AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual - Manual (Page 284)

278
© 2014 AEM Performance Electronics
Infinity User Manual
Ignition Coils
An ignition coil is charged when current flows through the primary side of the coil. A coil driver is
required to sink the current and dissipate the heat generated during operation. The coil outputs
from the Infinity are used to trigger the drivers. The drivers can either be contained within the coils
themselves or they can be contained within a stand-alone device installed between the Infinity
and the coils.
There are several different types of ignition systems in use on modern cars.
They are:
Distributed spark using a single coil and a distributor for all cylinders.
Wasted spark using one coil for two cylinders.
Direct Fire using one coil on plug of each cylinder.
Distributed Spark
Distributed spark systems have been around the longest. As the name implies, the spark is
distributed to the plugs via a coil output to a rotor, then through the distributor cap to the
appropriate plug via a high-tension (HT) lead. This is the most complex system because of the
relationship that has to be maintained between the firing point, rotor to cap terminal angle, and
engine position. Distributed spark systems also rely on a mechanical link between the engine
and ignition output, which adds another dimension of unreliability-and to a minor extent-
inaccuracy in timing. In addition to these problems, distributed spark systems typically produce
the least intense spark of all ignition systems. The time to achieve full charge diminishes as
engine speed increases; therefore the coil charge is reduced as a function of RPM. In spite of
the potential problems with distributed spark systems, they have been used successfully for many
years on high-performance engines. Distributed spark ignition systems respond well to spark
amplification within their design limits.