Coil input information

[hanleyclifford]

Originally Posted by ndutton

Here's the resistor I bought. It's rated at 0.85 ohm but measures at 1.0 ohm on my tester.

We'll have to see what Kelly comes up with in his neck of the woods, might give a new meaning to French Resistance.

I like it AND it has the terminal spades and mounting hole we require - far superior to the boutique offerings. Thank you, Neil.

[ndutton]

Gotta be careful where it's mounted, that baby gets HOT!!

I'm thinking of a simple angle bracket that fastens to the coil mounting bolt on the back of the engine. After successful testing I might fashion a heat shield for the coil to protect it from the exhaust (been talking off-list with thatch on that one) and incorporate the resistor into it.

[smosher]

This is going to get hot, I'm thinking of moving it away from the engine and a L brkt would work best.

I did see where there's a faston for 14 awg and thats the one I will use

I did send an email to Pertronix asking minimum current needed to create the spark. I haven't seen a response yet.

Steve

[ndutton]

Steve,

I think the minimum is directly affected by plug gap and the resistance of the plug wires and both vary boat to boat. A 0.035" plug gap will require more energy to arc than a 0.030" gap.

Therefore I'm not sure Pertronix can provide a definitive number given the possible variables.

[smosher]

Neil, thats makes sense,

ok so I'll try the .8 ohm you found at Napa


Steve

[ndutton]

Great Steve,

I hope it works but what I really like best is the variety of members involved. The post engagement debriefings should provide excellent information either way.

[Triton106]

Triton,
The coil - post is not a ground. Disconnected it has continuity to the coil + post reduced by the internal coil resistance. A switching ground is provided to the - post by the ignition regardless of whether it's points or EI. Readings taken at the - post will be confusing as it's switching on and off. Actually, to confuse matters more, what you're reading at the - post mimics alternating current. The significant reading you need is from the coil + post to the engine block with the engine running. That reading should be equal to the alternator output minus the ignition wiring voltage drop. On my boat the voltage drop is 1 volt.

Further, your alternator output voltage indicates it and your regulator need to be repaired or replaced, period. 17 volts is not right and will damage components as you have already seen. In my estimation, based on your description and my affection for single wire internally regulated beefy alternators, I'd replace the alt with a new one (I love my Delco), replace the coil with a new 4 ohm and replace the EI because it too has been stressed. All this will cost a couple o' hun but you'll be done with it and back out on the water.

Neil, that's a really clear and lucid explanation of the coil (-) terminal. It all makes sense now. I tried to call Pertronics and waited, and waited, and waited on the line but could not get through. So finally I left a VM to call me back. Two days now not a peep.

[sastanley]

Neil, your resistor looks the same as mine, however, I am running the 1.2 ohm version, which really measures at 1.6 if I recall.

part # ECH ICR23 - keep in mind I have this 'mated' to a 1.5 ohm coil at present.

[jpian0923]

Neil, do you have a voltage drop per foot equation? Or does it also depend on the wire gauge?

What I'm thinking is, in an emergency, adding lengths of wire to the + coil input should result in lower voltage.

Yep, another hair brained idea from Jim....but, could it work?

[ndutton]

Voltage drop is a function of voltage, amperage, wire gauge (cross sectional area), wire material and length. If it seems like a complicated formula, it is.

Instead there are several calculators available. The one I like for our needs is found here in the left column.

edit:
Please save me a trip to the boat for a simple answer to a simple question. What size are the 2 bolts that mount the coil bracket to the rear of the engine block? 1/4" or 5/16" if I remember.

[Kelly]

While waiting for news on my "French Resistance", here's a nasty little joke:

How many French soldiers does it take to defend France?

Response: We don't know, they've never tried. (Ouch!)




WARNING: Verify the nationality of everyone in the room before you tell this joke.

[ndutton]

Originally Posted by sastanley

Neil, your resistor looks the same as mine, however, I am running the 1.2 ohm version, which really measures at 1.6 if I recall.

part # ECH ICR23 - keep in mind I have this 'mated' to a 1.5 ohm coil at present.

Please note that according to the current calculation, your coil/resistor combination still has insufficient resistance.

Ha, current calculation! Allow an old guy life's simple pleasures.

[sastanley]

Hi Neil, yes..I am aware of that..back on page 2 I think..Napa has a pretty good selection in that line of resistors, from less than 1 ohm, up to it seems like 1.82 is the highest, so I should be able to find one. My current plan is to put the existing 1.82 ohm resistor I have (actually 2.2) onto the 1.5 ohm coil (actually 1.7) and get a 'smaller' 0.75-1.0 ohm resistor for the 3 ohm coil. If one measures the actual resistance, I am a little closer than it appears, but still 'on the edge', so to speak.

Originally Posted by sastanley

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.

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.

It has been raining here for something like 25 days. My wife and I saw the boat briefly last Wednesday evening for a light cleaning event with the intent to use it & go sailing this past weekend. Guess what..it rained..& we bailed on our plans and never made it to the boat.

We had thunderstorms at 0700 today. The weather's inability to cooperate with me is becoming exceedingly frustrating.

[ILikeRust]

Originally Posted by ndutton

Ha, current calculation! Allow an old guy life's simple pleasures.

That's revolting.

But don't let me impede or resist your attempts at humor.

In fact, I would find it shocking if someone didn't try to make a few bad puns here. I mean, watts the point if we can't joke around a little bit? Maybe someone will get a charge out of it.

After all, it's better not to be negative and instead be positive.

In fact, I tend to be a terminal punster myself. But some people just don't have the capacity for it.

[Kelly]

Tour de force!!

