#1
IP: 193.253.220.149
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Coil input information
Just fishing for comments here.
I am in the population of people who have fried multiple coils with minimal use (two that I purchased plus one that was already on the engine when I bought it). I have just recently lined up my ducks by eliminating possibly mis-matched parts in the ignition circuit: new plugs and wires from Moyer Marine, new Pertronix Flamethrower coil (oil-filled; 40,000V; 3.0Ohm) to go with my Pertronix electronic ignition. I made a few measurements today with my basic digital volt-meter. Positive was taken from the + on the coil and ground was a near-by head nut. Results: 1)Everything off: 0.25V 2)Ignition switch on: 11.12V 3)Cranking engine: 9.3V 4)Engine started at idle, cold (no alternator): 11.7V 5)Engine idling at 1000RPM w/ alternator excited: fluctuating from 5.4V to 13.5V 6)Engine warm at 1400RPM w/ alternator : settled at 14.04V 7)Engine warm at 800RPM: 13.0V 5, 6 and 7 are with the engine in gear. I am way over my head here so any comments? Missing information?
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Kelly 1964 Cheoy Lee Bermuda Ketch, Wind and Atomic powered ![]() Last edited by Kelly; 09-22-2011 at 09:15 AM. |
#2
IP: 107.0.6.242
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Oddly enough it seems that the members most diligent about ignition systems are the ones burning coils (right, Shawn?). I don't like #6, 14.04 volts but I'm not able to explain exactly why. I still run points and condenser with automotive type (cheapo) coils. Usually I test less than 10 volts at coil+ (no external resistor), BUT, I run my electric raw water pump and fuel pump on the same circuit. I'm afraid this thread could empty the barracks (again).
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#3
IP: 193.253.220.149
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Quote:
All hands on deck!
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Kelly 1964 Cheoy Lee Bermuda Ketch, Wind and Atomic powered ![]() |
#4
IP: 134.39.100.70
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From a WEB article on ignition systems:
"The coil is designed to operate on 9 volts. Battery voltage (12 volts) is reduced to 9 volts by the Ballast Resistor. When the ignition switch is in the run position, the coil is powered through the Ballast Resistor feeding it 9 volts; but when the ignition switch is turned to "start", the Ballast Resistor gets by-passed. This feeds full battery voltage to the coil for better starting. The starter motor is drawing battery voltage down to about 10 volts at this time." We must either run a ballast resistor of the correct resistance for the volts our system is feeding it or, as Moyer states, a coil with internal resistance. It too must have the correct resistance for the voltage our system is trying to shove through it. The type, operation and condition of the ignition switch is a key component here as well. As is the output of the charging system. mark
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Mark C30 "Kismet" |
#5
IP: 206.125.176.3
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Hi Kelly, Just for grins, can you measure the static resistance of the coil before you turn on the key? How many hours do you have on the new Flamethrower?
My 'dead' Flamethrower was in the 3.3 ohm range (I have to check my notes to confirm) at rest (cold), and 4.2 or 4.3 ohms when it would fail 25 minutes later. However, the voltage at the coil as the engine sputtered to a slow death never faltered from 13.94volts. No real way that I can tell to measure the secondary output voltage while the coil is active...except for a visibly weak spark that wouldn't start the motor again when I cranked it. I need to measure my new coil after I've run the engine, with the key off, to see if the resistance stays constant or is the same as it was cold..which I think it should. I think the resistance went up and caused the bad coil to fail...or rather, the higher resistance at failure is a symptom of a 'fried' coil...I am purely guessing here that the resistance gets high enough that the coil can no longer produce a reliable secondary spark (to the plugs) and it dies. I would expect a good coil's resistance to stay constant.
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-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) ![]() Last edited by sastanley; 09-22-2011 at 10:14 AM. |
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IP: 107.0.6.242
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#7
IP: 193.253.220.149
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Yay- coil comments!
