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  #276   IP: 64.228.143.126
Old 07-08-2013, 10:58 AM
BobMcD BobMcD is offline
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Question Flamethrower coil from Moyer

Hi all,

Just to throw a monkey wrench in the proceedings, I have a Flamethrower coil that I got from Moyer, that when measured shows only 2.9 ohms across the - and + terminals. In fact the case of the coil says 3.0 ohms, yet it was originally order from Moyer as the internally resistered coil. It has not been installed as yet, and I was wondering if I should be adding a external resistor to is as well?
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Old 07-08-2013, 01:18 PM
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Actually Bob, your situation is what this thread's about. To answer your question of resistor or not, it depends on your voltage between the coil + terminal and the engine block ground at cruising RPM. Divide that voltage by the coil resistance and make sure the result is under 4. In the calculator I factored in a 15% safety factor reducing the quotient to 3.4.

At first blush I'd say you should add a resistor but without the coil input voltage we won't know what size.

The calculator can be found in the first post of this thread.
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  #278   IP: 67.235.27.130
Old 07-08-2013, 07:25 PM
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Just to add a little more to Neil's comment...
Yes, MMI used to sell the 3Ω Flamethower on their site.
(In fact, I also bought one)

This was before Neil did some research (a lot actually) and discovered that their claim (PERTRONIX not MMI) of a perfect match to their EI unit was, in fact, bogus.
If I understand correctly, once we'd made the discovery of needing additional resistance to avoid overheating (sorry, you'll have to actually READ the thread)
that was when MMI stopped offering the Flamethrower coils.

The coil now offered is at the necessary 4Ω requirement.
As I said, give Ken a call and he'll make sure you're set up proper if you have any doubt.

Just wanted to clear up any confusion to Bob regarding the Flamethrower originally offered on the site.
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Old 07-08-2013, 07:35 PM
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Thumbs up

Jerry, that might be a couple of paint chips there around the coil on your museum piece!

Better get on that!
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Old 07-08-2013, 08:30 PM
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Quote:
Originally Posted by sastanley View Post
Jerry, that might be a couple of paint chips there around the coil on your museum piece!

Better get on that!
I know.
I'm outta paint!
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Old 07-09-2013, 12:49 AM
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Credit where credit is due

Jerry mentioned the amount of work that was done on this issue to reach the solution we have and he is correct, it was quite a bit but in fairness I had a ton of help from several forum members. It was a collaborative effort. Thatch, Shawn and a bunch of others were involved. Reading through this marathon thread you'll see the variety of contributions.

We started with Pertronix themselves, found contradictory information in their literature and when we provided identical failure data to two different techs we received wildly differing responses. We knew then and there we were on our own, flying without a net so to speak.

And the rest, as they say, is rock 'n roll history.
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Old 07-09-2013, 02:34 PM
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Smile

Thanks all, I was wondering about the flamethrower coil, in fact I got it a long time ago from Moyer as a spare and was planning on installing it ..just because I had it and the original coil is rather old.. The existing coil reads 3.9 ohms across the terminal (disconnected), and so I was concerned about installing the new coil. I read about 13 volts across the coil + to ground when the engine is running at cruising speed, so to use the new coil I will need to add about 0.9 ohms resistor to be safe... Thanks for the info.
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Old 07-09-2013, 11:06 PM
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Bob, I think you have the right idea.

I am of the opinion that you put as big a resistor in front of the coil as you can, but keep the motor from being hard to start....i.e., too much resistance in front of the coil while cranking does not allow enough voltage to the coil to fire the plugs.

I have enough confidence in this arrangement now, that I've removed my 'dual coil' mounting. I have a 2nd coil aboard, and it is another Flamethrower, but now stored in a locker with the other engine spares. I have 3 of those little $8 ceramic resistors aboard, 1.82Ω being the middle range I think, and if I recall correctly, a 2.2Ω and a 1.1Ω, so that I can tailor my input voltage to the coil if necessary.

I started mine today after a three week rest. My current setup is the 1.82Ω resistor in front of my 3Ω (3.3 actual) Flamethrower and it fired instantly. I have not put a meter on it in a while, but if I recall, the voltage to the coil (+) post while running is in the low 10v range, and I have had zero trouble with that set up from an ignition system standpoint.
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Old 07-10-2013, 12:33 AM
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Shawn,
Thanks. This makes sense. Did I see somewhere that you all got those resistors at NAPA stores ?
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Old 07-10-2013, 12:39 AM
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Bob, Affirmative...I had to do a little digging for the specifications, but I picked them up at my local NAPA between work and home.

