1990 MITSUBISHI ECLIPSE engine

9-10PISTONENGINE- Base Engine
For non-turbo engineldentificatlonForturbo engine
Pin;nterline y FPiston ceyerline
6EN01246EN0125Steel strut6EN0249
Ij(1) The piston is the autothermic type with steel
struts cast into it..(2) The depth of the trough in pistonhead varies for
the non-turbo and turbo engines.
Piston
pinConnecting
rod?\i
~Piston
6EN0250
No. 1 piston ringPISTON RINGS
No.3
For turbo engine
(1) The No. 1 piston ring IS of the barrel type.
(2) The No. 2 piston ring is of the taper type. The surface in
contact with the cylinder wall is coated with hard chrome
plating.-
(3) The oil ring is of the three piece type, consisting of two sLrails and an expander.
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,
(3) The piston pin is of the semi-floating type, press-fitted to
the connecting rod and rotates freely in the piston.

ENGINE- Base Engine9-11 7Oil jet
Front mark
6ENOO6lCONNECTING ROD
(1) The same connecting rod is used as that used in the 4663SOHC engine.
(2) The oil jet provided in the shoulder of the connecting rod is
used to lubricate the cylinder wall.
(3) The big-end bearing is the kelmet metal with metal backing.
CRANKSHAFT(1) The crankshaft is supported by the five main bearings.
(2) The oil passages drilled to the crankpins permit the flow of
lubricating oil from the main bearing to the connecting rod
bearing.(3) The crankshaft has been subjected to special surface
treatment. Therefore, do not grind it for reuse.
(4) The main bearing is an aluminum alloy with a backing of
another metal. The center bearing is provided with flanges
to receive the thrust load of the crankshaft.
Oil passage
6EN0089
16ENOOQO
Oil passage
INo. 51MAIN BEARING CAPSThe No. 1 and No. 2 main bearing caps are joined, as are the
No. 4 and No. 5 main bearing caps, by means of a beam to
minimize vibration of the bearing saddles and to enhance
rigidity of the crankshaft support.
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.--. _A

9-12
CRANKSHAFT PULLEY
ENGINE- Base EngineDrives the water
pump and alternator
Hub-
Pulley -Drives the air
conditioner
compressor
Fin
Rubber
6EMI2526EN0145 Timing belt cover
(1) The crankshaft pulley not only drives the water
pump and alternator, but also functions as a
torsional damper to reduce torsional vibration of
the crankshaft.
SILENT SHAFT SYSTEM(2) There are fins provided at the back of the pulley
that ventilate the inside of the timing belt cover:
when the pulley rotates, they draw air out of the._
timing belt cover.
Forward
@
/I
Center of crankshaftSilent shaft --
6ENl32The silent shaft system counteracts the secondaryreducing the vibration and noise generated by the
exciting moment in the engine’s vertical direction asengine. The system is exactly the same as that used
t uluv -well as the rolling moment, thereby drastically
in the conventional 4G63-SOHC engine.
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ENGINE - Base Engine9-13
VALVE MECHANISM
!
Rocker arm
Exhaustcamshaf
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Exhaust valve
bENOIntake valve6ENOlOOIft
(1) The valve mechanism is the DOHC 16-valvesystem.
.(2) The rocker arm with a roller follower. i.e., the
roller rocker arm, is used that reduces drastically
the friction loss of the valve train.
(3) The hydraulic type lash adjusters automatically
adjust the valve clearance, minimizing noisegenerated by the valve train. They also eliminate
the need for valve clearance adjustment.
(4) The valve springs, whose cross section is oval.contribute to the enhanced spring load. This in
turn ensures that the valves operate properly.
especially at high speed.
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ENGINE - Base Engine
ROCKER ARM
(1) The cam follower of the rocker arm is a roller with nea,.,-
bearings.
v
,I$- I- ‘Roller
Needle bearing6ENOlOI
6EN025-4
2-valve SOHC slipper type
9O-valve DOHC roller type1
02.5005.000Engine speed
rpm6ENOl o(Camshaft
I-Oil passage ,
EIr(2) A jet of oil spurts onto the contact area between the cam
and roller from an oil jet located on the fulcrum side of the
rocker arm.
(3) Since the roller rotates as the cam rotates, friction loss is
drastically reduced as compared with the conventional
slipper type.
(4) Due to the construction of the roller rocker arm, the valve
train driving torque is reduced to about half that of the
conventional slipper type, which is equivalent to, or
compares favorably with, the
2-valve SOHC slipper type. All
these factors contribute to enhanced engine performa
and fuel economy.
LASH ADJUSTER
,The hydraulic lash adjuster is of the end pivot type. It eliminates
the need for adjustment of the valve clearance. There are four
lash adjusters provided for each cylinder, 16 in all.
Rocker anIF=Lash adjuster
-
Cylinder head
--Valve
‘-Reservoir chamber
6E NO255
-6EN0256

5-jENGINE- Base Engine9-15Operation of the Lash Adjuster
When the valve starts opening
/f-b
During the valve opening stroke
n
6EN0254
When the valve coiqpletesthe opening stroke
6EN0257
6EN0256
(1) Before the valve starts opening:
--
No external load is applied to the
plunger, thus
causing the plunger to be pushed UP
by theplunger spring, maintaining zero clearance.
.(2) When the valve starts opening:
When the cam pushes the rocker arm, the ball inthe high-pressure chamber immediately is held
pressed against the seat by the hydraulic press-
ure. fully closing the high-pressure chamber. AS
the check ball closes, the pressure in the
high-pressure chamber surges causing the plun-ger to support the load from rocker arm, which
.allows the valve to start ooenino.
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(3) During the valve opening stroke:
A very small amount of oil leaks through the
clearance between the lash adjuster body and
plunger.
(4) When the valve completes its opening stroke:
There is no external load being applied to the
plunger as the valve closes, causing the plunger
to be pushed up by the plunger spring. This
causes the pressure in the high-pressure cham-
ber to be lowered, which pushes the check ball
open. The oil which has leaked is replaced in thehigh-pressure chamber from the reservoir cham-
ber.
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9-16ENGINE- Base Engine
Hydraulic Flow to Lash Adjusters
To lash adjuster onthe exhaust side
P
)
5-Valve body
.Lash adjuster
6EN0107
:.-.
2:.
4
‘.’Relief plunger
I?.,:.:.;
/Lash adjuster
-Cylinder head bolt hole
PlugTo
tash adjuster onthe intake side
Relief spring
-Valve body
6EN0108The oil moves through the cylinder head bolt hoie to
the oil passages drilled in the cylinder head. Andthen has its pressure regulated by the valve body k
pressure regulator) and is supplied to each
la:
adjuster.
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ENGINE- Base Engine9-17CAMSHAR
Exhaust camshaftStamped identification mark
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-
k--JL---J
No. 1 camsNo. 2 camsNo. 3 cams
No. 4 camsIntake camshaftIt’ II’ II1
NOTEJ = Journal
Crank angle sensor6EN0112
(1) Each camshaft is supported by the six bearings.(2) A hexagon between the No. 1 and No. 2 cams is
provided for holding the camshaft with a wrench
when loosening or tightening the
catishaftsprocket bolt.
TIMING BELT TRAIN
Exhmmt rid.Intake tide
Camshatt sprookec(No. of teeth: 461Camshaft sprocket(No. of teeth: 461
MN0139
6tNOl10
011 Pump stmoket(No. o! teeth: 18)
Crankshatr spmokst(No. of loath: 2416EN0114