EXHAUST MANIFOLD W/ TURBOCHARGER > SYSTEM DESCRIPTION

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1. State of Turbocharger Failure Repair:
   It is well known that turbocharger malfunctions cause many symptoms as shown below. However, the mechanisms resulting in these symptoms that indicate turbocharger malfunctions are not well understood. As a result, many unnecessary turbocharger replacements and other repairs are being performed due to lack of knowledge about the turbocharger and turbocharger failure. Therefore, knowing the facts regarding turbocharger malfunctions is useful for making effective repairs and saving time.
   

2. Turbocharger Failure Classification
   
   

   Symptom		Symptom Description	See page
   Noise	Whistling noise	Continuous high pitch noise proportional to engine speed	"NOISE" listed below Flowchart "Turbocharger Noise" (Click here)
   	Whining noise	Relatively low pitch noise compared to whistling noise
   Oil leak	External oil leak	Oil leak on surface of turbocharger visible from outside of turbocharger	"OIL LEAK AND WHITE SMOKE" listed below Flowchart "Turbocharger Oil Leak and White Smoke" (Click here)
   	Internal oil leak	Oil leak from inside of center housing to inside of either compressor housing or turbine housing through piston ring (seal ring)
   White smoke	Oil smoke	Oil smoke is emitted from exhaust pipe
   	Unburned fuel smoke	Unburned fuel smoke is emitted from exhaust pipe
   Black smoke		Black smoke is emitted from exhaust pipe	"BLACK SMOKE" listed below "Problem Symptoms Table" for ECD System (Click here)
   Lack of power or hesitation		Vehicle does not reach target speed	"LACK OF POWER AND HESITATION" listed below "Problem Symptoms Table" for ECD System (Click here)
   		Poor acceleration
   		Shock during acceleration
   MIL turns on (DTC)	P0045	Boost Control Solenoid Circuit / Open	Diagnostic Trouble Code Chart (Click here)
   	P0046	Boost Control Solenoid Circuit Range / Performance
   	P0047	Boost Control "A" Circuit Low
   	P0048	Boost Control "A" Circuit High
   	P0234	Overboost Condition
   	P0236	Boost sensor "A" circuit range/performance
   	P0237	Boost Sensor "A" Circuit Low
   	P0238	Boost Sensor "A" Circuit High
   	P0299	Underboost
   	P2564	Position Sensor "A" Circuit Low
   	P2565	Position Sensor "A" Circuit High

   HINT:

   This table shows only typical problems related to the turbocharger.

HINT:

It is easy to confirm whether the turbocharger is the cause of the noise or not, and confirming this before inspecting the turbocharger or removing it from the engine is an effective way to reduce troubleshooting time.

1. Connect the intelligent tester to the DLC3.
   

   HINT:

   The software version installed on the intelligent tester must be V2009.2 or later.

2. Start the engine and warm it up.
   

3. Turn the tester on.
   

4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VN Turbo Open.
   

5. Perform the Active Test and rev the engine up several times.
   

6. Check whether the noise is reduced or not compared with the noise under the condition that the Active Test is not performed.
   
   

   Result 

   Result	Cause of Noise
   The noise is reduced (or disappears)	Turbocharger
   The noise does not change	Not turbocharger (other parts)

   HINT:

   Refer to the flowchart "Turbocharger Noise" (Click here).

HINT:

1. Above illustration is an example.
   
2. When there is an internal oil leak, white smoke is emitted from the exhaust pipe and oil is consumed excessively. However, the cause of white smoke or excessive oil consumption can vary. Therefore, do not assume that the turbocharger is the cause of the failure when there is white smoke emission or excessive oil consumption.
   
3. When there is an external oil leak, the sources of the oil leak are limited to the points mentioned in the table above. If oil leaks from a compressor housing O-ring, replace the turbocharger. If oil leaks from an oil pipe flange or a hose connection, do not replace the turbocharger, but confirm and repair the flange or hose.
   
