Exhaust gas recirculation and control
with Pierburg components
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Pierburg components for exhaust gas recirculation
and exhaust gas control
Lowering fuel consumption and reducing pollutant
emissions – in conjunction with optimising performance,
comfort and safety – is of growing importance in the development of new engine generations. A catalytic converter
or a diesel particulate filter used with a combustion engine
cannot cope with this task alone.
Pierburg GmbH, part of the KSPG Group, is a specialist
in the areas of emission control, air supply and throttle
valves. Its decades of experience and comprehensive,
innovative and renowned expertise when it comes to
engines provide ideal foundations for Pierburg in the
ongoing development and production of pioneering
components, modules and systems. In addition to other
concepts, the manufacturer also offers technology for
exhaust gas recirculation (EGR) and exhaust gas control:
this can be used to meet the current limit values prescribed
by legislation and future requirements on national and
international markets in an efficient manner.
Although raw emissions from engines can be continually
reduced with technical measures, the tightening of
emission limit values also means that technologies in
non-engine measures must be improved. Consistently
developed, state-of-the-art EGR concepts also make a
valuable contribution to more effective use of fuels. On
top of this, they support the engine during the warm-up
phase, with flap systems also bringing it to the required
operating temperature more quickly.
Fig. 1: Compact EGR valve
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Due to strict emission limit values that are constantly being
tightened, the technical requirements for EGR components
are also becoming increasingly demanding in terms of
control in higher-level engine systems. The resulting high
degree of mechanical and electronic integration of function
groups leads to “tailor-made” mechatronic EGR components.
Pierburg EGR valves and exhaust gas flaps feature excellent
responsiveness and control and positioning accuracy at
high actuating forces. The use of EGR valves in conjunction
with an EGR cooler and exhaust gas flaps for controlling
the pressure difference enables a significant reduction in
nitrogen oxides.
100
Full load
diesel
80
Load [%]
With various components and modules, supported by
pneumatic or electrical actuators, Pierburg can provide its
customers with optimum EGR components for future engine
applications too. The engine specialist offers a modular
system that can be used to create the ideal customer
solution.
Full load
petrol
60
40
20
0
1000
EGR
range
diesel
2000
EGR
range
petrol
3000
4000
5000
6000
Speed [rpm]
Fig. 2: EGR ranges of conventional petrol and diesel engines
Overall, the intelligent integration of all EGR components
such as valves, flaps, bypasses, coolers and lines offers a
cost-effective solution with excellent durability that protects
the environment.
How exhaust gas recirculation works
Exhaust gas recirculation reduces nitrogen oxide emissions
in both diesel and petrol engines right at the formation
phase by lowering the combustion temperature and
reducing the oxygen content in the intake air.
Exhaust gas recirculation is not only used to minimise
nitrogen oxides; it is also used in petrol engines to reduce
fuel consumption.
Due to the lean operation of diesel engines, these can
handle much higher exhaust gas rates than petrol engines.
Fig. 3: EGR module
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Exhaust gas recirculation in petrol engine
applications
Exhaust gas recirculation in diesel engine
applications
In petrol engines, exhaust gas recirculation is used to
dethrottle the engine in the part-load range. This leads to a
reduction in fuel consumption.
In diesel engines, oxidation catalytic converters and
particulate filters are used to reduce hydrocarbons (HC) and
particulate matter (PM). To reduce NOx in diesel engines,
exhaust gas recirculation has become established as a wellengineered and cost-effective technical solution alongside
measures in the engine such as injection start timing.
Depending on the petrol engine concept, the EGR rates can
be increased. Petrol engines with direct injection in stratified
charge operation have the highest EGR rates (lambda > 1;
see Fig. 2).
Due to the continual tightening of NOx limit values, urea
catalytic converter exhaust gas after-treatment systems
(SCR) and NOx storage catalysts are used in addition to
EGR.
As lean operation of petrol engines with direct injection
means that three-way catalytic converters cannot be used,
the highest possible EGR rates are required to reduce
the raw emissions of nitrogen oxides. With exhaust gas
recirculation, the nitrogen oxides in the raw exhaust gas
are reduced down to 70 % and the air flow is also reduced
significantly. The reduced frequency of DeNOx catalytic
converter scavenging due to the lower raw emissions also
indirectly benefits fuel consumption. Future concepts may
contribute to increased engine efficiency by reducing the
engine’s knocking tendency in the high-load range.
