EXHAUST MANIFOLD W/ TURBOCHARGER SYSTEM DESCRIPTION

OUTLINE OF TURBOCHARGER FAILURE

State of Turbocharger Failure Repair
It is well known that turbocharger malfunctions cause many symptoms, such as those 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 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.

Turbocharger Failure Classification


Symptom		Symptom Description	See page
Noise	Whistling noise	Continuous high-pitched noise proportional to engine speed	Click here
Noise	Whining noise	Relatively low-pitched noise compared to whistling noise	Click here
Oil leak	External oil leak	Oil leak on surface of turbocharger visible from outside of turbocharger	Click here
Oil leak	Internal oil leak	Oil leak from inside of bearing housing to inside of either compressor housing or turbine housing through seal ring	Click here
White smoke	Oil smoke	Oil smoke is emitted from exhaust pipe	Click here
White smoke	Unburned fuel smoke	Unburned fuel smoke is emitted from exhaust pipe	Click here
Black smoke		Black smoke is emitted from exhaust pipe	Click here
Lack of power or hesitation		Vehicle does not reach target speed	Click here
		Poor acceleration
		Shock during acceleration
MIL turns on	P1251	Overboost condition (too high)	Click here
	P0299	Underboost	Click here
	P0046	Turbocharger actuator movement is irregular	Click here
	P0047	DC motor malfunction
	P0048	DC motor malfunction
	P2564	Nozzle vane position sensor malfunction	Click here
	P2565	Nozzle vane position sensor malfunction	Click here

Tip:

This table shows only typical problems related to the turbocharger sub-assembly.

NOISE

Table 1. Description
Probable Cause	Probable Failed Component
Turbine shaft imbalance	Turbocharger sub-assembly
Leakage from intake line	Intake line
Gear noise (Mistaken for turbocharger noise)	Transmission gear Vacuum pump gear

Tip:

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.

Connect the GTS to the DLC3.
Start the engine and warm it up.
Turn the GTS on.

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

Powertrain > Engine > Active Test


Tester Display
Activate the VN Turbo Open

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

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


Result	Cause of Noise
The noise disappears or is reduced compared to when the Active Test is not being performed	Turbocharger sub-assembly
The noise does not change	Not turbocharger sub-assembly (other parts)

Tip:

For details regarding the troubleshooting of noise, refer to the following.

Click here

OIL LEAK AND WHITE SMOKE

Table 2. Description
Oil Leak Type	Description	Main Trouble Area
Internal oil leak (White smoke)	Oil leak from bearing housing to either compressor housing (intake side) or turbine housing (exhaust side) through seal rings This type of oil leak is not visible from outside of turbocharger sub-assembly If oil leak occurs from turbine side seal, large amount of white smoke is emitted from exhaust side	Compressor side seal ring Turbine side seal ring Clogging of oil drain Shaft breakage Shaft or bearing seizure Compressor impeller damage
External oil leak	Oil leak from inside of turbocharger sub-assembly to outside of turbocharger sub-assembly Includes oil leaks visible from outside of turbocharger sub-assembly	FIPG sealing part Oil pipe flange Hose connection of intake pipe

*1	Turbine Housing	*2	Seal Ring
*3	Turbine Wheel	*4	Oil Drain (Inlet and Outlet)
*5	Bearing Housing	*6	Turbine Shaft
*7	Compressor Impeller	*8	Compressor Housing
*9	FIPG Sealing Part	*10	Compressor Inlet
*a	Internal oil leak to turbine housing	*b	Internal oil leak to compressor housing

Tip:

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 sub-assembly is the cause of the failure when there is white smoke emission or excessive oil consumption.
When there is an external oil leak, the sources of the oil leak are limited to the points listed in the table above. If oil leaks from a FIPG sealing part, replace the turbocharger sub-assembly. If oil leaks from an oil pipe flange or a hose connection, do not replace the turbocharger sub-assembly, but check and repair the flange or hose.
For details regarding the troubleshooting of oil leaks and white smoke, refer to the following.
Click here

BLACK SMOKE

Malfunctions are classified into 2 types as shown below.

Table 3. 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

Main Components Related to Black Smoke


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

Tip:

The components listed above are only the main components. Not all the components potentially related to black smoke are listed. For details regarding the troubleshooting of black smoke, refer to the following.

Click here

Relation between Turbocharger Sub-assembly and Black Smoke
If the boost pressure is below 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 sub-assembly 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 (Click here). For simple and effective troubleshooting, refer to the chart before starting troubleshooting.

LACK OF POWER AND HESITATION

Malfunctions are classified into 2 types as shown below.

Table 4. 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

Main Components Related to Lack of Power and Hesitation


Possible Faulty Component	Main Fault
Turbocharger sub-assembly	Abnormal boost pressure VN does not move smoothly
Intake system	Leakage between turbocharger sub-assembly 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 body assembly	Stuck or does not move smoothly
Exhaust system	Clogging of exhaust line

Tip:

The components listed above are only the main components. 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 following.

Click here

Relation between Turbocharger sub-assembly and Abnormal Boost Pressure
If the boost pressure is below 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 sub-assembly 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 (Click here). For simple and effective troubleshooting, refer to the chart before starting troubleshooting.

MIL TURNS ON

If a DTC related to a turbocharger malfunction is output, refer to the troubleshooting section for each DTC.

BRIEF OUTLINE OF TURBOCHARGER OPERATION AND CONSTRUCTION

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.

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 impeller. The compressor is driven by the turbine connected coaxially to 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 is available and the turbocharger boost increases.

*1	Compressor	*2	Turbine
*3	Air Cleaner Assembly	*4	Exhaust Manifold
*5	Intercooler Assembly	*6	Intake Manifold
*7	Diffuser	-	-
*a	See HINT below	*b	Intake Airflow

Tip:

*a: If sufficient exhaust gas energy is not available, the turbocharger sub-assembly cannot generate the required boost pressure even when the turbocharger sub-assembly does not have a malfunction.
Considering the fact that the turbocharger sub-assembly 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 sub-assembly does not have a malfunction. Therefore, when boost pressure is abnormally low, checking all the related components using the correct troubleshooting procedure is necessary to perform repairs simply and effectively.

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. If the VN is opened, the turbine inlet exhaust gas pressure decreases and the turbine speed and boost pressure decrease.

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

Tip:

If the VN is stuck open, the necessary boost pressure is not available. If the VN is stuck closed, overboost occurs.

Mechanical Construction of Turbocharger Sub-assembly

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

Tip:

*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.
*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.
*c: The seal rings are C-shaped rings, like piston rings, and have a gap. Therefore, complete sealing is impossible by the seal rings alone. 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.