I'll be happy to re-research when I have time to provide the data, but I think I found most of it on NAPA's site. Also, as I did with the internally resisted coils (a 3.0 ohm Flamethrower really being 3.3), I always check them myself with my own meter before installing..I have found that about 9 times out of 10 that the actual resistance is a little bit higher than advertised...which I think in this case is a good thing, as it lowers the overall voltage into the coil.
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  #286   IP: 64.228.143.126
Old 07-11-2013, 10:29 PM
BobMcD BobMcD is offline
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Cool

Thanks Shawn, I will go see what I can find at NAPA up here in Canada as the often have different or less stuff than the U.S. stores.
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Old 12-28-2014, 12:52 AM
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Wow.
I just finished reading all through this thread.
You folks are quite remarkable.
At this Pont there is on reason to toss out questions about my old wiring, big alt and and huge batteries. With regards to my plans on "converting" to EI. As a matter of fact I don't think I could come up with a reasonable question that you haven't already worked through.
Thanks for sharing all this good stuff!
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Old 12-28-2014, 09:49 PM
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Bill..as a follow up..I am currently running a Moyer coil, with the 1.1Ω resistor because I am a little bit chicken to totally trust it yet... The Moyer coil has performed well, & I've ditched the Flamethrowers.

My Motorola alternator is still pumping out 14.1v to the batteries with good success.
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Old 02-13-2015, 12:00 AM
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Quote:
Originally Posted by sastanley View Post
Jerry..of course you are correct. I think the coil sold by Moyer is over 4 ohms of internal resistance.
It is, or at least the one i just got does, 4.1
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Old 02-23-2019, 11:30 PM
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Ignition woes

I've got power to the starter motor-engine turns over, no spark at the coil? I've replaced the points with the petronix ignitor. Seems like i'm late to this party, maybe someone has had similar issues? Suggestions appreciated. Thanks.
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Old 02-25-2019, 10:28 AM
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  1. Did the engine ever run following the electronic ignition installation?
  2. Please measure the voltage between the small + post on the coil to the engine block with the ignition turned on and report back. Be sure to turn the ignition off after the measurement, should take only seconds.
The answers to those two questions should point us in a direction.
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Old 06-25-2019, 12:13 PM
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Coil selection and ballast resistors with Pertronix Ignitions

I read through this entire thread after I started having issues with my Pertronix Ignitor I ignition and I have some things to add after doing further research.

As was stated in this thread, the thing that makes this situation difficult is the large amount of coil "on" time or dwell while the voltage is being applied. The dwell time for the Ignitor I is apparently fixed at 45-50 degrees which is a lot longer duration that what a points ignition would have, such as 30 degrees. That means that after the coil saturates due to the current flow, the current continues and that current results in coil heating. Coils don't like to get really hot as they tend to fail.

My story:
Atomic 4 in a Pearson sailboat.
Two years ago I installed Ignitor I unit with the original coil (vintage 1974 ??) and noticed dramatically improved operation. After a few hours of operation the coil failed, fortunately at the dock while warming up.

Replaced original coil with an Accel Superstock 1.4 ohm coil along with an Autozone AL795 ballast resistor. That ballast resistor has a cold ohm reading of about .6 ohms. So cold, that is a total of 2 ohms. I used this setup for an entire year with zero problems. I knew the ohms was a little low since the Ignitor I instructions said I should have at least 3 ohms, so I carried a spare Ignitor I 1146A on the boat. This was the best I could with the local parts supply at the time.

Last fall, knowing that the ohms for the coil and the resistor was at 2 ohms I decided to install a 3 ohm (nominal) Volkswagen Bosch Blue coil, pn 00012. That setup worked for about 6 hours total before the coil failed while I was on the lake this year. The coil was found to be very hot and there was zero spark. The engine wouldn't try to run even with a whiff of starter fluid. Fortunately I still had the Accel Superstock pn 8140 1.4 ohm coil and the ballast resistor onboard, so I swapped it on the water and motored back to the dock.

So the reading and research began.

The AL795 resistor that I used was used on Dodge vehicles with the 318 engine for many years. If you do a search for Dodge 1968 pickup truck with the 318 engine, you will find this ballast resistor. It was also used on some other cars with great success.

Doing some digging I found out that the ballast resistor does not have a static resistance value - it truly is a "ballast" resistor in that it limits current to the coil and was designed to be used over a range of vehicles. When the resistor heats up, its resistance value changes. It doesn't stay at .6 ohms.

To test, I applied 2.75 amps of dc current to a new AL795 and the resistance changed to about 0.65 ohms and the resistor was about 140 degrees F. Not very hot. (I have electronic test gear including test power supplies). However it was obvious that the 2.75 amps was not sufficient to substantially change the resistance. So I resorted to other ways to heat the resistor. I attached a Fluke digital meter to the resistor and proceeded to heat the resistor with a cigarette lighter by waving it under the resistor element. Sure enough the resistance climbed the more I heated the resistor. What started at .6 ohms, quickly climbed up to a max I saw of 2.5 ohms. So the more heat (from current or other) and the resistance rises substantially!