Country/Year
‚
00
‚
01
EU
Euro 2 Euro 3
Hong Kong, China
Euro 2 Euro 3
India (petrol)
India (diesel)
‚
02
‚
03
‚
04
Turkey (petrol)
Euro 1
Turkey (diesel)
Euro 3
Russia
‚
06
‚
07
‚
08
‚
09
‚
10
‚
11
‚
12
Euro 5
‚
13
‚
14
Euro 6
Euro 4
India 2000 / Euro 1
Euro 1
05
Euro 4
Bharat Stage II / Euro 2
PR China (petrol)
‚
By significantly reducing the temperature of the recirculated
exhaust gas, EGR cooling makes exhaust gas recirculation
more effective and therefore further reduces nitrogen oxides.
Bharat Stage II / Euro 2
Bharat Stage III / Euro 3
Bharat Stage III / Euro 3
Bharat Stage IV / Euro 4
Euro 2
Euro 3
Euro 4
Euro 4
Euro 4
Euro 1
CIS States
Euro 2
Euro 3
Euro 4
USA
Tier 1
Tier 2
Tier 3
Canada
Tier 1
Tier 2
Tier 3
Mexico
SEMARNAT 2003/Tier1
Tier 2 /Euro 3, 4 equivalent
Fig. 4: Emissions legislation (selected areas) for Europe, America and Asia
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National and international emissions requirements
distinctions are made between diesel and petrol engine
combustion types and between the vehicle types of cars,
trucks and motorcycles.
Legislation is continually tightening emissions requirements
to limit the environmentally damaging influence of fossil
fuel combustion in engines.
In addition to the European emission standards (Euro 1 – 6),
other national standards also exist, which must be taken
into account in the relevant countries. In the USA, various
emission standards (Tier 2 EPA limit values, LEV II CARB
limit values) have been introduced. The EU and the USA are
the driving forces for emission standards. Most countries
is Asia and North and South America adopt the EU and
US emission standards. Motor vehicle manufacturers must
therefore take the various limit values into account at
different times.
Combustion produces end products such as carbon
monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx),
particulate matter (PM), sulphur dioxide (SO2), sulphuric
acid (H2SO4) and many more. The first common European
emission standards were introduced in the 1970s for cars.
The values for carbon monoxide (CO) and hydrocarbons
(HC) were restricted. In 1977, nitrogen oxides (NOx) were
also restricted. The limit value for soot particulates (PM)
was introduced for diesel engines in 1988.
Vehicles are assigned to specific emission classes using the
limit values. Among other things, these emission classes
are used to calculate vehicle tax and in pollutant group
classification for low-emission zones. With the limit values,
Petrol engine
Euro 3
0,05
0,04
Euro 4
0,03
Tier II, Bin 8
0,02
SULEV
ULEV
Tier II, Bin 2 Tier II, Bin 5
Euro 6
0,01
0
0
0,1
Euro 5
0,2
0,3
HC + NOx (EU) [g/km] / NOx (US+Cal.) [g/mi]
Fig. 5: Development of pollutant limitation for vehicles with
diesel engines
0,6
HC (EU) [g/km] / HC exception methane (US) [g/mi]
Particulate matter (EU) [g/km] / (US) [g/mi]
Diesel engine
Euro 3
0,2
0,15
Tier II, Bin 8
Euro 5
0,1
Euro 4
LEV
0,05
ULEV
Tier II, Bin 2
SULEV
0
0
0,1
0,2
NOx [g/km] / NOx (US+Cal.) [g/mi]
Fig. 6: Development of pollutant limitation for vehicles with
petrol engines
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CO2 and climate change
In the 1990s, the EU Commission published its strategy for
reducing CO2 emissions from cars and lowering the average
fuel consumption. On the basis of this, manufacturers
committed, on a voluntary basis at first, to reduce CO2
emissions in line with the EU specifications, with the
average emission limit being set at 140 g/km.
However, when the average CO2 emission per car was
around 20 g/km above the target value set for 2009, the
EU decided to take statutory measures. As a result, the
Commission lowered the limit values for average CO2
emissions per car continually and set a target of 95 g/km
for 2020.
