Why MSD coils alone on the LN2 ICM don't work. - Performance Forum

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Why MSD coils alone on the LN2 ICM don't work.
Sunday, January 18, 2015 12:08 AM
I write this in hopes that the forum masters see the value in this entry, and make it a sticky for all to see... So as to save the time of those who'd waste space upon these forums asking the question ad-nauseam.

Now, let's begin:

The LN2's ICM ha internal circuitry that senses & controls current-loading in the primary-windings of the ignition coils to a by-design fixed amount, as a method of protecting the rest of the "delicate" circuitry found inside of it. With the factory-replacement coils, this isn't a problem as it doesn't effect coil output (spark voltage) due to the nature of the coils primary winding design. (Factory designed, after-all!)

With the MSD coils, it's different:

The MSD coils were designed to work in-conjunction with the MSD "box" as part of a capacitive-discharge multiple-strike ignition system. The requirement of the coils in such a system is they "energize" quickly to allow multiple firings of them within the time that a conventional system would see only one. This is known as "quick-rise", and coils designed with such a nature have a difference in resistance--lowered typically compared to factory-standard replacement coils. It is this difference that effects why they don't work as-well as expected when used alone with the LN2 ICM, as the lowered resistance ironically plays against the ICM's design nature, causing the coils primary-windings to see no-more saturation than the minimal or what the factory-replacement coils would. This effects output, and the spark voltage that results is no-better--sometimes worse--than what would be had with the factory-replacement coils.

On the other hand, the Accel-brand bolt-on replacements work right-along with the ICM's nature & have an increased spark-voltage output... With no detrimental effects to the system's components or performance.

So in the end, the advice is: If you want to increase spark-output with just a coil change, get the Accel coils... Or save your money & get the full MSD system, in order to take proper advantage of every part involved.

Go beyond the "bolt-on".

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