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