•
•
•
•
•
•
•
•
Excellentreliability
Durabilityandrobustness
Highresistancetocontamination
Smallinstallationvolumeandlowweight
Hightemperatureresistance
Lowlevelsofleaks
Diagnosticcapability
Lowsystemcosts
In terms of design, functionally equivalent electromotive
EGR valves are used for intake manifold petrol engines
and direct injection (DI) petrol engines. EGR valves for
petrol engines are characterised by components with high
resistance to thermal loads and to contamination. Larger
valve cross sections are also typical in EGR valves for DI
petrol engines in lean operation.
Petrol EGR concepts
EGR valves for applications in high-load high-pressure
(HP) and low-pressure (LP) concepts
EGR valves for applications in part load
• Excellentdynamics
• Highcontrolquality/goodmeteringacrossthe
flow rate range
• Goodmixingofexhaustgasandfreshair
thanks to specifically adapted housing
• SufficientEGRratesinthedesiredloadrangeand
exhaust gas back pressure range
Stricter CO2 regulations and the associated requirement to
reduce fuel consumption are set to trigger a greater shift
of emphasis for exhaust gas recirculation in the direction
of high loads. Pierburg provides solutions for high-load
EGR systems, which are being increasingly used in petrol
engines with supercharging in particular.
Petrol engine
100
80
Load [%]
Exhaust gas recirculation in part load has become established
in engines with manifold injection and is used to some
extent for engines with direct injection. Future emission
limits such as the limit value of 95 g CO2/km, demand
specifically tailored external exhaust gas recirculation
systems in modern petrol engines. The function of an
exhaust gas recirculation system is determined centrally by
the layout of the EGR components. For this reason, EGR
components must be designed on an individual basis for
the application. Based on its many years of experience
with EGR valves, Pierburg has developed electrical EGR
valves for petrol engines that excel through the following
characteristics:
High-load EGR
60
40
WLTP
0
1000
Knock limit
Part-load EGR
NEDC
20
2000
3000
4000
5000
6000
Speed [rpm]
Fig. 7: Petrol HP EGR and LP EGR concepts
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As can be seen in the schematic depiction of an engine map
(see Fig. 7), EGR is used in two ranges.
aim is to reduce the knocking tendency at high loading
pressures and a simultaneous high compression ratio.
In the part-load range, non-cooled EGR is used for
dethrottling and therefore produces a reduction in fuel
consumption.
In contrast to EGR valves, which are used in the highpressure range, butterfly or high-flow valves can be used
in the low-pressure range – in a similar manner to in diesel
engines.
Due to increasing loading pressures in the high-load range,
the compression ratio of the engine must also be reduced
in order to reduce the knocking tendency of the engine
that is caused by these. However, this in turn lowers the
efficiency of the engine.
To counteract this (i.e. to maintain the compression ratio
or even to increase it), cooled LP EGR is used in the highload range at low engine speeds, alongside ignition timing
adaptation.
The application range of EGR may be expanded in future into
the high-load range for higher engine speeds. To do this, LP
EGR and HP EGR modules with high cooling performance
need to be integrated in the engine design. Here too, the
Diesel EGR concepts
There are various positions for exhaust gas removal
depending on the application. The classic method of
removing exhaust gas from the engine upstream of the
turbine and feeding it back into the fresh air is known as
high-pressure exhaust gas recirculation (HP EGR). With lowpressure exhaust gas recirculation (LP EGR), the exhaust
gas is removed downstream of the turbine and fed to the
compressor at a low pressure level. The mixing of the
exhaust gas and the fresh air via the compressor is at an
optimum for the engine.
Petrol engine LP EGR
Petrol engine HP EGR
ETC
HP EGR
ETC
Integrated
CA & EGR
cooler
Integrated
CA & EGR
cooler
EGR
valve
C
C
T
LP EGR valve
Cat
T
LP EGR
Cat
Pre-cooler
Fig. 8: High-pressure exhaust gas recirculation
Fig. 9: Low-pressure exhaust gas recirculation
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EGR valves for diesel high-pressure concepts
In this case, the exhaust gas is removed directly at the
exhaust manifold and fed through a tube at a high pressure
level to the fresh air side. The exhaust gas and fresh air mix
in the intake manifold or boost pressure tube.
