在这些活塞中，活塞环的数量减少到三个，即两个气环，一个油环。
On these pistons the number piston rings was reduced to three, two compression and one oil-control.
清洁活塞环槽或油环开缝，绝对不能损伤金属部分。
Be sure that you do not remove metal when cleaning ring grooves or oil slots.
事实上有两种活塞环，气环和油环。
Actually, there are two types of rings, compression rings and oil-control rings.
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