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Is this detonation?

Old Feb 1, 2015 | 07:43 PM
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Default Is this detonation?

Are these pits detonation or just debris sucked in. This engine is run in the sand and some gets sucked in.

If detonation would this be considered a lot or manageable.

This piston showes the most pits. Motor has about 500 hard hours on it
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Old Feb 1, 2015 | 08:04 PM
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I would say knock. Doesn't look too bad though, assuming you aren't trying to get tens of thousands of miles out of the motor.
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Old Feb 2, 2015 | 06:31 AM
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All knock is bad....but when you say the engine can ingest debris as well....harder to say for sure what the marks would be.

Usually it's assumed the engine draws clean air, so whilst it could well be detonation...it could also be from dirt, although you'd think sand would likely cause more harm to rings and bores than the top of the piston
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Old Feb 2, 2015 | 01:29 PM
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I was thinking the same thing. Looks like something could have gotten in there and bounded around but I don't think sand would cause divits like that, and I'm not really sure what knock/ping looks like.

If it is knock, is that amount concerning. Obviously any is not good but should I start changing things.
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Old Feb 2, 2015 | 02:10 PM
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Do you want more than 1000 hours out of a motor? Also what pistion of the piston are the marks on? ie 12 oclock (front) 3 oclock (right side)
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Old Feb 2, 2015 | 04:04 PM
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Originally Posted by Banshee Ben
I was thinking the same thing. Looks like something could have gotten in there and bounded around but I don't think sand would cause divits like that, and I'm not really sure what knock/ping looks like.

If it is knock, is that amount concerning. Obviously any is not good but should I start changing things.
Again, any knock is concerning, there should be none, ever.

What do the ring faces look like ?

If it is determined to be detonation, then yes you need to look at either the tuning, fuel etc in order that there is no detonation in the future.

That may be as simple as a little more fuel, 1 deg less timing, 1psi less boost, better charge cooling etc etc.
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Old Feb 2, 2015 | 07:23 PM
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I would disagree, alot motors knock frequently at high loads. Especially large bore, decent compression, boosted motors. All that matters is knock intensity, a couple bar won't hurt and can still show up on pistons, 20+ bar gets pretty sketchy. But overall yeah, if you're looking for some more life out of the motor down one variable down slightly
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Old Feb 2, 2015 | 08:38 PM
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I'll look at the other pistons. The one shown is pitted on the bottom (lowest point so 6)

Pretty sure It's a 9:1 comp and I run 93 with 13 psi. 383 motor. Would have to hook up computer to look at timing.
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Old Feb 2, 2015 | 08:49 PM
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Hook up the computer and get some data.
What computer?
Looks more like it ingested something, maybe a little rock. Run it. But get some data from that thing, that's what computers are for.
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Old Feb 2, 2015 | 10:38 PM
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Stock computer but I have HP tuners to interface.
All rings look/move fine
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Old Feb 3, 2015 | 07:00 AM
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Originally Posted by NoorJ
I would disagree, alot motors knock frequently at high loads. Especially large bore, decent compression, boosted motors. All that matters is knock intensity, a couple bar won't hurt and can still show up on pistons, 20+ bar gets pretty sketchy. But overall yeah, if you're looking for some more life out of the motor down one variable down slightly
Just because some are happy to take risks with detonation, still doesnt make it right they should run that way
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