The recirculated exhaust gas is added to the mix by an
exhaust gas recirculation valve located on the engine.
The recirculated exhaust gas reaches a temperature of
approx. 400 °C to 600 °C. Exhaust gas recirculation valves
must be securely sealed against the exhaust gas back
pressure and the boost pressure. They must also be resistant
to soiling, soot contamination and harmful condensates,
which can lead to corrosion.
Diesel HP EGR valves generally need to have:
•
•
•
•
Excellent adjustment dynamics
Good metering
Defined characteristic curve
Resistance to contamination
•
•
•
•
•
Robustness and durability
Diagnostic capability
Flexible design for the various installation spaces
Low weight
Low costs
HP EGR valves generally have a non-contact stroke sensor.
The engine control unit can use this sensor information to
adjust the desired valve stroke – and therefore the required
exhaust gas recirculation rate – in a closed control loop. If
necessary, the sensor information can be used for EGR valve
diagnostics.
HP EGR poppet valves
Electromotive EGR valves, or EM EGR valves, are used in
diesel engines. The shut-off component of the EGR valve
is a valve poppet, which is opened with or against the
direction of flow, depending on the design. A DC electric
motor with downstream gearing is used as the drive. The
rotary motion is transformed into a linear motion via an
eccentric drive. Reversing the direction of rotation of the
DC electric motor provides motor support to the closing
force. This produces quicker and more reliable closing with
low valve seat leakage. EM EGR valves are characterised
by excellent adjustment dynamics and at the same time,
high actuating forces. Single poppet valves are robust and
resistant to contamination. Lower pressure losses and
high flow rate can be seen in particular in EM EGR valves
that open in the direction of flow. The compact EGR valve
provides an especially space-saving model.
Both the standard EM EGR valve, which is more consistently
modular, and the compact EGR valve are particularly
lightweight.
Fig. 10: Diesel EGR Gen. II valve
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EGR valves for diesel low-pressure concepts
In order achieve the higher exhaust gas recirculation rates
needed to meet the Euro 6 exhaust gas regulation, lowpressure exhaust gas recirculation (LP EGR) will in future be
used increasingly in turbocharged engines in addition to the
established high-pressure exhaust gas recirculation
(HP EGR). In this process, the exhaust gas is rerouted
downstream of the diesel particle filter (DPF) and returned
upstream of the compressor. The required scavenging
gradient is set by supplementary engine throttling. Pierburg
offers the required fully electronic individual components
for the exhaust gas recirculation section, such as EGR
valves, throttle valves and exhaust gas flaps, as well as
complete EGR cooler modules for this process.
Diesel engine LP concept I
HP EGR
ETC
Integrated
CA & EGR
cooler
EGR
valve
C
T
LP EGR valve
Oxi-Cat
DPF
LP EGR
system
ECV
Pre-cooler
NOx
An LP EGR valve controls the exhaust gas recirculation rates
through continual adjustment of the flow cross section.
Fig. 11: Combination of EGR valve + exhaust gas flap
Pierburg develops appropriately adapted LP EGR valves for
this and other desired functions and requirements of our
customers operating around the world.
LP EGR butterfly valve
The Pierburg butterfly valve consists of an aluminium
pressure die-cast housing with a central butterfly valve and
an integrated actuating drive, made up of a direct current
motor and a two-stage spur gear unit.
Diesel engine LP concept II
HP EGR
ETC
Integrated
CA & EGR
cooler
The tried-and-tested assembly groups for the LP butterfly
valve were developed from existing throttle valves and EGR
valve assembly groups, which had already been in series
production for many years. This guarantees a perfectly
tailored solution for the customer.
