Technical Information Non-Resistor Spark Plugs

Non-resistor Spark Plugs

On a Honda engine, if the stock spark plugs have been replaced, it is very important to ensure that the replacement spark plugs have an integral resistor. Non-resistor spark plugs cause a large amount of electrical interference which may effect vehicle electronics, including the ECU.

Resistor spark plugs use an integral resistor to absorb the radio frequency energy generated from the spark.  In earlier Honda engines the resistor was often incorporated into the distributor cap or spark plug wires.  With the K-Series engine the only place for the resistor is in the spark plug. Almost all spark plugs are of the resistor type (actually we were surprised that people could still buy non resistor type plugs).

For more information:

Spark Plugs that can be used

You can purchase resistor type spark plugs from www.sparkplugs.com

Heat Range Stock # NGK Part #
8 2668 BKR8EIX
9 2669 BKR9EIX
10 4017 R6601-10

Some of these are for race use only and will not work in daily driven applications.

Oscilloscope Waveforms - Non-resistor spark plugs

DC voltage waveform for the ECU power supply.  The vertical scale is 20V per division. The red line is the trigger (at 80V). The voltage spike was in the order of 100V to 200V peak to peak.

DC voltage waveform for the ECU internal 5V power network.  The vertical scale is 20V per division. The red line is the trigger (at 80V). Again the voltage spike was in the order of 100V - 200V peak to peak.

Oscilloscope Waveforms - OEM spark plugs

DC voltage waveform for the ECU power supply.  The vertical scale is 10V per division. The largest voltage spike was very small - less than 0.4V

Conclusion

Non resistor spark plugs cause massive radio frequency interference which can affect any electronics in the vehicle.  There is no need nor advantage in using non-resistor spark plugs.