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Nah more likely be excess heat, insufficient ring end gap or collapsed ring lands/ pitted sides etc..

yeah your proabably right, but I've seen an oval bore before [but not in a turbo nissan I have to admit] where the rings are compressed at the top by the tight cross section and then you get big blow by for the other 80% of the cylinder where the rings aren't touching the bore. And those scuff marks are typical of this. And that is an 'induced' ring collapse.

Also if this happens then your ring end gap is shot to hell and back as well.

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please explain how there is no sign of det and yet broken ring lands?

Can someone tell me what all these parts are? I know you have a piston but I hear stuff about ring lands, crowns and all this stuff. I know the piston ring must be a seal around the thing but what are the other parts of the piston? Does the top of the piston have a specific name?

Can someone tell me what all these parts are? I know you have a piston but I hear stuff about ring lands, crowns and all this stuff. I know the piston ring must be a seal around the thing but what are the other parts of the piston? Does the top of the piston have a specific name?

The crown is the top of the piston the ring lands are the gaps between the rings and the skirt is the section below the bottom ring.

Here's a diagram for you;

piston.gif

Edited by D_Stirls

So... do ringlands break due to excess force exerted by the ring (either from pinging or just tons of power & boost) ?

OP do you know what power the pistons are specified for? Will you contact the manufacturer for comment on the failure?

So... do ringlands break due to excess force exerted by the ring (either from pinging or just tons of power & boost) ?

OP do you know what power the pistons are specified for? Will you contact the manufacturer for comment on the failure?

thats the way the guy explained it to me. that they broke from too much boost pushing down on them by the rings.

dunno what power there rated for. there only n/a replacements. was hoping theyd be same as nissan pistons where ya can make heaps of power on em and lots o boost. nar not gunna contact the manufacturer about them

Boost pressure has absolutely nothing to with breaking rings. Combustion pressure does.

You could fill the cylinder with 200psi of boost and it wont worry the rings. Put some fuel in there and light it, and thats another story.

Things that make combustion pressure too high = detonation, pre ignition or water.

Boost pressure has absolutely nothing to with breaking rings. Combustion pressure does.

You could fill the cylinder with 200psi of boost and it wont worry the rings. Put some fuel in there and light it, and thats another story.

Things that make combustion pressure too high = detonation, pre ignition or water.

Absolutely. Chamber pressures are indeed affected by boost pressures, but boost is not the only, and not the major factor in resulting chamber pressures.

Overadvanced ignition timing and preignition (mixture ignited by hot combustion chamber parts prior to spark) can cause very high pressures without any audible pinging.

What was the compression ratio in this engine?

Edited by Legionnaire

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