14/11/2020
Spark Plug Functions
The 2 main functions of the spark plugs are:
Igniting the air-fuel mixture: The spark plug is the last step in the ignition circuit. It transmits electrical energy that transforms fuel into work energy. The spark plug takes voltage charge from the coil and produces a high-voltage spark that ignites the compressed air-fuel mixture within each cylinder.
Remove heat from the combustion chamber: The spark plug works as a heat exchanger, drawing unwanted heat energy in the combustion chamber to the engine's cooling system. The thermal range of the spark plug is its ability to dissipate heat and is determined by:
Ceramic Insulator Length
Electrode center material
Insulator material
Temperature ranges
The temperature range of a spark plug determines its ability to remove the heat generated in the combustion chamber and carry it to the cooling system. The temperature of the spark plug tip must be low enough to prevent pre-ignition and / or destruction of the electrodes, but high enough to burn combustion deposits and not accumulate soot on the tip of the plug.
Different engines require spark plugs with different temperature ranges. Older or low-performance engines are cold engines and therefore require a hot spark plug (with low heat dissipation) to prevent the formation of deposits on the end of the insulating material of the spark plug. In contrast, new high-performance engines are very hot engines that require spark plugs to dissipate the excessive heat generated in them.
For this reason, it is important that when changing the spark plugs of our car we place the spark plugs with the thermal range specified by the vehicle manufacturer. Using the wrong spark plugs greatly reduces engine efficiency and spark plug life.
Spark plug coding
Each of the spark plug manufacturers has a code through which the temperature range can be known, whether or not the spark plug has resistance, type of electrode (platinum or copper), etc.
Using a spark plug manufacturer's catalog, you can select the spark plug recommended by the vehicle manufacturer.
Spark plug life
One of the most economical ways to keep your vehicle's engine running efficiently and avoid wasting fuel is by changing the spark plugs at regular intervals. With use, the spark plugs suffer electro-erosion that causes wear on the electrode, increasing the spark gap distance, this causes the spark plug to require a higher voltage to cover the distance and therefore, during situations of full acceleration or high speeds can be lost engine explosions wasting fuel and losing power.
The spark plug change interval depends mainly on the type of spark plug, the number of electrodes and the quality of the gasoline. Copper spark plugs with one electrode are regularly changed every 10,000 km. There are multi-electrode copper spark plugs that can last for up to 20,000 km per electrode to function properly (i.e. up to 80,000 km for 4-electrode spark plugs). The case of platinum plugs is different, since they can last up to 160,000 km depending on the number of electrodes.
Spark plug installation
To install the spark plugs it is very important to follow the tightening indications (torque) provided by the manufacturer. A loose plug can cause flue gas leakage, on the other hand, a tight plug can damage the threads of the engine head.
The torque to be provided to the spark plugs varies if the engine head is made of iron or aluminum. These torque values can be found in the manufacturer's spark plug catalog. If you do not have a torque wrench, it is possible to install the spark plugs with a certain number of turns also recommended by the manufacturer.
In addition to torque, it is necessary to calibrate the spark plug by adjusting the gap between the electrodes before installing it. Current spark plugs are sold pre-calibrated, however it is impossible for the factory calibration to be correct for all vehicles.