EGR
valve
C
T
LP EGR valve
Oxi-Cat
DPF
LP EGR
system
Pre-cooler
NOx
Fig. 12: Combination of EGR valve + throttle valve
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Fig. 13: Diesel EGR Gen. II valve
Max. flow rate
Fig. 14: Low-pressure butterfly valve
90 kg/h at Δ 50 hPa
Max. flow rate
150 kg/h at Δ 50 hPa
Internal leakage, valve seat
< 0.5 kg/h at 600 hPa
Internal leakage
< 3 kg/h at 600 hPa
Max. ambient temperature
-400C to +1600C
Max. ambient temperature
-400C to +1500C
Typical exhaust gas
temperature
4000C to 6000C
(with water cooling)
Typical exhaust gas
temperature
1600C
Nominal current
consumption
1.1 amp
Nominal current
consumption
1 amp
Permissible vibration
acceleration
25 g
Permissible vibration
acceleration
20 g
Weight
< 0.7 kg
Weight
< 0.7 kg
Actuation frequency
1 to 5 kHz
Actuation frequency
1 to 10 kHz
Position feedback
Non-contact sensor
Position feedback
Non-contact sensor
Installation position
Vertical -850 to +850
Installation position
-850 to +850
Specific characteristics
• Excellent dynamics
• Small installation volume
• Low weight
• High temperature
resistance
• Low leakage
• Modular construction
method
Specific characteristics
• Corrosion-resistant
materials
• Low installation weight
• High torque at the flap
• EGR rate precisely
controllable
• Flap is pressure balanced
Tab. 1: Typical values for an HP poppet valve with 25 mm Ø
Tab. 2: Typical values for a butterfly valve with 35 mm Ø
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Fig. 15: High-flow EGR valve
Max. flow rate
Fig. 16: Compact EGR valve
200 kg/h at Δ 50 hPa
Max. flow rate
150 kg/h at Δ 100 hPa
Internal leakage
< 0.5 kg/h at 600 hPa
Internal leakage, valve seat
< 0.5 kg/h at 600 hPa
Max. ambient temperature
-400C to +1500C
Max. ambient temperature
-400C to +1600C
Typical exhaust gas
temperature
1600C
Typical exhaust gas
temperature
4000C to 6000C
(with water cooling)
Nominal current
consumption
1 amp
Nominal current
consumption
1.2 amp
Permissible vibration
acceleration
20 g
Permissible vibration
acceleration
20 g
Weight
< 0.85 kg
Weight
< 0.6 kg
Actuation frequency
1 to 10 kHz
Actuation frequency
1 to 5 kHz
Position feedback
Non-contact sensor
Position feedback
Non-contact sensor
Installation position
-850 to +850
Installation position
Vertical -850 bis +850
Specific characteristics
• Corrosion-resistant
materials
• Low installation weight
• High torque at the flap
• EGR rate precisely
controllable
• Low pressure loss
• Low leakage
Specific characteristics
• Excellent dynamics
• High EGR rates
• Small installation volume
• Low weight
• Temperature resistance
• Low leakage
Tab. 3: Typical values for a wastegate EGR valve with 35 mm Ø
Tab. 4: Typical values for a compact EGR valve with 25 mm Ø
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LP EGR high-flow valve
The high-flow EGR valve from Pierburg is characterised in
particular by the flow cross section that is fully released
when open and a design principle resulting from this that
is optimised for loss of pressure. Compared to the butterfly
valve, this design has considerably less leakage when
closed.
LP EGR poppet valve
The EGR poppet valve from Pierburg is now also used in
the low-pressure range. Here, the advantages from the
high-pressure range are transferred to the low-pressure
range, such as the compact construction method and low
leakage for example.
Fig. 17: Exhaust gas flap
Max. flow rate
450 kg/h at Δ 50 hPa
Exhaust gas flap
Internal leakage
< 50kg/h at 600 hPa
If the pressure gradient in the low-pressure system is
insufficient to control the required EGR mass flow rate,
an electrical Pierburg exhaust gas flap is used to generate
ram pressure.
Max. ambient temperature
-400C to +1500C
Typical exhaust gas
temperature
6500C
Nominal current
consumption
1 amp
Permissible vibration
acceleration
5g
Weight
< 950 g
Actuation frequency
1 to 10 kHz
Position feedback
Non-contact sensor
Installation position
-50 to -450
Specific characteristics
• Corrosion-resistant
• Heat-resistant
• Lightweight design
• High torque
The exhaust gas flap can be adjusted between the “open”
and “closed” positions with continuous electromotive
adjustment. This enables a defined pressure build-up in the
entire adjustment range and as a result, controlled exhaust
gas recirculation and pollutant reduction. The flap position
response is sent via a non-contact angle sensor; in the
case of a de-energised drive, it is automatically set with
spring-loading to the “open” emergency running position.
