GLOW PLUGS

 Overview
 Sheathed type glow plugs
 Ceramic glow plugs
 NGK glow plugs viewed in detail
 Intelligent glow technology

Sheathed type glow plugs

The heating and control coil are enclosed in a “glow pencil” (glow rod or rod-like heating element) made of heat resistant light metal alloy. They form a joint resistance element, where the heating coil with the front part of the glow pencil represents the heating system and the control coil is fixed to the live, current-carrying connection bolts. The insulating powder (magnesium oxide) is packed between the coil and rod. 

 

The heating coil is not directly exposed to the combustion and the surges, which arise due to the rapid expansion of the mixture. The glow pencil provides the heating coil with a certain amount of protection from the carbon produced during the combustion. This does not deposit, so that a short circuit does not result.

 

Structure of a self-regulating glow plug

Standard-sheathed type glow plugs

 

These have a heating coil whose resistance does not change even under an increasing temperature. Special feature: They therefore always consume the same amount of electricity.

 

Quick-start glow plugs

 

These have a heating curve whose resistance changes with the temperature. The resistance is initially low so that plenty of current flows through the heating curve. The temperature increases faster than in standard plugs – and as a result the preheating time reduces. Special feature:

The resistance increases with increasing temperature, which causes the current flow to reduce.

 

 



Voltage proportion

QGS-sheathed type glow plugs

 

QGS sheathed type glow plugs heat up extremely quickly. However, a special QGS control device is needed.

 

There are two different, non-interchangeable types of quick-start glow plugs:

- with one heating coil

- with two heating coils

The first type has one heating coil with a low resistance which is designed for an extremely high current flow. The second type has both a heating and a control coil. This guarantees that the resistance increases with temperature and therefore provides a certain degree of temperature control.

 

Summing up:

These glow plugs have very short preheating times and improve the cold start performance.

 

Safety information:

If the voltage is generated for too long and the temperature is too high, the glow plugs can melt and crack. Therefore the control device or relay must either reduce or completely switch off the current flow as soon as a temperature of about 900°C is reached.

 

Self-regulating sheathed type glow plugs

These so-called SRM-sheathed type glow plugs have a heating coil and a control coil. The heating coil heats up very quickly. The control coil increases the resistance with increasing temperature.

 

Special feature:

Due to the properties of the control coil, such a glow plug heats up very quickly and is automatically limited once the temperature is reached. This preheating system requires hardly any external control. It provides excellent preheating and after glow properties!

 

Type of glow plug     Preheating times
Sheathed type
glow plug		 with one coil Standard e.g. Y-103-2, Y-173 20-25 Sec.
to 800°C
    Quick-start-glow plug e.g. Y-103 V, Y-106 V 15-17 Sec.
to 800°C
      Y-128 T, Y-204 T S1 13-14 Sec.
to 800°C
    Quick-start-glow plug e.g. Y-112 M 1 approx. 10 Sec.
to 900°C
      e.g. Y-107 R,
Y-112 R 1		 approx. 6 Sec.
to 900°C
  with two coils Quick-start-glow plug e.g. Y-707 RS,
Y-702 U		 approx. 6 Sec.
to 900°C
    self-regulating e.g. Y-701 J,
Y-515 J		 approx. 4 Sec.
to 900°C