Electronic Ignition

[ndutton]

Here are a few notes on Pertronix electronic ignition systems and their effect on coils. It's neither a drawing nor a schematic but I repeated it here to make the resistor calculator easier to find.:

Through testing and following an advisory from Pertronix regarding a 4 amp system maximum we found the addition of a ballast resistor in the ignition primary circuit significantly reduced coil heat in some cases. Internal coil resistance combined with coil input voltage were found to be consistent predictors of coil heat and subsequent failure. There is no indication a resistor will fix a sick coil. If your coil has overheated to a point of shut down, it's damaged internally and needs replacement.

We now have a simple ballast resistor calculator specific to the Atomic 4 with Pertronix electronic ignition. It applies what we've learned on the lengthy Coil Input Information thread and adds a 15% safety factor. You need to input two values, it provides a resistor value to one decimal place. Note that this is the best information we have at this time. Should new info emerge, we'll adjust the calculation as necessary.

Ballast Resistor Calculator.xls

For those unable to open the calculator or without Excel, smosher provided a free program to resolve the issue found here.

[Dave Neptune]

Wow

Nice work Niel! Now that you have done the Pertronix and understand it's limitations, I have a quick question. Do you have any numbers on the power rating on the Indigo unit? I'll dig around in my boat stuff and wee if I can find my paper work on it today.

Certainly hope that this eleviates the percieved problems regarding coil zapping.

Dave Neptune

[ndutton]

No Dave, I don't but I was thinking along those same lines. I wonder if Indigo has any system amperage limitations and how their dwell compares to Universal's specs.

edit:
Dave, I recall that you have had excellent performance from your Indigo ignition. Would please measure your dwell, coil resistance and input voltage at cruising RPM for comparison? Any other Indigo users care to contribute to the database?

[smosher]

wouldn't the issue be with the coil and not the ignition module.

[ndutton]

wouldn't the issue be with the coil and not the ignition module.

In the course of testing, the only difference I measured between points and Pertronix EI was dwell and the difference was significant, like double for the EI. I formed an opinion that the increased dwell - combined with our few number of cylinders and low RPM - might be oversaturating the coil. It's interesting that we've heard many stories of coils that worked for decades with points were quickly cooked after the switch to EI.

[Dave Neptune]

Ok

Niel, will do. I will check my paper work and see if I can find a dwell meter somewhere. For kicks I will check the specs on one of my old Allisons that we ran some really Hi-voltage performance colis with @ over 10,000 on some rotary apps. Also used them in many dune buggies as they were very durable. That was the first Electronic I used on my A-4 26 years ago, it is also a photo optic trigger not a "hall-effect" type.
I will be going by the boat tonight maybe and if I have time I get her lit, check my running voltages and get the part number off my "Flame thrower" coil.

Dave Neptune

[smosher]

Ah, good point. I was thinking along the lines of keeping the ei and decreasing the amount of current through the coil. The argument can certainly be to use points as the dwell is less and less dwell means less current flowing through the coil

[Dave Neptune]

Some checks

Niel, checked a few things. The Indigo paperwork doesn't have to much in the way of specs but it did state it was only rated up to a 3.8 ohm coil! I checked the voltage at idle and at cruise RPM with pretty much fully charged batteries (315 amps) they have been sitting for a few weeks though. After warming her up at idle 700RPM my battery voltage was 13.4v and the coil terminal was 12.9~13.1v. The terminal engine not running was 13.3. When operating at cruise 1800 RPM 13.8v the terminal held 12.6~12.8v. This drop as the RPM's increased seemed constant and I did run it up a down a few times to check. I did not bring a dwell meter but the whole point of the electronic ign. is it's ability to increase dwell for better saturation of the coil. My coil is the Flamethrower supplied by Indigo.
I also pulled an extra Allison I still have and it is full of info regarding spark times and dwell. The spark times varie at idle and shoorten up as the RPM starts to rise and stays there all the way up. It is also photo optic like the Indigo except it is rated to 16 amps . It is also rated to operate from a minimum of 3v to a max of 18v and an over voltage start rating to 30v for 3 minutes.

