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jdemaris
11-30-2005 11:33:14
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Re: Follow Up: 6 to 8 volt Cold Starting in reply to Jim bobb, 11-30-2005 08:43:47
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A few general comments without getting lost in technical data. A 12 volt system will outperform a 6 volt system in cold weather - even if all is perfect. I've yet to see a single exception. I've got several 6 volt tractors that I prefer to keep that way (for reasons of collector's value and perhaps nostalgia). For those that I want the ability to start when it's -25 below F - I either use a block heater, or a 12 volt battery stuck in temporarily for winter use, or both. In regard to voltage at the coil - at cranking, a 12 volt system coil is meant to perform at 9 volts, and a 6 volt system coil at 4.5 volts. The more voltage you feed to the coil, the more potential spark output and cold staring ability. The downside to this is - as the voltage gets higher, the life of some coils will be shortened, and the ignition points will not last as long, and - in some situations - the coil might put out more spark then can be delivered to the spark plugs (might jump to ground from a bad or wet wire, cap, etc). Deere Company had particular problems when they changed over to 12 volts. Many of their gas engines were lousy starters in cold weather - and subsequently - Deere put 6 volt coils on 12 volt systems - sometimes with no ballast resistor. This resulted in much better starting, but the points didn't last very long. On many of those tractors, if you replace the coil with a generic unit, they become poor starters in cold weather. So, those are just some of the reasons for all the jerking around with ballast and thermal resistors and ignition "thermosats." Today there are many types of high-quality coils on the market that will put out very high voltage (i.e. spark potential) if needed without sacrificing reliability. Couple that with a electronic ignition pickup (like Petronix) and the problem of ignition point pitting/arcing is also solved. I must admit, I don't use any of the high-end modern stuff. All of my high-use tractors are diesels. So - for the limited use equipment, I don't mind changing points and such once in awhile.
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