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Ignition cables - mode of function

When the spark flashes the high-tension voltage (up to 25 kV) produced by the ignition coil 

must first "flow" via the ignition cable to the spark plug. In order to make sure that this works, 

these cables must meet a number of requirements.

High-grade insulating properties, high temperature resistance (up to 200° C), 

resistance against vibration, temperature and humidity variations is the most important prerequisite 

high-grade ignition cables must feature.

And this consistently, reliably, and long-term, working in the most adverse conditions.

Resistance - not a contradiction

With all three Takumi types, ignition cable with copper cable and suppression plug (Fig. 1), ignition cable with active resistance (Fig. 2), and ignition cable with reactance (Fig. 3), one will notice that resistors are being used. In principle, low-loss transmission with low resistance is desired. A look into electrical physics shows that this is no contradiction. As we know, all electrically operated units produce more or less strong electro-magnetic fields which in most cases do not cause any problems, but are undesirable in certain circumstances (interference with radio reception) or maybe cause danger, by creating electronic smog. The ignition system, therefore, requires an optimum of short-distance interference suppression in order to ensure trouble-free operation of radio, communication electronics, and engine and gear unit control systems. Simplified, this could be explained as follows: Basically, the ignition system consists of a coil and a capacitor, also called a resonating circuit in electric engineering. These electric oscillations are reduced by suppression resistors (mostly 1-5 kOhm) integrated into the ignition circuit. These ensure trouble-free functioning of the various devices, what is generally called electro-magnetic compatibility (EMC). The behaviour of ignition cables with reactance (Fig. 3) is different, in so far as the resistance depends on ignition frequency (engine speed). In this case a higher resistance develops with higher speed because of the wire coil (inductive reactance).

Quality without loss of power

The assumption that resistors reduce the ignition power and, thereby, engine performance is found to be incorrect because the resistors used are so dimensioned that they can be neglected. But it is a fact that the cable systems offered by Takumi in original equipment quality provide best interference suppression combined with optimum ignition performance. Safely, consistently, and economically, over long periods of time.

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