engine MITSUBISHI COLT 2006 Service User Guide

BASE ENGINE
ENGINE MECHANICAL <4G1>11B-4
PISTON
AK403411
Frontview
Under view
A-AB -B
A
A B
B
AB
T
o co rrespo nd wi th the imp r ove d o u t put pe rfo r ma nce
by emplo
y in g the t u rbocharger , the strength is
imp
r oved in th e piston b ody .
PISTON PIN
AK403412
56
Ø8
Ø18
23.523.5 9
AB
T o co rrespo nd wi th the imp r ove d o u t put pe rfo r ma nce
by emplo
y in g the t u rbocharger , the strength is
imp
r oved in th e piston p i n.

GROUP 11A
ENGINE
MECHANICAL
<4A9>
CONTENTS
GENERAL INFORMATIO N . . . . . . . .11A-2
BASE ENGINE . . . . . . . . . . . . . . . . . .11A-3
GENERAL INFORMATION. . . . . . . . .11A-18
BASE ENGINE . . . . . . . . . . . . . . . . . .11A-19

GENERAL INFORMATION
ENGINE MECHANICAL <4A9>11A-2
GENERAL INFORMATION
M2112000100697
The newly developed 1.5L 4A91 engine features
4-cylinder, 16-valve, and double overhead camshafts
(DOHC).
The engine has the following features.
•Aluminum cylinder block
•MIVEC (Mitsubishi Innovative Valve timing Elec-
tronic Control system)
•Selective valve tappet of direct acting valve sys-
tem for valve clearance adjustment
•Timing chain
MAJOR SPECIFICATIONS
Item4A91
Total displacement mL1,499
Bore × Stro ke mm75 × 84.8
Compression ratio10.0
Compression chamberPentroof-type
Va l v e t i m i n gIntake openingBTDC 31° − AT D C 1 9°
Intake closingABDC 21° − ABDC 71°
Exhaust openingBBDC 39°
Exhaust closingATDC 5°
Maximum output kW (PS)/rpm77 (104)/6,000
Maximum torque N⋅m (kg⋅m)/rpm141 (14.4)/4,000
Fuel systemElectronically controlled multipoint fuel injection
Ignition systemElectronic-controlled 4-coil

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-3
BASE ENGINE
M2112001000864
CYLINDER HEAD
AK305050AB
Spark plug guide
Intake
side
Exhaust
side
Valve guide
The cylinder head is made of aluminu m alloy , which
is light
we ight a nd ha s an excelle nt co oling ef ficiency .
The pentroof type comb ustion chamb e r has a sp a r k
plug in the
cent er . The valve an gle is relatively small,
contributing to size redu
ctio n.
The int a ke an d exhaust port s a r e arrang ed in a
cross-flow construction.
Ea ch cylinde r has a p a ir of
int
a ke port s on one side and a p a ir of e x hau st po rt s
on the
other side .
Each o f the int a ke a nd exhaust ca msh a f t s is sup-
ported by 5 bearin gs. On ea ch camshaf t, th e thrust
load
is suppo rted by No. 1 b earin g. The No . 1 bea r
-
ings for the int a ke and exha ust camshaf t s ha ve a
common bearing
ca p.
VALV E S E AT
AK305052
d
AB
d
DD h
h
Intake
Exhaust
Sintered
alloy valve seat
ItemIntakeExhaust
D (Outer
diameter) mm31.528
d (Inner
diameter) mm2622
h (height) mm6.67.3

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-4
VA LV E G U I D E
AK305053
d
AB
Dh
The in
t a ke an d exhaust valves use the same -design
valve gu
ide.
ItemIntake
D (Outer diameter) mm10.5
d (Inner diameter) mm4.5
h (height) mm34.5
CYLINDER HEAD GASKET
AK305054AB
Water hole
Oil hole
Water hole
Th e met a l g a sket having he at resist ance, sea l ability
and low cost is use
d for th e cylin der hea d gasket .
CYLINDER HEAD COVER
AK402398AC
Cylinder head cover
A resin cylin der hea d co ver is used fo r the cylinder head.