Shawn,
I'll make the measurements the next time I can make it down to the boat- should be tonight or tomorrow at lunch at the latest. My Flamethrower is less than an hour old. Measured Volts at the coil + seem to reflect yours (13-14V). Taking into account Mark's response, I would like to think that my internal resistance coil is the perfect match for my electronic ignition (both Pertronix). My installation is very basic...I've just "upgraded" to the electronic ignition in the hopes of having fewer parts to adjust.
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Kelly 1964 Cheoy Lee Bermuda Ketch, Wind and Atomic powered ![]() |
#8
IP: 208.89.140.11
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I don't know what a coil is rated for in watts, but here's the calculations
based upon a 3.3 ohm coil. 14.2 volts / 3.3 ohms = 4 amps 4 x 4 x 3.3 = 61 watts 12 vdc / 3.3 ohms = 3.6 amps 3.6 x 3.6 x 3.3 = 47 watts 61 / 47 = 130 percent We know heat kills coils and at 14.2 volts the coil has to sink 30% more heat. To decrease the amps in a 14.2 system to the draw in a 12 volt system you would add a ballast resistor to the coil. 14.2 / 3.6 = 4 ohms - 3.3 coil = .7 ballast. So to me this means that if we add a ballast resistor we can reduce the heat in the coil by 30% and still provide the 14.2 to the battery. knock on wood, as I have an electronic ignition and I have used both a pertronix and an autozone coil, both oil filled and for 5 years I haven't had a problem. My Alt charges at 14.2 volts. The pertronix coil moyer sells is epoxy which is for vibration area's, oil coils have better cooling. The question is what coil and where are they mounted ? Steve |
The Following User Says Thank You to smosher For This Useful Post: | ||
TimBSmith (12-01-2020) |
#9
IP: 206.125.176.3
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Kelly, you essentially have the same setup as I had which just failed, however, seems to work just fine for everybody else. To remedy the problem I had this summer of running from storms in 15 minute chunks until the coil would die, I've gone to a redundant coil system: I have a (identical to the recently failed one) 3 ohm oil filled Flamethrower as my backup, and I am currently running a 1.5ohm (Accel brand) oil filled coil with a 1.5 ohm resistor in front of it, as recommended by Pertronix. I figured after burning up the 3 ohm coil, why not?
![]() Full disclosure - I've screwed up my 'testing grounds' too by dialing down the voltage a little bit..Those numbers reported above were in the "as failed" running conditions..I am seeing something in the 10v range at the externally resisted coil now. I'll have to do further testing (sorry, going cruising this weekend!) on the readings of the new 3 ohm coil to compare to my dead 3 ohm coil with the updated voltage settings. So, essentially, I've changed three things...a new externally resisted coil, an internally resisted coil as backup, and the voltage I am sending to the coil. So much for following my own suggestions for a methodical approach. ![]()
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-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) ![]() |
#10
IP: 161.213.49.1
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I Run Points
But here goes anyway R\E electronic ignitions.
I don't think burned out coils are the problem. They are a symptom of a bigger problem. To me burned out coils mean the electronic ignition is acting up. Why do some EIs work fine and others fry coils? (as others have noted) Maybe some dwell readings would be helpful. Dwell with engine (and EI) at idle cold, and dwell with cold engine reved up. Then dwell with engine (and EI ) warmed up at idle and then dwell with a throughly warmed engine (and EI) reved up. Just an idea. My $0.01 for the day. TRUE GRIT |
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IP: 107.0.6.242
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#12
IP: 208.89.140.11
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The ei does have a larger dwell than the points, larger dwell more heat in the coil.
All comes back to more heat in the coil. Mine is installed on the engine in the original location. I wonder if someone has remoted the coil and it had failed. I think this we though I'll hook up a 1/2 ohm ballast to the 3.3 ohm coil and see if it works. The primary side resistance is 3 ohms, while the secondary side is in the 1000's of ohms. Last edited by smosher; 09-22-2011 at 12:16 PM. |
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IP: 206.125.176.3
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I am guessing my regular run-of-the-mill multi-meter doesn't do dwell.
