Engine Mechanical - Mechanism & Function (H6DO): Piston
- The pistons are of a slipper skirt design for reduced weight and friction. The oil control ring groove utilizes a thermal design.
- The piston pin is offset either downward (Nos. 1, 3 and 5 pistons) or upward (Nos. 2, 4 and 6 pistons).
- Recesses are provided in the piston to maintain clearance between the piston and valve heads. All the right and left bank pistons are the same in shape. Each piston has a location mark (mark indicating the front of engine) on its top.
- Three piston rings are used for each piston; two compression rings and one oil control ring. The top piston ring has inner bevels and the second piston ring has an interrupt (cut) on the bottom outside to reduce oil consumption.
Courtesy of SUBARU OF AMERICA, INC.