The spark plugs - here the Bosch spark plug with four ground electrodes - are optimally adapted to the Focus engines. With its high thermal conductivity copper core intermediate electrode and airborne spark technology, it guarantees reliable ignition and durability. 1 - connecting nut of the ignition wire; 2 - ceramic insulator; 3 - the body of the spark plug; 4 - sealing ring; 5 - mass electrode; 6 - thermal cone of the insulator; 7 - intermediate electrode.
In addition, the intermediate electrode and the connecting rod are inserted into a conductive glass melt, which ensures that these parts are fixed and sealed from the side of the combustion chamber. If the desired ignition voltage is reached, it jumps in the form of an electric spark from the intermediate electrode to the ground electrode. This energy is sufficient to ignite the fresh gas in the combustion chamber.
Different heat number
In order for the spark plugs to work reliably, they must quickly reach the self-cleaning temperature after starting the engine (about 400°C). Otherwise, combustion products can be deposited on the thermal cone of the insulator. At full load, the temperature should not exceed about 800°C, although the operating conditions of spark plugs are not the same in all engines. Only the glow number decides whether the spark plug and the engine fit together. If you choose a spark plug with a too low glow number, then its thermal cone will get very hot. This would lead to uncontrolled pre-ignition which could even destroy the engine. On the contrary, if you use a spark plug with too high a glow number, it will not reach the correct self-cleaning temperature and the heat cone will become dirty.
The distance between the electrodes increases automatically
Along with the correct glow value, the spark plugs must have the correct distance between the electrodes. It is about 1.3 mm in new spark plugs, but increases over time: high voltage regularly separates small metal particles from the electrodes. With an increased distance between the electrodes, a higher ignition voltage is required. Consequence: This can lead to misfiring, the engine will no longer start reliably.
When replacing spark plugs, make sure that only spark plugs with the prescribed heat rating, the correct distance between the electrodes and the correct thread of the spark plug are installed.
Candles for Focus models:
- 1.4 L Zetec-SE (55 kW/75 hp) — Motorcraft AZFS 22C
- 1.6L Zetec-SE (74 kW/100 hp) — Motorcraft AZFS 22C
- 1.8 L Zetec-E (85 kW/115 hp) — Motorcraft AYFS 22РР1
- 2.0 L Zetec-E (96 kW/110 hp) — Motorcraft AYFS 22РР1
- 1.8 L Endura Turbodiesel (55 kW/75 hp), DI-Turbodiesel (66 kW/90 hp) — Motorcraft EZD 37
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