NGK’s precious metal spark plugs

The motive behind tipping spark plug electrodes with precious metals was purely performance driven. The smaller the centre electrode, the better the spark plug performs.

Reducing the centre electrode diameter of a standard nickel alloy spark plug, although easily done, would result in a very poor and unacceptable service life.

Using precious metals, NGK was able to decrease the electrode size while actually increasing service life. In doing so the spark plug was able to achieve performance benefits previously not possible.

Electrode wear or erosion is primarily caused by the high temperatures and pressures inside the cylinder.

The higher the melting point of the electrodes, the greater the wear resistance and life.

Another factor in electrode wear is oxidation. Depending on the metal, when a certain temperature is reached within the cylinder the electrodes will begin to oxidise.

If a metal is subjected to a temperature higher than its oxidation point, the erosion rate rapidly increases.

NGK's Iridium IX plugs have been designed with a patented two-stepped centre electrode which improves anti-fouling performance in all driving conditions.

Fouling occurs when carbon deposits build-up along the insulator nose, down to the point where the insulator meets the metal shell.

Carbon is conductive, and as carbon builds up it can form a leakage path on the insulator nose. This can then cause misfire.

Carbon build-up occurs when an engine has been running rich or has been not been given a chance to reach normal operating temperature, e.g. prolonged idling, driving in heavy traffic, or as a result of aftermarket modifications which act to keep the car relatively cool.

Previously the most common way to prevent carbon fouling was to burn the carbon off.

Spark plugs have been designed with a self-cleaning ability, where above certain engine speeds, the temperature of the plug is high enough to burn these carbon deposits away (approx. 450°C).

NGK's Iridium IX Spark Plugs are designed with a tapered cut ground electrode. This new shaped electrode serves two purposes. First, it allows for a better spread of flame during combustion. Second, in conjunction with the 0.6mm diameter centre electrode, it helps reduce the electrode quenching effect.

The flame kernel is therefore less inhibited while igniting the fuel mixture, allowing the flame to have a better spread and achieve more thorough combustion.

This increase in the flame spread means the fuel mixture is burnt faster and more completely, resulting in the engine delivering more power and acceleration, better responsiveness, and increased fuel efficiency.