Mitsubishi Evolution X. Manual — part 52
BASE ENGINE
TSB Revision
ENGINE
11-6
PISTONS
The pistons are made of a special aluminum alloy.
Their weight has been reduced by lowering their
overall height and increasing the depression at each
end of the piston pin.
The piston pin hole center is offset 0.5 mm (0.020 in)
towards the thrust side of the piston center.
The skirt portion along the perimeter of the piston is
finished with streaks that excel in oil retention and
seizure resistance.
PISTON PINS
The full floating type of piston is used to improve the
reliability by reducing the friction.
AK703206AC
Front mark
Piston offset
ITEM
SPECIFICATIONS
Basic diameter mm (in)
86 (3.4)
Pin hole diameter mm (in) 23 (0.9)
Overall height mm (in)
54.87 (2.160)
AK703727
d2
AC
D
h
d1
ITEM
SPECIFICATIONS
Outer diameter (D) mm
(in)
23 (0.9)
Inner diameter (d1) mm
(in)
11.5 (0.45)
Inner diameter (d2) mm
(in)
10.5 (0.41)
Overall length (h) mm (in) 60 (2.4)
BASE ENGINE
TSB Revision
ENGINE
11-7
PISTON RINGS
The piston rings consist of No. 1 and No. 2 rings and
an oil ring.
AK703207AC
Oil ring
Spacer
Rail
Maker mark
Piston ring No. 1
Piston ring No. 1
Piston ring No. 2
Piston ring No. 2
Oil ring
Item
Piston ring No. 1
Piston ring No. 2
Oil ring
Shape
Inside bevel
Taper undercut
3-piece
Surface treatment (cylinder
contact surface)
Ion plating
Parkerizing
Ion plating
Supplier mark
1T
2T
None
BASE ENGINE
TSB Revision
ENGINE
11-8
CONNECTING RODS
The connecting rods are made of highly rigid, forged
carbon steel. The cross section of the rod portion is
shaped like the letter H.
A fracture-split process has been adopted for split-
ting the big end of the connecting rod.
The fracture split connecting rod has the high inser-
tion force between the rod and the cap as well as the
high installation location accuracy.
The oil holes that feed oil from the main journals of
the crankshaft to the crankshaft pins lubricate the
bearings at the big ends of the connecting rods.
CONNECTING ROD BEARINGS
The upper and lower connecting rod bearings are the
same. Each connecting rod bearing is provided with
a backing plate. Its bearing portion is made of an
kelmet alloy and its backing plate is made of ordinary
sheet steel.
The width of the connecting rod bearing has been
made as narrow as possible in proportion to the
bearing cap in order to reduce friction loss.
AK703208AC
L
D
d
Item
Specifications
Small end hole diameter
(d) mm (in)
23 (0.9)
Big end hole diameter (D)
mm (in)
55 (2.2)
Center-to-center distance
(L) mm (in)
143.75 (5.659)
AK502492AH
A
H
Item
Specifications
Width (H) mm (in)
17 (0.7)
Thickness (A) mm (in)
1.5 (0.06)
BASE ENGINE
TSB Revision
ENGINE
11-9
CRANKSHAFT
A forged crankshaft has been adopted.
It has 5 main bearings and 8 balance weights.
The crankshaft pins are located at equal 180
° inter-
vals.
The oil holes feed engine oil from the journals to the
pins.
A crankshaft sprocket and an oil pump drive shaft are
press-fit to the front of the crankshaft.
CRANKSHAFT BEARINGS, THRUST BEARINGS
The upper crankshaft bearings have oil grooves and
the lower crankshaft bearings do not.
Each crankshaft bearing is provided with a backing
plate. Its bearing portion is made of an kelmet alloy
and its backing plate is made of ordinary sheet steel.
A thrust bearing, which sustains the load in the thrust
direction, is provided at each end of the No. 3 bear-
ing.
AK502493AD
Balance weight
Balance weight
Balance weight
Oil hole
Oil hole
Item
Specifications
Pin outer diameter mm
(in)
48 (1.9)
Journal outer diameter
mm (in)
52 (2.0)
AK703628AC
Oil hole
Oil groove
Upper bearing
Lower bearing
Engine front
Thrust bearing
Groove
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