Control modules/white ceramic heat sink paste/homemade electronic ignition

Thread Starter

James Siebold

Joined Dec 8, 2018
8
Let's recap. I few weeks ago I posted a question about using 2 magnetic reed switches in place of ignition points to ground the ignition coils. If they could open/close at 90 hertz. That's how I got on this forum. The consensus was these would probably not work.

A better idea might be to use a HALL effect system.

Here is the system I got working, but didn't like the looks of it. I removed three of the magnets on the plastic ring (was a 4 cylinder kit) and I'm using two points conversion modules. One magnet and two modules. One module for each cylinder and the car uses 2 ignition coils for each cylinder.


IMG_20181205_083912286-1612x1209.jpg

I got my dial indicator from Poland yesterday to double check my initial measurements using a ruler:

IMG_20181231_133344575-1612x1209.jpg

I discovered I was spot on, #1 cylinder but a bit off on #2 . In the photo below is where 4mm BTDC is supposed to be so the ignition has been retarded a bit.

Unlike my Citroen 2CV, the crankshaft is pressed together on the Trabant so the crankshaft can get out of phase. So that is why both sets of points have to be adjusted independently. That's why this engine does not use a wasted spark (one ignition coil and 2 plug wire outputs) like the Citroen.

I was aiming for 4mm BTDC. I don't know what that translates to in degrees.

IMG_20181231_133357569-1612x1209.jpg

OK, my question. Yesterday I cranked my Trabant up to go for a test run. I discovered #1 cylinder was not firing. HMMM. It was working fine yesterday. What's up with that?

I removed the mounting plates from the modules and moved them to the backside of the Lexan discs covered in aluminum foil tape and used longer 3mm bolts. On the backside of the green housings there is this white heat sink paste. This is the same paste used on GM HEI control modules. I had a tube of this paste I got from Radio Shack (back when there was a Radio Shack) and smeared it on the mounting plates.

It was my understanding this paste is conductive. But apparently is it not. So I wiped the paste off the plates and discs with carb cleaner and a rag but left it in the center behind the green housings. Now I have fire. So the white paste on the mounting plates was causing the module to not get a proper ground. What is misleading is the HEI modules has this stuff smeared all over the backside of the control module. So how does that particular module get a ground? Can someone explain to me what this white heat sink paste actually does?

I'm wanting to see if my neighbor can cut me some of these discs out of aluminum using his C&C machine. Lexan is supposed to be good for around 350 F so if the engine was to getting that hot, I've got bigger troubles.

One more thing. I aimed my heat pen at these modules after about 10 miles. I measured 160F / 70C and it was 75F / 24C yesterday. The input voltage is around 12.1 volts. I've heard if you push closer to use 14 volts, it can overheat the modules. Does the temperature reading sound "safe".

Here is a video I shot of my current system. NOTE: There looks to be quite a bit of wobble in the shaft that. This is an optical illusion. I used a flat washer under the head of the bolt and the center of the washer is a bit larger than the 10mm bolt.

 
Last edited:

yellowfish

Joined Feb 9, 2009
32
Like you wrote, heat sink paste is just that, to transfer excessive heat to the mounting plate. The HEI modules get their ground connection through the mounting bolts or a designated terminal. I would put the paste back. Automotive electronics are good up to +120C or more.
 

Thread Starter

James Siebold

Joined Dec 8, 2018
8
Like you wrote, heat sink paste is just that, to transfer excessive heat to the mounting plate. The HEI modules get their ground connection through the mounting bolts or a designated terminal. I would put the paste back. Automotive electronics are good up to +120C or more.
Yeah I forget about the screws!
 
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