The heat number is indicated in the designation of the candle. The designation is deciphered as follows.
Bosch candles
1 W - M 14x1.25 thread with a flat sealing surface, 21 mm wrench, F - M 14x1.25 thread with a flat sealing surface, 16 mm wrench, M - M 18x1.5 thread with a flat sealing surface, for key 25 mm, H - thread M 14x1.25 with a conical sealing surface, turnkey 16 mm, D - thread M 18x1.5 with a conical sealing surface, turnkey 21 mm.
2 R - there is an interference suppression resistor
3 - Heat number. Range of numbers - from 06 ("cold") up to 13 ("hot"). The number 7 corresponds to the old designation 175, the number 6 corresponds to 200-225, etc.
4 A - thread length 12.7 mm, thermal cone normal position, B - thread length 12.7 mm with thermal cone protrusion, C - thread length 19 mm, thermal cone normal position, D - thread length 19 mm, thermal cone normal position cones, three side electrodes, L - thread length 19 mm with a large protrusion of the thermal cone.
5 - Material of the central electrode: C - copper-nickel alloy, S - silver, P - platinum, O - standard spark plug with a reinforced electrode.
Beru candles
1 - Thread size (in this case M14x1.25).
2 - Design feature. K is a conical sealing surface, R is the presence of an interference suppression resistor.
3 - Heat number. The decoding is the same as for Bosch candles, except for Silverstone candles: here the designation S6 corresponds to the old designation 145-200, and S7 - 200-225.
4 - Thread length. The decoding is the same as for Bosch candles, except for Silverstone candles: here S6 is a short thread, S7 is a long thread.
5 - Material of the central electrode. U - copper-nickel alloy. A candle with a central silver electrode is designated Silverstone. According to Vega, its service life is 50,000 km. If the operating conditions of the engine are significantly different from normal and there are problems with its operation, you should select the appropriate spark plugs. If the candles have a large layer of soot, this means that during engine operation they do not heat up to the self-cleaning temperature (results of short trips). In this case, it is recommended to replace the candles with others that have a higher glow number. If the car is operated mainly at high speeds, then it is recommended to install candles with a lower glow number.
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