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Discussion Starter #1 (Edited)
Ok, I'm willing to put in some legwork on this one, but need a little help. It appears the transistor module is just 3 ignition modules packaged together. I am working on drawing up a wiring diagram to show this.

According to TM1591, "The ignition circuit is made up of three separate circuits, one for each cylinder. Each spark plug has its own separate pulsar, transistor switch [located inside transistor module (A2)] and ignition coil. This system eliminates the need for a distributor."

Seeing as these engines are meant to run at a fairly fixed speed, combined with the info in TM1591, I am fairly confident there is no timing advance circuitry in the transistor module.

This means we should be able to use a standard packaged transistor switch, for example, a LX301 (GM HEI ignition module).

Thoughts?
 

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There still has to be a condensor for each coil also. Is it in the coil(s) or in the transistor module? So if you can get your hands on a bad coil and transistor module and get to the inner components you could probably get it figured out.
 

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Discussion Starter #3
There still has to be a condensor for each coil also. Is it in the coil(s) or in the transistor module? So if you can get your hands on a bad coil and transistor module and get to the inner components you could probably get it figured out.
I thought condensor's were only used on points ignition systems in order to dampen the affect of the spark on the points, so that there is less wear on the points themselves. The 322 doesn't have points, but uses the pulsar's for the timing signal. A transistor module is just a very fast, solid state, switch, which opens and closes based on the signal it receives from the pulsar. In the attached diagram, the transistor module for the 322 would include the transistor switch shown, plus the components to trigger the switch control by the pulsar signal. Do I have this wrong (highly possible!)?


ignitran.png
 

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Just an idea but maybe you could read up on what Dave Kirk uses on his transdenser module. He basically uses the existing points to switch a IGBT similar to you are thinking you would use the pulsar to switch the same type of transistor. He does eliminate the condenser when you implement his part. Worth a read at any rate.

https://www.kirkengines.com/index.php#1
 

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Discussion Starter #5
Just an idea but maybe you could read up on what Dave Kirk uses on his transdenser module. He basically uses the existing points to switch a IGBT similar to you are thinking you would use the pulsar to switch the same type of transistor. He does eliminate the condenser when you implement his part. Worth a read at any rate.

https://www.kirkengines.com/index.php#1
I've used his products on my past 317 and 318... it works very well on points based systems. I'll take a look and see if it could help in this case. Thanks!
 

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I would email Dave Kirk and get his thoughts. I spoke to him in the past and saw some of his projects at his house. He's very sharp with this stuff and very friendly.
 
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Discussion Starter #8
I would email Dave Kirk and get his thoughts. I spoke to him in the past and saw some of his projects at his house. He's very sharp with this stuff and very friendly.
Just might do that... I spoke already to CDI Technology for about an hour on it. I also started attempting to "unpot" the broken one I have
 

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I have the Onan P218G and P220G and both have the electronic ignition module (Onan) down by flywheel with the halo trigger ring on the crankshaft. These engines both have a condensor on the plus side of the coil as compared to the standard points like on the B series, which has the condensor on the negative side of the coil. I think it protects the electronic switch from, a flow it can not handle, in the wrong direction. Ie diode conducts one way to a certain voltage and current limit, exceed it and the diode pops. Same principle, but in reverse it block the flow of current until the voltage jumps the gap (arcs) and the diode pops again.
 

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I thought condensor's were only used on points ignition systems in order to dampen the affect of the spark on the points, so that there is less wear on the points themselves.
Correct. Semiconductors need similar protection, which is usually done with a rectifier diode placed in parallel with the inductive load (or switch), but with reverse polarity. Similar to this:

diode.JPG

Al
 

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Discussion Starter #12
So after a rough go at it, I managed to get the circuit board out of the plastic and potting material. Anyone care to guess which part broke? :banghead:
burnt.jpeg
 

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Discussion Starter #14
Here is the board. The single IC chip is a 78L05, voltage regulator. The pair of chips are LM393 dual low voltage comparators. The switching transistors shown in the above post are D1976 NPN transistors. There is a small bank of capacitors on the back shown in the above post as well. Lots of small resistors / capacitors / diodes. No integrated, programmed chip though. It appears to be a straightforward NPN transistor switch controlled by the comparators looking for the signal off the pulsar.

