Page 201 of 796

02-42
(3) Functions
Piston transfers the combustion energy from engine to connecting rod. Especially in the direct injection
engine such as D20DTF, it provides the combustion space and largely effects to the engine performance
and exhaust gas.
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.
Piston pin
Connects the piston the connecting rod, and transfers the linear movement of piston to connecting
rod to convert it to rotating energy
Snap pin
Locks the piston pin. ▶
-
-
-
▶
-
▶
-
(4) Assembling the piston
Install the piston rings with the "Y" mark on
the ring facing upwards.
Position the end gap of #1 ring at 180˚
away from the end gap of #1 ring.
Position the end gap of oil ring at 180˚
away from the end gap of coil spring, and
position the end gap of oil ring at 90˚
away from the end gap of #2 ring. 1.
2.
3.
Page 202 of 796
02-430000-00
Selecting piston oversize
Top of piston Top of cylinder block
EnginePiston Cylinder bore
Part NO Marking NO.-
D20DTF 671 030 06 17 - -
671 037 07 01 A A
671 037 08 01 X X
671 037 09 01 B B
671 037 10 01 +5 -
671 037 11 01 +10 -
Page 205 of 796
02-46
3) Crankshaft
(1) Overview
Crankshaft is installed on the cylinder block.
(2) Arrangement
Crankshaft main bearing upperCrankshaft main bearing upper
Upper thrust bearing
Crankshaft main bearing lowerCrankshaft main bearing lower
Lower thrust bearing
Crank pin journalMain journal
Page 206 of 796
02-470000-00
Bottom of cylinder block
Selection of upper main bearing
Mating surface of crankshaft sprocket
Selection of lower main bearing
(3) Selection of crankshaft main bearing
Mark Color Thickness of main
bearing (mm)
V Violet +0.030
+0.025
W White +0.025
+0.020
R Red +0.020
+0.015
Y Yellow +0.015
+0.010
B Blue +0.010
+0.005
2.25
2.25
2.25
2.25
2.25
Selection of bearing according to pin punch &
color
Mark Color Thickness of main
bearing
* Blue 66.500~66.506
** Yellow 66.506~66.513
*** Red 66.513~66.519
Page 207 of 796
02-48
4) Cylinder Block
(1) Overview
The major dimensions in D20DTR are similar to
D20DTR engine. It has two mounting
bosses for knock sensor and meets the
requirements for EURO5 regulation.
(2) Layout
Right sideCylindrical pin
Expansion plug
Screw plug
Page 208 of 796
02-490000-00
Left sideExpansion plug
(3) Features
For simple manufacturing, the crankcase blow-
by gas passage and the oil return hole are
made by casting on the cylinder block.
Page 209 of 796
02-50
The bottom side of water jacket is desgined as sine wave to strengthen the structure of crankcase. The
main flow of coolant starts from outlet port of water pump and goes along the longitudinal direction of
engine. The coolant passage from cylinder head to inlet port of water pump is integrated in cylinder
head.
The engine oil from oil pump is supplied to the main oil gallery through oil channel, oil filter module and
cross bore in cylinder block without using external pipes. This oil is supplied to main bearing, cylinder
head and MBU. And, it is sprayed to the chain through the chain tensioner connected to cross bore.
Crankcase cross bore for oil supply
Water jacket core
Page 227 of 796

03-20
Water
separator
(2) Di engine and its expected problems and remedies can be caused by
water in fuel
System supplement against paraffin separation ▶
In case of Diesel fuel, paraffin, one of the elements, can be separated from fuel during winter and then
can stick on the fuel filter blocking fuel flow and causing difficult starting finally. Oil companies supply
summer fuel and winter fuel by differentiating mixing ratio of kerosene and other elements by region
and season. However, above phenomenon can be happened if stations have poor facilities or sell
improper fuel for the season. In case of DI engine, purity of fuel is very important factor to keep internal
preciseness of HP pump and injector.
Accordingly, more dense mesh than conventional fuel filter is used. To prevent fuel filter internal
clogging due to paraffin separation, SYMC is using fuel line that high pressure and temperature fuel
injected by injector returns through fuel filter to have an effect of built-in heater (see fuel system).
System supplement and remedy against water in fuel ▶
As mentioned above, some gas stations supply fuel with excessive than specified water. In the
conventional IDI engine, excessive water in the fuel only causes dropping engine power or engine
hunting. However, fuel system in the DI engine consists of precise components so water in the fuel can
cause malfunctions of HP pump due to poor lubrication of pump caused by poor coating film during
high speed pumping and bacterization (under long period parking). To prevent problems can be
caused by excessive water in fuel, water separator is installed inside of fuel filter. When fuel is passing
filter, water that has relatively bigger specific gravity is accumulated on the bottom of the filter.
Water drain from water separator ▶
If water in the separator on the fuel filter exceeds a certain level, it will be supplied to HP pump with
fuel, so the engine ECU turns on warning lamp on the meter cluster and buzzer if water level is higher
than a certain level.
Due to engine layout, a customer cannot easily drain water from fuel filter directly, so if a customer
checks in to change engine oil, be sure to perform water drain from fuel filter.
To separate the water from the fuel filter,
remove the fuel filter assembly first.