Damage Brochure MAHLE Original Turbochargers
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Transcript of Damage Brochure MAHLE Original Turbochargers
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AFTERMARKETTechnical information
TURBOCHARGER:DAMAGE PROFILES, CAUSES, AND PREVENTION
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Table of contents
1 Preface
2 Inadequate lubrication
3 Contaminated oil
4 Oil leakage at turbocharger
5 Foreign object damage
6 Damage due to excessive exhaust temperatures
7 Overspeeding
4
6
8
10
12
13
14
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Preface
Inadequ
atelubrication
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1 Preface
MAHLE s one of the most mpor tant development partners and man-
ufacturers of engne components and systems as well as filter systems
n the automotve ndustry. The engneers at MAHLE develop products
of the hghest qualty throughout the world n conjuncton wth engne
and vehcle manufacturers. The same hgh qualty gudelnes are also
appled for the spare parts n the aftermarket.
Numerous checks durng and after producton ensure the hgh qualty
level of MAHLE products. If falures occur n practcal operaton, the
causes are mostly found n the engne envronment.
TURBOCHARGERTHE FUNCTION
Turbochargers are used to enhance the performance and optmse the
combuston. To acheve good and complete combuston n the engne,
a mxture rato of 1 kg fuel and approxmately 15 kg ar s necessary
(stochometrc fuel rato). Ths ar volume corresponds to about 11 m.
Durng turbochargng, the densty of the ntake ar s elevated and the
ar volume ncreased.
The volumetrc eicency and thus the eicency of the combuston
engne are sgnficantly mproved by means of turbochargng. In add-
ton, the torque can be ncreased consderably, whch n turn serves
to enhance the performance. The turbocharged engne wth the same
power output as a naturally asprated engne can therefore be desgned
wth a smaller dsplacement and hence lower weght (downszng).
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Preface
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This brochure summarises typical damage scenarios and sheds light
on their possible causes. The information is supplemented by tips on
how to avoid such damage in the future.
In this way, we aim to make it easier for repair shops and engine
reconditioners to troubleshoot potential damage causes and ensure
appropriate engine repair, which in turn is necessary for the long and
reliable functioning of our products and hence the entire engine.
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Fig. 1
Impeller after contact with housing
Preface
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2 Inadequate lubrication
Inadequate lubrcaton s one o the most requent causes or turbo-
chargers to al. I the turbocharger s not suicently suppled wth ol,
damage wll occur wthn a very short tme. Ths s due to the very hgh
speeds o the turbocharger.
EFFECTS
The mpeller and turbne wheel can strke the turbocharger housng
on account o bearng damage (Fig. 1). Ths can be dscerned rom
wear marks on the housng (Fig. 2).
I the turbocharger boost pressure s too low, the engne wll not
perorm properly: the rotatng assembly no longer reaches themaxmum speed and can no longer buld up the ull boost pressure
as a result. The reason or ths s the mxed rcton caused by the
nadequate lubrcaton.
The exhaust system emts black smoke. These are the efects o the
engne not beng suppled wth enough ar and a correspondngly
too rch uel-ar mxture.
The shat shank exhbts clear dscoloraton (Fig. 3), whch arses
rom rcton and the resultant hgh temperatures between the shat
and the bearngs. The cause o ths s nadequate lubrcaton. I
the temperature exceeds a certan level, the bearng materal wll
become deposted on the shat (Fig. 4) or the bushng mght even
become completely used to the shat.
A broken shat shank (Fig. 5) s the result o operatng the turbo-
charger or a prolonged tme wthout enough ol. The shat materal
can th s b rn o t and break
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Fig. 5
Broken shaft shank
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CAUSES
The ol level n the engne s generally too low. As a result, not only
the engne but also the turbocharger receves an nadequate ol
lubrcaton and ol coolng.
The ol used s not suicently temperature-resstant, leadng to
ncreased carbonsaton. Ths mght cause problems: the ol supply
lne o the turbocharger and the ol bores n the bearng housng o
the turbocharger can become carbonsed.
