Spark plugs — general information

The spark plug consists of a central electrode, an insulator with a housing and a ground electrode. The central electrode is hermetically fixed in the insulator, the insulator is rigidly connected to the housing. An ignition spark occurs between the center electrode and the ground electrode, which ignites the air-fuel mixture. The ability to start the engine, the behavior of the engine at idle, acceleration time and maximum speed depend on the operation of the spark plugs. Therefore, candles should not be installed, the type of which differs from that recommended by the manufacturer, and which, among other things, characterizes the glow number.

The glow number characterizes the degree of heat resistance of the spark plug. The lower the glow number of the candle, the higher its heat resistance. That is, a candle is better able to remove heat, which prevents harmful incandescent ignition (engine knock). However, a candle having a high heat resistance has the disadvantage that its self-cleaning temperature is also higher. Therefore, it is more prone to smoking, especially when the engine often does not have time to reach its operating temperature (urban travel, short distance travel in winter). Usually on "hot" engines that require high power output are installed "cold" candles (glow number starting from 06).

The glow number is contained in the spark plug code. The code is decrypted as follows:

Bosch spark plugs

Example



1 W = thread M 14 x 1.25 with flat seal, SW 21; F = thread M 14 x 1.25 with flat seal, SW 16; M = thread M 18 x 1.5 with flat seal, SW 25, H = thread M 14 x 1 25 with cone seal, SW 16; D = thread M 18 x 1.5 with cone seal, SW 21, SW = wrench size.


2 R = with interference suppression resistor. It does not affect the functioning of the ignition system.

3 Heat number The scale of heat numbers is set by 06 ("cold") up to 13 ("hot"). At the same time, the glow number 7 corresponds to the old designation of the glow number 175, 6, respectively, 200, 5 - 225, etc

4 A = 12.7 mm thread length, normal spark position, B = 12.7 mm thread length, spark advanced position, C = 19 mm thread length, normal spark position; D = 19mm thread length, spark extended

5 Center electrode material: No designation = chrome-nickel alloy; C = copper-nickel center electrode; S = silver center electrode, P = platinum center electrode, O = standard plug with reinforced center electrode.

Thanks to the copper rod in the center electrode, and even more so thanks to the silver center electrode, heat dissipation and thus the heat resistance of the spark plugs are increased.

Beru spark plugs

Example:

• 1 Thread diameter in mm, here M 14 x 1.25
• 2 Design feature, e.g. K-tape fit, R - resistance to suppress radio interference.
• 3 Heat number (same as Bosch spark plugs).
• 4 Thread length (same as Bosch spark plugs).
• 5 Electrode material (e.g. U - copper rod).

Installing spark plugs

Replace spark plugs only when the engine is cold or warm.

Caution: Removing the spark plugs from a hot engine may damage the threads of the spark plug hole in the light alloy cylinder head.

Screw in the spark plugs by hand until they touch the cylinder head.

Attention: In this case, do not distort the candles.

Tighten spark plugs to 25 Nm.

Put on spark plugs. By moving in different directions, checking the reliability of the fit of the spark plug tips and ignition wires.