pcmhacking.net

Surge needs to stand up its next to useless lying on its side really

Better than cutting a hole in the tank to install a sump.

This is the problem and Its put a small mark in the bore which I can catch with my fingernail.

Is that off the piston or part of the ring? Hard to tell in the photo

It's the ring land, all the rings are in the photo and intact, I can see the missing section on the piston. I'd love to see a close up of the ring ends.

Like delco said, that surge tank needs to be stood up, it's not doing anything to stop surge being mounted like that.

Contrary to what I expected there was plenty of ring gap, over 0.030

Could be detonation. I know the subarus are bad for this from factory. the EJ20T, they broke lands in stock standard config. Det and shit pistons material is the main reason and not so much the ring gap for why they break, also another factor to their chronic blowing gaskets, also open deck doesn't help lol.

Could be something out of the ordinary like rings fluttering and det slamming the rings down hard enough to break the lands? Just a thought, not sure if that's possible or not?

Old used 304 cast pistons do that as well just over 330rwkw if you arnt carefull weather its det or you could of been too low on timing and getting a lot of heat expansion or a build up of carbon behind the rings so they can't expand anywhere or just that cylinder was a leaner one out of the bunch its it's hard when you are measuring the fuel ratio of 6 pots 1 or 2 can be lean and the rest safe and rich but the wideband saying it's perfectly safe.pm me you tune or post It up so we can have a look at it.was there much lip at the top of the bores it could of just caught the lip and punched the ringland out

going off the side of the piston is doesn't look like its too lean, but i'd love to see the top of it and the spark plug from that hole ?

and if your really hell bent on working out why its failed then you could always label all the injectors and get them flow tested, see if that one is lower flow than the others.

theres also the possibility you've found the limit of the cast pistons ? do that have a split in the skirt near the oil ring ? i've always found that to be a weak point.

Looks like detonation to me. Same thing happened to my EVO. All 4 pistons broke the ring lands off between 1st and second compression rings and they were forged pistons.