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      05-24-2019, 03:47 PM   #1
ssgm1x
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Black spot on spark plugs.

Can anyone tell me why these plugs have a black spot on them ?
2018 F80 M3 with NGK 97506 plugs that are only 1-2 months old running full E85 (measured E80)
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      05-25-2019, 05:34 PM   #2
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what's the gap on them?
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      05-25-2019, 05:42 PM   #3
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Quote:
Originally Posted by Fast4d View Post
what's the gap on them?
.021 NGK 97506 running E85. About 1 month old.
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      05-25-2019, 10:03 PM   #4
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Should be running .018 on e85
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      05-26-2019, 04:23 PM   #5
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Quote:
Originally Posted by ShoNufff View Post
Should be running .018 on e85
Not needed, but if I had upgraded my turbos and was pushing over 30psi of boost I would definitely gap down to .018, but with my stock turbos at 24.5psi of boost it is not needed.
Zero issues with gap. I Was just curious if anyone knew what these Black marks were.
I read it may be normal and the black mark is where the fuel/air ratio mixture is entering the cylinder and hitting that spot on the plug.

https://forums.24hoursoflemons.com/v...c.php?id=15480
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      05-27-2019, 12:51 AM   #6
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Did you look at your stock ones before you put in those 97506's? My stock ones that were running the OTS e30 map, looked the same, black mark on side. I think its just where the flame front ignites, nothing to worry about, as long as the electrodes look good. I'm running the same as you now, 97506 @.021. Haven't pulled any to look at them, but the car is stroooooong.....
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      05-27-2019, 07:28 PM   #7
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Quote:
Originally Posted by Shadow2 View Post
Did you look at your stock ones before you put in those 97506's? My stock ones that were running the OTS e30 map, looked the same, black mark on side. I think its just where the flame front ignites, nothing to worry about, as long as the electrodes look good. I'm running the same as you now, 97506 @.021. Haven't pulled any to look at them, but the car is stroooooong.....
Stock plugs were on 93Oct unfortunately. I agree with your analysis though.
I also believe that's the spot that is looking at the intake valve. It's hot and the fuel hit that spot and tars or carbons up before the plug sparks.
Running E85 is amazing. I Don't want to go back to 93Octane.
Ditch that E30 Map and get a Custom E85 Map. It's amazing!!!!!
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      05-29-2019, 08:29 AM   #8
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I misspoke, I had been running full e85 for at least 2-3 days on the stock plugs before I switched over to the colder NGK's, but they still looked the same. Yeah I love e85, I've been told its a good idea to run a tank of 93 through her ocassionally, I guess it cleans out the fuel system injectors filters etc. First thing I noticed was how smelly gasoline is, horrible, felt almost nauseous for a min while I re-acclimated to the smell of burnt dino-juice
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      10-22-2019, 11:18 AM   #9
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Quote:
Originally Posted by ssgm1x View Post
Can anyone tell me why these plugs have a black spot on them ?
2018 F80 M3 with NGK 97506 plugs that are only 1-2 months old running full E85 (measured E80)
I used NGK 97506 for a while and they look exactly the same as yours, with only 3000km on them. I have changed them back to stock plug.

Check this up: http://4secondsflat.com/Spark_plug_reading.html

This occurs for two reasons, excessive idling or rich idle condition leaving heavy soot deposits. These deposits will burn and create excessive porcelain temps causing the glass to melt usually resulting in a down track popping through the exhaust..
You will usually see splotchy deposits on the plugs after the run, either green or yellow in color and of course the tell tale shiny glaze. This glazing of the porcelain actually becomes a conductor and the spark will jump from the electrode to the porcelain resulting is a very weak small if any spark. The porcelain should always have a chalky or dull finish.
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