why does the wiseco piston have a tab on the bottom oil ring that locates into one of the oil holes on the piston itself, stopping the ring from being able to rotate.

the scrapper ring sits above it and another oil ring above that.

asking because after a rebuilt i lost compression on once cylinder.

on inspectom the ring with the tab got pushed out and bored the cylinder all.

engineers think the ring tried to rotate and only place it could go was out into cylinder wall.

 

As you said - its to stop the oil ring set from rotating/preventing the oil ring gaps from lining up, subaru use the same tabbed ring on O.E fitment.

If the engineers cant find any other any reason for it moving out of the ring land eg incorrect piston/bore clearance or signs of ring butting - it's quite possible the tang came out of the locating hole on assembly or when fitting the piston into the bore.

Mick

 

so what would happen if engineers straightened the tab, because the compression rings arent stuck and are allowed to rotate. and the oil rings have the scrapper ring inbetween. as all the oil rings to is remove excess all from bore and there are 2 rings and the scrapper ring, and piston has many oil holes.

would it be that bad to remove tab.

i cant see the rings linning up and and leaving oil in bore to be burnt, so burning oil. especially with the scraper ring sandwiched between the two.

just dont want to put it back together to have same issue. and many pistons dont have a fixed oil ring. and dont have issues.

but the other 3 where fine. so cud be paranoia and me messing up the one on installation