I the engne was turned of whle hot, the ol supply lne can become
carbonsed, whch means the turbocharger s no longer suppled
wth enough ol. I the cold engne was brought to hgh speeds mmedately ater the
start, there s a rsk that the ol supply n the turbocharger s not yet
suicent and hence the ol film n the turbocharger tears of.
I oregn substances make t n the ol crcut, such as drt or sealng
resdues, the ol supply lne o the turbocharger and/or the bearng
housng o the turbocharger mght be clogged.
I the vscosty o the ol s too hgh, the ol transport to the bear-
ng ponts s delayed, whch means that the tmely ol supply o the
turbocharger s not ensured. At too low a vscosty, the carryng
capacty o the ol s too low, whch can lead to mxed rcton.
I the engne s operated wth bodesel or vegetable ol, there s a
rsk o the engne ol gellng. Ths ncreases the vscosty o the ol
and t can no longer be transported through the thn ol bores n the
turbocharger.
Th t th b h l b ht b
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Fig. 1
Grooves in the radial bearing
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3 Contaminated oil
Dirt, soot, uel, water, combustion residues, or metal abrasion can
contaminate the oil. Even the smallest particles in the oil can cause
serious damage to the turbocharger due to its extremely high speeds.
EFFECTS
The smallest oreign substances in the oil cause grooves in the
bushings (Fig. 1). The piston rings in the turbocharger can undergo
serious wear. As worn piston rings can no longer adequately seal
the turbocharger, the oil enters the turbine side, which can be dis-
cerned by increased oil consumption.
The bearing play o the rotating assembly increases due to the wornbushings. This leads to wobbling movements and causes the tur-
bine wheel or impeller to come into contact with the housing (Fig. 2).
The shat might subsequently break of.
The bearing collar, i.e. the thrust washer o the axial bearing, exhibits
grooves.
Grooves or retting marks are discernible in the ax ial bearing.
Due to a blocked oil return line, the oil in the turbocharger can no
longer flow of and is instead orced out to the compressor and
turbine side. On the turbine side, the oil might then burn onto the
shat and coke (Fig. 3). Owing to the oil carbon layer, the bearing
housing and the piston rings might be significantly worn of as a
consequence.
The shat o the turbocharger shows clear signs o wear at the bear-
ing points (Fig. 4).
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Fig. 4
Clear signs of wear on the shaft at the bearing point
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REMEDY/PREVENTION
The maintenance intervals according to the manufacturer's recom-
mendations should always be complied with.
Only high-quality oil filters specified for the respective vehicle should
be installed.
Only engine oils specified by the vehicle or engine manufacturer may
be used.
A new charge air cooler and air filter should always be installed when
replacing the turbocharger. In addition, an oil change including oil
filter replacement must be carried out.
The air filter housing and charge air line should be cleaned bysuction.
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Fig. 1
Carbonised oil return line
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4 Oil leakage at turbocharger
If the engine shows signs of increased oil consumption and emits blue
smoke, it is imperative that the turbocharger is included in the cause
analysis. Important: Oil is forced out of the housing from a turbocharger
only if divergent operating conditions predominate in its environment.
EFFECTS
Oil is forced out of the turbine or compressor side of the turbocharger.
Blue smoke is emitted from the exhaust system.
Engine oil has accumulated in the intake section and charge air
cooler.
The engine experiences a power loss. Uncontrolled overspeeds resulting in the engine (so-called rising)
due to the engine oil accumulating in the charge air cooler, which is
blown into the intake of the engine and combusted.
The guide vanes might be coked in a VTG turbocharger.
CAUSES
If the oil return line of the turbocharger is clogged (Fig. 1) or con-
stricted by a kink, the oil can no longer flow out of the turbocharger
(Fig. 2, diagram B). A possible cause for clogged oil return lines is
the coking of the return line, which might be due to missing heat
shields, a poorly routed return line, heat soak, inadequate oil quality,
or the use of liquid sealants. As the turbocharger is still supplied
with oil from the engine circuit, the oil then escapes to the turbine or
compressor side.
