Page 366 of 1082
02-20
5) Cylinder Head Gasket
The cylinder head gasket is installed between cylinder block and cylinder head to seal the combustion
gas from the combustion chamber, engine oil and coolant.Overview ▶
Location ▶
Cylinder head gasket
3 Layer MLS Gasket
Thickness : 0.7 mm (Compressed)
PFP: Max. 85 bar -
-
-
Page 368 of 1082
02-22
1) Timing Gear Case Cover
Features ▶
Major function: Protecting the chain drive system, minor function: Shielding the chain noise
Timing gear case cover prevents the oil from leaking.
The crankshaft front seal and the engine mounting bracket are installed on the timing gear case
cover. -
-
-
Timing gear case cover
Do not touch the inner lip of crankshaft front seal installed on the timing gear case cover. -
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02-231311-01
Layout and Location
Hydraulic chain tensioner
In G20DF engine, the hydraulic auto tensioner is used to keep the tension for chain drive system of
engine. The auto tensioner is operated by the spring in tensioner and the hydraulic pressure.
2) Hydraulic Auto Tensioner
Oil gallery
Page 376 of 1082
02-30
Components
Piston assembly contains piston, #1 ring, #2 ring, oil ring, piston pin and snap ring. The expansion energy
from engine is transferred to the crankshaft through connecting rod to convert the linear movement to
rotating energy.Overview ▶
Layout and Components ▶
Top
Bottom
Oil ring
Piston ring
No.1 ring
Piston pin
No.2 ringSnap ring
Piston
Page 377 of 1082
02-311130-33
Functions ▶
Piston transfers the combustion energy from engine to connecting rod.
C. Snap ring
Locks the piston pin. - A. Piston ring
#1 ring (Top ring) : Prevents the high pressurized combustion gas from leaking into crank chamber,
and prevents the engine oil getting into combustion chamber.
#2 ring: Scrapes the engine oil on the cylinder bore, and prevents the leaked combustion gas from #1
ring from leaking into the crank chamber.
Oil ring: Scrapes the engine oil on the cylinder bore. -
-
-
B. Piston pin
Connects the piston the connecting rod, and transfers the linear movement of piston to connecting rod
to convert it to rotating energy. -
Piston ring ▶
Piston ring end gap (mm)
#1 end gap: 0.170 ~ 0.320
#2 end gap: 0.300 ~ 0.450Piston ring side clearance (mm)
#1 groove: 0.040 ~ 0.080
#2 groove: 0.040 ~ 0.080
Page 383 of 1082
02-371128-01
Front view
Rear view
Spring pin (cylinder head mounting)
Expansion plug (exhaust: 6)
Screw plug (water jacket plug) (30Nm)
Screw plug (oil gallery plug)
Spring pin (T.G.C.C) A.
B.
C.
D.
E.
Overview ▶
The cylinder block is made of special cast iron, and contains the major components such as cylinder
head, crankshaft and piston assembly. There are oil and coolant galleries to lubricate and cool the
engine.
Components ▶
Plug screw (water jacket plug) (70Nm)
Expansion plug (intake: 4)
Spring pin (A/C mounting)
Oil gallery (oil filter assembly)
Ctankshaft position sensor mounting
Plug screw (oil gallery plug)
Spring pin (RR seal mounting) A.
B.
C.
D.
E.
F.
G.
Page 384 of 1082
02-38
Engine oil
Coolant
Coolant and oil flows ▶
Cylinder head
Cylinder block water
jacket
Coolant pumpCoolant pipe
Thermostat
Supply line to cylinder head
Oil pumpSupply line to PCJ
Main bearing
Oil filter assembly
Page 406 of 1082

05-71745-01
1. OVERVIEW
This system purifies the exhaust gas generated by the combustion in the engine to reduce the pollutants
and noise during that arise during combustion.
Harmful materials produced in the combustion process is treated and reduced in the exhaust system.
Harmful materials discharged from the crankcase and fuel tank is drawn into the intake system again to
reduce discharge amount of harmful materials.
Emission aftertreatment system ▶
Catalytic Converter & O2 Sensor
The catalytic converter is a monolith type purification system composed of cordierite which purifies
exhaust gas through the small holes of active monolith catalyst from the exhaust manifold. As exhaus
t
gas passes through the small holes in the layer in the middle, its CO and HC are reduced by
oxidization reaction and its NOx is reduced by reduction reaction to Pt, Ph and Pd. The oxygen
sensor sends signals for feedback and determination of catalyst condition. For detailed description,
see the corresponding section. -
The fuel evaporative gas is a gas evaporated to the atmosphere in the section between the fuel tank and
fuel line, and its main component is hydrocarbon (HC). The fuel evaporative gas is temporarily stored in
the canister, and it is drawn to the engine through the throttle body when the purge control solenoid valve
is open according to the engine operating condition.
Gas in the combustion chamber is sealed by the piston. However, gas is leaked through the gap
between the cylinder and piston and drawn into the crankcase during the compression and explosion
strokes. This gas is blow-by gas and its main components are hydrocarbon and carbon monoxide. If this
gas is drawn into the crankcase, the system can be corroded and oil can be deteriorated. Also, if this
gas is discharged into the air, it can pollute the environment. To prevent these, the blow-by gas
reduction system (also called as crankcase ventilation system) draws the blow-by gas from the
crankcase to the combustion chamber for combustion.
Purge Canister Control ▶
Blow-by gas control system (crankcase ventilation system) ▶