SPARK GAP LOCATION AND DESIGN

For the purpose of a perfect use of the fuel energy and in order to ensure that the harmful exhaust gas emission does not exceed a minimum level, it is necessary to optimize the spark plug construction with regard to the requirements of particular engines.

The following parameters will influence the quality of the ignited air/fuel mixture in the combustion area:

• location of spark gap in the combustion chamber
• change in the electrode gap in course of the spark plug replacement interval.
• change in properties in the electrode material in course of the spark plug replacement interval
• free access of the flame face in its initial phase of propagation
• possibility of discharge location selection according to the instantaneous concentration of fuel molecules in the air/fuel mixture in the immediate surroundings of the spark gap area

Different engines require different spark plug arrangement and its location in the combustion chamber. In order to achieve longer lifetimes of spark plugs required by the engine producers, there are used multiple spark plugs and precious materials (such as platinum, silver, tungsten.).

By means of shifting the insulator tip suitably out, i.e. into the combustion chamber of the engine, better access and ignition of air fuel mixture is achieved.

Influence caused by shifting the insulator tip out on thermal range extension

Influence caused by electrode materials on the spark plug replacement interval

CORRECT ASSEMBLY

Spark plugs are constructed by using two different manners of sealing in cylinder head.

Methods of spark plugs sealing

Torque table

Selection of proper spark plugs

Heat range
Vehicles produced in series (which are not additionally modified for engine power output enhancement), whose engines are properly adjusted and in good technical condition, can be equipped according to the current application tables.

Any comparison charts of spark plugs are always for informative purposes only and they do not substitute the current application tables in full.

In the case of engine power output enhancement by means of additional modifications it is suitable to contact a producer's representative. There always applies a principle that in the case of medium modifications of the power output it is suitable to use the spark plugs "colder" by 2 degrees than those forming its original equipment (e.g. a change from 15 to 12). After driving several miles and subsequent assessment of the insulator tip appearance it is possible to decide about the most suitable equipment. This operation requires enough experience.

Proper length of the threaded shell