DESCRIPTION
Turbocharger is mounted to exhaust manifold on left side of engine. Turbocharger components include turbine and compressor impellers, impeller shaft, bearings, impeller housings, wastegate controller, and wastegate (exhaust bypass valve).
Pressure actuated wastegate, located at front of compressor housing, prevents excessive intake boost pressure. If it fails, an emergency relief valve located on intake manifold releases any excess pressure. Engine oil pressure provides constant lubrication to impeller bearings.
OPERATION
Turbine impeller of turbocharger is driven by exhaust gases expelled from cylinder combustion chambers. At idle, no pressurization of intake air takes place and engine operates like a normally aspirated engine.
With engine under full load, exhaust gases are at maximum pressure, which increases RPM of turbine and compressor impellers to an extremely high speed. Boost pressure of the intake air reaches a maximum.
When pressure in intake manifold reaches 6.08-6.85 psi (.43-.48 kg/cm 2 ), diaphragm of wastegate controller pushes against linkage which opens wastegate.
Some exhaust gases are then routed directly into main exhaust pipe, bypassing turbine impeller. This maintains boost pressure of intake air at a constant 6.19-7.35 psi (.44-.52 kg/cm 2 ).
If wastegate fails to function properly, an emergency relief valve located on intake manifold opens to atmosphere when intake manifold pressure reaches 7.35-7.73 psi (.52-.54 kg/cm 2 ). This prevents engine damage from excessive pressure.
LOW ENGINE POWER
- Inspect for air leak at connection of compressor housing and suction hose/inlet tube, or inlet tube and intake manifold. Correct connection as needed.
- Check for exhaust leak at connection of turbine housing and exhaust manifold, and connecting tube or exhaust outlet. Correct connection or replace gasket as needed.
- Test for stuck open bypass valve, stuck or worn journal. Check for broken shaft, sludge on back of turbine wheel, or broken turbine wheel. Replace turbocharger assembly if any of these problems are present.
EXCESSIVELY HIGH ENGINE POWER
- Inspect rubber hose at by-pass valve controller. Correct or replace rubber hose as needed.
- Check for stuck closed by-pass valve or broken controller diaphragm. If either of these problems exist, replace turbocharger.
TURBINE & COMPRESSOR IMPELLERS
- Inspect turbine and compressor impellers for cracks, clogging, deformity or other damage. Revolve impellers to be sure they turn freely without any abnormal noise or friction.
- Connect a dial indicator to end of impeller shaft and measure end play of shaft. Indicator should read.0005-.0036" (.013-.091 mm). (Scheme 50)
Measuring Impeller Shaft End Play. Scheme 50
BY-PASS VALVE CONTROLLER
| CAUTION | Do not apply more than 9.67 psi (.68 kg/cm 2 ) to by-pass valve controller diaphragm. |
Testing By-Pass Valve Controller Pressure gauge and dial indicator are required for test. Scheme 51
- Check operation of by-pass valve controller by moving valve to make sure it is not sticking or scratched. Measure rod end play of by-pass valve controller by connecting a dial indicator to end of controller pushrod. Connect a pressure gauge to controller. (Scheme 51)
- Apply 6.3-7.1 psi (.44-.50 kg/cm 2 ). Controller pushrod should move 0.015" (0.38 mm). Disconnect wastegate controller pushrod. Move wastegate lever back and forth and check for binding or sticking.
Removal
Drain engine coolant. Remove air duct and hoses, air intake pipe, exhaust front tube, heat shield plates, oil delivery tube and return hose, and water inlet tube. Remove turbocharger from exhaust manifold.
Installation
To install, reverse removal procedure. Replace gasket between turbocharger and exhaust manifold.
Exploded View of Turbocharging System (200SX). Scheme 52
- Remove compressor and compressor bracket, exhaust front tube, center cable, heat insulator for brake master cylinder, air duct and hoses, exhaust manifold connecting tube and heat shield plate, and oil delivery tube and return hose.
- Remove exhaust manifold and turbocharger as an assembly. Disconnect turbocharger from exhaust manifold.
To install, reverse removal procedure. Replace gasket between turbocharger and exhaust manifold.