4. Refer to the flowchart "Turbocharger Oil Leak and White Smoke" (Click here).
   

1. Malfunctions are classified into 2 types as shown below.
   
   

   Description 

   Malfunction	Main Fault
   Intake air volume shortage	Insufficient mass air flow due to, for example, excessively low boost pressure, which results in fuel injection volume being relatively excessive with respect to mass air flow.
   Excessive injection volume	Excessive injection volume or incorrect injection timing due to fuel system trouble.

2. Main Components Related to Black Smoke:
   
   

   Possible Faulty Component	Main Fault
   Turbocharger	Abnormally low boost pressure
   Intake system	Leakage between turbocharger and intake manifold
   Fuel system	Excessive fuel injection volume Incorrect fuel injection timing
   EGR valve	Stuck or does not close completely
   Diesel throttle	Stuck or does not move smoothly

   HINT:

   The components listed above are only the main ones. Not all the components potentially related to black smoke are listed. For details regarding the troubleshooting of black smoke, refer to the "Problem Symptoms Table" for ECD System (Click here).

3. Relation between Turbocharger and Black Smoke:
   If the boost pressure is lower than normal due to a turbocharger failure, black smoke may occur due to a lack of mass air flow. However, abnormally low boost pressure can be caused by the failure of various components such as intake lines, the EGR valve, etc. Therefore, do not assume that the turbocharger is the cause of abnormally low boost pressure, but check all the components possibly related to abnormally low boost pressure. Components related to abnormal boost pressure are shown in a chart listed in the On-vehicle Inspection for Intake System (Click here). For simple and effective troubleshooting, refer to the chart before starting troubleshooting.
   

1. Malfunctions are classified into 2 types as shown below.
   
   

   Description 

   Malfunction	Main Fault
   Intake air volume shortage	Insufficient mass air flow due to, for example, excessively low boost pressure, which results in fuel injection volume being restricted.
   Abnormal injection volume	Abnormal injection volume or timing due to fuel system trouble.

2. Main Components Related to Lack of Power and Hesitation:
   
   

   Possible Faulty Component	Main Fault
   Turbocharger	Abnormal boost pressure VN does not move smoothly
   Intake system	Leakage between turbocharger and intake manifold Clogging or blockage of intake line
   Fuel system	Abnormal injection volume Incorrect fuel injection timing
   EGR valve	Stuck or does not close completely
   Diesel throttle	Stuck or does not move smoothly
   Exhaust system	Clogging of exhaust line

   HINT:

   1. The components listed above are only the main ones. Not all the components potentially related to lack of power and hesitation are listed. For details regarding the troubleshooting of lack of power and hesitation, refer to the "Problem Symptoms Table" for ECD System (Click here).
      
   2. If obvious malfunction (lack of power) has not been reproduced, perform test driving another vehicle, which is the same model and has the same engine, and compare the engine conditions and performance. If a great difference does not present in engine performance, explain to the customer that lack of power the customer mentioned is not abnormal.
      

3. Relation between Turbocharger and Abnormal Boost Pressure:
   If the boost pressure is lower than normal due to a turbocharger failure, lack of power could occur due to an intake air volume shortage. However, abnormal boost pressure can be caused by the failure of various components such as intake lines, the EGR valve, etc. Therefore, do not assume that the turbocharger is the cause of abnormal boost pressure, but check all the components possibly related to abnormal boost pressure. Components related to abnormal boost pressure are shown in a chart listed in the On-vehicle Inspection for Intake System (Click here). For simple and effective troubleshooting, refer to the chart before starting troubleshooting.
   

1. A turbocharger is a component used to supply a larger air volume to the cylinders by recovering exhaust gas energy using a turbine coaxially connected to a compressor.
   





2. Principle of Turbocharging:
   Boost pressure is proportional to turbocharger speed, because the intake air is accelerated by centrifugal force generated by the rotation of the compressor and the increased kinetic energy, i.e. the velocity of the intake air, is converted to pressure energy by the diffuser located around the outlet of the compressor wheel. The compressor is driven by the turbine connected coaxially by the turbine shaft. The turbine is driven by exhaust gas energy. Therefore, when the turbocharger begins boosting the intake air, a larger air volume is supplied to the cylinders and more fuel can be injected. As a result, more exhaust energy will be available and the turbocharger boost increases.
   