Dave Neptune

[ndutton]

As far as I know Flamethrower coils max out at 3 ohms, maybe measure as much as 3.3 ohms. Given that I figure you're running at somewhere around 4.2 amps. Since you have the optical system I don't know what to make of the numbers except that they exceed Indigo's recommendation by about 10% and that assumes I'm reasonably accurate on the coil resistance. Whole lotta guessin' goin' on.

I want to be careful not to jump to any unfounded conclusions. Maybe Tom Stevens of Indigo could shed some light?

[Dave Neptune]

Stock?

Niel, when I bought the Indigo years ago I had them send me a complete kit. It came with the EI parts a coil and the stiffer springs for the advance mechanism to compensate for the loss of point drag on the breaker cam. I started the engine once installed and set the timing via a power time and it has been running flawlessly for 8~10 years now, not even a hic-up. I have replaced the cap and rotor once since and have used maybe 4 sets of plugs. That's all of the maintenance other than oiling the "felt" to keep the advance working once a year maybe. I see no reason that the Pertronix sholdn't have the same reliability.
I also think that a lot of the problems we are seeing here on the forum with coils is going to boil down to a wiring problem if using the recomended coil. Frankly I'm suprised that Pertronix hasn't taken a bit of an interest. I have done countless conversions over the years to many kinds of EI's on cars boats and buggies with no trouble. Many of the engines were 4 cyl's and some snarling V-8", but absolutely no coil problems.

Dave Neptune

[ndutton]

I wouldn't have jumped into this had it not been for the frequent reports of coil failures. Early on it could be seen factors in common were Pertronix electronic ignition and coil heat. Since I had electronic ignition it was important to me to figure out what was going on before I became a victim. It is interesting that there have been zero failure reports with either Indigo optical ignitions or Pertronix ignitions with Moyer coils. Far and away the common combination in failures has been Pertronix (Hall Effect) EI coupled with either after market or Flamethrower coils.

I contacted Pertronix first, seemed like the right thing to do. You saw the result of that effort. I dunno what ole Carl (Pertronix tech) smokes on his lunch break but the responses were counterproductive at best.

So we were left to our own devices. And here we are. I'm happy we were able to measure reduced coil heat with our remedy. I should say that although I've been critical of Pertronix's involvement, it was their 4 amp current advisory I used as a benchmark even though I tweaked it down a little.

[Dave Neptune]

Oops mistake.

I got my Flamethrower from MMI not Indigo, I found this out after contacting Indigo, it is not one they offered. Sorry for the confusion however I do have the Flamethrower and will get the numbers off of it this weekend.

I wonder how many are using the Indigo and the Pertronix with no problems though. It seems to me that the instances of coil failure seem isolated as so many of these systems have been sold. I wonder how many have been sold compared to how many are having trouble ?

If you are reading this thread and are having no trouble why not chime in to be counted?

Coils operating at over 190 degrees is normal and far higher underhood temps are not uncommon. An oil filled coil should be good for well over 220 with no problems.

Dave Neptune

[ndutton]

If you are reading this thread and are having no trouble why not chime in to be counted?

In a strange twist, count me as one without problems. In truth, I don't use my engine much, at least not since the switch to EI. Available time is my main issue.

[msauntry]

Count me in for no problems.

I have about 700 hours on my engine since adding the Pertronix module and have had zero problems. I'm using the old, unknown, black, slightly rusty coil that was originally on it with points. There's never been a hiccup, so I've never thought of replacing it. I've also installed Pertronix on my Scouts and had no problems, also with their original coils. Never tried the Flamethrower coil, though it'd be really ironic if the company's own coil didn't meet specs.

[Kelly]

Dave,

Your point is pertinent and echoes exactly my sentiments at the beginning of this saga, namely "why me?"

Those with multiple coil failures are clearly in the minority (Shawn, myself...) and we may be victims of our own zeal: cleaning up old wiring, replacing ignition switches, increasing alternator output...just generally improving the environment around the engine. If in doing so we cross some "critical line" and start suppling too much current to the coil then maybe our problems will be solved with additional resistance, either by adding it externally or by installing an appropriate coil (Moyer's 4ohm coil for instance).

What is important to me in this whole saga is getting informed opinions on what would be an impossible trouble shooting scenario for me alone. And as more and more A4 owners start rebuilding, renovating and replacing, this information could save quite a few owners the aggravation of serious engine trouble with what would appear to be the "ideal" ignition circuit.