Piston - Subaru impreza 2002 Service Manual

9. Piston

D
The pistons are of a slipper skirt design for reduced weight and friction. The oil control ring
groove utilizes a thermal design.
D
The piston pin is offset either downward (Nos. 1 and 3 pistons) or upward (Nos. 2 and 4 pistons).
D
The piston head has recesses to prevent interference with the intake and exhaust valves. It also
has engraved marks to identify the piston size and the direction of installation. All the pistons are
common in their design.
D
Three piston rings are used for each piston – two compression rings and one oil control ring.
The top piston ring has inner bevel and the second piston ring has a cut on the bottom outside
to reduce oil consumption.
B: STi MODEL
(1) Location mark (Engine front side)
PISTON
A: Top ring
B: Second ring
C: Oil ring
ME-5
Mechanical
NF0580
(a) Inner-bevel
(b) Cut
(c) Upper rail
(d) Spacer
(e) Lower rail