As opposed to the traditional route of designing another CDI system, Australian company ICE has chosen to use digital technology to create a range of hybrid products, offering the higher intensity of CDI systems and the longer duration of OE variable dwell systems. These two factors combine to produce the greatest possible total spark energy (#) at virtually all RPM's from the ICE Digital Inductive Spark (DIS) system.
Improved output is achieved through using a higher coil primary current, resulting in the secondary spark current being more intense. The system also uses mosfet switching technology which is faster as well as minimising heat dissipation and energy wastage, to produce the longest duration spark available.
The dwell period, that is the length of time the coil primary is switched on each cycle, to charge the coil in readiness for the next spark, is where the ICE system really shines. The microprocessor software incorporates an algorithm that senses the rate of acceleration (or deceleration) of the engine and computes just how much shorter (or longer) the next 90 degrees (on a V8 engine) of engine rotation will be, before it actually happens, so it can turn on the coil ahead of time so it will reach full current at exactly the moment it needs to be turned off to produce the spark.
At higher engine speeds, the microprocessor switches to an alternative program which deals with the problem of extinguishing the spark by turning the coil primary back on before the spark has gone out naturally. This is done so there will be sufficient time for the coil current to build up to the set amount of maximum energy for the next spark. It calculates the optimum compromise of time for coil charging versus time for spark duration.
All of this combined provides a hybrid system unmatched by any other in the world. Two versions of the ICE system are employed with different specifications (7 Amp and 10 Amp - not necessarily directly comparable with CDI systems with the same number prefix, as the ICE prefix relates to the amperage used to saturate the coil positive), depending on the application, resulting in phenomenal spark energy being available to ignite the mixtures in the chamber.
The biggest difference between the ICE system and its CDI counterparts, is the amount of total spark energy available between 1000 rpm and 8000 rpm or higher. Where the ICE system maintains a set intensity level with a varying amount of spark duration in time, to provide a constant amount of crank degrees of spark duration throughout the entire RPM range, CDI systems have a set intensity level and a set amount of spark duration in time, resulting in a short amount of crank degrees of spark duration at low to mid RPM levels, only growing to a slightly greater level at the upper extremities (8000 rpm plus) of the RPM range. Even then, they cannot provide the spark duration of an ICE system.
To understand this more fully, consider with an ICE system if 1.0 millisecond of spark at 4000rpm equals 24 degrees of spark duration, then 0.5 of a millisecond of spark at 8000rpm equals 24 degrees of spark duration. Conversely, with a CDI system if 0.15 of a millisecond of spark at 4000rpm equals 3.6 degrees of spark duration, then 0.15 of a millisecond of spark at 8000rpm will equal 7.2 degrees of spark duration at 8000 rpm.
There is no doubt that some CDI systems (only those that multiple spark, those that do not only have a hope of matching the total spark energy of an ICE system at the upper extremities of the rpm range) do provide a greater amount of total spark energy between 500 rpm and 900 rpm, where there is enough time to allow a greater amount of multiple sparks, and thus a greater amount of total spark energy. It is therefore possible a CDI system may provide a cleaner idle between 500 rpm and 900 rpm on an engine that is able to idle so low, due to its greater total spark energy at those idle speeds. However, once the engine speed rises above 900 rpm, the multiple sparks diminish rapidly, significantly reducing the total spark energy available. The time between these multiple sparks is also significantly longer. At approximately 3000 rpm, all CDI systems revert to a single high intensity / short duration spark, which can not provide as much total spark energy as an ICE system.
(#) Total spark energy is calculated as a combination of spark intensity, spark duration and arc voltage. This is determined by measuring the voltage drop across a 100 OHM resistor going to earth / ground in line with the spark from a KD2756 Tester Plug. This represents secondary current whereby spark intensity is expressed in milliamps and spark duration in milliseconds, the combination of which equals total spark energy expressed in millijoules.