Turbocharger Pontiac Sunbird II

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

APPLICATION

GENERAL MOTORS

DESCRIPTION

The turbocharging system is mounted on the top rear of 3.8L engine and on left side of 1.8L engine. It includes a turbine assembly, center house rotating assembly (CHRA), compressor assembly, plenum chamber, wastegate, and throttle body. Turbine is spun by exhaust gas and causes compressor to draw air.

Both engines use a port fuel injection system for fuel delivery. The throttle valve, located inside throttle body, determines amount of air delivered to engine.

Maximum manifold pressure (boost) is controlled by an exhaust by-pass valve called a wastegate. The wastegate senses pressure differences through a diaphragm type actuator, to determine how much exhaust should be routed to turbine. Any excess exhaust gas is by-passed into exhaust system.

On 3.8L engines two types of turbochargers are used. One for "E" models and one for "G" models. Both are similar in design and operation. The only distinction between the two will be in the Removal & Installation procedure. All testing, inspection and repair procedures are the same for both units.

OPERATION

With the 1.8L turbo, air is drawn through an air inlet duct, into the compressor, then forced into the plenum chamber, throttle body, and intake manifold. On 3.8L turbo, air is drawn through the air inlet duct, throttle body, and into the compressor, then forced through a plenum chamber into the intake manifold.

As engine load increases and throttle is opened, a denser air charge flows into combustion chambers. As this mixture is burned, a greater volume of hot exhaust gas enters exhaust system. This gas is directed into turbocharger turbine housing.

Some energy contained in exhaust gas is used to increase speed of the turbine wheel. The turbine wheel is connected by a shaft to the compressor wheel. As compressor wheel spins faster, it compresses the incoming air/fuel mixture and forces a denser charge into combustion chambers. Higher power output is the result.

TURBINE ASSEMBLY

The turbine assembly is connected to the compressor by a shaft. When turbine wheel turns, compressor wheel must turn. Hot exhaust gas is fed into turbine through a tube. Gas hitting the turbine blades causes blades to spin. The more exhaust gas piped to turbine, the faster both units will spin. Thus, the turbocharger assembly can produce more power as demand increases.

WASTEGATE & ACTUATOR

When manifold pressure (boost) reaches a certain predetermined level, there must be some method of controlling or limiting boost past that point. The wastegate performs this function. Exhaust gas is piped into turbine continuously. Once engine demand is satisfied and the proper boost level is attained, the wastegate, acting on command from actuator assembly, by-passes enough exhaust gas into exhaust system to maintain required turbine speed.

Actuator is a pressure sensitive diaphragm type unit which responds to boost pressure controlled by the ECM wastegate solenoid. Once the pressure differential across the compressor reaches a certain level, the diaphragm reacts in conjunction with an integral spring, to partially open wastegate. The wastegate is mounted to turbine assembly.

COMPRESSOR

The compressor is connected directly to the turbine by a shaft; therefore, the speed of the turbine wheel will be the same for the compressor wheel. No exhaust gas is actually passed into compressor. The spinning compressor forces a denser air charge into intake manifold than would normally be drawn in under atmospheric pressure.

With a higher intake manifold pressure and denser charge available, more mixture is drawn into combustion chamber on piston intake stroke. A denser mixture results in more power output from engine. The faster the compressor spins, the denser the available air charge. Thus, engine demand can be satisfied. see scheme 2

OIL SUPPLY

Rotating assembly, consisting of turbine wheel, connecting shaft, and compressor wheel, can reach speeds of 140,000 RPM. A sufficient supply of clean engine oil is absolutely necessary for proper operation of assembly. Engine oil is fed directly to center housing rotating assembly. Any interruption or contamination of oil will result in major turbocharger damage. An oil feed pipe runs from a fitting on engine block to turbocharger.

Whenever oil and filter are changed on a turbocharged engine, oil system must be primed with oil prior to starting. This can be done (after oil and filter are correctly installed) by disconnecting Pink wire (ignition switch) at H.E.I. distributor, cranking engine several times (not longer than 30 seconds at a time), and observing when oil light goes out. Reconnect Pink wire and start engine.

