Dawg wrote: I plan to... put a nice heatsink under the ignition module...

Damien, I don't know whether you've ever seen http://www.westcoastfieros.com/forum/forum_posts.asp?TID=949&PN=5 - This thread  in this forum.

I posted the same thing http://www.fiero.nl/forum/Forum2/HTML/095917.html - at PFF and there was a good exhange of information, including http://www.fiero.nl/forum/Forum2/HTML/096031.html - a spin-off thread which described the complete relocation of the ignition module and ignition coil away from the engine/heat. That might be the "ultimate" way to go.

Dawg wrote: If there is any interest, I could set up a demo for one of the club meetings.  I would bring my test gear and compare old and new.

Sounds good to me!

Romeo wrote: That would be SO gnarley.

Tristan, us old guys require a translation.

Car-2-Lo wrote: Patrick wrote: Romeo wrote: That would be SO gnarley. Tristan, us old guys require a translation. That's GROOVY

Okay, I can dig it!

Pat I added a reply to the other thread, its been over a year, have you fried a module due to exhaust heat yet?

No sir!

I hope Dawg doesn't mind, but if this is any idea of the direction he is going with his parts, I can't wait to see what results.

grokan wrote: would it be possible to just relocate the ignition module?

Yes.

Patrick wrote: Dawg wrote: I plan to... put a nice heatsink under the ignition module... Damien, I don't know whether you've ever seen http://www.westcoastfieros.com/forum/forum_posts.asp?TID=949&PN=5 - This thread  in this forum. I posted the same thing http://www.fiero.nl/forum/Forum2/HTML/095917.html - at PFF and there was a good exhange of information, including http://www.fiero.nl/forum/Forum2/HTML/096031.html - a spin-off thread which described the complete relocation of the ignition module and ignition coil away from the engine/heat. That might be the "ultimate" way to go. Dawg wrote: If there is any interest, I could set up a demo for one of the club meetings.  I would bring my test gear and compare old and new. Sounds good to me!

Damien, what are the multiple round silver things, and what function do they serve?

Those are Rare Earth Magnets.  The pickup coil relies on the magnets in the head of the dist shaft to do its work.  When those magnets get weak the cause the pickup no to work right.

I'll let Damien explain it better.  However in principle it should allow out pickup coil to function much better and last a great deal longer.

Dawg wrote: As for the magnets, yes, rare earth magnets inside steel cups pointing downwards.  Next one will have a custom enclosure machined for the magnets.  This will make them easier to mount. And yes, more magnetism, more signal from the pickup sensor.  Rare earth magnets last a LONG time too.

Is the relative position of the magnets on the head of the distributor shaft important? If so, how do you know exactly where to place them?

Dave, I wish you hadn't closed http://www.westcoastfieros.com/forum/forum_posts.asp?TID=949&PN=1&TPN=1 - the other thread .  There's no reason why a discussion can't take place in two threads on a similar topic. I was hoping to receive a reply from Chay to a question I had asked him there.

I think it's great that there's something/anything being discussed that's generating a little more traffic than usual around here. That's a good thing!

     Ok If you honestly feel that both are actually justified, I have re-opened it.

Thanks Dave.  

No doubt both threads will peter out on their own shortly, but it's nice that they can both now die a natural death.

Dawg wrote: The magnets need to be as balanced as possible...

I don't think you actually addressed my questions. Trade secret?

Patrick wrote: Is the relative position of the magnets on the head of the distributor shaft important? If so, how do you know exactly where to place them?

Dawg wrote: Ummm....Well basically, balanced means equal spacing between them.  Fit as many magnets on there as you can and make sure if you were to cut the rotor in half, there would be the same number of magnets on one side as the other. Is that clearer?

Ummm... not really.

I'm not sure why this is so difficult to get across. Okay, once more...

There's six poles (for lack of a better term) on the head of the distributor shaft. What determines where the magnets sit in relation to the poles? If you were to shift them all over an eighth of an inch for example, would that throw it all out of whack. (non-geek alert)

Is my question any clearer?

Dawg wrote: There's six poles (for lack of a better term) on the head of the distributor shaft. What determines where the magnets sit in relation to the poles? That's a better question.  I get it. Simple answer, doesn't matter.  You're magnetizing the flat piece of metal they're sitting on.  Ideally, the rotor is channeling all the magnetism to the poles (fingers). Happy now?.....:)

Getting there.  

So it doesn't matter where the rare earth magnets sit in relation to the existing magnets in the head of the distributor shaft? Or do the rare earth magnets attract/repel themselves into the optimum position? ie... 12, 2, 4, 6, 8, 10 o'clock looking down on the top of the distributor shaft head as opposed to 1, 3, 5, 7, 9, 11 o'clock.

Interesting. Thanks very much for the info, Damien.

