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397
ARTICLE INFO
Article ID: 02-17-04-0023
© 2024 SAE International
doi:10.4271/02-17-04-0023
History
Received: 16 May 2024
Revised: 08 Aug 2024
Accepted: 21 Nov 2024
e-Available: 10 Dec 2024
Keywords
Exhaust gas recirculation
pump, NRTC, LLAC, CSLA,
Engine electrification,
Emission reduction,
O-road diesel engine
Citation
Willoughby, A., Adekanbi,
M., Kakani, R., Ahamd, Z.
etal., “Fuel Eciency
Evaluation of an O-Road
Diesel Engine with an EGR
Pump and High-Eciency
Turbocharger across Various
Drive Cycles,” SAE Int. J.
Commer. Veh.
17(4):397-415, 2024,
doi:10.4271/02-17-04-0023.
ISSN: 1946-391X
e-ISSN: 1946-3928
Fuel Eciency Evaluation of an O-
Road Diesel Engine with an EGR Pump
and High-Eciency Turbocharger
across Various Drive Cycles
Audrey Willoughby,1 Michael Adekanbi,1 Raghav Kakani,1 Zar Nigar Ahmad,1 Greg Shaver,1 Eric Holloway,1 Eric Haaland,2
Matthew Evers,2 Adam Loesch,2 Josiah McClurg,2 Nilesh Bagal,3 James McCarthy,3 and Michael Coates3
1Purdue University, Ray W. Herrick Laboratories, Department of Mechanical Engineering, USA
2John Deere, Waterloo, USA
3Eaton Corporation, Marshall and Galesburg, USA
Abstract
As regulations become more stringent, engine manufacturers are adopting innovative technologies to reduce
emissions while maintaining durability and reliability. One approach involves optimizing air handling systems.
Eaton developed a 48V electric exhaust gas recirculation pump (EGRP) to reduce NOx and CO2 emissions while
improving fuel eciency when paired with a high-eciency turbocharger.
This study integrates an electric EGRP and a high-eciency turbocharger onto a 13.6L John De ere o-road
diesel engine to evaluate the impact on fuel eciency and NOx emissions across various drive cycles including
the nonroad transient cycle (NRTC), the low load application cycle (LLAC), the constant speed–load acceptance
(CSLA) test, and the ramped modal cycle (RMC). The study highlights the benefits and limitations of the proto-
type EGRP on an o-road engine. Since the setup did not include aftertreatment systems, engine-out emissions
were analyzed.
Experiments were conducted at selected operating points to achieve optimal brake thermal eciency
while keeping BSNOx within 25% of baseline values. These results helped develop a calibration map for both
transient and steady-state testing.
For the CS LA tests, the t ime response to achi eve 90% load was slower with t he EGRP-equip ped engine compa red
to the stock engine. Additionally, the NRTC, a regulatory cycle for the UnitedStates and the European Union, and
the LLAC did not achieve the desired torque set points with the EGRP and high- eciency turbocharger. The EGRP’s
slower-than-desired response when it decelerates led to excess EGR flow, which aected the engine’s ability to
produce torque. This was a key finding of the study.
The measured engine speed and engine load with the EGRP engine configuration were utilized to develop
a modified version of the NRTC and LLAC, referred to in this article as the modified NRTC and the modified
LLAC. The modified NRTC and modified LLAC were run on the stock engine to accurately compare the perfor-
mance of the stock hardware with the EGRP and high-eciency turbocharger hardware for the same transient
cycles, albeit cycles that are no longer specifically the regulatory NRTC and LLAC cycles. The intent of the
modified LLAC and the modified NRTC is to show what the possible benefits of EGRP and high-eciency
turbocharging may likely beif the transient response shor tcoming of the EGRP is addressed
BSFC improved with the EGRP and high-eciency turbocharger hardware for the modified NRTC, modified
LLAC, and RMC. The modified NRTC showed a 1.3% improvement, the modified LLAC exhibited a 2.5% improve-
ment, and the RMC demonstrated a 1.3% improvement. BSNOx increased by 12.9% for the modified NRTC,
decreased by 11.1% for the modified LLAC, and increased by 2.8% for the RMC with the EGRP configuration. The
BSPM increased by 34.2% for modified LLAC and improved by 33.1% for the modified NRTC.
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398 Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024
FIGURE 1 Eaton’s Electric Generation 3 exhaust gas
recirculation pump.