![]() edit - steve, sorry I missed your post until now. Yes, my failed coil was remotely mounted, as shown in this picture taken earlier this spring. That is actually the dead coil, and the location where it lived the last 26 months since it was new in 2009. My original bracket rusted off, and the mounting bolts are solid in the block, so I just left them there. It would be a bear to remove them to re-mount a coil to the engine.
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-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) ![]() Last edited by sastanley; 09-22-2011 at 02:38 PM. |
#14
IP: 161.213.49.1
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A Bit More Explicit
My theory is that it is a heat related problem with some EIs that is manifesting itself through the dwell angle.
By proving or disproving this theory hopefully some light will be shed on the final answer to the problem. TRUE GRIT Last edited by JOHN COOKSON; 09-22-2011 at 01:00 PM. Reason: spelling |
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IP: 24.152.131.220
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As part of my ongoing testing of another theory I have already measured EI dwell. My Pertronix dwell is 62 degrees and this is pretty much in line with an email exchange I recently had with Hot Spark, another Hall effect electronic ignition manufacturer who specifies a particular unit for the A-4. Theirs is 50 degrees.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#16
IP: 75.68.130.228
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Hi Shawn, was that a 3 ohm oil filled flamethrower ?
Steve |
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IP: 71.183.233.249
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Hey Shawn-
An off topic question: where can I find a raw water strainer like the one that you have? Who makes/sells it? Thanks! -Jeff Taylor |
#18
IP: 24.152.131.220
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Here is Pertronix's discussion on input voltage, primary resistance and acceptable levels:
Quote:
My view on this is to avoid tweaking down the voltage regulator because of the negative resultant effect on battery charging. I believe a ballast resistor is the preferred method to maintain the 4 amp maximum and maybe a little less, remember 4 amps is a maximum.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 09-22-2011 at 08:58 PM. |
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IP: 107.0.6.242
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Great research, Neil - I think you have nailed it down for us. BTW, I agree that for most members it is not wise to lower alternator output voltage below 14 v.
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#20
IP: 193.253.220.149
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I would like to run a few more tests as I try to get my head around all this.
The calculations are clear and would seem to point me in the direction of adding a ballast resister (1.5 ohm) in front of the coil+ in order to reduce incoming volts to the coil. In my case we have: 14.04V / 3.0 ohms = 4.68 amps (or 13.0V / 3.0 ohms = 4.33 amps in the best case scenario). Both of these values are outside of the acceptable range. Adding 1.5 ohms resistance would give us: 14.04V / 4.5 ohms = 3.12 amps I assume this would also mean running a wire from the starter+ to the coil+ to have full battery volts while cranking? And all this begs the question: why are the volts measured at the coil+ too high in my basic installation? Is this not the case for everyone?? If we reverse the formula for a circuit with 3.0 ohm resistance at the coil and 4 amps maximum desired at the coil+ we get 12V maximum. Any time you charge the battery you're going to exceed this value. This would also mean that the condition has existed "forever"? Are we chasing fireflies here?
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Kelly 1964 Cheoy Lee Bermuda Ketch, Wind and Atomic powered ![]() |
#21
IP: 24.152.131.220
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If we accept Pertronix's advisory as gospel, you are correct Kelly, anyone with an alternator that charges at more than 12 volts (that's all of us) and have a 3 ohm coil have trouble in our future.
So why the difference between those of us with and without overheating coils? I'm guessing there are variables from boat to boat:
As far as what size resistor, I'm figuring the charging voltage from my fixed point alternator at a worst case scenario of 15 volts (no ammeter run), will measure the internal coil resistance and calculate the target system amperage at 3.75 amps (see edit) (1/4 amp margin of safety). Assuming the coil is at precisely 3 ohms (before actual measurement for the sake of this example only), I'll need a 1 ohm resistor. Coil temperature measurements will be the acid test but I'm kind of excited that finally there's something solid to follow instead of grasping at clouds. Anyone else interested in making coil temperature measurements, it would be best if the measurements were made both before and after the addition of a resistor for comparison. edit: Later on in the testing process I arbitrarily decided to lower the target amperage to 3.4 amps or 15% below the maximum for a wider margin of safety.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 10-04-2011 at 11:59 PM. |
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IP: 206.125.176.3
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Steve - Yes..it is oil filled..the only difference is it was just the chrome model (#40501).