Whenever oiling system has been contaminated in any way, change oil and filter, and flush turbocharger assembly with clean oil. Any time center housing rotating assembly is replaced, in part or in whole, oil and filter should be changed.

VACUUM SYSTEM (V6)

Note. See illustrations for vacuum routing. (Scheme 42)- (Scheme 45).

Scheme 42

Scheme 43

Scheme 44

Scheme 45

1.8L

1. Inspect wastegate and actuator assembly for linkage damage. Check condition of hose from throttle body to wastegate solenoid and from wastegate solenoid to actuator, then remove hose.
2. Connect a hand operated Vacuum/Pressure Pump (J-23738) in series with component Gauge (J-28474) to actuator assembly hose.
3. With 4 psi (.28 kg/cm 2 ) pressure applied to actuator, rod should move .015" (.38 mm). Replace actuator if not operating properly. Check new unit and crimp threads on rod to maintain proper calibration.
4. Remove test equipment. Reconnect actuator to wastegate solenoid hose.

Note. Either road test or shop test may be used to check wastegate operation on 3.8L engines. It is not necessary to perform both tests.

3.8L

1. Inspect wastegate-actuator hoses and mechanical linkage for damage. Attach Vacuum/Pressure Pump (J-23738) in series with Gauge (J-28474) to actuator assembly.
2. Apply 8 psi (.56 kg/cm 2 ) pressure to actuator assembly, the rod should move .015" (.38 mm) actuating the wastegate linkage. If not replace the actuator.
3. If a new actuator has been installed, crimp the threads of the actuator rod to maintain correct calibration.
4. Remove test equipment and reconnect vacuum hoses.

3.8L Only

1. Install compound vacuum/pressure gauge between compressor and boost gauge or MAP sensor. Use enough tubing to place gauge in passenger compartment. CAUTION: Be sure that gauge and tubing are in good condition to prevent leakage of air/fuel mixture into vehicle while testing.
2. Disconnect and plug hose at wastegate solenoid. Perform a wide open throttle acceleration test from 0-50 MPH. Boost pressure should reach 8-9 psi (.56-.63 kg/cm 2 ). If not, replace actuator and retest.

Before beginning any unit repair procedures on a turbocharging system, several general precautions should be considered.

1. Clean area around turbocharger with non-caustic solution before disassembly.
2. Use extreme care during removal to avoid damaging turbine blades. Any damage may result in turbocharger failure when engine is started.
3. Scribe reference marks on turbine and compressor housing before disassembly to ensure correct reassembly.
4. If any joints are found to be coated with sealer, clean thoroughly and recoat with sealant during assembly.

Removal (1.8L)

1. Raise vehicle. Remove lower fan retaining screw. Remove exhaust pipe. Remove rear A/C support bracket bolt, loosen the remaining bolts.
2. Remove oil drain tube at turbo. Lower vehicle. Remove coolant recovery pipe and move to one side. Remove induction tube, coolant fan, oxygen sensor, and oil feed pipe at union.
3. Remove air intake pipe and actuator vacuum hose. Remove exhaust manifold retaining nuts and lift out assembly. Remove turbocharger from exhaust manifold.
4. Remove support bracket from turbine housing. Disassemble turbine and compressor housings from center housing.

Installation (1.8L)

Clean cylinder head and exhaust manifold mating surfaces. Install new gaskets and reverse removal procedure to install.

Removal (3.8L Riviera)

1. Remove air inlet tube at throttle body, throttle body vacuum harness, and 2 electrical connectors from throttle body.
2. Remove throttle valve cable from throttle body. Remove nuts securing throttle body to turbo compressor housing. Remove throttle body. Disconnect and plug oil feed and drain lines. Remove vacuum hoses at turbo compressor housing and at wastegate actuator.
3. Raise vehicle. Remove exhaust crossover pipe at turbocharger and loosen at both manifolds. Lower vehicle.
4. Remove 2 mounting bracket bolts at intake manifold. Remove support bracket bolt at cylinder head holding turbocharger exhaust outlet housing. Lift turbocharger from manifold adapter. Disassemble turbine and compressor housings from center housing.

