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5. Pilot Flow Control
The pilot flow represents the amount of fuel injected into the cylinder during the pilot injection. This
amount is determined according to the engine speed and the total flow.
A first correction is made according to the air and water temperature.
This correction allows the pilot flow to be adapted to the operating temperature of the engine. When
the engine is warm, the ignition time decreases because the end-of-compression temperature is
higher. The pilot flow can therefore be reduced because there is obviously less combustion noise
when the engine is warm.
A second correction is made according to the atmospheric pressure. -
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During starting, the pilot flow is determined on the basis of the engine speed and the coolant
temperature.
6. Cylinder Balancing Strategy
Balancing of the point to point flows
The pulse of each injector is corrected according to the difference in instantaneous speed measured
between 2 successive injectors.
The instantaneous speeds on two successive injections are first calculated.
The difference between these two instantaneous speeds is then calculated.
Finally, the time to be added to the main injection pulse for the different injectors is determined. For each
injector, this time is calculated according to the initial offset of the injector and the instantaneous speed
difference.
Detection of an injector which has stuck closed
The cylinder balancing strategy also allows the detection of an injector which has stuck closed. The
difference in instantaneous speed between 2 successive injections then exceeds a predefined threshold.
In this case, a fault is signaled by the system.
Load Engine speed Swirl
valveAmount of
swirlRemarks
Low speed,
Low loadbelow 3,000 rpm Closed HeavyIncreased EGR ratio, better air-fuel
mixture (reduce exhaust gas)
High speed,
High loadover 3,000 rpm Open LightIncrease charge efficiency, higher
engine power
The variable swirl valve actuator operates when
turning the ignition switch ON/OFF position to
open/close the swirl valve. In this period, the soot
will be removed and the learning for swirl valve
position is performed.
Swirl valve
Swirl: This is the twisted (radial) air flow along the cylinder wall during the intake stroke. This stabilizes
the combustion even in lean air-fuel mixture condition.
e. Features
Swirl and air intake efficiency
To generate the swirl, the intake port should be serpentine design. This makes the resistance in air
flow. The resistance in air flow in engine high speed decreases the intake efficiency. Eventually, the
engine power is also decreased, Thus, the swirl operation is deactivated in high speed range to
increase the intake efficiency.
Relationship between swirl and fuel injection pressure
The injector for DI engine uses the multi hole design. For this vehicle, there are 8 holes in injector. If
the swirl is too strong, the injection angles might be overlapped and may cause the increased PM and
insufficient engine power. Also, if the injection pressure is too high during strong swirl, the injection
angles might be overlapped. Therefore, the system may decreases the fuel injection pressure when
the swirl is too strong. -
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f. Relationship between swirl and fuel injection pressure
The injector for DI engine uses the multi hole design. For this vehicle, there are 8 holes in injector. If
the swirl is too strong, the injection angles might be overlapped and may cause the increased PM and
insufficient engine power. Also, if the injection pressure is too high during strong swirl, the injection
angles might be overlapped. Therefore, the system may decreases the fuel injection pressure when
the swirl is too strong. -
Anti-knock methods:
Shorten the ignition timing by pilot injection, lessen the fuel injection volume during ignition delay
period.
Increase engine speed.
Maintain intake sir temperature with intercooler or glow plug device.
Increase intake air pressure with turbocharger.
Warm up engine to keep the normal operating temperature.
Increase compression ratio.
Use the fuel with high cetane. *
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5) Guidelines on Engine Service
(1) Cautions before service works
Make sure to disconnect the negative (-) cable from the battery to prevent any damage to electric
systems.
Make sure to clean the working area and to prepare the necessary tools before service works.
Always place the ignition switch to OFF position if not required. Otherwise, there could be unexpected
damage to electric devices or personal injuries due to short-circuit.
To prevent the foreign material from entering into the fuel injection system, completely seal the inlets o
f
HP pump, fuel hoses and high pressure pipes.
To remoev the engine, use the dedicated equipments such as engine jack, transmission jack, engine
stand and engine crane. -
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(2) Engine and accessories
When disassembling the engine, related parts (bolts, gaskets, etc.) should be stored as a set.
Clean the components completely with engine oil before assembling if needed.
Fully drain the engine oil, coolant and fuel from the vehicle and seal the inlets with the plugs before
removing the engine.
All the interference should be eliminated before removing the engine. -
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- To prevent the personal injuries and vehicle damages that can be caused by mistakes during service
and to provide the optimized performance and safety after service works, the service technicials must
keep the basic cautions and service guidelines below. These could be easily forgotten during service
works.
Engine has a lot of precise components. The specified tightening torque and correct procedures should
be kept during service works. And, the working area is always clean and well prepared.
To prevent any damage to electric systems, make sure to disconnect the negative (-) cable from the
battery and place the ignition switch to OFF position before servicing.
Use only the specified parts with same ratings when replacing the electric devices. Check the
grounds and connections for looseness. -
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(3) Electric devices
Extraordinary care should be taken when servicing the electric systems. Currently, the engine uses a lot
of electric devices. Short circuit and poor contact may cause the low engine performance, incomplete
combustion and other abnormalities.
When working with the fuel or oil systems in enclosed area, always keep the working area well-
ventilated and never allow anybody to smoke.
Gaskets and seals on the fuel and oil systems should be replaced with new ones. All bolts and nuts
should be tightened as specified.
