Hyundai Develops Method To Check Spark Plug Wear Remotely

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Proven technology applied in a new way allows this Hyundai ignition system to monitor spark plug wear without a physical inspection.

Hyundai has devised a method to remotely monitor spark plug wear, according to a patent found by CarBuzz at the German Patent and Trade Mark Office (DPMA). This patent uses proven ignition system hardware but applies it in a clever new way to check the condition of aging spark plugs without actually removing those used plugs from the engine.

Naturally, this would save mechanics and DIYers time and effort, as well as prevent accidental damage to components; it's very easy to damage an expensive ignition coil or even a cheap spark plug. Worse still, an inattentive apprentice mechanic could crack a spark plug in its thread, making it painfully difficult to extricate from the cylinder head.


This is where Hyundai's ingenuity comes to the fore. To understand how this new technique works, we first need to broadly understand how ignition coils work. Modern gas engines, such as the ones in the Hyundai Tucson, have a separate ignition coil connected to each spark plug in a setup known as direct-fire ignition. These ignition coils each have two windings, in a manner similar to that of a transformer, with a primary (low-voltage) winding that is controlled by the engine's control unit linked to a secondary winding through an iron-based (ferrous) core. The secondary winding is then connected to the spark plug's center electrode.


Energy is stored in an ignition coil by the engine control unit's application of an electric current to the primary winding, which generates a magnetic field in the core. When the primary winding's current is then suddenly turned off to initiate ignition, the magnetic field induces a current in the secondary winding through the ferrous core and quickly dissipates the stored energy by creating a high voltage in the secondary winding.

If this secondary voltage is high enough, a spark will jump from the center electrode to the ground electrode - between the energized center electrode of the plug and the spark plug body that screws into the cylinder head. This spark ignites the air-fuel mixture in the combustion chamber, with the resulting expansion pushing down on the piston to convert the chemical energy in the fuel mixture into kinetic energy. That covers the groundwork, so let's move on to Hyundai's innovation.

CarBuzz/Ian Wright

When the spark occurs, an electric current is generated in the secondary winding. If the spark plug is fresh and new, this current will be lower than when it is old. This is because older spark plugs build up internal resistance and have eaten away their electrodes, with both factors making it more difficult for a spark to occur and increasing the required secondary current before firing. The secondary current is, however, too erratic to measure with compact and affordable equipment, so Hyundai takes the next best option by measuring the current in the coil's primary windings instead.

There is an inverse mathematical relationship between the currents in the primary- and secondary windings, with a high current in the high-voltage secondary winding corresponding to a low current in the coil's primary winding and vice versa. In other words, a new spark plug will show a higher primary current due to its lower secondary current requirement, and an old one will result in a reduced primary current because it needs a higher secondary current to fire.


Measuring the current in the primary winding is much easier than trying to measure the secondary current because the operating conditions are much more stable and give greater accuracy and easier measurement. Armed with this indication of spark plug condition, the engine's control unit can then easily adapt the coil charge time or even adjust the ignition timing to compensate for the reduction in spark plug efficiency.

This sort of thing does not appear to be difficult to implement, nor would it be too expensive as it's based on existing components. Mainstream production could well be on the horizon.

By improving quality and spearheading innovation, Hyundai is no longer tied to its past and is cementing an image that any legacy automaker would be proud of.

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