Its actuators are designed as a modular system and whilst
they have the same range of functions, they vary in terms
of flange size, attachment geometry and flap diameter. The
electromotive exhaust gas flap can therefore be adjusted
to the dimensions required in each case, according to the
installation space for various vehicle types and exhaust
systems.
Tab. 5: Typical values for an exhaust gas flap with 55 mm Ø
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In 2007, Pierburg developed the first electromotive exhaust
gas flap for the NAFTA market with a precision-cast housing.
Today, the further-developed exhaust gas flap has a lighter
sheet metal design. The use of high-quality materials
means that the flap can be operated in even the most
challenging environmental conditions. On the one hand,
the high resistance to corrosion enables use directly in
the exhaust system, which is subject to a particularly high
degree of soiling from outside and within due to prolonged
exposure to corrosive exhaust gas products. On the other
hand, high-strength material ensures seamless function for
the electrical flap, even at high exhaust gas temperatures.
Fig. 18: Combi valve
Pierburg exhaust gas flaps are also used in the area of
soundshaping.
LP EGR combi valve
The combi valve assumes the tasks of the low-pressure
EGR valve and the exhaust gas flap. In doing so, it controls
the exhaust gas recirculation flow, assists control of the
delivered exhaust gas flow and sets the required differential
pressure. As a combined component, the LP combi valve is
not only more cost-effective, but also offers the benefit of
a lower weight.
The valve is fitted with a non-contact position sensor for
position control. Together with an air mass sensor, this
enables precise EGR control in all operating states. The
valve is not sensitive to soot or particulate matter and is
resistant to condensate. The drive and valve construction
is particularly robust.
Max. flow rate
200 kg/h at Δ 50 hPa
Internal leakage
< 3kg/h at 300 hPa
Max. ambient temperature
-400C to +1500C
Typical exhaust gas
temperature
1600C
Nominal current
consumption
1 amp
Vibration resistance
5g
Weight
< 1,200 g
Actuation frequency
1 to 10 kHz
Position feedback
Non-contact sensor
Installation position
-850 to -850
Specific characteristics
• Corrosion-resistant
• Lightweight design
• Multifunctional
Tab. 6: Typical values for a combi valve with 30 mm Ø
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EGR modules
EGR modules for the high-pressure range
EGR modules consist of an EGR valve, an EGR cooler to cool
the exhaust gases and optionally, a bypass flap. Integrating
these functions in one component produces advantages
what it comes to size. Component interfaces and the
number of sealing points are reduced. As a rule, having
multiple individual components increases component
costs, whereas a module can make a major contribution to
cost reduction.
The bypass flap is used to regulate the controlled re-routing
of the hot exhaust gas flow past the EGR cooler or, in the
cooling position, through the EGR cooler. A pneumatically
controlled actuator is used to operate the bypass flap.
This means that at a cold start, the engine and catalytic
converter reach operating temperature more quickly.
The use of a bypass flap means that the typical “diesel
knock” at a cold start and the raw emissions of hydrocarbons
(HC) in the engine’s warm-up phase can be reduced. With
the bypass function, the engine and catalytic converter
operating temperatures are achieved more quickly after a
cold start.
EGR modules for the low-pressure range
For an engine design with a low-pressure EGR module, the
exhaust gas is rerouted downstream of the diesel particulate
filter (DPF) and returned to the intake air system of the
engine upstream of the turbocharger compressor impeller.
The exhaust gas is also cooled by a special low-pressure
EGR cooler. The exhaust gas cooling provides thermal
protection for the turbocharger compressor impeller.
A typical LP EGR module consists of an LP EGR valve in
conjunction with an EGR cooler.
+
Bypass flap
EGR valve
+
EGR cooler
EGR valve
+
EGR valve
+
Bypass flap
Fig. 19: EGR module versions
EGR cooler
Fig. 20: Diesel EGR valve with bypass flap and EGR cooler
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Pierburg GmbH · Alfred-Pierburg-Straße 1 · 41460 Neuss · Germany
Tel. +49 2131 520-01 · Fax +49 2131 520-645 · www.kspg.com
Subject to change. Printed in Germany. © KSPG AG – 09/2013
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