Anyone see anything else?

board.jpeg
 

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Discussion Starter #15
This is the basic schematic of the GM HEI ignition module... NPN transistor switch with circuitry to detect the magnet in the distributor passing the pickup sensor. Wires up the same as this module. I'm feeling more confident about ordering 3 of them to try out :bigthumb:

HEI module.png
 

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Great read as one who hopes to own some of the Yanmar-powered goodness that is the 322. I appreciate the move to consider tried and true parts from other worlds to improve on a solid product. Thanks for the ideas.
 

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It might be worth noting that the 322 coil is a three wire unit, so one side of the secondary is tied into the primary coil. This is easily inferred from the physical configuration (no case ground) an the test procedure in the manuals for the coils as seen here:
322 ignition coil tests.JPG

This might have some effect on the use of the GM module which switches ground to the primary side of the coil -- maybe the length of the grounding pulse there is more critical for the 322 as it also provides the return path for the high tension side discharge...

At any rate -- you are on the right track to 'build your own' so let us know how you fair when it comes to the testing part.

Chuck
 

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I have no dog in this fight except my own curiosity over whatchur doin.

Standard ignition coils "fire" when the DC charge is REMOVED from the primary of the coil. An ignition coil is just like any other transformer with the exception of the primary and secondary grounds often being bonded together inside the device since isolation is not a requirement. This works fine with electromechanical switches to ground ("points"). With electronics, you can do so much more and the primary winding is often isolated so that "firing" of the coil is not simply a single collapse of the primary magnetic field that results from opening the circuit but an actual series of pulses (AC) that can be used to extend the duration (and thus the energy) of the high voltage pulse delivered to the spark plug.

There is/was a technique for small engine ignition called CDI that was used especially in high RPM applications where the cycle time (time to discharge and recharge the primary winding of the coil) was longer than the time between engine cycles. After seeing all the capacitors on the PCB after you unpotted the device, I'm inclined to believe that (or a variant thereof) is what you are dealing with. That will require a lot more than just a simple transistor switch emulating a set of points to work.

Al
 

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Al,

You are absolutely correct that the spark occurs when the primary side current stops flowing, which is when the points open (or when the semiconductor switch element shuts off and blocks current flow...) Therefore my prior post was not correct nor relevant regarding any concern for the amount of time the coil primary is grounded causing current to flow.

Chuck
 

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Discussion Starter #20
I have no dog in this fight except my own curiosity over whatchur doin.

Standard ignition coils "fire" when the DC charge is REMOVED from the primary of the coil. An ignition coil is just like any other transformer with the exception of the primary and secondary grounds often being bonded together inside the device since isolation is not a requirement. This works fine with electromechanical switches to ground ("points"). With electronics, you can do so much more and the primary winding is often isolated so that "firing" of the coil is not simply a single collapse of the primary magnetic field that results from opening the circuit but an actual series of pulses (AC) that can be used to extend the duration (and thus the energy) of the high voltage pulse delivered to the spark plug.

There is/was a technique for small engine ignition called CDI that was used especially in high RPM applications where the cycle time (time to discharge and recharge the primary winding of the coil) was longer than the time between engine cycles. After seeing all the capacitors on the PCB after you unpotted the device, I'm inclined to believe that (or a variant thereof) is what you are dealing with. That will require a lot more than just a simple transistor switch emulating a set of points to work.

Al
Hi Al, thanks for the info. When I spoke to CDI technologies (because I originally wanted to try to use one of their products), I was explained that their products deliver a positive, high power signal when the spark should fire, as opposed to the 322 which fires when power is removed (as Chuck said, and as is stated in TM1591).

Chuck, I thought the screws that hold the coil to the frame served as ground, or is it just a safety for stray voltage?
 
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