Technical information

Spark Plug Anatomy / Construction

Resistor Spark Plugs

Precious Metal Spark Plugs

Spark Plug Installation

LPG Compatibility

Operating Temperature

Heat Range Explanation


Electrode Gap

Electrode Gap Adjustment

Modified / Performance Engines

Spark Plug Analysis

Technical information


< The projection of a spark plug is measured as the distance from the end of the metal shell to the tip of the centre electrode as shown here.

A projected spark plug protrudes into the combustion chamber further and provides higher ignitability and improved performance. Simply this can be understood by representing the combustion chamber as a circle. A projected spark plug in effect produces a spark in the middle of the circle (or combustion chamber) allowing for an even flame spread. Conversely, a non-projected spark plug means the flame spread is not even.