Description
Necessity of Turbocharger and Supercharger The turbocharger and supercharger are devices that force air into the cylinders creating a pressure that is greater than the atmospheric pressure in order to increase engine output. Generally, Generally, the engine output is determined by the amount of the air-fuel mixture, burned over a specified period of time, and becomes greater as the amount of the air-fuel mixture increases. That means in order to increase the engine output, either the engine displacement or engine speed must be increased. The problem is that as engine displacement increases, engine weight also increases and factors such as friction loss, vibration and noise of moving parts limit the increase of the engine speed. The super charger meets the opposing requirements of increasing engine output while keeping it compact and lightweight by supplying greater volumes of air and fuel without changing engine size. The devices are driven by two methods: The turbocharger is driven by exhaust gas and the supercharger is driven by the engine. Toyota adopted the turbocharger in 1980, and the supercharger in 1985 in Japan. Presently in 2002, only the turbocharger is used in overseas models. (1/1)
Turbocharger
Supercharger
Features of Turbocharger and Supercharger kPa 2 (kgf/cm ) 98 (1.0)
Both the turbocharger and supercharger are a kind of air pump, which force the air into the cylinder to increase the mass of the intake air. The conventional engine draws air in, using the vacuum generated when the piston goes down. The pressure inside the intake manifold becomes higher because the turbocharger or supercharger force the intake air into the cylinders at a pressure (boost pressure) higher than atmospheric pressure. Thus, the mass of the intake air into the cylinder is increased.
Turbocharger
Boost pressure
Supercharger
Engine speed
rpm
TURBOCHARGER
SUPERCHARGER
Type of charger
Turbine (turbine and compressor wheels)
Mechanical (roots type supercharger* using one pair of cocoonshaped rotors)
Driving method
Exhaust gas pressure
Engine crankshaft drive
Power loss
Small because turbocharger is driven by exhaust gas pressure.
Large because supercharger is driven by crankshaft.
Charging effect
Small in low-speed ranges and large in high-speed ranges. (The causes are a small amount of exhaust gases during low engine speed.)
Charging is possible in all speed ranges.
Response
The response during low engine speed is not as good as that of the supercharger.
Good response is obtained because supercharger is directly driven by crankshaft.
*The roots type supercharger is the most common type in use at present.
(1/1)
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REFERENCE Charging Efficiency 1. Charging efficiency The engine's ability to draw air in is called charging efficiency. The charging efficiency of a conventional engine is about 65-85% due to the resistance of the intake system and the exhaust gas remaining in the exhaust system. However the charging efficiency of an engine equipped with a turbocharger or supercharger can be more than 100%. 2. Compression ratio The gasoline engine has a greater tendency of knocking as the compression pressure is increased. Since air is compressed to a pressure greater than the atmosphere pressure and is fed to the cylinders of a turbocharged or supercharged engine, the compression pressure becomes higher than that of the conventional engine and knocking occur s more easily. Therefore the compression ratio of a turbocharged or supercharged engine is set lower than that of a conventional engine to prevent knocking. Mass of air actually taken in Charging efficiency(%) =
X 100 Mass of air in cylinder under standard conditions*
*Standard conditions: Standard atmosphere pressure at 20 C(68 F)
Turbocharger
Description
Turbocharger Turbine wheel
Compressor wheel
Actuator
(1/1)
Air flow meter Intercooler Waste gate valve Turbo pressure sensor
The turbocharger is a device which uses the energy of the exhaust gas to rotate the turbine wheel at high speeds. There is a compressor wheel on the same shaft as the turbine wheel which compresses air into the cylinders when it is rotated. In this way, engine output is increased. The waste gate valve and actuator prevent the boost pressure from rising too high. Some models are equipped with an intercooler to lower the temperature of the compressed intake air and improve the charging efficiency ratio. NOTICE: Caution is necessary for handling vehicles because the turbocharger becomes extremely hot due to the exhaust gases. Also, it is necessary to faithfully replace the engine oil at the determined replacement interval. Refer to the “Precautions for Turbocharger” for more information. (1/1)
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Components
Full-floating bearings Turbine wheel
The turbocharger consists of the turbine housing, compressor housing, center housing, turbine wheel, compressor wheel, full-floating bearings, waste gate valve, actuator, etc.