   
   
   
   
   

   Text in Illustration 

   *1	Compressor	*2	Turbine
   *3	Air Cleaner	*4	Exhaust Manifold
   *5	Intake Manifold	*6	Intercooler
   *7	Diffuser	*8	Compressor
   *a	See HINT below	*b	Intake air flow

   HINT:

   1. ^*a: If sufficient exhaust gas energy is not available, the turbocharger cannot generate the required boost pressure even when the turbocharger does not have a malfunction.
      
   2. Considering the fact that the turbocharger is driven by exhaust gas energy, if sufficient exhaust gas is not available due to abnormal injection volume, etc., the required boost pressure will not be available even when the turbocharger does not have a malfunction. Therefore, when boost pressure is abnormally low, checking all the related components using the correct troubleshooting procedure is necessary for simple and effective repair.
      





3. Boost Pressure Control:
   The amount of energy the turbine can obtain from the exhaust gas is proportional to the expansion ratio, which is defined as the ratio of the turbine inlet exhaust gas pressure to the pressure at the turbine outlet.
   To control boost pressure, a Variable Nozzle (VN) is used just upstream of the turbine wheel inlet, and controls the expansion ratio. If the VN is closed, the gap between neighboring vanes is narrowed and the turbine inlet exhaust gas pressure, and correspondingly the expansion ratio, increases. Therefore, when the VN is closed, the turbine receives more energy, and the turbine speed and boost pressure increase. On the other hand, if the VN is opened, the turbine inlet exhaust gas pressure decreases, and the turbine speed and boost pressure decrease. The VN is actuated by a DC motor. The ECM controls the VN opening angle in accordance with the engine condition. When a high engine power is required, the actuation rod is moved by the actuator to close the VN and boost pressure increases.
   

   
   
   
   
   

   Text in Illustration 

   *1	VN (Variable Nozzle)	*2	Turbine Wheel
   *3	Narrow Gap	*4	Wide Gap
   *a	VN Closed	*b	VN Opened
   *c	Exhaust Gas Flow	-	-

   HINT:

   If the VN becomes stuck open, the necessary boost pressure will not be available. If the VN becomes stuck closed, overboost will occur.





4. Mechanical Construction of Turbocharger:
   

   
   
   
   
   

   Text in Illustration 

   	Exhaust Gas Flow		Intake Air Flow
   *1	VN Actuator (DC Motor)	*2	VN Actuating Rod
   *3	Center Housing	*4	Turbine Shaft
   *5	Turbine Side Piston Ring (Seal Ring)	*6	Turbine Housing
   *7	Turbine Wheel	*8	Thrust Spacer
   *9	Compressor Side Piston Ring (Seal Ring)	*10	Compressor Housing
   *11	Compressor Wheel	*12	Bearing
   *13	Oil Drain	*14	VN (Variable Nozzle)
   *a	See HINT below	*b	See HINT below
   *c	See HINT below	-	-

   HINT:

   1. Above illustration is an example.
      
   2. ^*a: The clearances of the radial bearing and thrust bearing are on the order of 100 μm, and for the accurate measurement of these clearances, an accurate process and accurate tools are essential.
      
   3. ^*b: A certain amount of oil mist from PCV gas is contained in the intake air. Therefore, a certain amount of oil at the inlet of the compressor is normal, and is not an oil leak.
      
   4. ^*c: The seal rings (piston rings) are C-shaped rings, and have a gap. Therefore, complete sealing is impossible by the seal rings alone. The oil is sealed in with the aid of the boost pressure in the compressor housing, and the exhaust gas pressure in the turbine housing. These pressures prevent oil from exiting the bearing housing through the gap of the seal rings. Therefore, if the turbine shaft is inclined from the horizontal, oil may flow out through the gap of a seal ring. This should not be interpreted as an oil leak due to seal ring failure.