Spark plug question
#1
#2
Short answer:
6R10 is a plug that is 2 steps colder than a 6R12..... you're fine with the 6R12, if you go to a 6r10 without major mods, you may start fouling plugs and lose performance.... if your bike is stock HP or within 40-50HP+, no need to change to a colder plug... a good tune will dial you in....
Slightly longer, answer:
Here is a BASIC explanation of how a plug's heat range affects an engine...
Gasoline engines have an optimum combustion chamber temp between 500°C & 800°C. This temp is controlled by the heat rating of the plug. The tune will dial in the correct plug, but will not totally compensate for a plug too cold or too hot. The OEM HD plug is 6R12, selected because it provides the proper temp range for the design of the twin cam engine..... No need to change without major engine modifications....
No need to go colder unless you have added: higher compression, more timing, forced induction, alternate fuels, or sustained use of Nitrous oxide (note; all these things can affect the plug tip temp).
A plug too cold will foul, a plug too hot can cause severe engine damage.... better to err on the side of a colder plug.
General rule of thumb: Go one, full heat range colder for every 75-100HP added to the engine... A full heat range colder can reduce the combustion chamber temp by 70°c to 100°C
Just a down and dirty about plug heat ranges, hope this helps.....
6R10 is a plug that is 2 steps colder than a 6R12..... you're fine with the 6R12, if you go to a 6r10 without major mods, you may start fouling plugs and lose performance.... if your bike is stock HP or within 40-50HP+, no need to change to a colder plug... a good tune will dial you in....
Slightly longer, answer:
Here is a BASIC explanation of how a plug's heat range affects an engine...
Gasoline engines have an optimum combustion chamber temp between 500°C & 800°C. This temp is controlled by the heat rating of the plug. The tune will dial in the correct plug, but will not totally compensate for a plug too cold or too hot. The OEM HD plug is 6R12, selected because it provides the proper temp range for the design of the twin cam engine..... No need to change without major engine modifications....
No need to go colder unless you have added: higher compression, more timing, forced induction, alternate fuels, or sustained use of Nitrous oxide (note; all these things can affect the plug tip temp).
A plug too cold will foul, a plug too hot can cause severe engine damage.... better to err on the side of a colder plug.
General rule of thumb: Go one, full heat range colder for every 75-100HP added to the engine... A full heat range colder can reduce the combustion chamber temp by 70°c to 100°C
Just a down and dirty about plug heat ranges, hope this helps.....
Last edited by hattitude; 07-01-2017 at 11:35 AM.
#3
#4
Join Date: Jun 2011
Location: Mountain Top, Alabama
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I tip my hat to the HD Engineers that came up with their spark plug recommendations. They perform fantastic for me, look excellent every time I look at them, heat range appears to be right on the dime, so I am staying with them.
Special builds or engine conditions may need something different, but I am happy with the status quo.
Special builds or engine conditions may need something different, but I am happy with the status quo.
#5
Ok I know I'm going to get slapped for this but, I fail to see how a small spark at the tip of an electrode that is hotter than the recommended heat range can cause engine damage. You are igniting an air fuel mixture. The entire cylinder is filled for a fraction of a second with very hot and explosive gasses. I just don't understand how a little dot of a spark can cause trouble. You want the fuel air to burn and explode don't you? I have been told this for years and I do follow it but the logic behind it just doesn't sit well. Its not like you are getting a plasma arc of electricity like that of and electric welder. Now slap me.
randy
randy
#6
#7
Here is an article that explains Spark Plug heat ranges. It's not the spark that's colder or hotter. It's the plugs ability to dissipate heat.
http://www.enginebuildermag.com/2011...ug-heat-range/
http://www.enginebuildermag.com/2011...ug-heat-range/
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#8
Join Date: Jul 2012
Location: Cranbourne, VIC Australia
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Ok I know I'm going to get slapped for this but, I fail to see how a small spark at the tip of an electrode that is hotter than the recommended heat range can cause engine damage. You are igniting an air fuel mixture. The entire cylinder is filled for a fraction of a second with very hot and explosive gasses. I just don't understand how a little dot of a spark can cause trouble. You want the fuel air to burn and explode don't you? I have been told this for years and I do follow it but the logic behind it just doesn't sit well. Its not like you are getting a plasma arc of electricity like that of and electric welder. Now slap me.
randy
randy
#9
Ok I know I'm going to get slapped for this but, I fail to see how a small spark at the tip of an electrode that is hotter than the recommended heat range can cause engine damage. You are igniting an air fuel mixture. The entire cylinder is filled for a fraction of a second with very hot and explosive gasses. I just don't understand how a little dot of a spark can cause trouble. You want the fuel air to burn and explode don't you? I have been told this for years and I do follow it but the logic behind it just doesn't sit well. Its not like you are getting a plasma arc of electricity like that of and electric welder. Now slap me.
randy
randy
As stated above it isn't the actual spark that is hotter, but the actual plug, because of it's lesser ability to dissipate the heat. If it is too hot it can much more likely cause preignition which of course can be very harmful, especially the earlier in the stroke it occurs.
BINGO.... you've been slapped...
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