Spark Plugs


  • Overview
  • Analysis
  • Electrode Gap
  • Electrode Gap Adjustment
  • Projection
  • Modified and Performance Engines
  • Heat Range
  • Operating Temperature
  • LPG Compatibility
  • Precious Metal
  • Installation
  • Resistor Spark Plugs
  • Racing Spark Plugs

The Projection of a Spark Plug

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.

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