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Re: Next dumb question re: ignition coils

To: Roadster List <datsun-roadsters@autox.team.net>
Subject: Re: Next dumb question re: ignition coils
From: Ronnie Day <rday@hot.rr.com>
Date: Tue, 30 Mar 2004 17:55:27 -0600
> I tested the ohm rating of my coils - all four of them on a car or lying
> around.  My PL411 (no ballast resistor) and a spare came out around 3.5
> ohms, my SPL311 came out at .5 with a 1.6 ohm ballast resistor reading
> (do you add ohms together, and does the .5 reading mean my coil is
> dying or incorrect for my car?), and another spare coil read 1.5 ohms.
> 
> Back to Pertronix's website, they recommend 3.0 ohms as "city" use for 4
> cyl, and a 1.5 ohm coil for "racing" use with their Ignitor ignition
> systems.  They list 1.5 ohms for both city and race for an 8 cylinder
> car.  Why the difference in ohms?  What would happen if I used a 1.5
> ohm coil on a "city" car?

Not having a wiring diagram to look at, but based on tired (this evening
anyway) memory, the ballast resistor is in series with the coil so the
values should be added to calculate the total resistance, like 5 +2=7. If
it's hooked up parallel to the coil then the total resistance is calculated
by multiplying the the individual values (5x2=10) and then dividing that
product by the sum of the individual values (5+2=7), so in this example
you'd end up with 10/7=1.43. Just remember that in any case where multiple
resistances are in parallel, the total is always less that the individual
value of the lowest value resistor. Okay, school's out for today, but there
MAY be a pop quiz tomorrow. ;>)

Having gone through all that, I'd buy one of Gary's EI conversions. I think
the 2000 I'm getting already has one and I plan on using them on my 510s and
Z-car.

FWIW,
Ron






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