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Old 09-03-2019, 09:46 AM   #11 (permalink)
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Resistance plugs have a longer duration spark (coupling of milliseconds) due to the effect they have on the inductive time constant. Balancing this is the much higher applied voltage to the plug which can double the gap on non resistance. Net results are effectively the same for the ignition event but could be significant in some applications/engine conditions.

Properly functioning non resistance plugs do not emit more RFI than resistance plugs except when they foul

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Old 09-03-2019, 11:09 AM   #12 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
Resistance plugs have a longer duration spark (coupling of milliseconds) due to the effect they have on the inductive time constant. Balancing this is the much higher applied voltage to the plug which can double the gap on non resistance. Net results are effectively the same for the ignition event but could be significant in some applications/engine conditions.

Properly functioning non resistance plugs do not emit more RFI than resistance plugs except when they foul
I didnít realize that the spark will be a shorter duration. But even if it is, I donít think it would matter much (if at all) because after the air fuel mix is ignited, it becomes the ignition source to propagate combustion, so I think itís more important to ignite more air and fuel at once.

Great point about the gap! I gapped the plugs to the OEM spec of .0044 inches. Should I have gapped it wider to get the maximum benefit?
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Old 09-04-2019, 10:24 AM   #13 (permalink)
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Originally Posted by EcoCivic View Post
Great point about the gap! I gapped the plugs to the OEM spec of .0044 inches. Should I have gapped it wider to get the maximum benefit?
They should be gapped bigger,55 thou, but it has been so long since I did spark ignited engines I forgot the rule of thumb. Maximum gap is a mix of various worst case scenerios that prevent effective fire (aka fouling).

Ideally, they should also be indexed, but you need either gaskets or many more plugs.
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Old 09-07-2019, 02:26 AM   #14 (permalink)
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I didnít realize that the spark will be a shorter duration. But even if it is, I donít think it would matter much (if at all) because after the air fuel mix is ignited, it becomes the ignition source to propagate combustion, so I think itís more important to ignite more air and fuel at once.

Great point about the gap! I gapped the plugs to the OEM spec of .0044 inches. Should I have gapped it wider to get the maximum benefit?
It does matter, because the air in the combustion chamber is moving. This is why new engines have multiple spark events under some conditions.

I would imagine a bigger gap would be beneficial if the spark can make it across. The resistor doesn't change the potential before the spark forms, so a bigger gap won't produce a spark as easily.

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