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Old 03-26-2010, 03:32 PM   #1
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Default Spark plug feedback

hey guys,

I'm trying to clear up some discrepancy between a number of my logs regarding knock and the results on the spark plug. Are the black specs on the porcelain in the picture below signs of detonation? And the black ring on the base indicates I am running rich?

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Old 03-26-2010, 05:57 PM   #2
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Looks like it could be tiny bits of piston.
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Old 03-29-2010, 10:49 PM   #3
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any picture of the top of the piston? describe how it looks?
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Old 03-29-2010, 11:17 PM   #4
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No, the engine is not apart.
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Old 03-29-2010, 11:41 PM   #5
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You can get piston sprinkling from detonation. Just make sure it doesn't keep happening.
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Old 03-30-2010, 03:32 AM   #6
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Quote:
Originally Posted by dustinb View Post
You can get piston sprinkling from detonation. Just make sure it doesn't keep happening.
+1

Where are your logs showing knock?? At peak torque or somewhere else? Group buy is still going on for Jeff's DetCans, you might want to think about getting one...it's pretty cheap insurance for $50.
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Old 03-30-2010, 08:21 AM   #7
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Oh wow!

I never actually scrolled over to see the plug in focus in the other thread. Pic is too big. Yeah, that's definitely metal, and those 200 instances of knock in your log is apparently way too much.

What do your AFRs look like where you're seeing knock? I know your timing jumps 1.5* between the two cells you quoted, maybe roll it back some and smooth it out. Honestly you shouldn't be that close to detonation anyhow. Just about everyone should be able to add 2* to their whole table and not get any knock. If you can't then you're either really sure of your setup, or too aggressive, or the table has peaks in it that need to be smoothed out.
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Old 03-30-2010, 08:30 AM   #8
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Sometimes I get knock around 4800rpm and sometimes it's around 6500rpm. My AFRs are in the 11's in these areas. I'll be posting my map when I get home. I don't think it's too aggressive.

What sort of AFRs would induce detonation if my ignition is not overly aggressive?

Still waiting for a reply from Jeff about the detcans.

Yeah, sorry about the pic, I made it big to show the specks or black.

Last edited by dgmorr; 03-30-2010 at 09:25 AM.
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Old 03-30-2010, 04:51 PM   #9
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Here is the timing map I'm using. I have everything set to -5* from what you see in the map using my master ignition trim settings.

The 4 cells highlighted in white is where most of the knock occurred. At that knock point it was 16.4*, 6625 RPM, 159kpa. My rev limit is 7100, so you can ignore the untuned 8000 rpm and above cells.Any feedback is appreciated. Thanks.
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