SOHC.co.uk Forums > CB750
Spark Plug
Oddjob:
I was under the impression that colder plugs had higher number than hotter plugs. So an X24ES plug would be colder not hotter. As it happens it's recommended by NGK to go a step colder when using Ethanol so the X24ES would be better if that's the case.
Trigger:
I was talking about DENSO plugs, NOT NGK :o I think you need to go back to spark plug school as, they are a lot more complicated these days ;)
All spark plug manufactures have there own heat range, and that is heat transfer from the engine. The plug can differ from standard copper up to Iridium which all have there own heat dispersal ;)
JamesH:
The key point here is that higher performance engines require a ‘colder’ plug to help disperse the resultant heat from combustion faster. The ceramic insulators on ‘colder’ plugs are generally smaller, allowing faster heat dispersion.
In the Denso terminology, the bigger the number the colder the plug. So an X-22 is a ‘hotter’ plug compared with the X-24 which is ‘colder’ in Denso terminology.
Oddjob:
And as far as I can determine that’s exactly what I said, higher number colder. So an X24es would be a colder plug than the X22es not hotter.
Maybe I was there that day.
K2-K6:
--- Quote from: JamesH on March 16, 2023, 01:16:31 AM ---The key point here is that higher performance engines require a ‘colder’ plug to help disperse the resultant heat from combustion faster. The ceramic insulators on ‘colder’ plugs are generally smaller, allowing faster heat dispersion.
In the Denso terminology, the bigger the number the colder the plug. So an X-22 is a ‘hotter’ plug compared with the X-24 which is ‘colder’ in Denso terminology.
--- End quote ---
I agree James but with the nature of interpretation I describe the colder plug as having larger insulation for more dispersion in surface area from plug tip to plug wall and then onward to the cylinder head casting.
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It is a bit semantics though as so many describe in opposite direction as I've found over the years, champions I always have to reference the numbers as it just doesn't stick in my mind like NGK :)
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