to Intake manifold
Waste gate valve
from Air cleaner
Compressor wheel to Exhaust pipe Actuator from Exhaust manifold
Turbine housing Center housing Compressor housing
Waste gate valve
Actuator
Turbine and compr essor wheels
Turbine wheel
Compressor wheel to Exhaust pipe
from Air cleaner
from Exhaust manifold
to Intake manifold
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The turbine wheel and compressor wheel are mounted on the same shaft. When the turbine wheel rotates at high speed due to the pressure of the exhaust gas from the exhaust manifold, the compressor wheel on the same shaft also rotates, compressing the intake air into the cylinder. The turbine wheel must be heat resistant and durable because it is directly exposed to the exhaust gas and becomes extremely hot and rotates at high speeds. Therefore it is made of an ultra-heat resistant alloy or ceramic.
Center housing Oil channel
Coolant channel Coolant channel Oil channel
Bearing
Bearing
The center housing supports the turbine wheel and compressor wheel via the shaft. There is an oil channel in the housing to supply engine oil to lubricate and cool the shaft and bearings. Also, engine coolant is circulated through the coolant channel that is built into the housing in order to prevent the engine oil temperature from rising and the engine oil from deteriorating prematurely.
Shaft
Shaft
Full-floating bearings Shaft
Full-floating bearing
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Since the turbine and compressor wheels turn at speeds of up to 100,000 rpm, the full-floating bearings are used to ensure the absorption of vibrations from the shaft and lubrication of the shaft and bearings. The full-floating bearings are lubricated by the engine oil and rotate freely between the shaft and housing to reduce friction, thus allowing the shaft to rotate at high speed.
Waste gate valve and actuator The waste gate valve is built into the turbine housing. The waste gate valve opens and bypasses part of the exhaust gas to the exhaust pipe in order to stabilize the boost pressure when the boost pressure reaches the specified value, approx. 70
Turbine housing
Turbine wheel
Waste gate valve
kPa (approx. 0.7 kg/cm 2). The opening and closing of the waste gate valve are controlled by the actuator. (1/1)
Compressor wheel
Actuator
Air cleaner
Waste gate valve
No.1 turbocharger
REFERENCE Two-way Twin Turbo
Exhaust gas control valve
No.2 turbocharger
Exhaust gas bypass valve
Intercooler
Intake air control valve
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Two-way twin turbo features two turbochargers installed in one engine. When the turbochargers are operated efficiently under light loads or low speed, engine responsiveness such as acceleration is improved. When the turbochargers are operated efficiently under heavy load and high speed, high power output can be attained. When there is only one turbocharger, it is difficult to attain efficient operation for both heavy loads and light loads. In this case it is only possible to attain efficiency one way or the other. However, the twin turbo controls the exhaust gas control valve and exhaust bypass valve. It operates one turbocharger under light loads, and two turbochargers for high speeds and heavy loads in order to improve engine response in all speed ranges and attain high power. The illustration at left shows 2JZ-GTE engine produced in 1993-1999. (1/1)
How to Increase Fuel Injection Volume
1
An engine equipped with a turbocharger or supercharger forces a greater volume of air into the cylinder. The power output does not increase until the intake air is burned completely. For this reason, it is necessary to increase the fuel volume to burn the intake air completely. Thus, fuel consumption will increase as the power output is increased.
2
ECU ECU
1. Mechanically controlled type With a diesel engine, the boost compensator increases the maximum fuel injection volume in accordance with the boost pressure. (Refer to the chapter of the diesel injection pump in the book of diesel engine, for details.)