Reprin ted with permiss ion from Ref. [12] . © Eaton Corporat ion
TABLE 1 Eaton’s Electric Generation 3 exhaust gas
recirculation pump specifications.
Parameter Nominal specification
Pump revision level Gen 3
Motor revision level New 3kW motor
Nominal power rating 3kW (continuous)
Pump displacement 400 cc/rev
Power interface 48 VDC
Lubrication Engine oil
Cooling Engine coolant
Communication interface CAN
Maximum operating speed 10,000rpm
Power recovery Available up to power rating
Assembly mass 27kg
Reprin ted with pe rmission from Re f. [12]. © Eaton Cor poratio n
Introduction
The reliance on diesel engines across various sectors
such as agriculture, construction, mining, and forestry
is driven by the diesel engine’s notable attributes: high
thermal eciency, high-power output capacity, and robust
durability [1]. Unfortunately, diesel engines emit harmful
pollutants, including particulate matter (PM) and nitrogen
oxides (NOx) [2]. Inhaling PM can exacerbate respiratory
allergic reactions, while high exposure to NOx can damage
respiratory airways [3, 4]. Beyond the health impacts of NOx,
it constitutes environmental concerns of ozone depletion [5].
In 2023, approximately 1,557,000 tons of NOx were produced
by o-road vehicles, constituting roughly 23% of the national
emission total [6].
To address these environmental and health challenges,
regulatory bodies like the U.S. Environmental Protection
Agency (EPA) and the Cal ifornia Air Resources Board (CARB)
have enacted increasingly stringent emission standards.
Shortly aer the completion of this study, CARB proposed
Tier 5 Emission Standards, requiring up to 90% reductions
in NOx and 75% reductions in PM, respectively, contingent
upon the power category [7].
Original engine manufacturers are complying with
existing Tier 4 Emission Standards for NOx by utilizing high-
pressure-cooled ex haust gas recirculation (EGR). is met hod
entails circulating exhaust gas through an EGR cooler before
reintroducing it back into the engine [1]. EGR eectively
reduces the oxygen concentration and ame temperature,
thereby lowering NOx formation [8, 9, 10]. However, driving
EGR necessitates a turbocharger to maintain back pressure on
the engine, resulting in increased fuel consumption [8, 9, 10].
Eaton’s Electric Generation 3 EGR pump (EGRP) elimi-
nates the need for positive engine delta pressure to facilitate
EGR [11]. e less-ecient turbocharger can bereplaced with
a high-eciency turbocharger to reduce the engine delta
pressure, improve the pumping work, and enhance the
fuel economy.
Experimental Setup
To evaluate the benets of the new technology, the EGRP and
a twin-scroll high-eciency turbocharger were implemented
on a 13.6L John Deere Engine in Herrick Laboratories at
Purdue University.
The EGRP, depicted in Figure 1, is a rotary positive
displacement pump adapted from Eaton’s supercharger tech-
nologies [11, 12]. Equipped with a 48V motor, the EGRP can
sustain continuous power of up to 3 kW, either generating or
consuming power [12]. In already deployed applications, t here
are existing battery and hybrid electric vehicle systems that
provide voltage to electric components in commercial o-road
vehicles [13, 14, 15]. e EGR ow rate can beadjusted by
vary ing the commanded EGRP speed through a controller area
network (CAN) signal [12]. e specications on the pump are
shown in Tabl e 1. To power the pump, a regenerative power
supply was utilized. Additionally, a specialized coolant cart,
developed by the Eaton Team, was employed to continuously
circulate coolant through the pump at approximately 60°C.
e 510kW engine utilized an EGR valve, twin turbo-
chargers in series, and a boost control solenoid. e boost
control solenoid (BCS), commonly used as an active waste
gate system [16], was employed on the high-pressure turbine
to control and regulate the boost pressure. Details regarding
the specications of the diesel engine can befound in Tab le 2 .
Additional hardware was incorporated into the system,
including a split exhaust manifold and an intercooler. e
split exhaust manifold segregated exhaust gas from cylinders
1–3 to cylinders 4–6. Meanwhile, the intercooler, positioned
between the low-pressure compressor and the high-pressure
compressor, served to reduce the amount of work required to
compress fresh air. Lab-grade pressure, temperature, and ow
rate measurements were collected via Speedgoat. Engine
control unit (ECU) data was obtained through CAN a nd John
Deere’s soware, while EGRP data was collected via CAN.
