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Discussion Starter · #1 ·
A few years ago, we were at Kenny D's shop for a writeup in Hot Rod magazine.

While we were there, Kenny asked me to see if there was any way that a Buick coil pack module could be "souped up", for high boost applications.

I brought it back to the shop and spent a couple weeks that winter disolving the encapsulation. The manufacturer fills the module with tiny glass beads, then they pour in the potting compound.

As you can see, it is undamaged, and still works, so I was able to reverse engineer it and draw the schematic.

The module is an inductive discharge ignition, with coil current limited to about seven amps.

In an inductive system, the energy stored in the coil increases with the square of the current. Thus, going from four amps to eight amps would quadruple the stored energy.

For reference, the current limit in the GM HEI module is set to 5.5 amps.

In this design, the current limit point cannot be changed without cutting into the module, which is not practical.

At low RPM, there is plenty of dwell time available to achieve seven amps of coil current, where the limiter kicks in. If current limit is reached, then the energy stored in the coil cannot be further increased.

At high RPM, the dwell time may be insufficient to achieve seven amps of coil current. This is where the improvement can be realized.

Supplying the coils from a 16v battery, or 20v from a Boost-A-Spark, will let the coils reach seven amps in a shorter time.

Note that this will only bring the stored energy up to the design value, but not beyond. Still, it may be enough of an increase to make a difference.

Here's an inside look at the coil pack ignition module, and the schematic:




<small>[ July 16, 2003, 03:51 AM: Message edited by: JohnP ]</small>
 

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Now that I like.I've waited a long time to see the insides of one of those.
THIS definately belongs on Steve Wood's web site.
 

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Someone Crown My Ass!
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So what is it that goes bad in these and couldn't you just de-solder the bad piece and replace?
 

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John said it took him "a couple of weeks" to get the potting material out, to expose the circuits. That would seem to be the main problem with doing a repair. By the time you get the potting compound out, you could have paid for a new module, had it shipped, and have it installed.
 

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No doubt go new when your current one fails (just did this even though mine ended up not bad). But you have two choices after you buy the new one...throw the old one out....or fix it in a couple weeks time of de-potting and you now have a potential $120.00 spare for the next time it goes for a measly $2.00 fuse or resistor.
 

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Welcome John, that was an incredible first post!

I would like to ask what the reasoning was behind that goopy filler. What was it's purpose and how in the world did you get it all out of there? powersix
 

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You get around,don't you? headbang
 

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Heh, I have been to the that site before. :)

So, now that the IGN Module is apart... What can one change to improve upon an ancient (relatively speaking) design? To surpass the designed limitations?

Would this product <><><><> piggy back the system and jump the designed limitations or just be another "Boost-A-Spark" and reach said limitations?
 

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Discussion Starter · #11 ·
IMO, manufacturers use potting compound for a couple of different reasons.

Environmental is probably the biggest reason for potting, especially if the module has to go under the hood.

Flexible potting must be used on modules that undergo heat cycling. Hard compound can shear the solder joints on parts, resulting in intermittent operation as the part expands and contracts.

Potting is also used for product security. The hard compound is almost impossible to get through.

The cynic in me says that it's also used to hide the true value of the module from the consumer.

I have taken apart the Ford Motorcraft module and an aftermarket Chrysler module. Both had five transistors. The genuine Ford part listed for about $120. The Pep Boys replacement Chrysler module was about $25.

I remember reading scare stories from Ford about the danger of using cheap replacement modules. Maybe that's why I took it apart.

When I took took the Buick module apart, I used whatever shop chemicals I had on hand. I think the most effective one was toluene.

The chemicals would soften up the exposed surface, allowing me to scrape off a little goo and some glass beads. Layer by layer, more was exposed. It was like watching archaeology on the Discovery channel.
 

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Discussion Starter · #12 ·
If you want to stick with the module, increasing the current limit set point would be the thing to do. To take advantage would require a Boost-A-Spark or equivalent.

Trouble is, the current limit point is set with resistors, and they aren't easy to get to.

Might just be better off getting the MSD unit.

Or, look into our system. We can raise or remove the current limit point, and, as a bonus, it retards only the cylinders that are knocking.
 

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John, do you offer a unit for the GN's...Is it one of the four coil models?
 

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Thank you very much. :)
 

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That seems to be either $495, or $524, depending on whether it uses boost sensing. Not cheap... who wants to be the test case, to see if it's worth that much? The gain, I think, would come partly from the current set-point, improving ignition, but mostly from the fact that ONLY the knocking cylinder(s) will be retarded, not all six. Good info.. group purchase?
 

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Ormand:
That seems to be either $495, or $524, depending on whether it uses boost sensing.
What is the going price for a THDP? And that is just a tube. :p

I don't quite follow how a single knock sensor can tell you what individual cylinder is suffering from pre-ignition. Unless the module does a logical process of elimination by pulling timing (delaying spark signal?) out of each cylinder(s) until the knock dissipates.

And how does that work with a waste spark system? I mean if you are pulling enough timing (up to 20*) is there the possibility that the next (waste spark side) could see some adverse effect? Somehow I imagine the the waste spark side is at least 180* off of the firing cylinder, so 20* of retard shouldn't matter.

dunno
 

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wonder if having a repetitous firing order and logging the instant of detonation might help?
 

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And I know how he does it! :D

Goober how are you!

Damm newbies. powersix silly headbang

Never built that circuit by the way... :p
 
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