Jim and John, 100% agree with your comments. There is an interesting article in the SAE archives around this. WILLIAMS, J., "MAGNETO VS. BATTERY IGNITION," SAE Technical Paper 170050, 1917, doi:10.4271/170050
Seems that a combination of things went into the early decisions around Mag vs. battery ignition. One of them was the different operating environments for a automobile vs. tractor vs. industrial power unit.
A battery ignition as stated, produces a more consistent spark over a wider range of RPM's. No question there. However, a tractor or power unit is designed to be taken up to operating PRM's and run that way for long periods of time vs. an auto that is constantly changing speed accelerating or decelerating.
With that all said, a battery ignition will provide better spark characteristics at lower rpm's when considering high compression and different octane fuel. In the end, I 100% agree with the both of you (and Pete) about how the battery ignition behaves. I guess my point is, on a stock C123 engine (in the case of the Farmall 100) under normal use RPM's and standard Regular grade gasoline, I think the mag would perform the same as the battery ignition without noticeable difference in low RPM operations.
If you are going to jack up the compression, change the cam timing and lift, etc. then the battery is the only way to go. For normal operation, my point is there is negligible difference, if any. Plus, the inductance of the coil is related to voltage. Go take a voltage reading on your battery at -10 degrees while cranking. Take that same reading at 60 degrees while cranking. Since the coil's inductance is directly related to the input voltage, I like mags for starting in cold weather.
but John, you said it best. Both are good. Both have advantages and disadvantages, which I think I also said, just in more brevity in my initial post. I could have done a better job of stating that for this application, I don't think there is a significant difference in performance between the two.
Good posts, good thread. :D
This post was edited by Tom Fleming at 12:59:25 11/15/14.
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