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During my conversations with customers, I am frequently asked to explain Spark Survey Reports. The following parameters explain what is being measured and how the information can be used in analysis of the data. I hope this helps everybody that is using this automated Secondary Ignition Survey! - Mitch
I. Ionization Voltage -The voltage level required to ionize the compressed air/fuel molecules within the gap of the spark plug. This is also referred to as ignition breakdown voltage. Ionization refers to the splitting apart of the molecules to enable a current path for spark plug arcing. Higher ionization voltages produce a higher rise time. The typical unit of measurement is Kilo-volts (Kv).
A. In a controlled environment:
1. The wider the spark plug gap, the more voltage required to ionize the gap.
2. The narrower the spark plug gap, the less voltage required to ionize the gap.
3. Typical voltage measurements will range from 5,000 to 25,000 volts. Voltages over 20,000 indicate wide gaps and a greater potential for external flashover.
4. This voltage should go negative (-) with respect to ground if the secondary circuit is wired properly. If the voltage is going positive (+) with respect to ground, this is referred to as reverse polarity and indicates the wiring to the coil is reversed and may result in shorter spark plug life.
B. In a non-controlled environment, the air/fuel ratio and mixture consistency can affect the ionization voltage level between cycle-to-cycle measurements.
II. Arc Duration - The measured time period during which the actual arcing of the spark plug occurs. This is the time measured between the ionization voltage (breakdown) and the beginning of the ring down voltage. The arc duration is inversely proportional to the ionization voltage and rise time. The typical unit of measurement is micro-seconds.
A. In a controlled environment:
1. The wider the spark plug gap, the shorter the arc duration.
2. The narrower the spark plug gap, the longer the arc duration.
3. Typical arc duration measurements will range from 125 to 700 micro-seconds for different ignition systems. When measured times decrease, a widening gap and/or excessive ionization voltage requirements is indicated. As measured times increase, a narrow gap and/or an incorrect measurement due to a low ring-down voltage level is indicated.
III. Arc Voltage - The voltage level required to maintain the arcing of the spark plug gap. This is the voltage measured between the zero reference line and the arc duration level. This voltage is typically less than 1 Kv with high current flow. The typical unit of measurement is volts.
IV. Rise Time - The measured time required to ionize the compressed air/fuel molecules within the gap of the spark plug. This is also referred to as the ionization time. Ionization refers to the splitting apart of the molecules to enable a current path for spark plug arcing. The rise time increases with an increase in the ionization voltage. The typical unit of measurement is micro-seconds.
A. In a controlled environment:
1. The wider the spark plug gap, the more time required to ionize the gap.
2. The narrower the spark plug gap, the less time required to ionize the gap.
3. Typical rise time measurements will range from 5 to 50 micro-seconds. With rise times over 40 micro-seconds indicating wide gaps and a greater potential for external flashover.
V. Arc Slope - The measured slope of the arc duration. The measured slope can be one of the following:
A. 1 - Flat
This indicates the voltage level during the arc duration remained constant, as the voltage requirements to maintain the arc did not change during the arc.
B. 0 - Negative
This indicates the voltage level during the arc duration started at a lower voltage and increased as the voltage requirements to maintain the arc increased during the arc. This indicates high resistance across the spark plug gap.
C 2 –
Positive This indicates the voltage level during the arc duration started at a higher voltage and decreased as the voltage requirements to maintain the arc decreased during the arc. This indicates high resistance in the secondary wiring and connections, exclusive of the plug gap.
VI. Ring Down Voltage - The measured peak-to-peak voltage of the ring down oscillation of the coil. This is also referred to as coil oscillation and/or unused energy. This is the energy remaining after the spark plug arc demands can not be maintained. The typical unit of measurement is Volts Peak to Peak. Anything that affects the R-C time constant affects the amplitude and frequency of the ring down oscillations. A lack of ring down typically indicates a poor plug wire connection in the coil tower.
VII. No Arc, Voltage Problems Report - This report identifies problems with spark plugs and/or other secondary ignition components based on ionization voltage levels and arc duration measurements. Please refer to the report for detailed descriptions of each of the problems identified.
VIII. Arc Flyback - This report identifies the number of times each coil has a flyback following the ionization ramp. Please
refer to the report for a detailed description of the problem.
