Spacing between the electrodes of spark plugs: measurement, adjustment

The operation of the internal combustion engine largely depends on the condition of the spark plugs. They are responsible for the timeliness of the ignition of the fuel mixture in the chambers. Therefore, the slightest malfunction of at least one of them will inevitably lead to the fact that the motor starts to triple or even stall. This article will deal with such a concept as the gap between the electrodes of spark plugs. We will try to find out what it affects, how it should be, how it can be adjusted independently.

What is the gap?

Any spark plug of an automotive internal combustion engine has in its design two electrodes: central and lateral. The first of these is plus. It is on him through the contact tip, rod and conductive sealant (resistor) is supplied high-voltage current generated by the coil. Lateral electrode - negative. It is welded to the body of the device and is closed to the "mass" through the thread and skirt of the candle. The spark is nothing more than an arc discharge that arises between the electrodes. It jumps during the supply of an electrical pulse generated by the ignition coil. Its size and power directly depend on the mutual arrangement of the electrodes, that is, on the distance between them, called the gap.

What does the gap affect?

For each type of engine, depending on the type and octane number of fuel consumed, the volume, the developed power, the pressure in the combustion chambers, the car manufacturers produce different candles with different characteristics. In other words, simply to take and rearrange them from "Mercedes" to "Lada" will not work in any way. The gap between the electrodes of the spark plugs is the most important characteristic of them, on which depends the stability of the engine, its power, the number of revolutions developed, fuel consumption, the durability of the work of the piston group parts .

Reduced clearance

Reduced clearance between the electrodes of spark plugs is characterized by a powerful, but short-duration spark discharge. Reducing time leads to the fact that the fuel mixture does not have time to burn completely. As a result, the candles are flooded with fuel, the spark periodically disappears, the engine shakes. Naturally, fuel consumption also increases. The amount of toxic substances in the release sharply increases.

Such a phenomenon at high speeds often leads to the fact that the spark, being too short, does not have time to break between incoming electrical impulses, forming a permanent arc. As a result, we can get burned or completely melted electrodes, as well as inter-turn closure in the coil. Complementing this picture is the complicated start-up of the engine and the accelerated wear of the piston group parts .

Increased clearance

The increased clearance between the spark plug electrodes, on the contrary, causes the spark to lengthen, but becomes too weak to ignite the combustible mixture. In addition, the probability of breakdown of the coil, high voltage wire or insulator increases. If there is too much distance between the electrodes, electricity, which by its nature seeks the shortest way to equalize the potential difference, it is easier to pass through the ceramics than to overcome the increased clearance in the air. As a result, the spark in the cylinder either forms periodically, or disappears altogether. The engine is choked with fuel, troyts or stalls. A characteristic phenomenon for the increased gap is the rare loud claps caused by the misfiring.

What should be the clearance on the spark plugs?

As we have already said, the distance between the electrodes of the candles is different for each engine. To owners of modern foreign cars it is not necessary to think of such concept, as a backlash. Here everything is simple. There is an engine - there are certain candles to it with a certain distance between the electrodes. And the manufacturers of foreign cars strongly do not recommend their independent adjustment.

Everything is a bit more complicated with our cars. The size of the gap between the spark plug electrodes for domestic cars can be from 0.5 to 1.5 mm. First of all, it depends on the type of engine. In carburetor motors with contact ignition, for example, the gap varies from 1 to 1.3 mm, and with the contactless - 0.7-0.8 mm. For engines with automatic injection, manufacturers recommend a distance between the electrodes in the range of 0.5-0.6 mm.

Why check the gap? How often should this be done?

You ask: "Why check and adjust the gap, if you can buy the recommended candles, put and forget about them until the end of the required period of work?" The fact is that in the process of engine operation, the electrodes burn. As a result, the distance between them increases. Because of this, one-electrode candles are recommended to be checked at least every 10-15 thousand km, multi-electrode - after 20-30 thousand km.

How and how to measure the gap?

Determine the value of the distance between the electrodes will help a special probe to measure the gaps. Buy it can be in any store that specializes in the sale of auto parts. The only thing that you should pay attention to when buying it is the manufacturer. Do not buy a measuring instrument of doubtful origin and quality. A deviation of a hundredths of a millimeter can negate all your efforts to adjust the gap. There are three types of probes:

• Coin-like;
• wire;
• Lamellar.

The first probe for measuring gaps in appearance resembles a conventional coin with the surrounding rim. It has different thicknesses at different positions of the circle. At the same time, the "coin" itself shows a scale indicating its magnitude. The wire probe has a similar design. Only instead of the rim, the role of the meter is played by loops of wire of different diameters. The most popular tool for measuring the gap is a measuring instrument in the form of a Swiss knife. Here, instead of blades, steel plates of a certain thickness are used.

How is the clearance determined?

First of all, the candle must be cleaned of dirt and carbon deposits that may be present on its contacts. The method of measuring for each type of probe is different. If you have a coin-shaped meter, place its bezel between the candle electrodes. Slowly rotate it until it connects the contacts. Now look at the scale of the "coin". The value deposited on it at the location of the electrodes, and will be the size of the gap. To increase it, simply bend the side contact with the rim of the gauge and again check the distance. To reduce the gap, the electrode must be slightly bent, resting it in some fixed object.

If you have a wire dipstick, we measure the measurements by placing a wire loop between the contacts. Each of them has a certain diameter. The thickness of the eyelet, which will block the distance between the electrodes, will be a gap. The lateral contact is bent by means of special figured plates located on the body of the wire probe. Plate meter to check the gap is easiest. It is enough to choose a plate that will fit tightly between the electrodes, and see its thickness, indicated on its surface. Adjustment of the gap is also carried out using the meter itself.

What should be the clearance between the spark plug electrodes on the gas?

All car owners, whose cars are converted to HBO, are wondering which candles are best suited for this type of fuel and what should be the distance between the electrodes. Indeed, the process of combustion of a gas-air mixture occurs a little differently than an air-fuel mixture. First, propane has a large octane number (105-115). Secondly, the temperature of its combustion is above the gasoline by about 30-50 degrees. Thirdly, for combustion of gas, a higher compression ratio in the cylinder is necessary.

In other words, if the engine of your car is designed for the 80 th or 92 th gasoline, when operating from HBO conventional candles very quickly fail. In addition, the engine of the machine will constantly overheat, and the parts of the piston group wear out quickly. To avoid this, it is necessary to use candles with a minimum glowing number provided by the car manufacturer. If the car's engine is tuned for gasoline with an octane rating of 95 or higher, the conversion to gas will not affect it in any way. As for the gap, it should be as recommended by the manufacturer.

Design features of some spark plugs

Modern technologies allow manufacturers to produce spark plugs with improved power and size characteristics of an electric spark. This can be achieved through the use of precious and rare earth metals. Each of the manufacturers is trying to find the ideal design, in which the spark is the most powerful, and the gap is large. Candles Denso, NGK, Bosch, Champion, despite the high cost, are in great demand because of its reliability and durability. So what are they different from the usual ones?

Take, for example, the Denso candles. Their electrodes are made of iridium, and the central contact has a diameter five times smaller than that of conventional candles. "What does this give?" - you ask. First, this metal is very resistant to high temperatures. Secondly, if you use iridium spark plugs, the gap between the electrodes allows you to create the greatest spark. So you not only increase engine power, but also reduce the amount of harmful impurities in the exhaust. And thirdly, they will serve twice, and even three times longer than usual.