Hyundai's New Spark Plug Safeguards The Future Of The Combustion Engine

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This clever new patent maximizes energy use in a gas engine's ignition coils, giving greater efficiency and cleaner emissions.

While Hyundai is highly focused on the developing EV market, a radical new spark plug design from the South Korean manufacturer shows that it also wants to extract greater efficiency from the internal combustion engine. According to a patent found by CarBuzz at the US Patent and Trademark Office (USPTO), Hyundai's engineers have found a very clever way to extract even more efficiency from a gas engine's ignition coils. In turn, this could be key to Hyundai keeping the combustion engine alive for future N models like the Elantra N.

The idea of twin-spark ignition is nothing new, of course, since Alfa Romeo pioneered it in 1914. Since then, it has been used by many other manufacturers to improve combustion efficiency and achieve cleaner exhaust emissions. It will even make a comeback in the next evolution of the Mazda Skyactiv X engine. But the one thing that all true twin-spark engines throughout history have in common is the need for two spark plugs and dual ignition coils.


We're also familiar with multi-prong spark plugs, where multiple ground electrode designs can improve the chances of a successful ignition event, and special center electrode designs with needle tips or slotted grooves to cater to the needs of specific combustion chamber designs. But, regardless of the number of ground electrodes or the shape of the center electrode, there will only be one spark per ignition event because that's how many times the coil fires.

This Hyundai patent will enable actual twin-spark ignition from a single spark plug and achieves this goal with some really clever thinking. After taking a fresh look at the voltage conditions in an ignition coil's high-voltage side during a spark event, the engineers realized that there was an unused spike in the output voltage graph. That's when inspiration struck, and they added a second center electrode to a single spark plug to make use of this extra output spike.


In current ignition systems, the spark is triggered in an ignition coil when the engine's control unit switches off the primary coil. When the primary coil windings are given an input current, it generates a standing magnetic field, which is transferred to the secondary coil winding by way of their shared ferrite core. This magnetic field stores energy generated by the primary coil, and when the primary coil is switched off, this energy is discharged through the secondary coil to generate a high-voltage spark with a positive polarity at the center electrode's tip.

However, this discharge is followed by a negative voltage spike immediately after due to magnetic lag effects in the secondary coil. In effect, the secondary coil windings momentarily switch polarity and create the possibility for a second spark event by generating a voltage spike that is lower than the spark plug's ground electrode's voltage.

Current ignition systems ignore this negative voltage spike because the plug has sparked and the job is done, but this Hyundai patent demonstrates that it is possible to generate a second spark using this inverted polarity spike as well.

To make this work, the spark plug was redesigned. The ground electrode can take on various shapes in the current fashion, but another center electrode joins the traditional center electrode. One of the two electrodes is the conventional positive electrode and is connected to one side of the secondary coil windings. The second electrode is connected to the other end of the secondary coil windings. The two center electrodes are encapsulated in the same isolating material, and they both fire to the outer ground electrode, which is always at the engine's reference ground voltage.


When the positive voltage spike occurs, the positive center electrode ignites the air-fuel mixture against the ground electrode in the usual way, and when the negative voltage spike comes around shortly after, it creates another spark between the negative center electrode and the ground electrode. It is a very simple technique to generate two sequential sparks from one spark plug and doesn't even need a specialized control system to work. The only difference is that there are two center electrode connectors (one positive and one negative) jutting out from the top of the spark plug instead of the usual one.

The advantages of this invention are numerous and revolve around the extra spark being added to the ignition event. When both center electrodes have sparked to the ground electrode, they combine and create a larger flame front inside the combustion chamber.


This speeds up the flame travel, which leads to a quicker and more-complete burn of the air-fuel mixture, giving improved energy conversion efficiency and reducing emissions. The increased energy in the flame also enables the engine to run on leaner air-fuel mixtures without the risk of misfiring, which will improve fuel efficiency and further reduce exhaust emissions.

With this system employed, the operational improvements may be significant enough to nudge a borderline engine into ultra-low emission territory, or it may clean up an engine that might otherwise not have conformed to emission standards at all. The best advantage of this system is of course that improved combustion efficiency should also liberate a bit of extra performance, and for many drivers, that alone will be enough reason to embrace this new development.

And, thanks to another new development from Hyundai, you wouldn't even have to worry about premature wear on these plugs as you could check that remotely.


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Current and voltage for a new spark plug, E = 32.6 mJ – laboratory tests (capacity spark discharge)

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