T
here are a number of advantages to running coil-per-cylinder ignition systems, which is exactly why you see them on every new engine rolling off the assembly lines. With today’s advanced technology, the ignition timing can be controlled to match the fuel delivery in each cylinder to result in the best performance. Thanks to advanced drivetrain management capabilities in motorsports, these advantages are being pushed to the extreme. To keep pace with the high voltage needs of racers, the team at MSD have always been pushing the ignition envelope with new products. One of their latest systems, the Smart Coil Big Wire Kit offers a number of different advantages that we’ll dwell on for a bit, (you’ll get our pun shortly.) But first, let’s answer the two most common question about this new
104
september 2021 | RPM Magazine
coil-per-cylinder performance ignition coil set: What exactly is a Smart Coil and how does increasing dwell time affect spark output? To understand the intelligence level of coils, we need to review a coil’s function and explain dwell time. An ignition coil consists of two sets of windings placed around an iron core. The primary winding is made up of
a thicker wire with fewer turns while the secondary set of windings is a finer wire wound very tightly. This is where you get the term “turns ratio”; the comparison of the secondary windings to the primary, such as 100:1 or 80:1. Low voltage with higher current is carried through the primary windings which produces a magnetic field when the circuit is closed, but when opened (triggered) the magnetic field collapses inducing a very high voltage with lower current into the secondary windings. These windings are connected to the spark plug terminal of the coil which then leads this high voltage through the plug wire and across the electrode of the spark plug. Whether a standard ‘dumb’ coil, or ‘smart’ coil, they each share this common make up of a primary and secondary winding set along with an