![]() Quote:
and now back to our regularly scheduled programming: Neil, Wow..this is interesting information to say the least. However, your theory is supported by some facts that a typical older installation (mine certainly met that criteria) with long runs and voltage drop between the alternator and the coil (& possibly undersized wire with old, or inferior terminations) could be helping the coil. Remember this spring, the ONLY thing I did was remove my ammeter completely from the circuit and replace all the primary (4 gauge) cables in my electrical system with nice new wire & nice tinned copper lugs. The runs actually got longer, but I eliminated a lot of small wire sizes & inferior connections. So, the result, the first 1+ hour run on the coil, BAM!, failure. ![]() As to your question about coil & ballast resistance as compared to what is on the packaging: My personal experience has been that the numbers run slightly high, meaning they are built with a tad more resistance than advertised...maybe providing a little bit of a safety net, but not when you jam it with too much voltage and fresh, big gauge wire runs like I did. ![]() I did not measure voltage the way Pertronix recommends. I did my readings right on the two terminals of the coil. I can re-measure pretty easily. So, with that, & working from memory (my notes are not with me at work): My NAPA/Echlin 1.35 ohm ballast resistor = 1.6x ohms (part # ECH ICR11) My Accel 1.5 ohm coil = 1.70 ohms. Need to measure my new Pertronix 40511 oil filled (boring black) coil = x.x currently in the spares bin - My dead Pertronix 40501 oil filled chrome coil = 3.3 ohms My NAPA/Echlin 1.82 ohm ballast resistor = 2.1x ohms (part # ECH ICR13) When my charging voltage jumped with the new wires to near 15v (i know, too high) I was seeing 13.95-14.05 volts at my (now dead) coil. That puts the amps at 4.26. That sounds to me like it is over the threshold. When that coil was seeing 13.1-13.2v last year with old cabling, I was probably right at the edge. Actually, 13.2/3.3 = 4.00amps Now, I have done the following: Adjusted my charging voltage down to 14.1v Currently running the 1.35ohm resistor ahead of the 1.5ohm coil. Using actual numbers measured above that is about ~3.3 ohms. Assuming we have a drop of 0.9 volts at the coil to 13.0v from the lowered charge voltage I am right on the edge at ~3.93 amps. I need to measure this to be sure, I think I mentioned somewhere else I was seeing lower voltage than this at the coil. So..there's my numbers..Neil, I am thinking about maybe incorporating BOTH resistors into my system..maybe trying the 1.35 ohm in front of the 3 ohm coil and the 1.82 ohm in front of the 1.5 ohm coil and re-testing. It may also be interesting to try one of those resistors in front of the OLD coil and see how long it would last. ![]()
__________________
-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) ![]() Last edited by sastanley; 09-23-2011 at 11:52 AM. Reason: removed info that clouded the issue |
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IP: 199.173.226.236
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See my notes:
Quote:
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#24
IP: 24.152.131.220
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A word of caution
Before we start piling on a bunch of resistance on the input side of the coil we need to consider the output as well. Having a cool running coil that puts out a weak spark is not a solution. Accordingly, not any random resistor will do.
I can speak only to my system and how I intend to approach this new strategy:
Regarding coil spark output, as I recall the standard points type coils were 28K volt. The Pertronix Flamethrower I installed as part of the conversion to electronic ignition is a 40K volt coil so I'm thinking I could tolerate a 30% output reduction and still run as well as when I had the old points ignition and original coil. Dang this is interesting. edit: To repeat, I eventually lowered the target amperage to 3.4 amps for a wider margin of safety.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 10-05-2011 at 12:01 AM. |
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IP: 173.166.26.241
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This has turned out to be one of the more interesting and informative threads in a while thanks in large part to Neil and Mark and others. Good shot Kelly! Since the coil (automotive type) is designed to run on 9 volts it seems we have a large voltage cushion to work with. I will do the math as recommended by Neil to see where I fit in the equation. 40K volts
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