[joe_db]

4 thoughts:

I could build a current limiter that would hold the coil to 3 amps as voltage varies up and down

Millions of engines get by without anything like this

I never had one coil issue until I got electronic ignition.
The score - pre electronic: 1 coil after about 15 years
Electronic: At least one per year if not more
Post electronic: None so far


I wonder if coils were better back in the day?

[smosher]

Wouldn't the ballast resistor be more reliable than a current limit circuit ?

Steve

[sastanley]

Ok...I have a little more updated information.

I tried the voltage check at rest with the jumper.

10.7 volts on the battery side of the resistor.

5.72 volts on the coil (+) with the ignition switch on, engine not running.

Incidentally, the brand new Pertronix coil at rest also = 3.3ohms..just like the bad one.

[ndutton]

Got the ballast resistor installed today and took some coil temperature measurements. This report is incomplete because I forgot to take my voltage tester and camera.

I think I'll post a complete report on a new thread at a later time but for now here's what I can tell you:

I made 2 independent sets of temperature measurements 2 weeks apart. One set was with the original ignition set-up - Pertronix EI and their #40511 Flamethrower coil. Measurements were made from a dead cold start and targeted the Flamethrower label on the coil. RPM was 1200 to bring the alternator into play.

The second set of temps were measured exactly the same except with a ballast resistor installed. The resistor was the only difference.

Without resistor the coil temp achieved 162 degrees in 30 minutes.
With resistor - 133 degrees in 30 minutes.

I don't know if either temp maxed out in 30 minutes although the with-resistor temps were rising at a lower rate than the no-resistor by a factor of 1:4 at the 30 minute mark. That may imply the with-resistor temps were approaching max while the no-resistor temps were not. More measurements with longer run times will tell us more.

And finally, there was a thought that the resistor and resultant lower coil voltage may have a negative effect on starting. That was not my experience. My engine fired up in it's normal 1/2 second crank, no noticeable difference at all.

[smosher]

Neil, Good data, where did you mount the resistor ? and where is the coil mounted.

I ordered the same resistor at Napa and plan on installing this we.

Steve

[Kelly]

Neil,

Thank you for being so thorough and rapid in reporting your test results.

Do your results confirm your suspicions fully or were you thinking there would be more/less difference in the temperature measurements once the resistor was in the circuit?

I'm holding my breath until you're able to report back with results of Volts at the coil+ after the resistor was installed. I'd like to compare with you and Shawn concerning: Volts with ignition on, engine not running; Volts with the engine running at idle and cruising RPM.

And for personal puzzlement, what do you get at the coil+ with everything turned off (power supplied to the ignition switch but the switch turned off)?

TIA

[ndutton]

Originally Posted by smosher

Neil, Good data, where did you mount the resistor ? and where is the coil mounted.

My coil is mounted in the standard location on the back of the block and I mounted the resistor on an angle bracket using the right (looking at the back of the engine) coil bracket bolt. I'll get pictures and voltage readings today.

I want to repeat that I see this resistor business as a remedy for inadequate coils in terms of internal resistance. Get the right coil and the resistor is not needed, simple as that.

Do your results confirm your suspicions fully or were you thinking there would be more/less difference in the temperature measurements once the resistor was in the circuit?

Kelly,
I veered from my original theory and testing when I clumsily stumbled upon an obscure Pertronix advisory about the 4 amp system maximum. I had no expectations, just followed where the information lead me with the goal of lower coil temps in mind. Looks like we're there.

My original theory which I still may test at some point was whether or not a greater, more complete discharge of the coil would reduce the operating temperature. The tests would have been with increased plug gap, like 0.050" instead of 0.035". As stated earlier, that would require more energy to arc the gap. I was curious what effect it would have on coil temperature, if any. Think I'll save that exercise for a rainy day.

It's kind of funny that our tired old electrical wiring with poor or corroded connections everywhere and the resultant voltage drop is nirvana for our coils. Shawn cleaned up his wiring improving the voltage so much he poofed the coil that had run beautifully with the old funky wiring.

[hanleyclifford]

Neil - Your research seems to reinforce the wisdom learned from the sixties when we were building "street" machines and dropping our money into a different kind of "hole". In those days the ignition "horsepower" race was on among the aftermarket suppliers, Accel and Mallory come to mind. The theory was that more was better - 50,000 volts from the Mallory RevPol system I used on a 426 wedge with 13.5:1 compression. But that was another era and now we have 6:1 compresion and just flat don't need that level of ignition. This is the punch line that your research is now quantifying - there is no point in elevating ignition voltage above that which will ignite the mixture. It follows that we can afford to lower voltage at coil+ to the minimum that will fire the mixture. Knowing that cranking reduces effective voltage at coil+ the OEM guys developed the "override" that we run from solenoid "R". FWIW I have been using the same points and coil for 1000 hrs by constantly supervising the points with a dwell meter,not a feeler gauge. As far as I can see the only real advantage to electronic ignition is the low maintenance feature.

[Kelly]

Call me the cobbler. I just found two resistors @ 0.22ohms each. Wired in series I should reach the holy grail of 3.75amps at the coil+

I'll report back with actual measurements after testing...

Hanley- can you elaborate on the

the OEM guys developed the "override" that we run from solenoid "R"

comment??

[hanleyclifford]

Kelly - Sometimes, especially in cold weather, engines can have trouble starting because cranking voltage can be as low as 9 or 10 volts. If ignition voltage is being further reduced by resistors ahead of the coil it is possible that insufficient voltage will be available to fire the coil. The remedy? Bypass the coil resistor during the cranking cycle by running a wire from solenoid "R" which is activated only when cranking. Once the key (or button) is released "R" goes dead and the coil must draw thru the resistors.