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There are a number of advantages to running coil-per-cylinder ignition systems, which is exactly why you see them on every new engine rolling out of the factories. 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 (you’ll get our pun shortly.)
But first, let’s answer the two most common question about this new 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.
One of the most important parts to this kit is the beefy gauge wires. With the longer dwell time and increased current to the coils, the thicker wire ensures the coil gets a full dose of current and voltage.
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 wiring set along with an iron core.
Dwell time refers to the amount of time that a coil has to build the magnetic field through the primary windings. In the old days, setting the breaker points of a distributor allowed you to lengthen the amount of ‘charge’ time before the distributor triggered the next cylinder. (Which is why Accel and Mallory offered Dual Points distributors!) With a standard inductive ignition system, the longer the dwell time, the higher output could be achieved. However, one must keep in mind that as engine rpm increases, the amount of time between each firing of the coil is reduced which adversely affects the amount of voltage the coil has time to create. And on an 8-cylinder engine with a single coil ignition, there wasn’t much time to charge between firings.
Thanks to coil-per-cylinder technology, an inductive coil has a lot more time (eight times more) to charge between firings compared to a single coil system. Plus, with MSD’s smart coil technology and Holley’s advanced EFI technology, you can control the dwell time of the coil to increase the spark output.
A Smart Coil has the same basic winding design to convert a low voltage to a high voltage (at the expense of current) but with the addition of a PC board with an Insulated Gate Bipolar Transistor (IGBT) which provides quick switching and efficiency. This is where the coil is deemed smart as it can regulate its current while being able to handle higher voltage and energy. With these built-in features, MSD’s Smart coils are perfect for use with the advanced dwell control adjustments that can be made through Holley’s Dominator or Terminator X EFI controllers.
MSD’s IGN-1A Coils feature a machine mounting pattern allows them to easily be installed in place of common LS1-LS7 coils. They also will bolt directly to Holley’s cast aluminum LS valve covers with 72mm spacing.
MSD’s new Smart Coil Big Wire Kit allows you to tune the dwell time of each coil to over five milliseconds. That allows each coil to produce up to 190 millijoules of spark energy along with a peak of 50,000 volts. The initial blast of voltage jumps the plug gap while the spark energy is what really ignites the fuel mixture go achieve full combustion of the fuel mixture (even with loads of boost or nitrous).
An important part of MSD’s Smart Coil Big Wire kit is that the harnesses supplied use a much heavier gauge wire to handle the increased current that each coil demands under hardcore performance use. The harnesses are labeled for use with GM and Ford cylinder banks, as well as for universal installations. The harness is a direct connection with 7-pin connector for the ECU and plugs for each of the coils, commonly referred to as IGN-1A coils. The coils are compatible with 12- or 16-volt systems and operate with a max of 17 volts. MSD’s coils feature elongated mounting holes so they will fit in place of popular LS engine style coils.
If you’re running extremely high cylinder pressures, the Smart Coil Big Wire Kit could be the advantage you’ve been looking for. Being able to increase the dwell time gives each coil a considerable boost in output which can make the difference between a misfire or a power-producing combustion event and power stroke. Check out what a difference an increase in dwell can make below.
As the dwell time is increased (X-axis), note the increase in spark energy output (Y-axis) compared to a competitors IGN-1A coil. At 5-milliseconds, the MSD coil puts out 132mJ compared to the other coil at 105mJ.
The dwell increase also affects the voltage output with the MSD coil coming out on top consistently.