Re: coils

Posted by John T on December 18, 2006 at 08:06:40 from (66.244.90.5):

In Reply to: coils posted by bm3501466 on December 17, 2006 at 19:33:52:

BM,

"What is the purpose of the ballast resistor?"

It is to reduce the amount of curent flow through the coil (so it doesnt overheat) and that same amount of current flow which the breaker points are switching on and off. As Bob so well pointed out, if much more then 3 or 4 amps is switched using those mechanical points they will burn up prematurely. An in line voltage dropping (12 to 6) current limiting ballast resistor is typically used when one has a 12 volt battery but wants to use a 6 volt rated coil, cuz if you use 12 volts on a 6 volt coil it draws twice its rated current and will overheat plus, as noted above, the points will not last.

"I just ordered an Accel Supercoil for my 460 pulling tractor. Will it make any noticable difference in running with the high voltage coil?"

VERY LITLE IF ANY DIFFERENCE IN PERFORMANCE (Although the super coil may be slightly more efficient and transfer more energy and waste less in heat) PLUS (depending on coils primary resistance) it may burn the points up quickly if its a low primary resistance coil. Heres what many people DO NOT UNDERSTAND. The voltage at which the plugs fire is dependant upon the plugs gap distance and the medium (compression and fuel mixture etc) in which it fires GIVEN THE SAME PLUG GAP AND MEDIUM, the firing voltage of a stock coil will be the same as the Accell super high voltage coil !!!!!!!!!!! YOU GAIN NOTHING AND THE PLUGS FIRE AT SAME VOLTAGE notwithstanding the coil may be more efficient
and waste less as heat. WHAT THE ACCEL COIL CAN GIVE YOU is the ability and capability to fire at a higher voltage say if the plug gap was much wider and/or the compression is much higher which necessitates a higher voltage to arc current across the plugs gap butttttttttt just cuz it has that capability DOES NOT mean it fires at any higher voltage then a stock coil provided the stock coils voltage can rise to a sufficient high level to fire the plug in the first case!!!!!!!!!!!

"Where can I get an electric ignition system made just for my tractor?"

Try Pertronix

"Also what happens if I run the tractor without the ballast resistor?"

If its a full true 12 volt rated coil nuttin happens butttttt if its a 6 votl rated coil and you dont use a ballast, it will overheat the coil.

BOTTOM LINE: If you buy a high performace coil but still use mechanical points, you gain little if any in performance plus if the coil resistacne is too low (i.e. its made for use with an electronioc ignition switch) the points could burn up quickly. The way to get the bang for the buck is to match up a high performace coil with an electronic coil current switch like Pertronix sells.

NOTE this is NOT to say you cant get an accell coil of high enough resistacne to still use points with, they are made n used n sold no problem BUTTTTTTT their secondary voltage will ramp up only high enough to fire the plugs NO HIGHER which will be the same voltage as the stock coil given the same conditions. Jus cuz they can rise higher does not mean they will, but if the compression is way high and/or youre running a wider plug (like a hi perf pulling tractor),they will and can still fire the plug where the stock coil may not..........

If you wanna use full elec ignition with a hi perf coil and an elec switch then YOU CAN GAIN SOME IN PERFORMANCE, but if you still use mechanical poiints youre not gonna gain all that much improvement DESPITE what coil you use. HOWEVER if youre at extreme high compression and use exotic fuels etc, then an elec ignition can work fine where a stock points ignition may well fail.

John T in Indiana

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