wonder if the ZX rotor shape gets the signal above positive quicker so that it can start charging the coil again. I'm assuming that the trace has to be in a certain region for charging to start. Could be wrong.

General Motors 7-pin HEI Ignition Control

[Captain Obvious]

At the time I took that shot I didn't really care what direction it was spinning. I just wanted to see the wave shape.

However... When you look down at the distributor as installed, it spins CCW. I used a drill on the distributor shaft to spin it, and I see no reason why I would have switched the drill to reverse for the pic. So that would mean that the shaft spinning CW as viewed from the bottom would result in the correct spinning direction as viewed from above?

In other words, my pic could very well be the correct spinning direction. There's no reason why Datsun couldn't have used the falling edge to trigger. The best edge to trigger something like this is the steepest one with the greatest rate of change regardless of the direction (rising or falling). I'm sure the trigger point is the center of the pulse where the steepest section occurs by the zero crossing. I doubt the triggering is amplitude based, and I also doubt they are triggering on either of the curved lower sloped areas leading up to or trailing where the reluctor passes the pickup.

But regardless of the true direction, it's easy to see how changing the polarity would mess with the timing.

I might have a ZX distributor laying around... If I do, I'll snap a pic of that output. And I'll be sure to actually pay attention and verify the correct spin direction.

[Captain Obvious]

I would bet the trace for a points ignition wouldn't be so nice

Absolutely. With all that coil ringing being pushed back into the primary side!

But do remember... My pic is in the quiet environment of my bench. I could do the same thing and take a pic of a points style distributor using a pull up resistor instead of a coil and I would get beautiful clean square waves. It's not until you put the distributor it in a car and get all that flyback noise from the coil that things get messy.

In fact, I wouldn't be surprised if there was some coil noise that would show up in the electronic distributor as well. The ignition module would help isolate the pickup from the coil noise, but I bet $5 that it wouldn't get rid of all of it. In other words, I bet that same pic would look a lot dirtier when taken "as installed" with the engine running.

[Zed Head]

In other words, my pic could very well be the correct spinning direction. There's no reason why Datsun couldn't have used the falling edge to trigger. The best edge to trigger something like this is the steepest one with the greatest rate of change regardless of the direction (rising or falling). I'm sure the trigger point is the center of the pulse where the steepest section occurs by the zero crossing. I doubt the triggering is amplitude based, and I also doubt they are triggering on either of the curved lower sloped areas leading up to or trailing where the reluctor passes the pickup.

Good point and clarification. I made an assumption from a collection of french model statements, off the internet. The HEI module only has G and W as pin ID's anyway, with W identified for "positive" from the distributor in the various writeups, but G and W are just GM wire color letters (green and white). I think that people just used positive because the correct wire from the Nissan distributor is red.

In retro, when I first got in to the HEI game, I remember wondering what "positive" really meant since each wire sees both positive and negative current. "Direction" is different but I don't know what the proper name for that is. Even rising and falling don't mean much.

The ZX trace will be really interesting. You might start a run on ZX distributors if a performance benefit is found. There's definitely a rumor floating around out there but no data.

[Captain Obvious]

The ZX trace will be really interesting. You might start a run on ZX distributors if a performance benefit is found. There's definitely a rumor floating around out there but no data.

Rumor? Really? Now that piques my interest!

I didn't get the chance to look to see if I had a ZX dizzy laying around, but I'll try to do that tomorrow.

[Zed Head]

Here's an article that will probably make much much more sense to you than me. The comment about the reluctor is at the top of page 3.

From the article (by Lou Dudzik) - "If a reluctor of different design is used, the dwell may end up longer or shorter than the ideal time. The HEI reluctor rotor is comprised of a wheel with short-duration spikes on it. If a rotor is used with long-duration ramps before the spikes, the bias voltage on W may increase too much, creating the aforementioned stumble at higher RPMs."

Somewhere out there also is a thread about how the ZX distributor is better for high RPM. Not clear if the poster is talking about the module, the distributor or the combination. I'll post it if I find it.

I also had a conversation with a guy about the ZX module was better, for him, than a GM HEI module, when used with a ZX distibutor. So it may be that the ZX reluctor's different shape is actually bad for the GM HEI, but the Z's is good. That would be nice to know. He said that he was going to get some traces but he never came back. It was on Hybridz.

All I know right now is the Z distributor works great with the GM HEI module. If the ZX has the same waveform it seems reasonable that it would to.

In over my head...

Edit - I started a new thread just to focus on the odd bits about the HEI module. Didn't want to load up this thread. They re neat little devices and people are using them for all types of ignition systems, from motorcycles to old muscle cars.

Here's a link to the other thread - http://www.classiczcars.com/forums/electrical-s30/52651-gm-hei-module-odds-ends.html#post459994

HEI Notes - Dudzik.doc

Edited July 11, 2014 by Zed Head

[EuroDat]

I have been driving for a couple of days now and its still running much better. I must admit I was not to eager to drive it after all the problems, but now its brillant. My faith has returned.

The engine revs hard to 6000rpm and sounds better than before. Not sure if thats due to the new coil or HEI module since I had to changed them at the same time. I think most of my problem was in the TIU.

Once everything has proven itself, I will make a tech article maybe after I upgrade to the flame thrower.

If anyone is interested in a base plate I made a simple drawing. Its on scale 1:1, but all the measurements are there so if the scale gets messed up it wont matter.

Chas

BasePlate001.pdf

Edited July 11, 2014 by EuroDat

[EuroDat]

I played around with the resistor today. If you look at the photo's in post #1 you can see I fitted all the positives to one terminal bypassing the resistor altogether so I could use the 12V coil.

This was ok for testing, but I wanted to keep the stock look as much as possible. Toyed with the idea of pulling the resistor apart and bridging it internally, but then it would not be reversable and maybe in the future I would want to go back.

The easiest way seemed to be fitting a plate over all three terminals. I used a copper strip to fit under the termials. The strip is covered with a double layer of heat shrink to prevent arcing if it gets pushed down onto the resistor bracket. Now its not quite original, but looks a lot better than with all cables on one terminal.

Now if it would only stop bucketing down I can take if out for another spin.

Chas

[Captain Obvious]

That's nice work. You'd have to know what you're looking for to catch that.

[EuroDat]

A quick update and status report.

The HEI module is still working fine, although it has not been driven over the winter months. I put the battery back in and started it last weekend with not problems.

 

In my last post I showed a plated mounted on the resistor. That was done as a temporary measure until I ordered a new 6 volt coil. The coil I was using in the testing required 12volts.

 

The system is now fitted with a Pertronix Flame Thrower II HEI Module D2000 in the TIU and a Flame Thrower 45000 volt 0.6 ohm coil P/N: 45011.

 

I made a simple instruction document for anyone interested in doing this swap.

 

Chas

Instruction - Fitting a 4-pin HEI module to 280Z 1977.pdf