From the Megasquirt website:

GM and most other electronic spark driven reluctor electronics trigger on the negative going zero transition after a positive voltage. While they could trigger on the rise that is not how they were designed. Thus polarity of the reluctor signal is critical to proper function.

In the GM 7/8-pin HEI, the module converts the AC signal from the variable reluctor pick-up {on pins P & N} in the distributor to a 'square wave' tach signal {on pin R} suitable for MegaSquirt-II.

Be sure to get the variable reluctor pick-up wires connected properly. Reversing the variable reluctor sensor wires and thus the polarity of the sensor causes the leading voltage to go negative first and the electronics ignores the positive going transition. Thus trigger signal, if ever recognized, is the falling edge of the voltage as the end of the tooth passes.

The only way to get proper triggering at the center of the tooth is to have the positive ½ cycle first (tooth approaching) and the negative ½ cycle last.

So, from this I get that the polarity is critical as DAWG already noted, amplitude is not so important, and the 0 transition should be as clean as possible (Crosses 0 once, not multiple times). If we can acheive this, then remoting is a good posibility. A 0 crossing detector is a good choice to limit interference, which is probably why they used it.

Chay

 SO how is the test mule doing in the wifes car, been able to drive it much?    I know she probably won't rev it that high, but have you had a chance to scream the RPMS up for any prolonged sessions?  Any chance to get it hot enough for the rad fan to kick on in Traffic?  I am sure a lot of interest will be there once people know this is a bonified save your butt item.

How is this probe hooked up?...bottom of the coil to common(Ground)? It looks like that's it.

I would like to see ch1 across the coil, and ch2 hooked to a current probe (.01ohm maybe, 5A = 50mV signal at max) in the primary to show primary charging current...that would nail it.

I think this module is suspect.

To define what I'm talking about, the period where the waveform is high is when the ig module is open circuit. When the voltage is low, but not 0 the current is building in the coil and the module is conducting. The small voltage is due to the saturation voltage of the transistors in the module. Then, the negative going spike is when the energy in the coil primary is transfered to the secondary and a spark occurs.

Now, look at the timing...When it's cold, is it open circuit for 4ms, then charging for 5ms or so (This is the dwell on a points system, btw), then it discharges to the plug over 1-2ms period. Good stuff.

Now look at the last one, the ugly. It's o/c for about the same period, then charging for a very short period of time...1ms or so. This causes a dramatic reduction in spark energy, because the coil only has 1/5 the time to build up energy. The current builds linearly, so 1/5 the current, but the enery is proportionl to the square of the current, so something like 4% of the previous energy is delivered. Not good, and it shows in the discharge waveform, which is very low amplitude and I suspect the spikes are due to multiple crappy arcs.

The dwell is supposed to be fixed in this system...ie, the module is shot.

It probably is not strong enough to deliver a signal to a timing light.

Chay

I was wrong about dwell being fixed...it is controlled dynamically from the ecm...

So, were these screen shot taken at abou the same rpm? Looks close from my count...9ms vs about 9 ms period, so about 2222rpm?

Am I close?

Chay

I read some more via megasquirt, and their typical values for dwell are 2-4ms, depending on the L of the coil used.

For us, if we assume a spark discharge time of 3ms, and dwell of 4ms (Each of these is conservative) we have a total system time of 7ms for each spark. We should be able to maintain this until:

7ms*3sparks/rev = 21ms, 21ms^-1*60 = 2857rpm, at which point the ecm would lower the dwell and the resulting spark time in order to keep it firing on time.

So, we get a really good spark at up to 2800rpm, then by 3000rpm, the spark energy is about 1/4 of what it was at 2800 (Because the dwell is /2).

Chay

I keep posting, but I realize this suggests something.

If you need better high rpm energy, get a coil with less L and more secondary windings. This will respond better to lower dwells at higer rpm, but will deliver a lower energy spark at sub 2800rpm.

My guess is this is what the MSD blaster is all about.

Chay

Oh, yeah, one MORE thing. The amplitude of the reverse voltage on the coil primary will be equal to the spark plug breakdown voltage*ratio of the ignition coil. Essentially, the ignition coil becomes a transformer, with the primary and secondary "disconnected". Therefore the voltage will build on the primary and secondary until one or the other exceeds the voltage level required to drive current...it lets go on the secondary when the spark plug fires.

This means that there is no good way of reducing this spike, because in doing so you'll be absorbing energy which ought to go to the spark plug. The focus should be on attaining a good dwell time, so the spark plug fires once strongly rather than the weak restrike I see in the last of your scope shots.

Comments?

Chay

CFoss wrote: I don't get how it works...

That makes (at least) two of us.

Seems as though there's plenty of discussion on this topic... http://www.fiero.nl/forum/Forum2/HTML/105003.html - Here .

 Damian, when you do sell one, make sure to get the buyer to keep a report on how well it works.   Another interesting test would be to take some "bad" modules or pickup coils, and test them in your fancy device and see if the bad parts come back to life.