NGK glow plugs under the spotlight

four glow plugs on a working table, a workshop is seen in the background
Niterra has a long and successful history as a pioneering automotive components supplier and one of the key items in its NGK Ignition Parts brand portfolio is the glow plug. Niterra is a major OE and Aftermarket supplier of glow plugs in the EMEA region. Its state-of-the art product range has approximately 270 part numbers in NORDICS that cover 80% of vehicles in operation in the area.

The heart of a diesel engine

Like the spark plug, the glow plug plays an important role in starting an engine. In this case, it is the diesel engine. But unlike the spark plug, which ignites the fuel, the glow plug's main function is to raise the temperature required for the diesel fuel to burn itself. And as with spark plugs, millions of vehicle owners around the world rely on the reliability and robustness of NGK glow plugs. For decades, the brand has worked to create a product that not only saves fuel, but also helps to make the vehicle in which it is installed more environmentally friendly.

Durability is the key to efficient ignition in a combustion engine. The drive train of a diesel engine works by drawing ambient air through the piston into the cylinder, where it is highly compressed. This compression raises the temperature of the air to over 500 degrees Celsius. When diesel fuel is fed into the chamber, the fuel ignites. However, when the engine is cold, it has difficulty reaching the right temperature for ignition, and this is where the glow plug plays a major role in preheating the combustion chamber. However, modern glow plugs do more than just preheat, they continue to work while the engine is running and help to maintain a constant temperature. In this way, the engine runs more smoothly, emissions of hydrocarbons and carbon monoxide are significantly reduced and fuel is saved. In modern diesel engines, glow plugs play an even greater role, as they significantly support the regeneration of diesel particulate filters (DPF) in vehicles by helping them to quickly reach the required temperature to burn off the accumulated soot. In addition, their services are essential in vehicles with automatic start-stop systems, where temperatures fluctuate frequently.

 

More than a sibling

There are two types of glow plugs: metal glow plugs and ceramic glow plugs. Both technologies work in a similar way and have the advantage that they can be heated to high temperatures, making them suitable for a wide range of vehicles. Ceramic glow plugs, however, are materials based on metal oxides, which enable the plug to conduct electricity just as well as its metallic cousins. Ceramic glow plugs were developed by NGK to meet the increasingly stringent emission regulations. Thanks to their high heat tolerance and suitability for extremely cold conditions, ceramic glow plugs can maintain a so-called “afterglow” at temperatures of up to 1,350 °C for more than ten minutes after activation. This reduces engine smoking and thus the release of harmful hydrocarbon and carbon monoxide emissions and contributes to smoother engine running.

Modern metal glow plugs are made of heat-resistant metal and their filaments are protected by a magnesium oxide layer, which not only provides excellent thermal conductivity, but also protects the filament from vibrations and shocks that could damage it. There are essentially three main types of metal glow plugs: standard glow plugs, self-regulating glow plugs and AQGS (Advanced Quick Glow System) glow plugs.

NGK glow plugs are the first choice for both original equipment manufacturers and aftermarket customers looking for outstanding durability and the ability to restart repeatedly at low ambient temperatures. In addition, they ensure stable idling during the engine warm-up phase. Thanks to their robust design, they offer high corrosion resistance and unparalleled heat transfer properties. Their design ensures perfect gas sealing, good protection of the internal heating coil as well as high resistance to deformation and high shear torque.

 

The nature of maintenance

As with spark plugs, it is always important to check the instructions for the best way to replace glow plugs.

In order to achieve the maximum service life of the components, special attention must be paid to the removal and replacement of glow plugs. There are also a number of problems that can impair the proper functioning of glow plugs. These include, above all, the tendency of the diesel engine to soot up the glow plug bore. After removing the old glow plug, it is essential to clean this bore with a special reamer to remove any deposits before installing a new plug. Otherwise, the new glow plug may be damaged during installation or the glow plug may not reach the optimum operating temperature. Other problems relate to the application of incorrect torque when fitting the plugs and their loosening during operation, both of which can be rectified by tightening to the correct torque. In more extreme cases, the glow plugs can also be damaged by thermal shock. This can happen if a defective fuel injection valve does not close completely or if oil or water gets into the combustion chamber.

This article aims to provide some technical background on one of NGK's most important products and a key component in diesel vehicles. This article is the second in a series of articles designed to draw attention to the technical background of Niterra's state-of-the-art automotive products. The next topic is ignition coils, ignition cables and spark plug connectors. The first article in this series on spark plugs can be found here.

Weitere Informationen zu den Glühkerzen der Marke NGK finden Sie im TekniWiki, einer technischen Plattform mit interaktiven Lernmodulen unter https://www.tekniwiki.com/de/wiki/gluehkerzen/.

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