Hi
Im back with serious problems with pistons, just to confirm that it wasnt caused by water/ethanol injection.
5000km ago I get damaged pistons. They was damaged in strange way, no damage at all at the top of the piston or top edge, but complete destroyed between the rings. Engine was rebuilded. Now I have same damage. It looks very strange for me. Garage told me that reason is too high compression/boost pressure caused melting piston. But this should leave clear signs on the top of the piston, isnt it?
Anyway, here are pictures:
top of the piston, no visible damage (4 dots are marks for No. of piston)
http://www.ukazto.com/?img=P101000x.jpg
side of the piston, damage
http://www.ukazto.com/?img=P1010004-wxy1.jpg
Edit: just note that top comp. ring is undamaged.
Thanks for your advice.