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So I gotta question. I was talking to my buddy and we were talking about STI and how it has more ring line failures happen than the regular ol WRX. Can anyone explain this to me?
 

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Ring lands, not ring lines. The ring lands are separated by grooves into which the 3 individual rings fit, and you can think of the lands as plateau-shaped. Material failures here are frequently the result of poor mapping.

Subaru has (correctly, IMO) chosen a ~10+% Si aluminium alloy (I don't recall the exact %) hypereteutic piston design that allows good dimensional consistency and therefore adequate bore clearances to control emissions regardless of whether the motor is cold started, warm, etc. For this I can only applaud them, because emissions are the only performance metric that actually matters at this point in history. Power and torque are not interesting, especially from internal combustion engines that are now over a century old and on their way out (the sooner, the better). Those that want to go faster can buy an electric, or at least leave the house earlier instead. Their friends will just wait at the mall. There's a bench outside Ambercrombie. Anyway, I digress -- the point is the engine has tight tolerances and a decent design to control emissions.

Problems arise with knock events, excess cylindre pressures, etc. Problems have also arisen, apparently, with stock engines, and I don't know about that, sorry.

Since you and your buddy have stated that the STi experiences more failures than the WRX, the onus of explanation is on you. Besides, I don't have any buddies so I cannot relate.

So let us know what you find out.
 
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