A Pertronix Ignitor (and maybe the kit on eBay too) still has its limits, just
like points. They can't tolerate more than 4 amps for a 4 cylinder
application, which means you have to provide a lot of resistance in the
circuit to protect the Pertronix, just like points. This resistance is
provided by your old fashion ballast resistor (old as the days of points)
having 1.7 ohms of resistance. The roadster coil has its internal resistance
of 1.7 ohms to add to that. With the ballast resistor in the circuit, the
voltage is dropped from 12 volts to 6 - 9 volts. Do the math (shown below)
and you'll see why a ballast resistor is required to not exceed a Pertronix
current limit of 4 ohms.
But, with a real electronic distributor like the Hitachi for Nissan (like the
ones I convert for a roadster), the voltage supplied is 12 volts because the
EI distributor is designed to take it, so the ballast resistor is removed from
the circuit. The 12 volt EI coil used with the EI distributor is low
resistance (from 0.84 to 1.02 ohms). Do the math again (shown below) to see
how much current flows.
Ohm's Law - E = IR or I = E / R or R = E / I
where:
E = electricity in volts
I = current in amps (cannot exceed 4 amps for a Pertronix Ignitor)
R = resistance in ohms
Original roadster system (best case):
I = 9 volts / (1.7+1.7) ohms = 2.6 amps
EI system (worst case):
I = 12 volts/1 ohm = 12 amps
Now compare the power fed to the primary windings of the ignition coil for a
roadster ignition versus a 12 volt electronic system:
Power Formula - P = IE
where:
P = watts
I = amps
E = volts
original roadster system (best case):
P = 2.6 amps X 9 volts = 23.4 watts
EI system (worst case):
P = 12 amps X 12 volts = 144 watts
That's a lot more power to the coil for the EI system. More power in, more
power out, less misfires, wider spark plug gaps, etc. You get the idea.
Gary
datsunmike wrote:
> Go with a Pertronix setup. That thing must be from the 70s.
>
> Mike
>
> ----- Original Message -----
> From: "L Jordan" <ay107@lafn.org>
> To: "Datsun Roadster List" <datsun-roadsters@autox.team.net>
> Sent: Monday, September 02, 2002 1:54 PM
> Subject: Electronic ignition x-mac-creator="4D4F5353"
>
> > List,
> > Does anyone know anything about the electronic ignition kit on ebay? Was
> > wondering if it is the correct type and if anyone else has used it.
> > Thanks,
> > Linda
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