Make sure to check the connections for leak after installation. -
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(4) Fuel and lubrication system
3. GUIDELINES ON ENGINE SERVICE
G20DF engine is for FF (Front Engine Front Drive) type vehicle. Therefore, there are some deferent
maintenance and repair works compared to the engine for FR (Front Engine Rear Drive) type vehicle.
For safe and correct works, you must observe the working procedures and instructions in this manual.
And, use the designated tools as follow:
: Power train mounting stand / Engine hanger / Engine stand / Heavy duty engine jack.
Cautions before service works
G20DF engine is FF (Front Engine Front Drive) type engine, and the engine and transmission are
integrated in a same module. Remember that there are many differences compared to
conventional engine in FR (Front Engine Rear Drive) type SUV vehicle.
To remove the engine, use the dedicated equipments such as engine jack, transmission jack,
engine stand and engine crane (1 ton).
To prevent the engine from abruptly starting during service in engine compartment, never allow
anybody to stay in the vehicle.
Make sure to disconnect the negative (-) cable from the battery to prevent any damage to electric
systems.
Make sure to clean the working area and to prepare the necessary tools before service works.
Always place the ignition switch to OFF position if not required. Otherwise, there could be
unexpected damage to electric devices or personal injuries due to short-circuit..
To prevent the foreign material from entering into the fuel injection system, completely seal the
inlets of HP pump, fuel hoses and high pressure pipes.
Do not remove the engine while supporting the oil pan with a jack. -
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Lifting up the vehicle
Before lifting up the vehicle with a lift, correctly support the lifting points.
To prevent the vehicle from rolling down, put the chocks under the tires (when using a 4-post lift).
Make sure to support the correct lifting points (when using a 2-post lift). -
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Engine and accessories
Engine has a lot of precise components. The specified tightening torque and correct procedures should
be kept during service works. And, the working area is always clean and well prepared.
When disassembling the engine, related parts (bolts, gaskets, etc.) should be stored as a set.
Carefully read the disassembly and reassembly procedures in this manual before starting the
works.
Clean the components completely with engine oil before assembling if needed.
Fully drain the engine oil, coolant and fuel from the vehicle and seal the inlets with the plugs before
removing the engine.
All the interference should be eliminated before removing the engine. -
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Tightening the fastener
When reassembling the parts to G20DF, use the angle tightening as a final step.
1. Clean the mating surfaces before tightening.
2. Place the marks with paint to tighten by angle if the angle wrench is not available. Exhaust system
Wear the protective gloves before removing the exhaust pipe.
The exhaust pipe is very hot immediately after stopping th engine. Check if the exhaust pipe is fully
cooled down before servicing the exhaust system. -
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Cooling system
Scalding hot coolant and steam could be blown out under pressure, which could cause serious
injury. Never remove the coolant reservoir cap when the engine and the radiator are hot. -
The position and direction of the componets is based on the rear view.
Do not tighten the fasteners with excessive force. Especially, the threads of cylinder block could be
damaged.
The self screw bolt makes the thread itself when tightening it. Do not apply excessive force.
Do not reuse the bolt that has been tightened with angle tightening method.
Fuel and engine oil system
The engine oil and fuel damages the painted surfaces and rubber material of the vehicle.
Disconnect the negative cable from the battery before servicing the fuel system, and prepare the
service plug grip.
When working with the fuel or oil systems in enclosed area, always keep the working area well-
ventilated and never allow anybody to smoke.
Do not allow the gasoline to contact to rubber or leather parts.
Carefully separate the pipe between high pressure fuel pump and fuel injector so that any fuel can
be spilled out.
Fully release the pressure from the fuel system before removing any parts of fuel system.
To release the fuel pressure in high pressure line, let the engine fully cool down.
Gaskets and seals on the fuel and oil systems should be replaced with new ones. All bolts and nuts
should be tightened as specified.
Prolonged exposure to the engine oil make cause a skin cancer or an irritation.
Used engine cotains the hazardous material that may cause the skin cancer. Do not allow the used
engine to make contact with your skin.
Make sure to wear the protection gloves and goggle when handling the engine oil. If contact
happens, rinse affected areas immediately with plenty of water. Do not wash it with gasoline or
solvent. If irritation persists, consult a doctor.
Improperly disposed engine oil can pollute the environment. Dispose the used engine oil and oil
filter in accordance with local environmental regulations.
Make sure to check the connections for leak after installation. -
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Electric devices
To prevent any damage to electric systems, make sure to disconnect the negative (-) cable from the
battery and place the ignition switch to OFF position before servicing.
Use only the specified parts with same ratings when replacing the electric devices. Check the
grounds and connections for looseness. -
- Extraordinary care should be taken when servicing the electric systems. Currently, the engine uses a lot
of electric devices. Short circuit and poor contact may cause the low engine performance, incomplete
combustion and other abnormalities.
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4) Intake/Exhaust Valve Assembly (Installed on Cylinder Head)
(1) Features
Automatic adustment of valve clearance by hydraulic pressure system (Maintenance Free)_Hydraulic
lash
Decreased valve operating noise
Decreased friction loss by introducing the roller type finger follower
Decreased running amount by compact design (increased valve following movement in high speed
and improved fuel economy by decreased friction loss) -
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(2) Layout and components
Intake camshaft assemblyExhaust camshaft assembly
Valve stem seal
Valve upper
spring seat
Valve guide
Hydraulic lash
adjuster
Exhaust valve assembly
Valve spring
Finger follower
Intake valve assembly