The correct selection method of automobile spark plug

The spark plug is an important element to support the work of the gasoline engine (the diesel engine is compression-ignition work, there is no spark plug). The body is small but the knowledge inside is not small. Today we will talk about the basic knowledge that needs to be paid attention to when replacing the spark plug, so that you can choose When buying spark plugs, the choice is more accurate, and the heart is more informed.

●Working principle

The function of the spark plug is to make the pulsed high voltage electricity released by the ignition coil into an electric spark at the tip, ignite the air-fuel mixture in the cylinder to perform work, *In layman’s terms, it is equivalent to the flint of a lighter, an activated component. The main structure of the spark plug is: 1. The wiring screw; 2. The central electrode; 3. The ground electrode; 4. The metal shell; 5. The insulator, the most important of which is the two electrodes. More basic knowledge will not be repeated in this article. If you want to learn more about spark plugs, I recommend you to read this article: “Practical Technical Manual (4) Secret of Spark Plug Technology”. Let’s talk about the things we need to know before replacing spark plugs.

★Select the hard index of the spark plug

1. Size

To replace the spark plug, you must choose the size that suits your vehicle. The length and diameter must match. This does not need to be judged. If you buy the wrong model, you can’t install it. Even if you can install it, the slight difference in size will affect the performance. Cause adverse effects, severe cases will damage the engine. Each spark plug has its model number printed on it. The second letter in this string of characters represents the size of the spark plug, which also contains the diameter and length of the thread.

Thread diameter

There are three main thread diameters: 10mm, 12mm and 14mm. Among the models on sale in China, 14mm is the mainstream size. However, as the engine design becomes more and more compact, various parts will also be miniaturized. Spark plugs No exception, the trend of getting smaller and thinner has been set. In the future, spark plugs with smaller diameters such as 10mm and 12mm will become the mainstream.

Thread length

Another important dimension is the length of the thread. Many friends also call it “tooth length”. There are many models in the list, but it is too difficult for ordinary users to remember these models, and they are not too big. Meaning, you just need to remember what size spark plug your car requires to be replaced. Some friends will ask what model of my car is? This problem is found in the product introductions of major spark plug manufacturers. It is not difficult to find the spark plug model corresponding to your own car model.

2, calorific value

The heat value parameter is also very important. *The popular explanation is the heat dissipation capacity of the spark plug itself. However, different manufacturers have different naming rules for the heat value of the spark plug, so it cannot be summarized as “high” or “low”. It can be simply It is divided into “cold type” spark plugs with good heat dissipation capacity and “hot type” spark plugs suitable for low-speed engines. For example, for the champion spark plug, the larger the value, the more the spark plug is biased toward the “hot type”, while the larger the value for the NGK spark plug, the more the month is biased toward the “cold type”. When purchasing spark plugs, you must choose according to the calorific value that matches the vehicle. If the selection does not match, it will affect the performance of the engine.

Cold spark plug: The higher the calorific value of the spark plug, the better the heat dissipation capacity. This type of spark plug is more suitable for high-horsepower engines. On the contrary, its disadvantage is that the heat dissipation is faster, so it is easier to produce accumulation for small-displacement engines. Carbon, and the most serious consequence of the accumulation of carbon is ignition misfire. If you are driving a high-powered car or often high-speed “drag racing”, then you can consider this kind of spark plug.

Hot spark plug: Under the same working temperature, it is not easy to produce carbon deposits, but the heat dissipation capacity is relatively poor. It is suitable for family cars that do not pursue power performance. The disadvantage is that if the heating value of the hot spark plug is too high, pre-ignition and knocking may occur.

Different engines have different requirements for the calorific value of spark plugs. For high-power engines and good power, it is recommended to choose cold spark plugs, which have good heat dissipation; for small displacement engines, it is recommended to choose hot spark plugs, which are not easy to produce carbon deposits.

It should be noted that different spark plug manufacturers have different ways of expressing the calorific value. For example, the higher the value of the champion brand, the more biased the model. The larger the value, the more cold the NGK brand is. Therefore, when buying spark plugs, you must follow The calorific value corresponding to different models in the product catalog is used to select spark plugs.

After the two parameters of size and calorific value are determined, it can be guaranteed that the spark plug can meet the normal use. As for the performance and life, it depends on the material and other parameters.

★The effect of spark plug material on performance

The spark plug is composed of two parts: an iron shell and a central ceramic body. The ceramic body also contains the wiring screw and the electrode. When we usually select the spark plug, the “certain gold” refers to the material of the small electrode. The materials of other parts are negligible for engine performance.

The common electrode materials on the market now include copper, nickel alloy, platinum, and iridium (platinum and iridium are commonly referred to as precious metals). The electrical conductivity of the metal increases from left to right (copper <nickel alloy <platinum <iridium gold) ), the voltage required for ignition is reduced from left to right (copper>nickel alloy>platinum>iridium), so the precious metal spark plug has a smaller load on the engine, which is beneficial to reduce fuel consumption; in addition, the precious metal has a longer service life, of course the price It also increases with the increase in performance. The price of iridium spark plugs is generally more than one hundred yuan per piece.

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