Removal (3.8L Regal)

1. Remove air inlet tube at throttle body and throttle body vacuum harness. Disconnect and plug heater hose at throttle body.
2. Remove throttle body by removing attaching nuts. Disconnect and plug oil feed line.
3. Disconnect exhaust inlet pipe from turbocharger and exhaust manifold. Disconnect exhaust outlet pipe at turbocharger.
4. Remove upper-to-lower turbocharger mounting bracket nuts on right side. Remove turbocharger bracket bolt at compressor housing on left side. Remove turbocharger from manifold adapter.

Installation (All 3.8L Models)

Clean adapter sealing surfaces at intake manifold and turbocharger. Apply Loctite anti-seize compound to all exhaust pipe to manifold or turbocharger bolts. Reverse removal procedures to install.

Removal (All Models)

Disconnect induction tube (1.8L only). Remove wastegate-to-actuator rod clip. Remove vacuum hose. Remove retaining screws/bolts from actuator-to-turbo. Remove actuator assembly

Installation

To install, reverse removal procedure.

INTERNAL INSPECTION

Note. Each turbocharger has a unique sound distinction or noise level when operating. If the sound cycles up and down, check for air restrictions in the intake tube and dirt build-up in the compressor housing/wheel. If a high pitched noise or whistle occurs, look for an inlet air or exhaust gas leak.

1. Remove exhaust outlet pipe from elbow assembly on turbocharger. Using a mirror, observe movement of wastegate while operating actuator linkage manually.
2. If wastegate fails to open or close, replace elbow assembly. Remove turbocharger assembly from engine. DO NOT separate center housing rotating assembly from turbine housing.
3. Inspect for loose back plate-to-center housing rotating assembly bolts. Tighten if needed. Gently spin compressor wheel. Replace if binding.
4. Remove oil drain from center housing. Check housing for sludging in oil drain area. If slightly dirty, clean. If heavily sludged or caked, replace center housing rotating assembly.
5. Inspect compressor wheel for signs of oil leakage. If present, replace center housing rotating assembly (CHRA). Inspect compressor wheel for damage or caking. Replace as necessary. NOTE: If CHRA is being replaced, lubricate with clean engine oil.
6. Inspect compressor housing (on engine) and turbine housing for gouges, nicks, and/or distortion. Replace either housing if damaged.
7. If CHRA is not being replaced, remove turbine housing from CHRA and check bearing clearances as described in the following procedures. If clearances are correct, install oil drain and turbocharger assembly.

Note. Before connecting exhaust pipe to turbocharger assembly, gently spin turbine wheel to be sure it is not binding or scraping housing.

Scheme 46

1. Attach dial indicator with 2" long, 1" offset extension rod contacting shaft of turbine. Insert shaft through oil outlet port. (Scheme 46) (Scheme 46): Dial Indicator Installation Measuring Journal Bearing Radial Clearance
2. Apply finger pressure to both turbine and compressor wheels to move shaft AWAY from dial indicator plunger. Set indicator to ZERO.
3. Move shaft TOWARD dial indicator, rotating slightly to ensure it moves as far as possible. Record maximum reading. Move shaft away from indicator and check to be sure indicator moves to ZERO.
4. Repeat procedure to ensure clearance has been measured accurately. If not within.003-.006" (.08-.15 mm), replace center housing rotating assembly (CHRA) and inspect turbine and compressor housings.

Thrust Bearing Axial Clearance

1. Mount dial indicator on turbine end of housing so tip rests on end of turbine wheel. (Scheme 47)
2. Manually apply pressure to turbine shaft and move it toward and away from indicator plunger. Record maximum travel indicated.
3. Repeat procedure after rotating turbine several times. If clearance is not within.001-.003" (.03-.08 mm), replace CHRA and inspect housings.

Dial Indicator Installation Measuring Thrust Bearing Axial Clearance. Scheme 47

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS