Surface Ignition — Is a Rare But Highly Undesirable Process In Your Auto

Administrator posted this 18 July 2019

The principle of the internal combustion engine’s duty is known to every motorist, but what about surface ignition? Maybe you don't know enough about this process.

The temperature reaches more than 2000°C in the combustion chambers. For optimal operation of the engine, it must be cooled. Due to the efficient operation of the elements of the cooling system, the temperature in the combustion chambers drops significantly, and on average is 90°C.

Nevertheless, the temperature indicators remain their high position and heat the operational elements of the power unit. The electrodes of the spark plug are heated more strongly and faster. These highly heated elements can lead to ignition of the fuel mixture. The ignition process becomes uncontrollable.

The fact is clear: what cannot be controlled is likely lead to negative consequences. Accidentally running the fuel ignition process, provokes the subsequent phases of the engine, and therefore the phases of work incorrectly.

Preignition leads to:

  • the piston’s bottom destruction
  • the burning of electrodes and insulators of plugs
  • the burrs on the surface of the cylinder and pistons appear
  • the pistons can be stuck during the work

What is the plug’s heat grade? 

First of all note, that: the various manufacturers have own and different heat rating for plugs. There is no single system for plug’s heat grade, but there are tables of comparison. Another indicator, which you should take into account, is the type of plug. The heat grade of the plugs used in the industrial sphere, simple-car plugs and for the plugs equipped to the engine on a sports car will be totally different. Therefore, for the ordinary driver, and for sufficiently experienced drivers, the figure of the plug’s heat grade has many variables.

Simplifying all of the above, it can be noted that this term indicates the time for which the electrodes of the candle are heated sufficiently strongly to provoke a surface ignition.

A high heat grade indicates slow and low heating of the plug, they are called “cold”. If the electrodes gain temperature in a short period of time, their number will be correspondingly low. Such plugs are “hot.”  On powerful engines, it can cause an unexpected ignition of the fuel mixture.

The temperature gain and the subsequent heating in different engines occurs at different speeds. It is necessary to carry out individual selection of spark plugs based on the type of engine and driving conditions of the car.

Anyway, the indicator for this parameter varies from 11 to 26. Some manufacturers do not specify these data at all, since there are no standards for determining the heat grade of spark plugs, and it is installed in the course of tests.

How to choose a spark plug, if the number of heat grade is only a conditional indicator?

  1. Hot (11—14) - for low power motors
  2. Warm (14—17) - medium power engine
  3. Cold (20—26) - powerful motors, medium power boosted engines

How to understand that you have problems with plug’s heat grade?

The answer is simple, follow the temperature of the engine and monitor its condition regularly. For this, diagnose the car using inCarDoc.