If th i i li d ith t h il th il l fl
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Preface
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REMEDY/PREVENTION
The engine must only be filled to the specified maximum oil level.
Only engine oils specified by the vehicle or engine manufacturer may
be used.
The oil return line must be routed exactly as in the original state. In
addition, it must be ensured that all heat shields are attached.
The oil return line and the connections to the crankcase must be
checked for continuity. We generally recommend replacing the line
and the connecting piece.
The crankcase ventilation must be checked and replaced, if
necessary. The piston and piston rings must be checked for wear and replaced,
if necessary.
A new charge air cooler and air filter should always be installed when
replacing the turbocharger. In addition, an oil change including oil
filter replacement must be carried out.
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Fig. 1
Damaged air guide plates of the VTG unit
Fig. 2
Impeller damaged by foreign substances
Preface
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5 Foreign object damage
I oreign substances, such as dust, sand, screws, parts o piston
rings or valves, and sediments, enter on the intake or exhaust side,
this will usually lead to total ailure o the turbocharger due to the
very high speeds. Damage to the charge air cooler might also be the
consequence.
EFFECTS
On account o previous damage, oreign substances rom the
engine or the exhaust maniold can damage the gas entry edges o
the turbine wheel.
The air guide plates o the VTG unit are damaged and bent (Fig. 1),leading to a significant power loss.
Foreign substances in the intake air result in damage to the impeller
(Fig. 2). The vanes might become completely worn as a result. In
addition, the intake passage o the compressor housing might be
damaged (Fig. 3).
The impeller might be damaged by condensation rozen in the intake
section. Damage to just one vane is characteristic o this cause:
owing to the high speeds, the ice particles burst when encountering
the first vane, with no other vanes being damaged (Fig. 4).
CAUSES
I a valve is torn of or the piston rings racture, or example, these
parts come into contact with the guide vanes o the VTG unit and the
turbine wheel via the exhaust maniold.
B th l k i th i t k ti d t i t d d ti
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Fig. 1
Crack in the turbine housing
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Each turbocharger s desgned or only a defined temperature range.
I ths range s exceeded, the turbocharger can al ater just a ew
seconds.
EFFECTS
Cracks n the housng o the turbocharger (Fig. 1).
Ol lnes can become coked: I the supply lne s carbonsed, the
turbocharger wll not be suicently suppled wth ol. I the return lne
becomes coked, the ol can no longer flow of and ol s orced out
o the turbocharger (see also secton 4 Ol leakage at turbocharger
on page 10).
CAUSES
The temperature level has changed due to tunng.
Combuston aults have occurred n the engne.
The engne was turned of whle stll hot.
REMEDY/PREVENTION
The turbocharger may only be nstalled n the specfied vehcles.
The turbocharger may only be nstalled and operated n the orgnal
state as suppled. Techncal modficatons are not permtted.
The engne must always be cooled down at moderate speeds ater
hgh stress, such as drvng at ull load.
6 Damage due to excessive
exhaust temperatures
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Fig. 1
Dents on the rear of the impeller
7 Overspeeding
The parts instal led in the turbocharger are designed for a defined
speed range. If this range is exceeded, major turbocharger damage
can occur within seconds.
EFFECTS
Small dents can be seen on the rear of the impeller (Fig. 1). The
material (mostly aluminium) has deformed plastically due to high
centrifugal forces at overspeeds. It begins to flow and the outer
diameter increases.
If the speeds increase further, the impeller can come into contact
with the housing and/or break apart (Fig. 2).
CAUSES
The maximum permissible speed of the turbocharger was exceeded
due to tuning.
The VTG air guide plates become blocked in the position for
low speeds due to carbonisation. If the engine speeds are then
increased, the turbocharger enters the overspeed range.
The pneumatic or electric control is defective or leaking.
REMEDY/PREVENTION
The turbocharger must always be left in the original state as supplied.
The turbocharger may only be installed in the specified vehicles.
The engine must always be cooled down at moderate speeds after
high stress, such as driving at full load.
O l i il ifi d b th hi l i f t
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