Coil input information

[joe_db]

Things to consider:

1. Cars routinely run over 14 volts. My BMW is about 14.4 for one example.
2. My original A4 coil lasted from 1973 to about 1989 and we ran the engine thousands of hours in that time.

I have wondered if maybe since these types of ignition coils are no longer used in new cars if they are still as good as they used to be. Maybe production has shifted to second or third tier manufacturers and they just can't hold up like they used to. I am surprised if a Pertronix coil is being killed by a Pertronix ignition!

I also recall being told I was nuts to get rid of my Indigo electronic ignition, but I got tired of having my wife make me show her a replacement coil before we left the dock. She knew we'd need it! The last straw for the Indigo was when the coil died headed towards a closed bridge with 15 knots of wind and 2 knots of current on our stern

[hanleyclifford]

Originally Posted by joe_db

I also recall being told I was nuts to get rid of my Indigo electronic ignition, but I got tired of having my wife make me show her a replacement coil before we left the dock. She knew we'd need it! The last straw for the Indigo was when the coil died headed towards a closed bridge with 15 knots of wind and 2 knots of current on our stern

I can relate - I have learned to have anchor at the ready when approaching bridges. Can be a scary experience.

[smosher]

Same here on the anchoring. mine is the Agawam River and the engine died going from idle to power. Later found out I have used a 1/4" barb instead of 5/16 and the pump doesn't like air in the system.

Steve

[sastanley]

So...tomorrow, off we go...and take powerboat friends as guests....I am gonna put my 1.82 ohm resistor on the 1.5 ohm coil & the 1.2 ohm resistor on the 3.0 ohm coil (nominal readings, actual a little higher) for testing & field reliability purposes. The male half of our guest(s) is a retired Air Force pilot...he'll love to be tinkering with the motor while the ladies are on deck.

[ndutton]

During this process I've learned or realized a few basic facts as they pertain to coil heat.

Fact 1
Energy stored by the coil heats it up. The more energy or the longer it's in the coil, the more heat is produced and regardless of age, brand, configuration or resistance it can heat itself to the point of destruction. To prove this, what temperature is the coil when the engine has not been run for a week? See, no energy = no heat. At the other extreme, try turning on your ignition without starting your engine and let it sit that way for a couple of days. You know the outcome, it will cook off. Therefore we need to find the sweet spot between the amount of energy stored and how long it's held in the coil.

Fact 2
The energy is held in our coils for a looong time because our engine is only 4 cylinders and it runs at very low RPM. This means fewer coil discharges (dumping stored energy from the coil) per minute compared to other engines.

An eight cylinder engine running at 2000 RPM discharges it's coil twice as much as a 4 cylinder engine at the same RPM. This means our coil is holding a charge twice as long. Comparing a 4 cylinder automotive engine running at 3000 RPM to our engine cruising along at 1800 RPM and again, we're holding charge 2/3 longer. And remember, the longer the charge is held by the coil, the hotter it gets.

Fact 3
Electronic ignition provides around twice the dwell than specified for our engine. In terms of what the coil receives, dwell is the amount of time energy is being delivered so our coil is getting far more energy with electronic ignition than with points. More heat again.

Fact 4
Resistance in the coil circuit is there specifically to balance the charge/discharge/heat dynamic. If it weren't, all coils would be the same. Since we are charging the coil for a longer time and discharging the energy at a slower rate, we need to reduce the charge going in but only to a point. Too much reduction and the coil won't function and the engine won't run (thanks Tom, great testing).

Fact 5
Pertronix, the manufacturer of most of our electronic ignition systems, has provided us with a recommended maximum ignition circuit parameter of 4 amps. I want to emphasize their recommendation is in amps, not volts and is a maximum, i.e., not to exceed.

Fact 6
Volts = current times resistance, V=IR. If current (I) is fixed at 4 amps by design, higher voltage requires higher resistance to maintain the balance. Lower voltage requires less resistance. See how this last statement pertains to the next fact.

Fact 7
Our boats are aging and many if not most have electrical wiring, connections and decades of repairs in varying stages of decay. The result of this decay is voltage drop (it doesn't get higher). Other factors affecting voltage drop are at play too like wire gauge and circuit length. As a result, no two of our boats are the same in terms of voltage applied to the coil circuit.

Example for Fact 7 or why our coil has run fine for years
Let's say your ignition wiring is deteriorated and/or Heaven forbid you have a Catalina 30 with 2 corroded rubber trailer plugs in the circuit all of which imparts enough voltage drop to reduce your 14VDC alternator output to deliver 11.3VDC to your 3 ohm coil. Using V=IR, V= 11.3, R=3 so the current (I) = 3.8 amps, well within the recommended maximum of 4 amps. Life is good.