Turbine wheel Compressor wheel to Exhaust pipe
from Air cleaner
Boost compensator
Boost pressure (Compressed air)
Waste gate valve
Actuator
Exhaust gas
Diesel injection pump
2. Computer-controlled type Turbine wheel Compressor wheel
Air flow meter from Air cleaner
to Exhaust pipe Waste gate valve
Air flow meter
Boost pressure (Compressed air)
ECU ECU
Actuator
Turbo pressure sensor Exhaust gas
Injector Diesel injection pump
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The computer-controlled engine detects the intake air volume with the air flow meter and the intake manifold pressure with the turbo pressure sensor, and increases the maximum fuel injection volume with the engine ECU. (The fuel injection volume is determined by the injection duration.) Although the illustration on the left shows the diesel engine, the fuel injection volume is increased in proportion to the volume of the intake air in a gasoline engine. (1/1)
Lubrication and Cooling System from Oil inlet pipe Coolant channel
Oil inlet pipe
2. Cooling system
Oil outlet pipe to Oil outlet pipe Coolant outlet pipe
1. Lubrication system Engine oil is supplied from the oil inlet pipe to lubricate and cool the full-floating bearings inside the center housing. After that, the oil passes through the oil outlet pipe and returns to the oil pan.
Coolant inlet pipe
Oil channel
Coolant channel from Thermostat housing to Water pump
Oil channel
to Oil outlet pipe
The turbocharger is cooled by the engine coolant. The engine coolant is introduced into the coolant channel inside the center housing via the coolant inlet pipe. The engine coolant returns to the water pump via the coolant outlet pipe after cooling the turbocharger system. (1/1)
from Oil inlet pipe
Boost Pressure Control Turbine wheel
Compressor wheel
Intake air (from air cleaner)
to Exhaust pipe
Waste gate valve
to Combustion chamber
Exhaust gas (from combustion chamber)
Actuator
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The turbocharger attains a high output by pumping compressed air into the cylinders. However engine parts will be unable to withstand the explosive force if the boost pressure rises too high. In this case, the waste gate valve is activated by the actuator, and controls the boost pressure so that the boost pressure does not rise above the specified value.
1. Boost pressure control (1) Control when the boost pressure is below the specified value When the boost pressure is below the specified pressure, the actuator does not operate. All the exhaust gas is therefore routed into the turbine wheel because the waste gate valve remains closed.
(2) Control when the boost pressure is above the specified value When the engine speed rises and the boost pressure supplied by the turbocharger exceeds the specified value (intercept point), the actuator diaphragm is depressed. This causes the waste gate valve to open and part of the exhaust gas bypasses the turbine wheel. By allowing part of the exhaust gas to bypass the turbine wheel, the rotational speed of the turbine wheel is regulated so that the boost pressure becomes within the specified value. HINT: With some gasoline engine, the boost pressure is also controlled in accordance with the octane rating of the fuel used (premium or regular gasoline). (1/1)
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REFERENCE Relationship between Boost Pressure and Engine Speed
Waste gate valve opens
The relationship between the boost pressure and engine speed when the accelerator pedal is fully depressed, is shown on the left. The relationship between the boost pressure and engine speed varies according to the load placed on the engine. (1/1)
Intercept point
e r u s s e r p t s o o B
Engine speed
REFERENCE Turbocharging Indicator Lights ( Some Models Only) 2
3
1. Turbocharging indicator lights
4
ENGINE
The turbocharging indicator lights are built into the combination meter, and inform the driver about operating condition of the turbocharger with green and amber LEDs (Light-emitting diodes). When the turbocharger operates the specified boost pressure, the green LED is turned on. The amber LED is turned on when the turbocharger exceeds the specified boost pressure.
