The document provides an overview of turbochargers, explaining their function, components, and common issues such as turbo lag, wastegate operation, and diagnostic methods for failure. It discusses how turbochargers compress air to enhance engine power, the significance of lubrication and cooling systems, and the effects of exhaust flow control by wastegates. Additionally, it details potential causes of failure, such as oil starvation and foreign object damage, emphasizing the importance of maintenance for longevity.

1. REPAIR TURBOCHARGER
What is a turbocharger, how to install
a turbocharger and much more!!!
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2. What is a
Turbocharger?
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om/howto/what-is-a-
turbocharger.htm

3. What is a Turbocharger?
• A Turbo is run by the exhaust gasses. Its main function is to compress air and force it into the engine,
thereby more fuel can be burnt and thus more power can be generated.
• The turbo has been around almost as long as the internal combustion engine. A turbo has 2 wheels on it
one called the turbine and this sits in the exhaust system. The exhaust gas leaving the engine forces the
turbine to spin as well as the shaft attached to it.
• On the other side there is the impeller or compressor wheel which forces air into the motor. For this to be
effective the impellor wheel spins at 120,000 - 150,000 RPM (rotations per min)
• Many kinds of bearings used at these high rotational speeds need lubrication and cooling systems. The
turbo's lubrication system can be an isolated system or receive oil from the engine's oil supply. The
lubrication system can also double as a cooling system and separate coolant can be pumped through
another outside source for additional cooling or the turbine may be air cooled. In automotive applications
using the engine cooling and oil system to cool the turbo is common place. Specialized types of bearings
can eliminate the need for oil cooling or engine coolant to cool the turbo.
• Turbos rely on the flow of exhaust gas through the turbine housing they only start spinning after the
engine ignition has started to take place. When the turbo begins to create boost there is a lag from when
the throttle body is opened and when the boost begins to build and that is referred to as "turbo lag".
• The turbine and impeller are each contained within their own housing on opposite sides. These housings
collect and direct the gas flow. The size and shape can dictate the performance characteristics of the
overall turbocharger. The area of the cone radius from center hub is expressed as a ratio (AR, A/R, or A:R).
Often the same basic turbocharger assembly will be available from the manufacturer with multiple AR
choices for the turbine housing and sometimes the compressor cover as well. This allows the designer of
the engine to tailor the compromises between performance, response and efficiency to the application or
preference.
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4. What is a
Wastegate?
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om/howto/introduction-
to-the-wastegate.htm

5. What is a Wastegate?
• The wastegate is a small valve, which is used to control the amount of boost the turbo makes. It opens at a predetermined
limit, to allow surplus exhaust gas to bypass the turbine and disappear straight down the exhaust pipe once the boost limit is
reached.
• Most engines can handle a small amount of additional boost but the temptation is to keep going, as it's relatively easy
power.
• But there is only so much boost that a turbo can produce. For a given turbo, the boost pressure is dependent in the amount
of exhaust gas going through the turbine. This is controlled by a small valve, known as the wastegate. This opens at a pre-
determined limit to allow surplus exhaust gas to bypass the turbine and disappear straight down the exhaust pipe once the
boost limit is reached.
• Normally, wastegate will have a spring on one side of the diaphragm and boost pressure on the other side. At the point
where boost exerts force greater than the spring pressure, the gate opens to bleed off the exhaust gases. Reducing the
pressure seen by the wastegate or increasing the strength of the spring will make the wastegate open at higher boost
pressure hence the engine will get more boost and power. However, the limit to this is what the turbo can handle, both
physically and from the air flow point of view. If too much exhaust gas is sent through the turbine, the unit can over-speed,
which puts mechanical stresses on it and can lead to all sorts of problems, such as breaking shafts or compressor wheels
failing.
• In Addition, the air flowing into the engine can start to get very unpredictable, a situation known as "surge". This can have
very detrimental effects on the engine's internals and power delivery. The solution is to tailor the turbo itself to the
requirements, and if necessary replace a standard version with one designed for the job. This can be a physically bigger
turbo or a different turbine and compressor characteristics.
• There are two types of wastegates the first one is an internal wastegate. An internal wastegate is a component on the turbo
itself. The gate is opened via an actuator which is a diaphragm type system. Excess exhaust is then fed directly into the
exhaust system. They may also have what is called an external wastegatewhich it is separate from the turbo unit and does
not require an actuator.
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6. What is
Turbo Lag?
source:
http://www.buyautopar
ts.com/howto/understa
nding-turbo-lag.htm

7. What is a Turbo Lag?
• Turbos rely on the flow of the exhaust gas through the turbine housing. As the engine RPMs increase the turbo spools and
begins to build boost. The delay between the opening of the throttle and the turbo spinning and producing boost is known
as "turbo lag".
• Typically, a turbo with a physically small turbine and compressor wheel will have low inertia and therefore accelerate faster
for a given exhaust flow. However, because of their small size, the amount of boost they can produce will be limited at
higher engine speeds. Conversely, a turbo with a physically larger turbine and compressor wheel will have higher inertia and
will take longer to "spool up" or get to speed. With increased lag however the trade-off is increased boost at higher RPM.
• On average a small turbo can deliver good power early on but run out of steam pretty quickly. Similar to a supercharger.
While a larger turbo will give a fair kick when the boost comes on and will hold that through the rest of the rev range. This
can be an issue because it can make a car difficult to drive.
• Various methods of minimizing turbo lag have been attempted over the years. To get a combination of boost pressure and
hence power along with fast throttle response and drivability. Mazda used a sequential turbo on the last of the RX-7 models,
with a small turbo spinning at low to mid-range engine speeds and then a bigger version taking over at high speeds.
• The current crop of World Rally cars probably have the most efficient system, known as anit-lag (ALS). Details vary from
manufacturer to manufacturer but they all work on the same basic principle. A small amount of compressed charge air can
bypass the throttle when it's closed. The ignition spark in retarded at the same time and un-burnt fuel is dumped directly
into the exhaust turbine housing, where it mixes with the air and is spontaneously ignited by the red hot wheel. This keeps it
spinning so that as soon as the throttle is opened, the turbo's ready to give full boost. Because the throttle is closed during
the above process the inlet tract is filled with compressed clean air, so that when the throttle is opened, the cylinders are
immediately filled and when the fuel is injected, response is instant. The downside is the ALS process is the massive thermal
loads it puts on the turbo and exhaust system, and the heat generated in the engine.
• Another method to reduce lag (partly) when changing gear is a dump valve. Normally on a gearshift the throttle is closed
and the air from the spinning turbo backs up against the closed throttle and stalls it. But a dump valve vents the pressurized
air off.
source: http://www.buyautoparts.com/howto/introduction-to-the-wastegate.htm