Then one day you can't stand looking at all the spaghetti any longer. Perhaps you've been inspired by Msauntry's or Rust's or that PITA ndutton's pics and decide the time has come to clean the mess up. So you rip out the old and install all new wiring using the proper gauge, new corrosion free and tight terminations and no more butt splice repairs everywhere. There, she looks great and functions much better. So much better that the voltage drop is now reduced to a point where you're delivering 13.2VDC to your coil, the same 3 ohm coil that has worked fine for years.

Again, V=IR, V=13.2, R=3 so the current (I) is now 4.4 amps and there's trouble in your future.

Okay, I've blabbed long enough. Hope all this helps.

[hanleyclifford]

Excellent recap, Neil. I nominate that post for Best of Best status.

[ndutton]

Thanks Hanley, appreciate it.

Three more (brief) things I should have added:

For those with electronic ignition (and twice the dwell), what to do about it all?
I recommend modifying your ignition with the addition of a ballast resistor ahead of the coil to bring the sum of resistances (coil + resistor) to 4 ohms. This will cover applied voltages up to 16VDC. You'll need to know the resistance of the coil to select a properly sized ballast resistor.

OR . . .
replace your coil with a 4 ohm internal resistance coil, it will produce the same result.

OR . . .
confirm your existing coil has 4 ohm internal resistance.

Kelly,
Just a suggestion but if you're going to add a resistor, why not get one designed for an ignition application? Seems like a more reliable solution to me.

[Marian Claire]

This is when it really bites being 7 hrs from the boat. I want to do some testing on my coil. Wonderful post Neil. Dan S/V Marian Claire

[hanleyclifford]

What started out as a Kelly fishing expedition has turned out to be a very educational and useful thread due in large measure to our detail-oriented west coast A4 brother Neil Dutton. In my particular system where I have run the same coil for many years and a set of points for 1000 hrs at 10 - 11 volts, not thru the use of resistors, but rather by ganging up fuel and salt water pumps on the same circuit, it seems I have achieved the desired result by accident (should this be in the "Captain's Confessions" department?). A now identified by product has been the frequent replacement of the cheap, salt water pump cartridge made to run at less than 12 volts. The changes I am going to make in my wiring scheme are going to save money and pumps. Thanks to Kelly for getting us out of the barracks for this one!

[thatch]

Neil's post (#105) is the "Gettysburg Address" of A4 ignition systems. When you consider the fact that he has no ignition or electrical problems of his own, and has spent many hours of testing and posting to help others, I feel that this puts him in the catagory of "Super Hero".
Thank's, Tom

[dvd]

Boy am I glad I don't have any coil issues.

dvd

[smosher]

Neil, how do you have the ballast resistor wired in, looks like your coming off the + side of the coil to the resistor.

Where is the other side of the resistor going, maybe ignition switch ?

I'll hook mine up tomorrow.

Where can I get a cheap temperature scanner ?

I don't have a problem yet with the coil, but for the $ 20 sure is cheap insurance.

Steve

[ndutton]

Steve,

My resistor is installed just ahead of the coil. One resistor terminal gets the ignition wire from the switch, the other goes to the coil +. Here is the scanner I have.

Full disclosure:
Thatch emailed me a Pertronix diagram he uncovered that showed a ballast resistor. On their drawing the Ignitor module positive (red wire) is connected ahead of the resistor whereas mine is connected after the resistor. My way delivers lower voltage to the ignition module but I don't think it's any big deal. Pertronix specifies 8-16 volts range for their Ignitor so I think we're good either way. Without accurate measurement yet I estimate I'm running at 11 - 11.5 volts to the coil and module (after the resistor). I was unaware of their drawing when I installed my resistor, just did it without regard for the module. It's working fine though, starts instantly and runs smooth.

Stewing on it overnight I think I prefer the slightly lower voltage to the module. It might prolong its life. This is pure speculation. I could just as well start a thread next week on module failure, who knows?

dvd

In thatch's gracious post his comment that I wasn't having problems is correct but I'm not as magnanimous as he implies. With the coil failure experiences of many on the forum, I ain't waitin' around for it to happen to me. Something was clearly going on and it was high time we figured out what. We certainly weren't getting much help from Pertronix.

[sastanley]

Hi all...The weather here was (to say the least) crappy, however, we did take the boat out, with some guests, to a friend's beautiful waterfront home for his birthday party yesterday, and stayed aboard last night.

We motorsailed the entire way (left the dock at 4:30 PM yesterday & arrived just before sunset) and returned this morning. The weather was adverse, and of course, upwind, so mainsail up to help, but it really just stabilized things. We had a skinny channel to navigate thru, and actually bumped on the way out this morning as we rushed to get out at near high tide about 8:00 AM.

