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EuroDat

Fitting a HEI Module in Transistor Ignition Unit 1977 280Z

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I posted this in someone elses thread, but decided to start a new one here. It may be useful for other members having problems with the TIU. These systems are getting old and starting to fail more often than not.

A couple of months ago I had problems with water in the fuel system. After cleaning it all out, draining the tank replacing the fuel filter the engine ran normal again. When I took it for a drive I was lucky to limp back home with the engine coughing and backfiring. Went through the EFI bible test and found some poor soldering joints on the aftermarket injector connectors and some minor things. It still would not run right once it warmed up. It was great cold, but once it warmed up bang it started all over again. The tacho was bouncing a little, but it didn't seem enough to be the ignition module and it checked out ok. I thought the tacho bounce was due to the lurching forward and stalling of the engine.

To eliminate the ignition I changed to a HEI Module (a cheap $10.00 unit to test with) and the engine has ran perfectly ever since. The ignition unit played up fierce when it was hot, but its been running perfect for the last two months.

Here are some photo's of the temporary fix to see if it was the TIU.

post-26512-14150829290211_thumb.jpg

This is the unit I used to do the testing and if all goes well I plan to upgrade to Flame Thrower.

post-26512-14150829290979_thumb.jpg

Now its up and running my next step will be to install the HEI Module in the old TIU casing.

Chas

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I made a simple wiring diagram of the setup Im now building. Its a little different around the resistor.

Im using a 12V coil and bypassing the resistor. The wire from the ignition switch is connected, but doesn't have any purpose atm.

post-26512-14150829291149_thumb.jpg

Thanks to Wayne (wal280Z) for the awsome effort he has done with the color wiring diagram.

Some photo's of the work in progress.

post-26512-14150829292045_thumb.jpg

Chas

post-26512-14150829291449_thumb.jpg

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Did you use a conductive material between the HEI and metal plate to act as a heat sink?

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Did you use a conductive material between the HEI and metal plate to act as a heat sink?

Yes, I used a white heat tranfer paste we use at work for pt100's in thermowells etc. If you look closly at the photo under the wiring dagram, you can see a white smear after wiping away the excess paste.

post-26512-14150829295055_thumb.jpg

Edited by EuroDat

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I like the looks of it. It certainly eliminates the look of a kludge factor.

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This a very good idea and method of execution is very clean. Well done. Nothing beats a modern ignitor to replace 40 year old crap. It is little surprise that your car runs better than it did before.

I feel compelled however to lend some advice. The generic cheap GM HEI ignition module is not the best component for this purpose. There is/was a lengthy (older) thread on hybridz about ignition instability at higher RPM's with some of the more bargain basement varieties of thes items. At the time, there weren't a lot of options, though MSD and others had "high performance" versions of the basic HEI module that performed better. jegs or summitracing.com probably sell several varieties. I'll try to find the hybridz thread and you can decide if its helpful.

Good news is that there are more modern and well tested components. DIY autotune has one of the better ones, the BIP373 is the one that comes to mind.

DIYPNP BIP373 Ignition Module and Heatsink Kit DIYAutoTune.com

This thing can replace the HEI module, or the E12-80/92 module on a ZX dizzy or any reluctor based distributor and will fire any basic 12v coil. And its smaller. And at $9.80, I buy three to carrytwo as spares, JIC....

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I don't think that the BIP373 has "dwell" control, or the current-limiting function that the HEI module does (and the 280Z and ZX modules). That is one of the things that makes the GM HEI module so useful, it won't allow the system to overheat from too much current. The BIP373 is used with ECU dwell control, I believe, and would probably burn up itself if used. If it triggered from the VR distributor. Not really sure that it would work. Are you using one? How does it control dwell?

I think that you could use the BIP373 in place of the ignitor on the 280ZX ignition systems though. People use the HEI module to replace the ignitor, but the BIP3737 seems like it would do the job, for cheaper and in a smaller package. Might have problems with the engine heat though if it was installed in the same spot.

Here's something interesting on the GM HEI modules - it looks like Bosch licensed the technology from GM or vice-versa for a few years and several of the outside-the-US manufacturers used the design, in different form factors. The very last one on this page looks like it is the same as the 4-pin HEI module but the pins seem more convenient. I think I've seen the same on a BMW model out there somewhere.

Bosch Ignition Modules

Edit - BUT, I just found it on Rockauto and it costs $204. So the more compact form comes with a cost.

Edited by Zed Head

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I have done a little research on the HEI Modules too. Not to say Im any kind of expert, far from it. More like enough knowledge to be a little dangerousLOL

The Mopar guys seem to be very fond of the HEI module and there is plenty of good and bad information on their forums.

What I have found on the net and through talking to a Buik guy in the street behind us. The GM HEI is considered one of the better modules, but it is also a lazy module and can run with a higher ohm coil, it just won’t go to current limiting control. To get the best out of a HEI Module you should use a 0.5 or lower ohm coil. That way the module will use its current limiting abilities and produce the best spark.

Here is a good example of what a low and high ohm coil will do to the HEI's performance.

post-26512-14150829295534_thumb.jpg

I think this could be some of the problems people are having with poor performance and not revving past 5000rpm.

If my mod goes well I am planning to use the Pertronix Flame thrower HEI and (stock looking canistor) Coil.

post-26512-14150829296087_thumb.jpg

With a bit of luck Ill have the mod done tonight and test drive tomorrow.

Chas

post-26512-14150829295816_thumb.jpg

Edited by EuroDat

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You're right, there is a lot of stuff out there, and it's hard to tell what's right and what's wrong. I gave up and just installed the GM HEI external coil to match the module. I think it ohms out at 0.7. I figured I couldn't go wrong with the original GM specs., used on cars like the Camaro with a V8. You know those will see some high RPM.

I think that the Pertronix HEI module (there are other brands also like Accel) just has a higher current limit. With a low ohm coil, the heat dissipation is probably the key ot making it last.

The new module in the old box in the cabin is certainly cooler than sitting in the engine bay or under a GM distributor cap though. Shouldn't be a problem, I'd think. Plus you can reach over and touch it while driving, and turn on the AC to keep it safe.

Here are some of the other brands. Still popular.

http://www.summitracing.com/search/department/ignitions-electrical/part-type/ignition-modules/distributor-type/hei

Edited by Zed Head

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Hi Zed, I was thinking along those lines as well. Cooling should not be a problem in the car.

For now Im running the el cheapo and I have a spare. The coil is a 40kv with 0.6ohm. It was the closest I could get without special ordering. Good enough for R&D and normal driving.

The link you posted has some good alternatives. I was looking at the Accel 35361 and the Flame thrower.

Chas

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Well the TIU in back in and the engine is running fine again.

I had one little glitch. Managed to get the reluctor wires mixed up and the engine would not rev past 2500 rpm. I remember reading about this somewhere and after checking found the green and the red wires on the wrong terminals. One of those Homer Simson "doh" moments:stupid:

Next step is a small strip across the resistor so it looks stock, but the resistor then has no function.

Ill post some photo's later.

Chas

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"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:

distbenchtest2.jpg

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"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:

distbenchtest2.jpg

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

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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.

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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.

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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.

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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.

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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 by Zed Head

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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 by EuroDat

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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

post-26512-14150829355582_thumb.jpg

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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

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