Mitsubishi Eclipse. Technical Information Manual (1994) — part 6
ENGINE <NON-TURBO>
- General Information
ENGINE <NON-TURBO>
GENERAL INFORMATION
This 420A
engine is a product of Chrysler Corporation. It is not equipped with a turbocharger.
MAJOR SPECIFICATIONS
Items
Specifications
Total displacement
1,996 (121.8)
Bore x Stroke
mm (in.)
87.5 (3.45) x 83.0 (3.27)
Compression ratio
9.6
Camshaft arrangement
DOHC
Valve timing
At 0.5 mm
in.) lift
Intake
Open
1.3” BTDC
Close
39.7” ABDC
Exhaust
Open
36” BBDC
Close
1.1” ATDC
Rocker arm
Roller type
Lash adjuster
Equipped
LUBRICATION SYSTEM
System is full flow filtration, pressure feed type.
The oil pump is mounted in the front engine cover
from rod bearing throw-off and slinger slots
and driven by the crankshaft. Pressurized oil is then
on the connecting rod assemblies. Camshaft and
routed through the main oil gallery, running the
valve mechanisms are lubricated from a full-length
length of the cylinder block, supplying main and
cylinder head oil gallery supplied from the crankcase
main oil gallery.
rod bearings with further routing. Pistons are
ENGINE <NON-TURBO> Base Engine
BASE ENGINE
CYLINDER HEAD
Features a Dual Over Head Camshaft (DOHC)
per cylinder cross flow design. The valves
are arranged in two
banks. Incorporated
CYLINDER BLOCK AND BED-PLATE
Five different engine designs were considered, the
only engine design that met all the criteria was one
that utilized a bed-plate. There are several forces
at work in the lower end of an engine block.
These are:
l
Vertical bending
l
Horizontal bending 90 degrees to the cylinder
bore
l
Torsional bending along the crankshaft axis
l
Individual main cap flutter co-inciding to indi-
vidual cylinder firing
All these factors contribute to noise, vibration and
harshness. Because this is a four cylinder engine,
design criteria becomes even more important.
PISTON
The piston has an oval shape (elliptical) that expands
as the engine warms-up. This reduces cold engine
piston noise, helps the piston fit into the bore better
and avoids piston scuffing.
The piston pin has a 1 mm
in.) offset toward
the thrust side of the piston for improved noise char-
acteristics. The top ring is a steel unit with a plasma
sprayed molybdenum faced center section for reli-
able compression sealing. The upper ring is not
directional. The black coating as a rust preventative.
A taper faced cast iron second compression ring
der metal valve guides and seats. Integral oil galleys
within the cylinder head supplies oil to the hydraulic
lash adjusters, camshaft and valve mechanisms.
plate design makes for a much stronger lower end
because it ties all of the main caps together to sub-
stantially improve block stiffness. The block is a
two-piece assembly, encompassing the bed-plate
and the cylinder block. The bed-plate is made of
cast iron and is totally separable from the block.
When installed, it becomes part of the block and
strengthens the lower end considerably. The
plate and block are cast separately, then machined
together. Once machined, the bed-plate and block
are drilled and doweled together to become a mated
unit. This ensures that the bed-plate and block are
in perfect alignment even after assembly and disas-
sembly.
is used for additional cylinder compression control.
Both compression rings are 1.2 mm
in.) thick.
The oil ring is a three piece design using chrome
faced fails and a separate center expander. Use
the running clearance notches and is identifiable
by a slight dish at the top of the piston.
This engine is pressed-in piston pins to attach forged
powder metal connecting rods. Incorporate hex head
cap screw threaded into the connecting rod. Piston
and Rods are serviced as an assembly.
I
No. 1 piston ring
N
o
.
p i s t o n r i n g
J
Side
rail
extender
Oil ring
CENO066
ENGINE <NON-TURBO> Base Engine
CONNECTING RODS
The connecting rods are different from past designs
because the manufacturing process has changed.
The connecting rod is forged as one piece from
powdered metal. The powdered metal is placed
in a form that is slightly oversized and then sent
to sintering furnace. It melts the powdered metal
in the mold. The mold travels to a forging press
where the rod is forged to the final shape. This
is done while the rod is still warm, but not molten.
After the forging process, the inside diameter of
the crankshaft end of the rod is scribed with a laser
and is fractured in a fixture. This creates a rod cap
and rod that only fit together one way. The final
step in the process is shot peening which increases
CAMSHAFT
The camshafts have six bearing journals and 2 cam
lobes per cylinder. Flanges at the rear journals con-
trol camshaft end play. Provision for cam position
CRANKSHAFT
The engine has 5 main bearings, with number 3
flanged to control thrust. The 52 mm (2.0472 in.)
diameter main and 48 mm (1.8898 in.) diameter
crank pin journals (all) have undercut fillets that
are deep rolled for added strength. To evenly distrib-
ute bearing loads and minimize internal stress, 8
counterweights are used. Hydrodynamic seals
the surface hardness slightly. This design process
eliminates the need for several machining opera-
tions that are required for cast iron, connecting rod
assemblies. Other designs required machining the
connecting rod and connecting rod cap individually,
then finish machining, honing, and balancing are
performed as an assembly.
Note
The new process and the different metal does not
prohibit the use of standard tools. If the connecting
rods require removal from the engine a center punch
can be used to identify the correct position of the
connecting rod and cap.
sensor on the exhaust camshaft at the rear of cylin-
der head. A hydrodynamic oil seal is used for oil
control at the front of the camshaft.
vide end sealing, where the crankshaft exits the
block. Anaerobic gasket material is used for parting
line sealing in the block. A sintered powder metal
timing belt sprocket is mounted on the crankshaft
nose. This sprocket provides motive power; via tim-
ing belt to the camshaft sprockets (providing timed
valve actuation) and to the water pump.
ENGINE <NON-TURBO> Base Engine
CRANKSHAFT AND CAMSHAFT TIMING
This engine does not have broken-belt valve clear-
ance. The reason for this design is to improve hydro-
carbon emissions by eliminating valve pockets cut
into the pistons that would normally provide this
clearance. If the engine is rotated with the timing
belt removed or the cam timing is set improperly,
the valves will hit the pistons. However, if the
AUTOMATIC TENSIONER
This engine uses a timing-belt cover, crankshaft
sprocket, timing belt, “automatic” belt tensioner, two
camshafts, and camshaft sprockets. The belt ten-
sioner is spring activated, hydraulically dampened,
and self contained. The tensioner consists of a free
piston, orifice, silicone fluid, a spring, check ball,
and a plunger rod. The check ball is seated as
the plunger rod is depressed, trapping the fluid and
shafts are out of time on engines, the valves can
strike each other as well as the pistons. This is
due to the intake and exhaust valve-to-valve interfer-
ence design. Therefore, it is necessary to time the
camshafts and crankshaft simultaneously to prevent
damage to pistons, exhaust valves, and intake
valves.
creating a high pressure area. The area below the
plunger rod is the high pressure area for hydraulic
dampening. The area between the free piston and
the plunger rod is a low pressure area. And, the
area above the free piston provides a place to con-
tain aerated fluid. The spring below the plunger
rod holds a constant pressure for the belt tensioner
pivot bracket.
Dust seal
Aerated
Low
fluid
pressure
area
Free piston inner seal
Compression ring
CEN0099
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