Ok Joel, so the Ignitor sounds like the old Hall sensor style, which also
allows coil current with key off. Our OE systems do not and they should
actually work as well or better, with proper coils and no ballasts.
See, the sparking voltage & power stem from the change in primary current, not
its value (X amps). So, the purpose of the amplifier is to turn off that
primary current as fast as possible when the dist says so. You can think of
the energy stored in the coil’s magnetic field as “ampere-turns”, meaning amps
times the number of primary turns of wire. The magnetic core also has a
direct effect, but we’ll just assume it’s as good as can be.
With a magnetic field B (flux) established in the core during points (or
amplifier) dwell, and proportional to primary ampere-turns, the dist tells the
amplifier it’s time to generate spark, so the amp opens the primary circuit as
fast as it can. The change in magnetic flux due to the collapsing primary
current we can call dB/dt – flux change per second. The spark voltage is
basically the number of secondary turns (N) times dB/dt.
So, B is proportional to how many amps flow through how many primary turns.
And spark output is proportional to how many secondary turns there are and how
quickly that B goes to zero. That and dwell establishment are the amplifier’s
So, for a 12V system, the coil’s primary resistance should be as low as
possible, to allow the biggest current in amps to flow through the primary and
set up the biggest B we can. The Ignitor’s preference for a 3 Ohm primary
sets us back on that score, compared to the 2 Ohm OE coils, and performance
coils, which are about 1 Ohm. I’d go back to the OE amplifier (and no
ballast). Glad you moved the coil to the fenderwall.–
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.
In reply to a message from Doug Dwyer sent Wed 2 Jan 2008:
Doug, thanks for the info. Always good to read and learn.
To quote from Pertronix literature,
‘‘2. The Ignitor is compatible only with a ‘‘points style’’
coil. Coils in six & eight cylinder engines require a
minimum of 1.5 ohms of resistance. 3. If your ignition
system presently has a ballast resistor, do not remove it.
4. Caution: never use a ‘‘HEI’’ type coil with the Ignitor.
This type of coil will damage the module, cause it to fail,
and void the warranty. 5. The red wire from the Ignitor
must be connected to the positive (+) side of the coil and
the black wire must be connected to the negative (-) side of
Also, some interesting Q and A’s under the Pertronix
‘‘Ignitor COMMON QUESTIONS AND ANSWERS’’ literature section:
‘‘Q. The engine still will not start or runs rough. Are
there any tests I can do ?
A. Yes, remove the red Ignitor wire from the coil. Connect
a jumper wire from the positive side of the battery to the
red Ignitor wire just removed from the coil. If the engine
starts you have a low voltage problem (This is a very common
problem). Remember this is just a test. Not intended for
Q. How can I fix a low voltage problem ?
A. First, if you have an external ballast resistor, connect
the red Ignitor wire to the ignition wire prior to the
ballast resistor. Second, if you do not have a ballast
resistor you must connect the red Ignitor wire to a 12-volt
source that is controlled from the ignition switch.
Q. What type of a coil do I need?
A. Any ‘‘points style’’ coil with minimum 1.5 ohms of
Q. How do I check my coil for resistance?
A. First you need an ohmmeter. Remove all the wires from
the coil. Attach the meter to both the positive and
negative terminals. The reading must be 1.5 ohms or
greater. (Your local auto parts store can do this for you
if you do not have an ohmmeter)
Q. What do I do if my coil does not have enough resistance ?
A. You may purchase and install a 1.5 ohm ballast resistor
from our local auto parts store. You may also choose to
purchase a Flame-Thrower 40,000-volt coil which provides 1.5
ohms of resistance internally and is compatible with the
Ignitor. Note: Many vehicles came equipped with a resistor
wire or a ballast resistor. These applications may not need
an additional resistor.
Q. What happens if I leave the ignition switch on when the
engine is not running ?
A. This can cause your coil to overheat, which sometimes
will cause permanent damage to the coil and the Ignitor.’’
The archives and FAQ will answer many queries on the XJ series…
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