This explains why my second setup using an Accel Super stock coil with 1.4 ohms and the 0.6 ohm (cold) resistor AL795 worked successfully. My Atomic 4 runs about 150 degrees at the block surface where the coil is attached to the back of the engine. I had the AL795 resistor attached under one coil bolt. So the resistor would have been about 150 degrees with no current flowing through it. Add current and the resistance would have been substantially higher than .6 ohms.

So now the question remains, why did the Bosch Blue coil pn 00012 fail? I have no idea ! The points based system for a VW bug engine is to set the dwell to 45-50 degrees. It has been reported that the dwell created by the Igniter I is about 45-50 degrees, so in theory this should not result in excessive coil heating. I had an Ignitor I installed on a Ford NAA tractor with a Bosch Blue coil and that coil failed as well. I bench tested it and it had some spark but it was very very weak. I think the HV coil was shorting to the case internally. That makes me think that some of the Bosch Blue coils pn 00012 are defective. I replaced the Bosch Blue coil on the tractor with a Pertronix 3 ohm coil and it has survived for 15+ hours so far.

However, I believe that the ballast resistor inside a coil can is basically a fixed resistance since it is cooled to the temperature of the coil can contents. This means that it is basically a fixed resistance. Using an external ballast resistor is actually an advantage. The more current that flows, the higher the resistance! Plus, because the resistor is external to the coil can, the resistor is not heating up the coil itself.

Lesson learned: Going retro with a conventional coil of about 1.4/1.5 ohm along with a ballast resistor that actually increases resistance with temperature may be "old school" but it was a very good solution. Those guys back in the late 50's and 60's were thinking!

Ok.. one more thing: When I went to buy another Accel Superstock 8140 coil as a boat spare and another AL795 ballast resistor locally, I had a hard time finding them! Our boats are getting old, and time is moving on, so you might want to stock a spare onboard if you are going to travel. I ended up finding one AL795 at an Autozone (they had one) and I had to go to an Oreilly parts store to find the Accel Superstock 8140 coil, and they had exactly one as well. The beauty of all of this is that even though this stuff is getting old, I changed my coil out in the lake. Parts were available with some looking. The same could not be said for a 20 year old marine diesel.

So the Atomic 4 lives another day. :-)
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Old 06-26-2019, 10:12 AM
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Ignition issues continue on.....
I have posted this before more than once, but IMHO since no new cars use these parts anymore, the manufacturing of coils and so on has moved to second or third tier factories and thus coils that lasted decades back in the day no longer do.
Combine that with 99% of modern shops knowing nothing about old marine engines and you are likely to get a coil that is both below par and wrong. I am really lucky living on an island the local Western Auto guy knows that coils to hand out for A4s. I was part way into explaining it was an old boat engine and he said "Oh an Atomic 4, use one of these". I think he handed out a Standard UC15, which if memory serves, is 3.8 ohms or so.
Moyer happens to sell a coil that works well too
The "other place" - AKA Indigo - has got an electronic ignition that cuts the dwell back at low RPMs to prevent coil overheating. It is on my list to install at some point, but I keep putting it off because my points are good. I also have an ignition combiner so I might finally get around to my dual coil ignition idea.
I have thought about trying the scheme a coil on plug system, but the dang engine keeps running fine and reducing my motivation
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Old 07-08-2019, 03:49 PM
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>>I think he handed out a Standard UC15, which if memory serves, is 3.8 ohms or so. <<
Probably not since the Standard UC15 says "Requires an external resistor" right on the coil can. It might work fine with an external resistor, however its a fairly cheap coil at about $15.00.

The coil that I used, the Accel coil "claims" to have better connections internally than cheap coils.

Honestly, I don't know how anyone could make and sell a coil for $15 that wasn't made in China and "perhaps" of lower quality materials. However I could be entirely wrong. Like you said, this stuff is of dubious quality. I have found the same to be true of newer car parts as well. Sometimes you get good stuff, other times you get junk. In the past (old racer) I have had good luck with Accel branded parts.

That said, I have a spare Accel coil and ballast resistor on board as we speak. Its hard to get to the store when the wind dies, and the engine coil dies miles from the dock! :-( Spares are pretty cheap compared with marine tow bills.

Dave
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Old 07-08-2019, 05:49 PM
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Dave, what was the original internal resistance of the VW coil, not what the label or spec sheet said but the real measured resistance? What is your alternator output voltage at over 1000 RPM and again, measured voltage? What was your ignition system current? If you read through this entire thread you will know how critical these values are.

Same questions for the current setup (Accel coil + Auto Zone resistor)? If they are duplicated as reported in your June 25 post and assuming a minimum 13.8V alternator output, there is trouble in your future, guaranteed.
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Old 07-10-2019, 10:13 PM
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>> what was the original internal resistance of the VW coil

Bosch says the 00012 coil is a 3 ohm coil, but it measures more, 3.4 to 3.6 ohms and that's with a good Fluke meter.

