Pop Quiz

[Moonshine]

OK, here's a pop quiz for our assortment of engineers, mechanics, amateur gearheads, and hotrodders. The subject is multi-cylinder, water cooled, 4 stroke, fuel injected, supercharged engines, something we all have some interest in. The test question is based on the following -

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For clarification;

Photo 1 shows some significant scoring on one side of a cylinder wall (the exhaust side, if that helps you). The other side of that cylinder looks pristine, as do all of the other cylinders. Incidentally, the pictured scoring is significant enough to cause a 30 PSI loss on compression in said cylinder.

Photo 2 shows the piston that came out of that cylinder. As noted, the other side of the piston looks fine. You will note that the scoring is all below the rings, the rings themselves do not appear to be seized, and there's no evidence of damage above the rings.

Photo 3 shows some scoring on the crankshaft journal for the same cylinder. Again, no damage is noted on the journals for any other cylinders.

The last photo shows similar scoring on the cam lobes for the same cylinder. Again, no damage to the cam on any other cylinders.

The test question is two part - 1. What would cause the noted damage?, and 2. Why is the damage limited to one cylinder only?

I'm open to guesses, speculation, or well reasoned thoughts. At present, I do not know the answer to the question(s). For the time being, I will not identify the application or manufacturer, as I am still working with the manufacturer of the engine and do not want to compromise any possibility of them assisting me with repairs. Their engineers will be looking at photos in the coming days/weeks, so I do expect to learn what they think caused this, but I'm also interested in the collective knowledge of TALON.

[L8 APEX]

The pitting of the cylinder wall is suspicious. Kind of looks like corrosion as if water sat in the cylinder for an extended period of time or detonation strikes. But I don't see how detonation could hit the cylinder wall. I don't see how it could get hot enough to pop out the wall. Cylinders wear on the outsides where the piston pushes against the block under the force of combustion. I am not sure if that is the side where the wear is present. The top of the piston would be a good piece of data. The mains and cam look like some trash circulated through the system.

[BigBobsL]

Most likely started out as detonation, would need to look at plug for specks of aluminum piston or missing porcelan, melted electode; piston crown for pitting, and especially top half of the rod bearing for damage (shiney or scuffed spot generally limited to the middle of the shell.

[BigBobsL]

other possibilites would be too little cylinder clearance causing scuffing and/or too lean A/FR on causing that cylinder too overheat and scuff.

[Moonshine]

Plug was fouled, but showed no other issues. Piston crown looked fine, not sure about the rod bearing. Wouldn't a lean A/FR cause damage to all cylinders and not just one?

[BigBobsL]

Plug was fouled, but showed no other issues. Piston crown looked fine, not sure about the rod bearing. Wouldn't a lean A/FR cause damage to all cylinders and not just one?
Yes, if all were equally lean. Sometimes an injector can plug and lean out a cylinder. If rings and piston shirt is damaged, the spark plug will oil foul.

[Moonshine]

The engineers have made a determination. The damage seen was caused by hydro lock, tilting the piston in the cylinder. Water ingestion is the proximate cause of the hydro lock. There are several likely scenarios that can cause water ingestion.

[L8 APEX]

Funny one cylinder ate enough water to damage itself. You would think that would be in the oil as cream or intake tract...
You would think water would distribute and compress evenly not tilting. The only damage I have seen from hydro is bent rods. Water in a cylinder also tends to clean the carbon deposits off.