Why did my Piston and Rings Blow Up?

[Rusty Heap]

I've got Blown Piston dome and Rings on my 2021 KRX Side x Side with 1500 miles. It started smoking on the trail. I did a compression test. Left was ~150 psi, Right was only 60. It was time for the dealer and warranty coverage. They tore the top end down to find right piston missing most of the rings and piston dome/skirt that retains the rings.

Detonation? Doesn't look like I'm running lean........always use Premium 92 octane so it's not pinging.


Brain Trust thoughts?

[908/930]

Not sure but I think you floated your exhaust valves and they made contact. Any marks on them?

[cstreit]

...boy that sure LOOKS like detonation. Bad gas?

[Jeff Higgins]

Classic high rpm detonation. I wish you had seen these before you stopped by yesterday, I could have shown you some Porsche pistons that look like that.

When you get it back, we should put my LM1 on it and get some A/F readings. What with modern emissions requirements, even on "off road" equipment, I bet it's running lean as hell. Is there any way to alter the fuel injection to provide more fuel?

[sc_rufctr]

It could have been an incidental failure... As in "One in then thousand".

Sometimes thing break for no apparent reason.

[Tobra]

Originally Posted by cstreit

...boy that sure LOOKS like detonation. Bad gas?

yeah

[911boost]

It’s not a Polaris!

Haha just kidding that sucks. I agree detonation.

[LWJ]

Yikes!

I agree that it is almost certainly tuned very lean.

Dirty filter, bad gas, something else, can make it go even more lean very quickly.

And, then this is the result.

[Jeff Alton]

Detonation..........

[pavulon]

There seem to be forums for almost everything ever made. Any mention of this or similar in those?

[wdfifteen]

Ring land collapse like that is almost always premature ignition. As many here have said, a lean mixture can cause it. So can timing going too far advanced at working rpm. Given how black and moist the combustion chamber looks my money would be on timing.

[1990C4S]

Originally Posted by wdfifteen

Ring land collapse like that is almost always premature ignition. As many here have said, a lean mixture can cause it. So can timing going too far advanced at working rpm. Given how black and moist the combustion chamber looks my money would be on timing.

It can also be insufficient ring gap, no? Rings expand, lock up, and the land fails?

[red 928]

Originally Posted by cstreit

...boy that sure LOOKS like detonation. Bad gas?

That's what I was thinking.

[wdfifteen]

Originally Posted by 1990C4S

It can also be insufficient ring gap, no? Rings expand, lock up, and the land fails?

I suppose so. There would probably be a lot of cylinder wall scoring and I would expect the ring land would have failed pulling up instead of collapsing down.

[Bob Kontak]

Injector flow may have been compromised if everything is stock as to factory settings.

[gduke2010]

Extreme heat or an injector stuck open.

[wdfifteen]

How is the top ring fitting in the other piston?

[Por_sha911]

Originally Posted by cstreit

...boy that sure looks like detonation. Bad gas?

+1

[Bob Kontak]

A neighborood car acquaintance showed me the pistons out of his 930 that suffered detenotation. They were melted on that edge and down the side a half inch.

Different variables.

[Dan J]

Bad injector