NGK Multiground Spark Plug – MAR9A-J


Part Number: MAR9A-J

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NGK are the worlds largest manufacturer of Spark Plugs
Japanese designed and engineered for precision and quality
NGK Multiground Spark Plugs can have two, up to four electrodes
Even wear, spark distrubution and reduced cold start fouling
Spark plugs come in many different ground electrode configurations. Based on engine design and original equipment manufacturers’ specifications, there are several different ground electrode spark plug configurations used today. Some manufacturers have elected to use spark plugs with more than one ground electrode—why?

Multiple-ground electrode spark plugs can have two and up to four ground electrodes. Multiple-ground electrodes can maximize the life of a traditional material (nickel-alloy) spark plug. As the spark plug fires, plug wear is distributed more evenly among the ground electrodes. Another added benefit to multiple-ground electrodes is that of reduced cold-start fouling, in that should the plug start to become fouled, the spark can travel across the insulator more easily.

With these benefits, why doesn’t every manufacturer use multiple-ground electrode plugs? As the spark plug fires and the initial flame kernel is created, more quenching is experienced, as there is more plug mass in the way of flame travel. The quenching effect refers to an area during the combustion process where heat (flame) is inhibited by an interfering mass (ground electrode). Traditionally, single-ground electrode and especially precious metal, platinum and iridium plugs have superior ignitability.

A common misconception of multiple-ground electrode spark plugs is that they can fire more than one spark at a time. For example, a plug with four ground electrodes must fire four sparks at once; the laws of electrical physics tell us this just isn’t possible. Electricity will take the path of least resistance, meaning one spark will occur between the center electrode and whichever ground electrode is easiest to ground to.

Multiple ground electrode plugs should only be used when replacing an OEM plug with multiple ground electrodes. If an OEM plug has only one ground electrode, you should not replace it with a multiple ground electrode.


Spanner Size:
14,0 mm

Outer thread [mm]:

Thread Length [mm]:

Spark Plug:
Fixed SAE connector
Nickel Middle Electrode
2 – Earthed Electrode
Interference Suppression 5K?
With gasket seat

Spark Position [mm]:

Part Number:

Manufacturers warranty


Spark Plugs – Multi Point


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