Page 271
The Saab Turbo has been designed to start operating at
relatively low engine speeds, in order to provide increased
torque at engine speeds typical of normal driving conditions. In contrast to the Saab Turbo, earlier turbochargers
have been designed po provide increased performance,
which implies that they are only utilized at full throttle.
The turbine shaft which rotates at very high speed has
been very accurately balanced. The shaft is mounted in a
floating sliding-contact bearing through which there is a
7
--
A
relatively high oil flow. Thus, during rotation, the shaft
floats on a film of oil.
The lubricating oil is supplied by the engine lubricating
system through a special line running from the oil pump.
Return oil flows through a relatively large-bore pipe back
to the sump.
Sealing between the shaft and the bearing housing consists
of sealing rings (piston ring type) installed in grooves in the
shaft.
6
F
Inlet air
Exhaust gases
TURBO-COMPRESSOR,
1. Turbin housing
2. Bearing housing
3. Compressor housing
4. Radial bearing
5. Axial bearing
6. Turbo shaft
7. Turbine impeller
8. Compressor.impeller
SECTION
A. From exhaust manifold
B. To exhaust pipe
C. From air cleaner
D. To inlet manifold
E. Lubricating oil.line
F. Lubricating oil return pipe
....
511'\EI
291-3
Page 272
Charging pressure regulation
The charging pressure in the inlet manifold is governed
mainly by the speed and loading of the engine. However,
under high load conditions, the charging pressure is limited by a charge pressure regulator.
The charge pressure regulator is located on the exhaust
side of the engine and controls the exhaust gas flow by
means of a by-pass passage at the side of the turbine.
When the load on the engine is normal or below normal
the charge pressure regulator valve (waste-gate) is closed.
As the load increases and the charge pressure approaches
the preset limit, the waste-gate opens, which decreases
the load on the turbine by allowing exhaust gases to flow
through the by-pass passage.
The charge pressure regulator contains a spring-loaded
diaphragm valve which is kept closed under normal conditions by means of the spring. The valve is connected by
means of a pipe to the exhuast manifold and is actuated
by the exhaust gas pressure. Presetting of the charging
pressure is achieved by adjustment of the spring.
The valve spindle of the charge pressure regulator is
cooled by means of a pipe running from the compressor
to the charge pressure regulator bearing housing.
CAUTION
Never increase the preset pressure as specified in
section Oas this is likely to damage the engine.
5
3
1
2
4
Inlet air
Exhaust gases
291-4
ENGINE IDLING
1. Turbo-compressor
2. Turbin impeller
3. Compressor impeller
4. Charge pressure regulator
5. Pressure switch
6. Throttle valve
SM&
S 5866
Page 273
Inlet a1r
-
Exhaust gases
PARTIAL
-Inlet
-
LOAD
S 5867
air
Exhaust gases
S 5868
FULL LOAD
SAAB
291-5
Page 274
-
lnletair
-
Exhaust gases
s 5869
OVER-PRESSURE IN THE INLET MANIFOLD AT FULL
LOAD (E.G. STICKING CHARGE PRESSURE REGULATOR)
Over-Pressureguard
To prevent overstressing of the engine in the event of
failure of the charge pressure valve, an over-pressure guard,
which is actuated when the charging pressure in the intake
manifold exceeds the preset limit, is provided. The overpressure guard comprises a pressure switch connected to
the inlet manifold by means of a hose. When the charging
pressure exceeds a preset limit, the switch will break the
current to the fuel pump.
TRYCKVAKT
291-6
A rotor with a built-in centrifugal switch prevents overrevving of the engine by breaking the ignition at excessive engine speeds.
A pressure gauge showing the charing pressure is fitted
in the instrument panel.
TURBOINSTRUMENT
SA.ft&
Page 275
Turbo unit
Removal
1. Remove the charge pressure regulator and blank off
the exhaust pipe.
2. Disconnect the hose between the compressor and the
throttle housing .
..
3. Disconnect the oil supply line and the oil return line
at the turbo unit.
4. Remove the bolts securing the turbo to the exhaust
manifold and remove the turbo unit.
Plug all holes in the turbo unit.
Assembly
1. Secure the turbo unit to the exhaust manifold, fitting
a new gasket between the mating flanges.
2. Fill the lubricating inflow of the turbo unit with engine oil and connect the oil return line at the turbo,
using a ~ew gasket.
3. Connect the oil supply line, using a new gasket and new
seals.
4. Fit the hose between the compressor and throttle
housing and the hose between the air flow meter and
the compressor.
5. Fit the c~arge pressure regulator using new gaskets
and locking plates.
6. Turn the engine on the starter for about 30 seconds
with terminal 15 on the ignition coil disconnected, in
order to fill the lubricating system of the turbo before
the engine starts running.
SAAB
291-7
Page 276
Charge pressureregulator
Measuring the charging pressure
Adjusting the charging pressure
Cleaning the diaphragm housing (every 24 000 miles)
Sealing the charge pressure regulator
The following operations are included:
Removal, fitting
Dismantling, assembly (charge pressure regulator removed)
Grinding of valve (charge pressure regulator dismantled)
Changing the diaphragm (in the car)
10
11
12
13
14
General
16
The charging pressure regulator's valve stem is cooled by
a pipe which runs from the compressor to the regulator
bearing housing.
The spring in the charging pressure regulator is canted
slightly because the inner spring seat is intentionally offset ;n relation to the valve stem in order to reduce valve
chatter. An uneven wear profile in the valve seat, valve
guide and valve stem is therefore perfectly normal and is
not detrimental to the operation of the unit.
