Prop size.

[ndutton]

Actually Gordon, it wasn't the voltage. The coil's internal resistance was too low causing the amperage to be higher than the EI manufacturer's specification. It's not the voltage, it's the amperage.

Example:
A Moyer coil at 4.3Ω internal resistance does not overheat with input voltage of 14.2 volts and no external resistor whatsoever. The reason is the system amperage is 3.3 amps (V=IR or Ohm's Law), well below the 4 amp maximum specification. This is the basis for the resistor calculator you used and it targets the ignition system amperage at 3.4 amps or a 15% margin of safety below the specified maximum. In real world practice it has enjoyed a 100% success rate over the 5 years since it was first recommended.

[Shrek]

Thanks

Thank you for clarifying this. I meant to say amperage, of course. Only the resistance needed to be increased to a number similar to that achieved by the Moyer coil.
Glad to hear of the 100% success rate since 2011. lets hope it holds up.
I will sally forth with renewed confidence.

BTW The re-rigging is completed and she looks just spiffy, almost like new !

Thanks again - GF

[ndutton]

Thank you for clarifying this. I meant to say amperage, of course. Only the resistance needed to be increased to a number similar to that achieved by the Moyer coil.

It's not a coincidence the resistance calculator approaches the MMI coil value. The MMI coil is manufactured to specifications determined by the same research that produced the calculator.

Try finding a 4.3Ω coil at any auto parts store, they don't exist. There's a darn good reason they are available here though. We can't say it often enough, Don takes real good care of us.

[Shrek]

Don Moyer is the man !

Hi Neil,
Thanks for sharing the specs. on Don's coil. Next time I should buy a coil from Don ? or is it just the same if I keep buying from my auto store, now that I have a resistor.
The only reason I could see for not keeping my new set up, is that according to a previous posting in this thread, my resistor is going to be very hot to touch. Do I really want something that hot enclosed in my engine compartment ? Or, should I just not touch it ?
LOL GF

[hanleyclifford]

Hi Neil,
Thanks for sharing the specs. on Don's coil. Next time I should buy a coil from Don ? or is it just the same if I keep buying from my auto store, now that I have a resistor.
The only reason I could see for not keeping my new set up, is that according to a previous posting in this thread, my resistor is going to be very hot to touch. Do I really want something that hot enclosed in my engine compartment ? Or, should I just not touch it ?
LOL GF

The whole idea of the resistor is to take the "heat" that the coil would otherwise get. Don't touch that resistor when the engine is hot and running; but do touch the coil, and draw your conclusions.

[ndutton]

Gordon, you can certainly keep the generic coil + resistor setup and it should give you reliable operation. As for the heat it generates, just don't mount it on a sensitive or flammable surface like a wood or fiberglass bulkhead. However, if you want ultimate reliability you'll reduce the number of components and connections wherever possible, every one of them is a possible failure point. Using a Moyer coil eliminates the resistor and its connections.

Full disclosure:
I still have the original Flamethrower coil and ballast resistor I used for testing purposes 5 years ago installed on my boat. It continues to act as a successful test platform in terms of longevity for the conclusions reached in the electronic ignition study. My spare engine that I rebuilt a year or so ago has the Moyer coil however. If you're considering buying a coil anyway and can plan a few days ahead for a little shipping time, why not?

[Shrek]

Heat transfer from a hot resistor.

Thanks Neil, I assume it will be too hot for the bulkhead it is mounted to in the engine compartment (fibreglass) so can I hoseclamp it to some part of the engine (not the coil) or just leave it free floating in mid air. Do the wires attached to it get hot as well. Sounds like the Moyer coil is the way to go. I should buy 2 just in case, and I could use a new bracket, anyways, but I'll wait until after Saturday's run back to home base, just to make sure I have solved this issue. Thanks for the heads up regarding the fibreglass bulkhead incompatability !
GF

[ndutton]

Fiberglass is one of the most flammable materials around. We fought a fire of a Columbia 45 hull still in the mold and it was amazing-scary. We were told a 30 foot boat in the water will burn to the waterline in 10 minutes.

A simple angle bracket with two holes mounts the resistor nicely to a coil bracket bolt. Some anal retentive guys like to make them fancy but it's not necessary. Hanging the resistor on its connecting wires is bad form. The wires do not get hot.

And yes, in my opinion the Moyer coil is a superior solution to adding stuff (resistor, connections, possible starter solenoid bypass wiring) to a generic coil that's insufficient for our purposes. What's better than a new coil specifically manufactured to suit the Atomic 4 with electronic ignition?

[Shrek]

Fire hazard

Thanks for this timely warning. The new bracket will be fabricated today.

GF

[hanleyclifford]

Anal Retentive

aka "optimal engineering given specific circumstances" is best practiced before the fact. First prize on coil mounting is to get it away from the engine for obvious reasons. The coil resistor location should be selected for best air circulation and heat dissipation - it does not have to be mounted on or particularly near the coil. The purpose of the ceramic is to insulate the business portion from the surrounding area. Some heat will transfer from the ceramic to the bracket, and thence to wherever the resistor is mounted. That is what must be minimized. Of course, the "safest" place to mount the resistor is on metal, ie the engine. But that is not optimal for the coil. Engineering is about forward thinking and compromise.

[hanleyclifford]

Wiring of the Innocent

There are creative options for developing resistance between two points. Consider again the pictures in post #12 (the middle one). The hot juice arrives at the resistor via the purple #14 at the bottom of the resistor. The top terminal wire (#18) disappears into the grey sheathing which goes to the 1-10 el cheapo ammeter on my panel, then back thru the same sheathing to coil. Thus the resistance, and it's associated heat, is spread over a greater area. Newer automobiles utilize the same sort of "long" resistors. The objective is always to have it both ways.

[ndutton]

Dare I ask?

Why would this be preferable over a Moyer coil, no resistor and fewer connections?

[Shrek]

Seems logical !

I got rid of my Christmas Tree coil setup and love the look of the new bus bar tidiness and I agree with you 100% regarding too many connections in a system. Every connection = Loss. Whether that be voltage or Db of transmission. Perhaps it is most simply explained like this. If you put a light bulb on the end of a piece of cable and apply 12 Volts, then run the wire all the way around the planet and back to your switch, then turn on the switch. Do you think the bulb is gonna light up? Doh !

[sastanley]

Shrek, I also went to a small bus bar to get all the stuff off my (+) coil post. Need to take an updated pic though as I don't have any handy.

[hanleyclifford]

Why would this be preferable over a Moyer coil, no resistor and fewer connections?

The Moyer coil is always preferable - it is sold by The Man with all the experience, integrity and guarantee that implies - nevertheless, it should be defended by a quality resistor.