No, I think you're not reading the follow up messages carefully enough. The
resistor doesn't just drop the voltage, it limits the peak current in the
coil. If you're running a total loss system, you could probably do with less
resistance, but eliminating it could cause burned points, burned distributor
caps, and worse, a brand new burned out coil. The voltage on a battery
doesn't drop linearly over time. It's an electrochemical reaction that
takes place at a specific voltage per cell. The voltage will hold within a
fairly narrow range unitl most of the charge is gone, then drop more
quickly. Another advantage of the points-and-coil system is that it will
fire at a lower voltage than a spiffy modern electronic gizmo that expects
a modern alternator keeping it well fed. I would leave the resistor in and
rig a switch to short it out if you have to restart the car after a spin
with a low battery. Most vintage sessions don't last long enough to drain
a standard car battery. The small racing batteries are another matter, but
these usually get boosted on pre-grid. There's something to think about,
too. If you jump start the car from a booster battery, or the tow rig, you
could well be feeding 15 volts into your coil with no limiting resistor.
I've been running a standard 12 volt car battery (VW bug type) in a Formula
Junior with a total loss system. I've been on the same battery for 5 years.
I charge the battery up between sessions from my tow rig. I have to leave
the resistor in or it's guaranteed to burn points and cap. It's a Mallory,
BTW. The 80 minute rating would almost cover an entire weekend. Charge it
back up between sessions, and you won't have a problem leaving the resistor
in.
Gregory_Schulz@mil-elect-tool.com wrote:
>
> I've just redone the ignition system on my vintage 58 Sprite. Put on a Mallory
> dual-point distributor and a Mallory coil as well. A note found in the coil
>box
> stated that OEM resistors should not be removed or bypassed when the Mallory
> coil is installed. It went on to say that even if the vehicle doesn't have an
> OEM resistor by design, one should be installed. That's Mallory's 2 cents...
> probably generic advice for performance street cars.
>
> A point made earlier about the ballast resistor being necessary to drop the
> normal (alternator) voltage level of 15V or so down closer to the 12V
> requirement of the ignition system sounded right to me. If you're running a
>12V
> system (no alternator) and throw a ballast resistor into the mix, your
>ignition
> system may only be running at a fraction of design output. A professor in a DC
> course told me that a 12V ignition system will refuse to function when the
>coil
> voltage reaches 9.2V. To me, 9.2 V is not that far away if you're dropping
> (losing) voltage through a ballast resistor in a battery-powered system that's
> continuously being discharged.
>
> BTW, for anyone depending on a Group 24C battery in their racer: a fully
>charged
> battery - per the industry standards for 24C's - will last approximately 80
> minutes with no other current draw other than the ignition system. Of course
>an
> engine start-up or two, or a couple periods of sustained idling on the grid
> reduces that 80 minutes substantially.
>
> That's why I wonder how much margin for error there really is. If you have
>your
> original 12V being reduced by the voltage drop (through the ballast resistor)
> and that reduced voltage level is constantly decaying to a degree (no
> alternator), and your ignition goes silent at 9.2 V, and maybe your voltmeter
>on
> the instrument panel is 'a tad bit' off... I don't know - I'm going home and
> pull-off that resistor!
>
> G. Schulz in WI
> 58 Sprite (vintage)
> 82 Vette (street)
>
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