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-5
CYLINDER BLOCK
AK402339AC
Front view
Right side view
Under view
Top view
Rear view
Left side view
Thermostat case installation positionOil filter bracket installation position Front
Front Front Front
Nipple
The cylinder b
l ock is ma de of ligh twe i ght aluminum
allo
y .
The crankshaf t jo urnal is supp orted b y 5 b earing s .
The crankshaf
t thru st load is supporte d by No . 4
bearin
g.
The water jacket is of a full-siamese de sig n .
A nipple is p r ovid ed at the fr o n t of the block to su pply
engin
e oil onto the timin g ch ain.
ItemDimension
Overall height mm280
Overall length mm375.1
Top face to crankshaft
center mm205
Crankshaft center to
bottom face mm75
Bore mm75
Bore pitch mm83
Stroke mm84.8

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-6
REAR OIL SEAL CASE
AK305061AB
AA A-A
The rea
r oil seal ca se is a sheet -met al wor k . The
case is
inst alled with sealant ap plie d onto th e mou n t
-
ing face to prevent oil leaka ge.
PISTON
AK403222
AB
Front mark
Piston pin offset
The pisto n is made of spec ial a l uminu m all o y . W e ig ht
reduction
is a c hieved by minimizin g the o v erall
heigh
t while maximizing th e recess on bo th end s of
the piston
pin.
The center o f the p i sto n pin hole is of fset by 0.5 mm
from t
he ce nter of the piston towards the th rust side .
The piston skirt ha s a streak finish to enha nce oil
retention an
d anti-seizin g prope rty .
ItemDimension
Base diameter mm75
Pin diameter mm18
Overall height mm46.04
PISTON PIN
AK305064
d
AB
D
h
The piston pin is o f a semi-floating type, p r ess-fitte d
into t
he co nnecting rod small end wh ile cap able of
floating re
lative to the piston .
ItemDimension
D (Outer diameter) mm18
d (Inner diameter) mm11
h (Overall length) mm50

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-7
PISTON RING
AK305365AB
Piston ring No.1
Spacer RailMaker mark
Piston ring No.2
Oil ring Piston ring No.1
Piston ring No.2
Oil ring
Ea ch pisto n is provided with No. 1 and No. 2 com-
pression rings and an oil rin g .
ItemNo. 1 piston ringNo. 2 piston ringOil ring
ShapeBarrelUndercut3-piece
Surface treatment (Contact
face with cylinder)Ion platingParkerizedIon plating
Maker markNo mafking2RNo marking

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-8
CONNECTING ROD
AK305065AB
dD
L
The connecting rod is made of high ly rigid, forged
carb
on stee l. The rod p o rtion h a s an H- sha ped cro s s
section.
The connecting rod big end bearing is lu bricated
thr
oug h an oil p a ssage ru nn in g f r om the main jo urn a l
to the cranksha
f t p i n.
ItemDimension
d (Small end inner
diameter) mm18
D (Large end inner
diameter) mm43
L (Center distance) mm135.6
CONNECTING ROD BEARING
AK305309AB
H A
Identification
color
The up
per and lower conne ctin g rod b earin g halves
are id
entical.
The connecting rod be aring is e quip ped wit h back
met
a l. While the b earin g it se lf is ma de of a l uminum
allo
y , the back met a l is no rmally mad e of ste e l shee t.
The connecting rod be aring is n a rrower tha n the
bearin
g ca p, this is to minimize wear .
ItemDimension
H (Width) mm13.5
A (Thickness) mm1.5

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-9
CRANKSHAFT
AK305068AD
Oil pump drive
gear shaft
Crankshaft
sprocket
Crankshaft sensing ring
CrankshaftOil hole
Oil hole
Balance weightBalance weightBalance weight
A casted crankshaf
t is used for t he cr ankshaf t.
The crankshaft consist s o f 5 ma in be aring s an d 8
balan
ce weight s.
The crankshaft pins a r e arrang ed at 1 8 0° inte rval s.
The oil hole supply lu brication oil from t he jo urnal to
the crank p
i n.
A cranksha f t sprocket and an oil pump drive gea r
shaf
t are press-fit t ed on to the f r ont of the crankshaf t.
The crankshaft is also fitt ed with a crankshaf t sens-
ing ring.
CRANKSHAFT BEARING, THRUST BEARING
AK305070
Upper bearingOil groove
Oil hole
Identification
color
Lower bearing
Identification
color
AB
Thrust bearing
Groove
Front
The upp er cra n kshaf t bea ring (with oil groove) is
loca
ted on the cylinder block side wh ile the lo we r
bearin
g (witho ut oil groo ve) is he ld by the b earin g
cap.
The crankshaft bea ring is e quipp ed with back me t a l.
While the b
earin g it self is ma de of a l uminum alloy ,
the back met
a l is no rmally made of steel sheet .
A thrust bearing is inst alle d on b o th sides of th e No.
4 cran
kshaf t bearing.
ItemDimension
Crankshaft
bearingWidth mm16
Thickness mm20
Crankshaft
thrust bearingThickness mm3.275