1000r/min
1
5 6 TURBO
Over-charging warning light (amber)
Turbocharging indicator light (green)
2. Pressure switches Spring
Two switches are used to sense boost pressure: Lowpressure switch and high-pressure switch. The difference between these two switches is the strength of the springs. When the boost pressure applied to the diaphragm exceeds a certain level, the switch is turned on. (1/1)
Diaphragm
Boost pressure
Moving point
Fixed point
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Variable Nozzle Vane The variable nozzle vane changes the flow speed and direction of the exhaust gas to optimize boost pressure from low speeds to high speeds using the engine ECU to control the pitch of the nozzle vane, which is mounted on the circumference of the turbine.
Step motor
Turbine wheel Motor rod Linkage Unison ring Nozzle vane
Flow of the exhaust gas
1. Operation At low speed As the nozzle vane passage becomes narrow (closes), the flow speed of the exhaust gas flowing into the turbine wheel becomes faster and the turbine wheel operates more efficiently. In this way, as the exhaust gas pressure applied to the turbine wheel is increased, the increase of boost pressure becomes faster, and engine output is increase even at low speeds.
Step motor
Nozzle vane Turbine wheel Motor rod Unison ring Linkage
Step motor Flow of the exhaust gas
Nozzle vane Turbine wheel Motor rod
Unison ring Linkage
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At high speed/heavy load As the nozzle vane passage becomes wide (opens), the boost pressure is controlled because the flow direction of the exhaust gas changes and the efficiency rate of the exhaust gas, which is activated on the turbine wheel, decreases. However, the excess rotation of the turbine wheel is prevented with improvement of the fuel consumption and engine output because the boost pressure is controlled to the specified pressure. (1/1)
Intercooler (Some Models Only) Air-cooled type intercooler
Air-cooled type intercooler Vehicle wind stream
Intercooler
Intercooler Compressor wheel Intercooler Water-cooled type intercooler
Compressor wheel
Sub-radiator
Coolant
Electric water pump
The intercooler is mounted between the compressor wheel and engine, and operates to cool the intake air, which is compressed by the turbocharger and heated up. Air temperature rises when compressing the air in the turbocharger. The charging efficiency rate is lowered because the high-temperature air expands and it is lowered. The intercooler increases the air density by lowering the air temperature and improves the charging efficiency rate. It also acts to control knocking. There are two types of intercoolers: The air-cooled type and water-cooled type. Only the air-cooled type intercooler is used at present. The intercooler is in different locations depending on the model. 1. Air-cooled type intercooler The air-cooled type intercooler utilizes the vehicle wind stream or an engine cooling fan to cool the compressed air. (1/1) REFERENCE Water-cooled Type Intercooler
to Air intake chamber Intercooler Coolant level sensor Coolant reservoir
from Turbocharger Intercooler computer
Sub-radiator Electric water pump
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The water-cooled type intercooler utilizes coolant to cool the intake air. Although it utilizes coolant, the intercooler has its independent cooling system, not introducing the coolant from the engine cooling system. It consists of the intercooler, electric water pump, subradiator, and intercooler computer. The illustration on the left shows the 3SGTE engine produced from 1989-1999. (1/1)
Precautions for Turbocharger 1.Precautions on handling (1) The engine oil used for the engine equipped with the turbocharger is used for not only lubricating the engine but for lubricating and cooling the turbocharger. As the engine oil is exposed to the heat of the turbocharger, its temperature rises easily. For this reason, the engine oil and engine oil filter maintenance should be carried out faithfully. Otherwise it causes the turbocharger to damage. If the recommended engine oil is not used, it causes the bearings of turbocharger to be damaged. Therefore, be sure to use the recommended engine oil. HINT: Refer to the Owner's Manual or Maintenance Schedule as the replacement intervals of the engine oil and oil filter vary by the model or condition under which the vehicle is used.