I have a new alternator on the engine and it runs just below 14 volts at speed.

Pertronix says that they want less than 4 amps of current. The bogus thing about that is that the current is not DC when the engine is running. The inductance in the coil along with any resistance in the coil or external creates an RL network.
https://en.wikipedia.org/wiki/RL_circuit

The inductance of the coil will resist the change in current flow (inductors don't like current changes). So the current flow is not calculable by a simple voltage / resistance calculation. That only works when the engine is not running but the ignition is on and the ignition is triggered.

I believe the Atomic 4 will fire the ignition twice every revolution. So at 1500 rpm, that is 25 rotations per second, and 50 ignition firings per second, or 50hz. Household AC current is 60 hz. So the current through the coil is pulsed DC.

I'm ok with my existing setup. The Accel coil is 1.4 ohms and the resistor is between .6 ohms to 2.5 ohms depending on the amount of heat in the resistor. I have quite a few hours on the Accel and resistor setup and that worked fine.

I dissected a Bosch coil that failed on a Ford Tractor I had. Turns out the coil failed from water intrusion. The top of the Bosch 00012 coil is not well sealed probably because its potted in epoxy. Unfortunately the epoxy had cracks in it and it was not well potted. It might have worked fine in a dry environment, but not on a tractor that is exposed to rain once in a while.
I have pictures if anyone would like to see the internals of a Bosch Blue 00012 coil. The quality of the parts look good. The quality of the potting not so much.

I retested the Bosch coil I took off the boat that had failed. I bench tested it and it seems to work fine now. But I won't be using it on the boat anytime soon.
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Old 07-10-2019, 10:25 PM
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OK Dave, your boat, your choice.

I'll repeat an indisputable fact that has been mentioned in this and other threads on the subject of electronic ignition. Since recommending the EI voltage/current/resistance balance aka the Rule of 2011, coil cook-offs with EI, once commonplace, disappeared overnight for those who followed the advisement faithfully.

Pretty good track record.
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Old 07-11-2019, 11:05 AM
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>>I'll repeat an indisputable fact that has been mentioned in this and other threads on the subject of electronic ignition. Since recommending the EI voltage/current/resistance balance aka the Rule of 2011, coil cook-offs with EI, once commonplace, disappeared overnight for those who followed the advisement faithfully. <<

You should re-read my messages.

The reason for the cooked/overheated coils with the Pertronix 1146A (fixed dwell), is due to the internal resistor in the coils. If you have a 3-4 ohm resistor in the coil, the heat generated by that resistor heats up the coil and cooks it. Remove the resistor from the coil and the source of the heat is removed from the coil. (Which many have done) . A 3-4 ohm coil is a bad match for a Pertronix 1146A. Use a low ohms coil such as the 1.4 ohm coil I mentioned and use an external / variable resistance "ballast resistor". The ballast resistor heats up and that heat is external to the coil - so the coil doesn't get hot and "cook".
Also, you can't use ohms law to establish coil current in a pulsed DC RL network. The math doesn't work when your engine is running.
And yes, I'm an electrical engineer.
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Old 07-11-2019, 12:28 PM
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Coil internal resistance

Hi Dave, thanks for your explanation regarding the role of inductive resistance in the primary ignition circuit whenever the engine is running. I have a follow-up question regarding the way coil manufacturers add internal resistance. You seem to imply that they add a separate resistor inside the coil. It was my understanding that coil manufacturers vary internal primary resistance by simply using heavier or lighter gauge wire in the primary windings. Would this alter the heat buildup/distribution concern you described? Don
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Old 07-11-2019, 02:46 PM
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The heat in the coil is I^2(R).
So assume a coil at 4 ohms and voltage at 12 and the engine just sitting points closed - not running.

4 ohm coil = 36 watts.
1.4 ohm coil = 102.8 watts
4 ohms total, 2.6 ohms in external ballast and 1.4 in coil = 36 watts total, ballast is 23.4 watts in the resistor and 12.6 watts in the coil.
Note 1: It does not matter if there is an actual resistor in the coil or more/thinner primary windings. Same heat - same place.
Note 2: Coils are not running as straight DC resistance heaters. This is a trace from my engine on the output side.
The small peak between ignition events is the points closing again. The actual power dissipated is a bit less. The higher the RPMs, the less heat I am pretty sure. This is why A4s are tough on coils, we run a lot lower RPMs for longer than many other use cases.




Note 3: The Moyer coil and other 4 ohm coils have been well proven to last on A4s. Empirical data is good here
Note 4: I think a 4 ohm coil produces higher voltage than a 1.4 ohm coil ballasted to 4 ohms.

Last edited by joe_db; 07-11-2019 at 02:50 PM.
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