Page 21
a
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 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 exhaust 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 0 as this is likely to damage the engine.
'.
"
5
,f
,,,,
"
3
1
2
4
Nov. 1977
ENGINE IDLING
Inlet air
Exhaust
gases
S 5866
1. Turbo-compressor
2. Turbin impel/er
3. Compressor
impel/er
4. Charge pressure regulator
5. Pressure switch
6. Throttle valve
291-4
Page 22
-
291-5
Inlet air
Exhaust
gases
PARTIAL LOAD
S 5867
Inlet air
Exhaust
gases
S 5868
FULL LOAD
-
SA~
Nov. 1977
Page 23
, I
-,
-
I nlet air
Exhaust
gases
OVER-PRESSURE IN THE INLET MANIFOLD AT FULL
LOAD (E.G, STICKING CHARGE PRESSURE REGULATOR)
S 5869
I
Over-pressure
guard
To prevent overstressing of the engine in the event of
failure of the charge pressure valve, on 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.
A rotor with a built-in centrifugal switch prevents overrevving of the errgine by breaking the ignition at excessive engine speeds.
A pressure gauge showing the charging pressure is fitted
on top of the instrument panel.
t
PRESSURE SWITCH
Nov. 1977
TURBO PRESSURE GAUGE
SAAa
29'\-6
Page 24
Turbo unit
Removal
1. Remove the battery, heat shield and battery shelf.
2. Remove the charge pressure regulator and blank off
the exhaust pipe.
REMOVING THE TURBO UNIT
REMOVING THE CHARGE PRESSURE REGULATOR
3. Disconnect the hose between the compressor and the
throttle housing.
4. Disconnect the oil supplv line and the oil return line
at the turbo unit.
5. Remove the bolts securing the turbo to the exhaust
manifold and remove the turbo unit.
Plug all holes in the turbo unit.
291-7
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 new gasket.
3. Connect the oil supply line, using a new gasket and new
seals.
4. F it the hose between the compressor and throttle
housing and the hose between the air flow meter and
the compressor.
5. Fit the charge pressure regulator using new gaskets
and locking plates.
6. Mount the battery shelf, heat shield and battery.
7. Turn the engine on the starter for about 30 seconds
with terminal 15 on the iqnition coil disconnected, in
order to fill the lubricating system of the turbo before
the engine starts running.
. Nov. 1977
Page 25
Measuring the charging pressure
Adjusting the charging pressure
Cleaning the diaphragm housing (every 24000 miles)
Charge pressure regulator
The following operations are included:
Removal, fitting
Dismantling, assembly (charge pressure regulator re-
Sealing the charge pressure regulator
moved)
Grinding of valve (charge pressure regulator dismantled)
Changing the diaphragm (in the car)
10
8
10
11
12
13
14
16
CHARGE PRESSURE REGULATOR
1_Bellows pipe
2. Valve
3. Regulator housing
4. Gasket
5. Bearing housing
6. Gasket
7. Heat shield
8. Gasket
9. Diaphragm housing
10. Flat washer
Nov. 1977 .
11. I nner diaphragm washer
12. Diaphragm
13. Outer diaphragm washer
14. Diaphragm nut
15. Inner spring seating
16. Spring
17. Inner spring seating
18. Lock nut
19. Diaphragm housing cover
17
S6215
•
291-8
Page 26
Removing the charge pressure regulator
2. Fit the bellows
1. Remove
means of the locking plate.
3. Remove the plug from the exhaust pipe and connect
the pipe with taper seal ring to the charge pressure
the battery,
heat shield and battery
shelf.
pipe retaining
bolts, locking "them by
regu lator housi ng.
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.
.i
I
Dismantling the charge pressure regulator
(Charge pressure regulator removed)
1. Remove
REMOVING
THE BATTERY
the diaphragm
housing
cover.
SHELF'
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.
, 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
Fitting the charge pressure regulator
1. Bolt the charge pressure regulator to the turbo (fit
new gasket) and lock the nuts by means of locking
plates.
291-9
MEASURING
-
SA~
THE LENGTH OF THE COMPRESSED SPRING
Nov. 1977
Page 27
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.
MARKING
THE VLAVE
5618
REMOVING THE LOCK NUT
FOR FITTING
15
16
17
THE CHARGE PRESSURE REGULATOR SPRING
18
S 5872
15. I nner spring seating
16. Spring
MARKING
Nov. 1977
OF SPRING SEATING AND SPRING
17. Outer
spring seating
18. Lock
nut
5. Remove the diaphragm nut (13 mm ring spanner).
Prevent the valve from turning QYinserting a short,
thick screwdriver in the groove in the valve disc.
SAAB
291-10
Page 28
I
I
Assembly
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.
"
S62:H:
c:
REMOVING THE DIAPHRAGM
6. Remove
NUT
the parts (see illustration)
in the following
order:
Diaphragm nut, outer diaphraqrn washer, diaphragm,
inner diaphragm washer, flat washer, diaphragm housa , ing, gasket,
heat shield, gasket, bearing housing and
gasket. Fit the valve assembly in the reverse order.
FITTING
THE DIAPHRAGM
12
13
;;:,
S 6318
CHARGE PRESSURE REGULATOR
5. Bearing housing
,
6, Gasket
7. Heat shield
8. Gasket
9. Diaphragm housing
291-11
10. Flat washer
11. I nner membrane washer
12. Diaphragm
13. Outer diaphragm washer
14. Diaphragm nut
Nov. 1977
Page 29
2. Check that the inner diaphragm ridge engagesthe
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 vaive 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
engagesthe groove in the diaphragm housing.
MEASURING THE LENGTH OF THE COMPRESSED SPRING
5. Fit and tighten the lock nut, using polygrip pliers to
hold the spring seating.
6. Fit the gasket and cover to the diaphragm housing.
Check the charging pressure and adjust as necessarv.e-and then seal the charge pressure regulator.
MARKING
THE VALVE
FOR FITTING
Grinding the valve and valve seat (charge pressure regulator removed)
1. Secure the valve body and bearing housing togetlier
by means of two bolts.
2. Fit guide pin 8392805 in'the valve spindle guide.
3. Grind the valve seat using a 450 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).
s eaee
GRINDING THE VALVE SEAT
Nov. 1977
SAAB.
..
291-12
I
Page 30
CAUTION
Always grip the valve seat when
nut to avoid damaging
11.
removing
Fit the diaphragm
with the two diaphragm
wash-:
ers. Ensure that the inner ridge on the diaphragm
engages the groove in the diaphragm washer.
the spindle.
the diaphragm.
"
..
6.
Fit two nuts to the outer thread
spindle
and tighten
on the valve
both nuts.
REMOVING THE DIAPHRAGM
12.
nuts.
FITTING THE NUTS TO THE OUTER THREAD ON THE
SPINDLE
7.
Holding
the two nuts, undo the diaphragm
Fit the diaphragm nut and the two other nuts, and
tighten the diaphragm nut. Remove the other two
nut.
FITTING THE DIAPHRAGM NUT
13.
Fit the. inner spring seating and then align the
valve with the previous markings.
REMOVING THE DIAPHRAGM NUT WHEREUPON THE TWO
NUTS A~E GRIPPED
8.
9.
10.
Remove the two nuts, the diaphragm
nut, the
outer diaphragm washer, the diaphragm and the
inner diaphragm washer.
Clean the diaphragm
housing and all dismantled
parts.
Check that the flat washer inside the inner diaphragm washer is in position.
Nov. 1977
291-14