(2) Since the bearings are not sufficiently lubricated just after starting a cold engine, racing or sudden acceleration of the engine causes damage to the bearings. (3) After the engine is placed under heavy loads, such as after high-speed driving or long distance driving, allow the vehicle to idle for a few minutes before shutting it off. NOTICE: The turbocharger temperature does not rise too high while driving as the turbocharger is cooled by the oil and coolant. When the engine is stopped immediately after high-speed driving, etc., circulation of the oil and coolant stop. This causes the turbocharger to remain uncooled, leading to damage such as sticking. Thus, it is necessary to idle and cool the turbocharger.
Driving condition Normal city driving High speed driving
Steep mountain slopes or continue driving above 100 km/h (63 mph)
Idling time Not necessary About 80 km/h (50 mph) -About 20 seconds About 100 km/h (63 mph) -About 1 minute About 2 minutes
(1/3)
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(1)
2. Precautions on maintenance (1) Do not start the engine with the air cleaner or air cleaner case removed. Otherwise it will allow foreign particles to enter causing damage to the compressor wheels and turbine. (2) In the case that the turbocharger malfunctions and must be replace, first check the following items for the cause of the problem and remedy as necessary. Engine oil level and quality Conditions under which the turbocharger was used Oil lines leading to the turbocharger • • •
(4)
(3) When removing the turbocharger, plug the intake and exhaust ports and oil inlet to prevent dirt or other foreign materials from entering the system. (4) When removing and reinstalling the turbocharger, do not drop it, bang it against anything, or grasp it by easily deformed parts, such as the actuator or rod. (2/3)
(5)
(5) When replacing the turbocharger, check for the accumulation of carbon sludge in the oil pipes, and if necessary, clean out or replace the oil pipes, too. (6) When replacing the turbocharger, put the oil into the turbocharger oil inlet and turn the compressor wheel by hand to spread oil on the bearings. (7) When overhauling or replacing the engine, cut the fuel supply after reassembly and crank the engine for 30 seconds to distribute oil throughout the engine. Then idle the engine for 60 seconds. (3/3)
(6)
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Exercise These are the pre-course study materials for the Frequent Service Job Course. The objective of this course is to learn the work pr ocedure and points of frequent service jobs. In the pre-cour se study, you will study the basic knowledge needed for repair work, and the basic mechanism and operation of automobiles. After you finish studying all of the chapters, please take the Examination.
Chapter Page with Related Text
Exercises
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Incorrect Answer
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Exercises
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Incorrect Answer
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Question- 1 Mark each of the following statements True or False. No.
Question
True or False
1
The turbocharger and supercharger are devices that force air into the cylinders at a pressure that is higher than the atmospheric pressure to increase engine output.
True
False
2
A turbocharger is driven by the belt to increase engine output.
True
False
3
One of the functions of an intercooler is to cool the intake air that has reached a high temperature by compression.
True
False
Correct Answers
Question- 2 The following statements pertain to turbocharger control. Select the statement that is True. 1. The waste gate valve is slightly open when the boost pressure is within the specified pressure. 2. The waste gate valve is open when the boost pressure is above the specified pressure. 3. The intake air is bypassed when the waste gate valve opens, and this prevents the boost pressure from increasing above the predetermined pressure. 4. The actuator opens the waste gate valve when its diaphragm is pushed by the exhaust gas.
Question- 3 The following statements pertain to the pr ecautions for handling a turbocharger. Select the statement that is False. 1. Make sure to use the recommended type of engine oil. 2. Race the engine immediately after a cold engine starting in order to thoroughly lubricate the bearings before driving the vehicle. 3. When stopping the engine after it has been driving at high load, idle the engine for a few minutes. 4. To prevent damage, do not operate the engine with its air cleaner removed.
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Question- 4 The components of a turbocharger are illustrated below. From the following word group, select the words that correspond to the numbers in the illustration. 3 2 1
4
5
a) Compressor wheel b) Turbine wheel f) Full-floating bearings
Answer: 1.
c) Actuator
d) Waste gate valve
2.
3.
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4.
e) Variable nozzle vane