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Spark Advance Curve

The rate at which ignition timing advances as plotted on a graph; the line rises from some initial amount of advance and levels off at the maximum advance.

Spark Amplitude

The greatest voltage created during a spark event ( the height of the firing line ).

Spark Decal Valve

A vacuum valve, located in the line between the distributor and carburetor, to advance the spark during deceleration, to reduce emissions.

Spark Delay Valve (SDV)

A vacuum valve acting like a restrictor, used in the vacuum line between the distributor and carburetor, to delay vacuum-timing advance under certain driving conditions to reduce NOx (oxides of nitrogen) emissions.

Spark Duration

The time a spark is established across the gap of a spark plug.

Spark Ignition (SI)

An engine-operating system where the air/fuel mixture is ignited by an electrical spark.

Spark Knock

A term used for detonation or ping.

Spark Line

The line on an oscilloscope that indicates the voltage required to fire the spark plug and the number of degrees the distributor turns while the spark exists.

Spark Output

Ford SPOUT The output signal from the processor which triggers the Ignition module to fire the ignition coil.

Spark Plug

An ignition component threaded into the cylinder head that contains two electrodes extending into the cylinder that form a gap across which high-voltage electricity arcs to ignite the compressed air-fuel mixture.

Spark Plug Fouling

An accumulation of deposits on the lower, exposed end of the spark plug that act as an electrical conductor, thereby creating a path for electricity to leak to ground rather than jump across the electrode gap.

Spark Plug Heat Range

The temperature limits, hot, normal, or cold, within which a spark plug is designed to operate. It is determined by varying the length of the exposed lower section of the plug ceramic insulator.

Spark Plug Well

The recess in a cylinder head for a spark plug.

Spark Plug Wire

A special high-voltage wire from the distributor cap to the spark plug.

Spark Plug, Resistor Type

A spark plug having an electrode resistance of 5,000 to 10,000 ohms to increase electrode life and suppress radio interference.

Spark Retard

Causing less spark advance to be added, resulting in a spark which is introduced later on the compression stroke.

Spark Test

A quick check of the ignition system made by carefully placing a metal end of one of the spark plug wires close to the engine while cranking the engine to see if there is a spark gap and to determine its intensity.

Spatter

The metal particles expelled during fusion welding that do not form a part of the weld.

Spatter Paint

The technique of applying two separate colors of paint simultaneously to provide a speckled finish.

SPDT

Single pole double throw.