9. How to Diagnose a Failed Turbocharger
• A failed turbo can be much more than just an
immediate issue, the turbocharger failure may have
occurred due to external issues. Turbochargers are
designed to operate in very specific tolerances that
don’t leave much room for variation. Failures can
occur for a number of reasons from metal fatigue to
overheating and physical damages caused by
external debris.
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10. External Housing Issues
• The exhaust housing or rear section of a turbocharger (pictured above) houses many parts of
the turbo that control the boost levels. The Turbine wheel which is moved by the exhaust
gases is located here as well as the wastegate if the unit has an internal wastegate. Failures
do not generally happen in the exhaust housing involving the turbine but can happen
involving the wastegate door. The wastegate can become stuck open or closed which will
cause issues with the boost levels of the turbo. When the door is stuck open it will cause all
the pressure to be released and the turbo cannot create boost. One the other hand if the
door is stuck closed it can cause over boosting due to the units inability to release pressure
between shifts. Both of these issues can be incorrectly diagnosed and sometimes can be
fixed by adjusting the wastegate actuator.
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11. Internal Housing Issues
• The center housing of a turbocharger may be the smallest part of the turbo but is easily the
most important. All of the bearings and oil lines are run through this section which means
that if there is an issue here it spells trouble. The bearings sit in this center section and are
cooled by oil that runs through the unit and in some turbos coolant as well. With the oil flow
restricted or stopped for even a faction of a second, the bearings will fail due to overheating.
This section is also where the shaft is housed, riding on the bearings and relying on oil flow as
well. Many failures that are blamed on manufactured defects can be tracked back to this
section once the unit is disassembled.
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12. Wastegate Issues
• The wastegate is the part of the turbocharger that releases built up exhaust gasses when
needed. Some turbo units have an internal wastegate like the ones shown above and others
have external. Both versions of wastegate function in the same way they are triggered by the
actuator when the pressure in the system reaches a predetermined point. If the actuator or
wastegate fails the turbo will not be able to perform correctly. When the wastegate is stock
open boost cannot be created since all of the exhaust gasses are bypassing the turbine wheel
flowing straight down the exhaust downpipe. In the case of a wastegate stuck closed the
turbo will continue to build boost without a way to release it which can cause back pressure
in the engine and many other serious issues.
source: http://www.buyautoparts.com/howto/diagnosing-a-defective-turbo.htm

13. Foreign Object Damage
• Foreign objects can enter an intake system in many forms sometimes they are as small as
dust particles and others as large as rocks. The smaller debris will usually pass through the
motor with no issues but can become harmful if allowed to build up. If small debris is
entering the system the air filter may need to be changed or there is an opening in the intake
system. Larger debris such as rocks and bolts that may be dropped into the intake system will
impact the blades causing complete failure of the turbo. This damage can be seen very
clearly on the blades of the impeller. (see image above)
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14. Oil Starvation
• Oil starvation is the number one cause of failure on turbochargers, not only is it the cause of the original
failure but it can cause repeat failure as well. Oil starvation is when the oil flow to the turbocharger is
restricted in anyway. All the components in a turbo spin at velocities so high even a fraction of a second of
oil starvations can cause huge amounts of damage. When the oil flow is restricted it causes a lack of
cooling as well as a lack of lubrication for the bearings in the center section of the turbo. The bearings
begin to overheat which damages them and they begin to wobble. Once a bearing begins to wobble it is
ruined, the turbo will need to be rebuilt or replaced. Oil starvation can be caused by a blockage in the oil
system but can also be caused by sludging. Oil sludging is created by oil that overheated and began to
burn in the oil lines near the turbo. Oil sludge can settle in the oil pan and if it gets pulled though the oil
lines it can slow the flow of oil to the turbo. Turbos that are starved of oil are not covered by warranty and
the failure will continue until the restriction is removed.
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15. How to Diagnose a Failed Turbocharger
• Just like any other auto parts turbochargers will only last if
they are properly taken care of. Any part will fail with lacking
maintenance but a turbo is particularly fragile due to its
nature. The only true turbo failure is metal fatigue which is
caused by the metal in the turbo becoming fragile due to heat
cycling thousands of times. The unfortunate fact is that a
turbocharger has an average life span of about 80 – 120K
miles. On a diesel motor that life span can be closer to 4 times
that but still the turbo will eventually fail. When the turbo
does fail be sure to check for a cause before replacing the
unit, otherwise it could cost much more than expected.
source: http://www.buyautoparts.com/howto/diagnosing-a-defective-turbo.htm

16. REPAIR TURBOCHARGER
The End
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