Chrysler PT Cruiser, Руководство по обслуживанию и ремонту, Страница: 1270 / 2078

CONDITION POSSIBLE CAUSES
Blue smoke from exhaust Oil return line blocked
Engine breather clogged
Turbocharger shaft seals damaged
TURBOCHARGER
DESCRIPTION
CAUTION: The turbocharger is a performance part
and must not be tampered with. Tampering with the
wastegate components can reduce durability by
increasing cylinder pressure and thermal loading
due to incorrect inlet and exhaust manifold pres-
sure. Poor fuel economy and failure to meet regula-
tory emissions laws may result. Increasing the
turbocharger boost WILL NOT increase engine
power.
The turbocharger is an exhaust-driven super-
charger which increases the pressure and density of
the air entering the engine. With the increase of air
entering the engine, more fuel can be injected into
the cylinders, which creates more power during com-
bustion.
The turbocharger assembly consists of four (4)
major component systems (Fig. 18):
•
Turbine section
•
Compressor section
•
Bearing housing
•
Wastegate
OPERATION
Exhaust gas pressure and energy drive the tur-
bine, which in turn drives a centrifugal compressor
that compresses the inlet air, and forces the air into
the engine through the charge air cooler and plumb-
ing. Since heat is a by-product of this compression,
the air must pass through a charge air cooler to cool
the incoming air and maintain power and efficiency.
Increasing air flow to the engine provides:
•
Improved engine performance
•
Improved operating economy
•
Altitude compensation
The turbocharger also uses a wastegate (Fig. 19),
which regulates intake manifold air pressure and
prevents over boosting at high engine speeds. When
the wastegate valve is closed, all of the exhaust gases
flow through the turbine wheel. As the intake mani-
fold pressure increases, the wastegate actuator opens
the valve, diverting some of the exhaust gases away
from the turbine wheel. This limits turbine shaft
speed and air output from the impeller.
The turbocharger is cooled by engine coolant. The
coolant is delivered to the turbocharger by a supply
line that connects from engine block to the turbo-
charger. A coolant return line connects the turbo-
charger to heater tubes.
The turbocharger is lubricated by engine oil that is
pressurized, cooled, and filtered. The oil is delivered
to the turbocharger by a supply line that is tapped
into the cylinder block. The oil travels into the bear-
ing housing, where it lubricates the shaft and bear-
ings (Fig. 20). A return pipe at the bottom of the
bearing housing, routes the engine oil back to the
crankcase.
The most common turbocharger failure is bearing
failure related to repeated hot shutdowns with inad-
equate “cool-down” periods. A sudden engine shut
down after prolonged operation will result in the
transfer of heat from the turbine section of the tur-
bocharger to the bearing housing. This causes the oil
to overheat and break down, which causes bearing
and shaft damage the next time the vehicle is
started.
Letting the engine idle after extended operation
allows the turbine housing to cool to normal operat-
Fig. 18 Turbocharger - Typical
1 - TURBINE SECTION
2 - EXHAUST GAS
3 - BEARING HOUSING
4 - COMPRESSOR SECTION
5 - INLET AIR
6 - COMPRESSED AIR TO ENGINE
7 - EXHAUST GAS
8 - EXHAUST GAS TO EXHAUST PIPE
11 - 14 EXHAUST SYSTEM AND TURBOCHARGER
PT
TURBOCHARGER SYSTEM (Continued)