The gap between the electrodes of the spark plugs

The apparent simplicity of the spark plug design is somewhat deceptive. In order to provide them with the correct and most functional work, it is necessary to regularly monitor their condition and some preventive measures. In this case, you should know what should be the gap on the candles, contributing to the best performance performance.

A sufficiently powerful electric charge passing between the electrodes is a positive sign of the quality of the electrical components. Many negative factors can have a negative impact on their work. In this case, the combustion of the fuel mixture will deteriorate.


  • 1 What is affected by the gap on the spark plugs
  • 2 Inflated clearance
  • 3 Too close interelectrode distance
  • 4 The value of optimal clearances
  • 5 What is the gap on the candles on the gas
  • 6 Setup Methods

What is affected by the gap on the spark plugs

For a clear understanding of this process, you should know the operation of the automotive fuel system in gasoline engines. With an understanding of the functioning of the ignition system, the degree of influence of the distance between the electrodes on the performance of the power plant as a whole becomes apparent.

what is the gap on the candles on the gas

In simple execution, the step-by-step algorithm for obtaining mechanical energy from the work on burning fuel consists of the following points:

  • Having removed the exhaust gases from the combustion chamber through the valve system of the cylinder head, the piston begins to move to the lowest point. When it reaches the opening of the intake valve, so that, inside the cylinder penetrates the mixture of fuel and air.
  • On the next cycle, the piston moves upwards to compress the mixture.
  • When the top dead center is reached, the automatics supplies a high-voltage discharge to the electrodes. Thus, a spark jumps into the gap between the electrodes of the spark plugs. Its high temperature ignites the mixture, resulting in an explosion and release of energy.
  • The generated force pushes the piston down, transforming thermal energy into mechanical work.
  • The finish is the stroke in which the exhaust valve opens, and combustion products are removed from it.

The ignition system operates with a pulse on a coil whose voltage is more than 20 kV. The supply of current for sparking is carried out automatically by the signal from the controller. The used winding can withstand increased voltage for a long time. However, changing the gap between the electrodes will affect the formation of the spark.

Inflated clearance

Before you set the gap on the candles, you need to know that when its value is more than 1.3 mm, this interval will be considered increased. If the distance between the electrodes is this, it will lead to the following consequences:

  • the calculated power of the coil will be less than that required in reality, therefore, sparking will not occur in each cycle, but gaps will appear in the work;
  • the engine will work intermittently unstable, which will contribute to the occurrence of unwanted vibrations;
  • non-burning fuel will penetrate partially into the crankcase, flowing down the walls of the cylinders, and also partially sent to the exhaust system;
  • the power of the engine will decrease noticeably, and the consumption of gasoline will increase significantly;
  • a noticeable undesirable layer of carbon will form on the cylinder, the working part of the candle, and a soot will appear on the piston.
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what does the spark plug gap affect

It is important to bear in mind that an increase in engine speed will contribute to an increase in the skips of effective strokes and an increase in gas mileage.

Penetration of fuel to the crankcase oil provokes a dilution of the lubricant and the formation of combustible vapors, which freely penetrate into the combustion chamber. This is facilitated by all sorts of connections and the presence of an air path.

In addition to the drop in power parameters, the negative will be an increase in wear of the mating elements.. Their effective operational period is significantly reduced. The car starts less confidently, especially noticeable when you start "on the cold." An unheated motor often requires several attempts at the plant.

Overly close interelectrode distance

The smallest permissible gap between the contacts of the NW specialists call a gap of 0.6 mm. Although in the operating mode the omissions of the sparking are completely excluded, but there will be another negative - small ignition.

It is important to understand that an excessively short spark is not able to effectively ignite the fuel mixture inside the combustion chamber during the piston stroke, as it has low energy.

Incomplete combustion of the air mixture leads to consequences similar to the situation with an increased gap. Power drops and gas mileage increases. Additional negatives include not only the rapid deterioration of the piston group, but also the occurrence of problems with the fuel supply, the risk of breakdown of insulation of high-voltage cables, etc., increases.

The value of optimal clearances

Acceptable operating parameters in which the system remains fully operational are gaps in the range of 0.6–1.2 mm. Clear values ​​are selected depending on the type of power plant, different power systems and ignition. You should focus on the following characteristics:

  • old carburetor engines, in which there are engines with a small degree of compression by the mechanical function of sparking, will work optimally at 0.6–0.7 mm;
  • similar power plants with upgraded contactless ignition on electronics will be effective at 0.8–0.9 mm;
  • for aspirated turbine-reinforced and equipped with an injection type of injection, it is preferable to provide a gap of 1–1.2 mm.
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what should be the gap on the candles

In order not to be mistaken with the value for a specific brand of engine, we recommend that you study in detail the user's guide. There are various parameters, including the preferred clearance.

What is the gap on the candles on the gas

Recently, the trend in resource savings has been reflected in the automotive industry. Many car owners install modern HBO in their cars. However, not everyone knows that calibration is required for high-quality sparking.

After installation of all gas-cylinder elements of the system, it is worth raising slightly the clearance on the candles by one tenth of the gasoline passport value. Although the load on the built-in coil will slightly increase, the fuel gas mixture will be better ignited, which will positively affect the power of the car. Also, when choosing candles it is important to give preference to products with a high calorific number so that the candles are “cold”.

The gap of the iridium candle has little effect on its performance. Contacts made of precious metals are more durable and form a spark better. Additionally, the discharge bypasses the central contact along the diameter of the circle and ensures self-cleaning of the element.

Setup Methods

In order to check the interelectrode distance, it is necessary to use the probe for spark plugs in the following cases:

  • upon completion of repair of the power plant or the power and ignition system immediately prior to monitoring compression in the cylinders;
  • before installing the newly purchased candles, because some manufacturers in the factory provide a small gap that requires fine-tuning to the standard in each car;
  • when detecting unstable operation of the motor, the drivers first of all unscrew the plugs, cleaning the contacts and controlling the gap.

It should be borne in mind that all measurements are carried out after cooling the engine - "on the cold". It is enough to insert a flat screwdriver into the gap for pushing it in, and to reduce it, you will need to tap a little on the contact.