291-8
Sft1'B
L
17
18
CHARGE PRESSURE REGULATOR
8
19
1. Bellows pipe
13. Outer diaphragn-;'~asher
2. Valve
14. Diaphragm nut
3. Regulator housing
15. Inner spring seating
4. Gasket
(Model 1979 six holes,
5. Bearing housing
as from model 1980
6. Gasket
four holes)
7. Heat shield
16. Spring
8. Gasket
17. Inner spring seating
9. Diaphragm housing
18. Lock nut
10. Flat washer
19. Diaphragm housing cover
11. Inner diaphragm washer 20. Cooling air pipe
12. Diaphragm
Page 277
Removing the charge pressure regulator
Fitting the charge pressure regulator
1. Remove the battery, heat shield and battery shelf.
1. Bolt the charge pressure regulator to the turbo (fit
new gasket) and lock the nuts by means of locking
plates.
2. Fit the bellows pipe retaining bolts, locking them by
means onhe locking plate.
3. Remove the plug from the exhaust pipe and connect
the pipe with taper seal ring to the charge pressure
regulator housing.
1-♦-1·11·11
Lubricate the charge pressure regulator nipple with
NEVER SEIZE or MOL YCOTE 1000 to prevent it
welding stuck.
4. Connect the exhaust and cooling air lines.
5. Fit the battery shelf and the battery.
6. Test drive the car, checking the charging pressure and
adjusting as necessary.
7. Seal the charge pressure regulator and fit the heat
shield.
REMOVING THE BATTERY SHELF
Dismantling the charge pressure regulator
(Charge pressure regulator removed)
2. Disconnect the exhaust and cooling air lines from the
charge pressure regulator.
3. Unbolt the exhaust manifold flange. Save the taper
seal ring and plug the exhaust pipe.
4. Prize up the locking plate and remove the bolts from
the bellows pipe.
5. Prize up the locking plate, remove the bolts from the
turbo and remove the charge pressure regulator.
1. Remove the diaphragm housing cover.
REMOVING THE DIAPHRAGM
HOUSING COVER
2. Measure and note the length of the compressed spring
(distance between the outer and inner spring seatings,
see illustration). Measure the length at two diametrically opposed points and note the mean value.
REMOVING THE CHARGE PRESSURE REGULATOR
MEASURING THf
•_ENGTH OF THE COMPRESSED SPRING
291-9
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Page 278
4. Loosen the lock nut using a 10 mm ring spanner and
polygrip pliers and then remove the nut, the outer
spring seating, the spring and the inner spring seating.
CAUTION
Always grip the valve seat when removing the
spindle nut to avoid damaging the diaphragm.
MEASURING THE LENGTH OF THE COMPRESSED SPRING
"""
3. Mark the position of the valve and outer spring seating so that they can be refitted in the same position.
REMOVING THE LOCK NUT
MARKING THE VLAVE FOR FITTING
15
16
THE CHARGE PRESSURE REGULATOR
17
SPRING
18
S 5872
15. Inner spring seating
16. Spring
17. Outer spring seating
18. Lock nut
5. Remove the diaphragm nut ( 13 mm ring spanner). Insert a short thick-shafted screwdriver or an Allen key
into the groove in the valve disc to prevent the valve
turning.
MARKING OF SPRING SEATING AND SPRING
291-10
SAAB
Page 279
Assembly
Apply a thin layer of NEVER SEIZE or MOL YCOTE
1000 to the valve spindle and threads to prevent them
welding stuck.
1. Insert the valve using one hand to hold it in position.
Fit the gasket, bearing housing, gasket, heat shield,
gasket, diaphragm housing, flat washer, inner diaphragm washer, diaphragm, outer diaphragm washer
and the diaphragm nut.
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....
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6. Remove the parts (see illustration) in the following
order:
Diaphragm nut, outer diaphragm washer, diaphragm,
inner diaphragm washer, flat washer, diaphragm housing, gasket, heat shield, gasket, bearing housing and
gasket. Fit the valve assembly in the reverse order.
FITTING THE DIAPHRAGM
CHARGE PRESSURE REGULATOR
5. Bearing housing
6. Gasket
7. Heat shield
8. Gasket
9. Diaphragm housing
10. Flat washer
11. Inner membrane washer
12. Diaphragm
13. Outer diaphragm washer
14. Diaphragm nut
291-11
Page 280
2. Check that the inner diaphragm ridge engages the
groove in the diaphragm washer and tighten the diaphragm nut, preventing the valve from turning by inserting a short, thick screwdriver in the groove in the
valve disc.
3. Align the valve with the previous markings and fit the
inner spring seating, the spring and the outer spring
seating. Check that the outer ridge on the diaphragm
engages the groove in the diaphragm housing.
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5. Fit and tighten the lock nut, using polygrip pliers to
hold the spring seating.
Check that the spring is working correctly by
pressing it together a few times. If it wobbles or
cracks turn the spring to another position. The
spring can otherwise give noise.
""'
MARKING THE VALVE FOR FITTING
6. Fit the gasket and cover to the diaphragm housing.
Check the charging pressure and adjust as necessary,
and then seal the charge pressure regulator.
Grinding the valve and valve seat (charge pressure regulator removed)
1. Secure the valve body and bearing housing together
by means of two bolts.
2. Fit guide pin 83 92 805 in the valve spindle guide.
3. Grind the valve seat using a 45° valve cutter. (The
grinding work will be easier if the hard surface is first
removed by means of emery cloth.)
FITTING THE OUTER SPRING SEATING
4. Adjust the spring roughly, by setting the compressed
length to the same value as was noted before dismantling (or in accordance with the specifications).
GRINDING THE VALVE SEAT
291-12
SAMI