Yesterday morning, I put my 1.82ohm resistor (2.2ohm actual measurement) in front oh my 1.5 ohm (actual 1.7ohm) coil. The engine ran for 2+ hours yesterday into the wind at 1,900 RPM, and probably 3 hours today on the way home (did a little creek exploring). Absolutely zero troubles..I did measure the voltage yesterday after installing the 'larger' resistor..running voltage = 9.70volts at the coil..ahead of the resistor=13.2volts.

edit July 2012 - in reviewing this thread, I want to update this post to reflect my updated set up - I am now running 1.82 resistor in front of 3 ohm Pertronix coil..(the 1.5 ohm coil did not last long as the 1.82 resistor was not enough with only 1.5 ohm internal resistance & 14.2v from the alternator.) No problems with this current setup combined with my slightly higher than normal charging voltage this season.

Since we had guests, no cushions were pulled or access doors opened, no infrared thermometer, etc.. but the engine did great.

I'll try to get out again soon and get some temps on the coil while she is running to see if the resistor is helping to keep the coil cool. I also need to go swimming before it gets too cold and scrape the prop one more time.

Where is the sunshine on the East Coast?

edit - Neil..just read your post #105. Nice work, sir. +1

[joe_db]

Pertronix seems to have some ideas for low RPM with the Ignitor II unit. See the graph. Dwell is quite low at 1,000 RPM. It also can work with coil resistance as low as 0.6 ohms. I may get one of these units and I think Moyer needs to switch up to these as well.

See this also:
Features
Ignitor II systems develop up to 4 times more energy between 3000 and 5000 RPM than standard ignition systems.
High RPM performance is improved when used with the Flame-Thrower II super low resistance (0.6 ohms) 45,000 volt coil.
Adaptive dwell maintains peak energy throughout the entire RPM range, reducing misfires while improving engine performance.
Develops on average 4 times more available energy between 3000 and 5000 RPM, and 2 times more available plug voltage.
Peak current level is reached just prior to spark for maximum energy without the heat build-up, increasing coil and module life.
Adjusts spark timing at higher RPMs to compensate for the inherent electronic delay.
Senses startup and develops more energy for quicker, easier starting. Built in reverse polarity and over current protection shuts down the system, preventing component damage.

[smosher]

I connected the .85 ballast resistor today between the neg lead out of the ei and the neg side of the coil. I measured the coil and it is 3.8 ohms, its not a flamethrower, but a napa standard.

I also picked up a scanner and after 1 hr at fast idle the temp stabilized at 130.

I measured at the same spot as Neil,

Interesting note is that the engine temp at the coil holder is 120

Voltage drop across the resistor is 2.3 vdc, This makes the current flow at 3 amps.

Engine ran fine.

[hanleyclifford]

I don't know where the info on that graph comes from but the notion that standard points typical dwell for an 8 cylinder engine is 55 crankshaft degrees doesn't square with anything I've ever heard.

[joe_db]

See http://www.pertronix.com/prod/ig/ignitor2/default.aspx

I am thinking that if Pertronix took the trouble to engineer a way to vary the dwell to control coil heat with the Ignitor II, it must have been an issue for them with the Ignitor I.

Originally Posted by hanleyclifford

I don't know where the info on that graph comes from but the notion that standard points typical dwell for an 8 cylinder engine is 55 crankshaft degrees doesn't square with anything I've ever heard.

[hanleyclifford]

Thank you for the link - now I see where the data comes from. The Moyer Manual specifies dwell for Prestolite distributors at 38 degrees and Delco 31 - 34 degrees, very different from that Pertronix source. I would caution members about relying on that link.

[joe_db]

Assuming that diagram is actually a 4 cylinder, the dwell is less than the point system until past about 1500 RPM and not as high as an Ignitor I until about 2000 RPM. I think the "typical breaker point system" line really should be labeled the Ignitor I, which is fixed at about 50 some degrees. Thus you have less coil heat below 2000 RPM. Also they seem to vary the connection instead of binary on-off.

Originally Posted by hanleyclifford

Thank you for the link - now I see where the data comes from. The Moyer Manual specifies dwell for Prestolite distributors at 38 degrees and Delco 31 - 34 degrees, very different from that Pertronix source. I would caution members about relying on that link.

[ndutton]

Steve,
GREAT numbers. I hope everyone who goes this way has the same result.

Joe & Hanley,
I hadn't looked at the Ignitor II until Joe mentioned it but studying the provided graph I'm skeptical as to the benefit for us. Here's why:

Comparing the adaptive dwell of the Ignitor II to a flatline points dwell of 55 degrees isn't significant to us. Our points system dwell is 31 degrees so if we lower the points line to where it belongs, beyond about 1500 RPM we're right back in the dwell figures of the original Ignitor system and any coil issues it may cause. As nearly all of us cruise at 1800 - 2400 RPM I think the benefit of adaptive dwell is lost.

I'm not trying to discourage testing it out. Joe, if you're up for it, give it a try and report back. I think the acid test would be without a supplemental resistor to see how the Ignitor II mitigates heat in a 3 ohm or less coil and that only applies with more than 12 volts delivered to the coil. As said earlier, onboard wiring could hold the coil voltage to less than 12 in which case there's no heat issue in the first place. At 4 ohms coil issues seem to disappear anyway.

edit:
Oh-oh, another concern. The graph is identified as an Ignitor II system with a Flamethrower II coil. I don't see how the coil affects dwell but since Pertronix is pushing the Flamethrower II coil with the Ignitor II system it's worth mentioning that all the Flamethrower II coils I saw listed have a 0.6 ohm internal resistance.

edit 2:
My graph analysis may be a steaming pile of Shinola. The graph is clearly labelled for 8 cylinder engines so who knows what the effective dwell is for their 4 cylinder version or how it varies with RPM? There are too many unknowns to make a worthwhile analysis. Joe, if you try it please measure everything including volts at the coil, coil internal resistance, coil temps over time and now - dwell at various RPMs. Oh yeah, and based on my first edit - what coil you're using.

edit3:
That graph that doesn't apply to us is reporting dwell in terms of crank rotation rather than distributor (or cam) rotation. At least that's how it's labelled. Why would they do that? Anyway, so Hanley - divide the dwell values by 2. Man, this is a great example of why we need to test these things ourselves.

[smosher]

From the Pertronix web site troubleshooting tips

Four and six cylinder engines should not exceed 4 amps. Eight cylinder engines should not exceed 8 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor.

Maybe we should of been adding the ballast resistor all along,



Steve

[ndutton]

Maybe we should of been adding the ballast resistor all along,

Oh, I agree Steve. My issue with Pertronix on this is the information is buried deep in their website much like a newspaper's corrections are found in a corner of page six in fine print. It's no wonder we didn't know it before, sad that so many of us destroyed coils in the process.

I bought my EI used from a forum member packaged in a sandwich bag without instructions so I was left to my own devices to find the instructions online. See below.

Even when Shawn and I contacted their tech department independently with the exact same failure data (Shawn's) we received two completely different responses and without rereading them again to be sure, I don't think either one mentioned a resistor.

I found their installation instructions on line (attached) and the only mention of resistors is "First, if you have an external ballast resistor, connect the red Ignitor™ wire to the ignition wire prior to the ballast resistor. Second, if you do not have a ballast resistor you must locate a 12 volt source that is controlled by the ignition switch to connect the red Ignitor™ wire to" and "A RESISTOR WIRE OR BALLAST RESISTOR MAY OR MAY NOT BE INCLUDED IN THE ORIGINAL EQUIPMENT." Both speak to an existing resistor, nothing about needing one.

And then from the Q & A section on the first page,
Q. What type of coil can I use?
A. The Ignitor™ is compatible only with a "points style" coil.

With this information is it any wonder we've been having problems?

[joe_db]

I think I might just use something like this for a test:
http://www.ebay.com/itm/High-Quality...#ht_2408wt_921

The imposed noise and RF in the ignition circuit may not play nice with a digital meter.

[sastanley]

Originally Posted by ndutton

Even when Shawn and I contacted their tech department independently with the exact same failure data (Shawn's) we received two completely different responses and without rereading them again to be sure, I don't think either one mentioned a resistor.

Hi Neil, The response I received from Pertronix did recommend adding a ballast resistor (approx 1.5ohm) in front of my coil, however the tech also recommended I change from my current 3.0ohm internally ballasted Flamethrower coil to a 1.5ohm coil (which to my knowledge, neither is available from Pertronix.)

At any rate - this weekend's engine activities went off without a hitch and it is a good thing. The weather was awful and if the engine had failed, we may very well have been up a certain creek, etc.. Well..we had wind & sails, but traversing a skinny channel with 6-9" of extra depth, along with a cross wind & chop is not something I prefer to sail in. With the help of this forum and all the data we've been gathering, this weekend was an absolute success over here in the rainy (& cold!) Chesapeake.

I have the Pertronix Ignitor (+) ahead of the resistor, attached to the (+) bus bar, as per Pertronix's instructions. I'll try to get to the boat sometime soon in more 'controlled conditions', to get more test data.