SOHC.co.uk Forums > CB500/550
Plugs fouling at idle
deltarider:
--- Quote from: K2-K6 on April 24, 2024, 10:47:39 AM ---
--- Quote from: Bryanj on April 24, 2024, 10:28:55 AM ---The fact that the L was a half grade came from the same reptat suggested d7ev to me, and that man knew how to read plugs
--- End quote ---
Thats noted on some published charts too .... the -L designation.
https://www.ngk.com/ngk-spark-plug-numbering-systems this lists that design element, although note that they have a statement of NOT being NGK USA official scource.
The listed data looks comprehensive though.
--- End quote ---
Compare the above to what they gave me as answer, after I took the effort to contact them.
My question was:
Dear Cust,
Here's a question owners of motorcycles that had the NGK D8ES-L sparkplug prescribed, never had answered:
Is the D8EA plug, as far as heat range, the same as its predecessor D8ES-L?
In addition:
Is the D7EA plug just a renamed D7ES, or does the -A suffix ('Special Design') imply the D7ES was indeed modified?
Core of our uncertainty is, that we have no clue what the meaning of 'Special Design' is.
We realise it may be difficult for you to find the answer. You may have to consult older employees who can remember. Somebody must know.
The issue has been debated over and over in various fora around the world (Germany, Holland, France, UK and US) and no NGK chart ever solved the uncertainty. https://www.ngk.com/ngk-spark-plug-numbering-systems
And here the answer:
Hello,
Thank you for contacting us! D8EA had a heat range of 8 and D8ES-L heat range 8.5. The (L) stands for Half Heat Range.
As a Distributor for NGK the -A suffix ('Special Design') is still a mystery to us. You will have to contact NGK directly at 1-877-473-6767 ext #1 or www.ngksparkplugs.com they may have more details on this.
Personally I find it hard to believe that the D8ES-L has heat range 8.5.
Your comments please.
Bryanj:
Why not? If you can design for whole numbers you can design for half way
deltarider:
--- Quote from: Bryanj on April 28, 2024, 03:44:46 PM ---Why not? If you can design for whole numbers you can design for half way
--- End quote ---
In my understanding most of us took the D8ES-L heat range for in between 7 and 8.
Johnwebley:
Using the 8-L would make them even more prone to fouling at tickover and low load,
Must be for high load ,like racing
Sent from my SM-A546E using Tapatalk
K2-K6:
--- Quote from: deltarider on April 28, 2024, 04:36:22 PM ---
--- Quote from: Bryanj on April 28, 2024, 03:44:46 PM ---Why not? If you can design for whole numbers you can design for half way
--- End quote ---
In my understanding most of us took the D8ES-L heat range for in between 7 and 8.
--- End quote ---
Thats my view of extending the central electrode out into the combustion chamber too. It would allow it to heat more than a straight 8 to raise potential tip temperature, but not as much or as far as a 7 ..... well that's how I visualise it, whether that's true or not.
Any arrangement with longer route from porcelain at tip into the surrounding structure SHOULD make the tip retain more temperature .... that's generally what plug design achieves.
Wouldn't an 8.5 be called a "9-L" by that description ?
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