Spark plugs (VW Beetle)

The spark plug consists of a middle electrode, an insulator and a ground electrode. An ignition spark jumps between the middle and side electrodes, which ignites the fuel-air mixture. Spark plugs determine the reliability of starting, idle parameters, engine responsiveness and the maximum speed of the vehicle. Therefore, it is not recommended to change the spark plug type prescribed by the manufacturer, which is determined by the heat rating and other characteristics, unless necessary.

The heat rating indicates the maximum permissible thermal load of the spark plug in the engine under certain operating conditions. Spark plugs for each specific engine are selected so that they reach self-cleaning temperature as much as possible under any engine operating conditions. The lower the glow plug's heat rating, the higher its glow ignition resistance and the lower its resistance to fouling. The higher the glow plug's glow number, the lower its glow ignition resistance and the greater its resistance to fouling.

The heat rating is indicated on the spark plug markings. The markings are deciphered as follows:

Bosch spark plugs:

Example	W	R	7	D	WITH
	1	2	3	4	5

1. W - thread M14x1.25 with a flat seat for a 21 mm key; F - thread M14x1.25 with a flat seat for a 16 mm key; M - thread M18x1.5 for a 25 mm wrench; H - M14x1.25 thread with a conical seat for a 16 mm wrench; D-M18x1. 5 thread with a 21 mm turn-key taper fit.

2. R - with additional resistance.

3. Heat rating. Heat ratings range from 0.6 (cold) to 1.3 (hot). A heat rating of 7 corresponds to a heat rating of 1.75 (old designation), 6 - 200, 5 - 225, etc.



4. A - thread length 12.7 mm, spark of normal length; B - thread length 12.7 mm, elongated spark; C - thread length 19.0 mm, spark of normal length; D - thread length 19.0 mm, elongated spark.

5. Material of the middle electrode. Cr-Ni - chromium-nickel alloy, C - copper-nickel alloy, S - silver, P - platinum, O - standard spark plug with reinforced central electrode.

In the presence of a copper (Cu), and especially a silver, rod of the central electrode, the thermal conductivity of the spark plug, and therefore the maximum thermal load, increases.

Beru candles:

Example	18	TO	7	IN	U
	1	2	3	4	5

1. Thread diameter in mm (here is M18).

2. Design feature. K - conical fit, R - with resistance for protection against interference.

3. Heat rating (like Bosch spark plugs).

4. Thread length (like Bosch spark plugs).

5. Material of the middle electrode (U - copper-nickel alloy). Spark plugs with a silver center electrode are designated "RS" (for example, RS35).

It is possible to install spark plugs with a heat rating different from that recommended by the manufacturer if operating conditions differ significantly from normal and this causes engine malfunctions. If the spark plugs are constantly covered in carbon deposits, they have not reached their self-cleaning temperature and should be replaced with spark plugs of the next highest heat rating. If the engine is not producing full power, spark plugs with a lower heat rating may be required.