Coil input information

[Kelly]

Can anyone point me to a reliable source for ballast resistors?

[jpian0923]

Triton asks a good question.

[ndutton]

Kelly et al,

Please keep in mind that all this resistor business is as yet untested, purely what we're thinking at this point. I picked up my resistor yesterday and will get it installed and tested for hopefully reduced coil temps as soon as I can. There are a few other listmates at a similar level of progress.

We think we're on to something based on theoretical analysis but until real world testing is complete we don't know for sure.

Something recently dawned on me though. Have you noticed that with the recent rash of overheating coil reports not a single one was a Moyer coil? Why would that be? What's different about his coils?

I'm pretty sure it's the internal resistance. The auto parts boutique coils - and the Flamethrowers - are 3 ohm coils and Moyer's are 4 ohm. That 1 ohm difference doesn't seem like much until you look at it in terms of percentage. Moyer coils have 33% more resistance than the others.

Well, enough talk-talk. It's time to get the testing done.

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.

[hanleyclifford]

1 ohm ballast resistors can be had at the Radio Shack or other electronics boutiques (wicked cheap). They can be lined up in series ahead of coil+ until you get the desired voltage. If you want to be fancy, run a starting circuit override from solenoid "R".

[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.

[hanleyclifford]

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]

Oooh, that's a spicy meatball

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.