Resistors are not a contradiction

Resistors are used with all NGK ignition cables, although a low-loss transmission is desired as a basic rule. A look into the electrical technology makes clear that there must not be any contradiction there.

All electrically-operated devices create electromagnetic fields of greater or lesser strength. In most cases they are only negligible, but under some circumstances they are undesired (e.g. interference with radio reception) or even dangerous (keyword: electromagnetic pollution). The ignition system requires optimal low-pass interference attenuation in order to ensure interference-free operation of radios, communications equipment, and control devices for engines or gearboxes.

Oscillating circuit and electromagnetic compatibility

In simple terms, low-pass interference attenuation can be presented as follows: The ignition system consists of a coil and capacitors, which are also referred to as an "oscillating circuit" in electro-technical terms. Interference suppressors (at least 1-5 kOhm) integrated into the ignition circuit reduce these electromagnetic fluctuations and ensure the fault-free interplay of the various equipment. This is called "electromagnetic compatibility" (EMC).

Ignition cables with inductive resistor have a special feature: with this design the resistance changes considerably depending on the ignition frequency (engine speed). In this case, a greater (inductive) resistance is built up due to the coil.

Quality without loss of performance

The assumption that resistors reduce the ignition energy and thus the engine performance proves to be mistaken. The resistors which are used are dimensioned so that they can be unattended. The ignition cable systems offered by NGK provide the best interference suppression with optimal ignition performance in original equipment manufacturer quality. Ignition cables from NGK - safe, durable and affordable over a long period of time. 

Ignition cables - principles

Related topics

  • Electromagnetic compatibility (EMC): Wherever electric current flows, electromagnetic fields are formed, such as with mobile phones and radio waves.
  • Electrical resistance: With spark breakaway at the spark plug, the applied voltage and the current are briefly increased. The resistor has the effect of limiting the current in the system.