MATLAB and Simulink soware were used for data analysis.
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Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024 399
Fuel consumption was calculated by measuring the weight
dierence using a load cell and fuel bucket. John Deere’s NOx
OEM Sensor was utilized in measuring NOx emissions, with
the relative accuracy being ±10%, at a particular reading. e
specications of the instrumentation used are provided in
Tab le 3 . Figure 2 presents the test cell schematic, incorporating
the EGRP and high-eciency turbocharger, along with the
locations for pressure and temperature measurements.
Drive Cycles
Dierent transient cycles were used to assess emissions and
fuel consumption. In this study the following transient tests
were employed in experimental testing: the constant speed–
load acceptance (CSLA) test, the nonroad transient cycle
(NRTC), the low load application cycle (LLAC), and the ramped
modal cycle (RMC). e cycles were selected based on relevance
and importance to the regulatory bodies [18, 19, 20].
Depending on the o-road application, a nonroad engine
may experience dynamic changes in engine speed and engine
load such as a crawler tractor, while other applications, like
the agricultural tractor, do not encounter the drastic changes
in engine speed and load, but require the ability to quickly
produce power and sustain that high power, as shown in
Figure 3 [21].
e CSLA test is utilized to access the time response to
90% load and examine the peak soot measurement during the
transient response. It helps determine how quickly the engine
can increase output torque while the engine dynamometer
maintains a constant speed. e throttle is snapped a total of
three separate times to reach 100% load for a specied engine
speed. Figure 4 is an example of the CSLA test for the 1900rpm
operating point.
To rapidly generate torque, fuel is injected early into the
cylinder [22]. Excess fuel injected into the cylinders can lead
to incomplete combustion resulting in higher peak soot
measurements [22]. e main objective of the CSLA test is to
minimize the time required to achieve 90% load whi le keeping
peak soot emissions within acceptable limits.
Variations in engine speed and brake torque are typical
in o-road applications, impacting both fuel consumption and
emission levels in diesel engines [23]. In an eort to have a
more representative cycle to measure emissions from nonroad
activity, the U.S. EPA, in collaboration with the Engine
Manufacturer’s Association (EMA) and the Southwest
Research Inst itute (SwRI), developed the NRTC [24]. is cycle
encompasses various o-road duty cycles including a backhoe
loader, a rubber tire loader, a crawler-dozer, an agricultural
tractor, an excavator, an arc welder, and a skid steer loader [24,
25]. e NRTC serves as a standardized cycle for the U.S. EPA
Tier 4 and EU Stage V emission standards [24, 26]. is test
assesses emissions from compression ignition engines used in
nonroad machinery under dynamic conditions. e NRTC
consists of a cold star t, a 20-min soak, and a hot start, featuring
signicant variations in speed and torque, making it one of
the most rigorous transient cycles compared to other legisla-
tive tests [24, 27]. In the UnitedStates, emissions are calculated
by adding 5% of the cold start emissions with 95% of the hot
start emissions, while the EU’s Stage IV certication uses 90%
hot mode and 10% cold mode [24, 26, 28]. In this study, the
analysis of the NRTC focuses on the hot start. e cold NRTC
was outside the scope of this particular study due to the small
modest impact it has on fuel consumption.
The concern regarding overall cycle emissions was
addressed by ensuring that, when the engine was equipped
with the EGRP and hig h-eciency turbocharger, the following
conditions were met compared to the stock engine: (1) the
engine exhaust throttle outlet temperature and exhaust mass
flow rate were maintained, ensuring adequate thermal
management; (2) the BSNOx and BSPM, for both congura-
tions in steady state, were either similar or lower for most
operating points, ensuring tailpipe emissions were no worse
than the baseline case. e NRTC was run twice for repeat-
ability. e normalized speed and torque of the NRTC are
shown in Figure 5.
Another cycle bas ed on real-life applicat ions is the LLAC. is
cycle was developed aer CARB requested that SwRI evaluate a
TABLE 2 John Deere’s 13.6 diesel engine specifications.
Performance data
Rated power 510kW (684 hp)
Rated speed 2100rpm
Peak torque 3050 Nm (2250 lb-ft) at 1550rpm
General data
Type 6-cylinder, in-line, 4-stroke, water-
cooled
Bore and stroke 132 × 165mm
Fuel system Electronic high-pressure common rail
(HPCR)
Aspiration Turbocharged, air-to-air aftercooled
Turbo Series (fixed, wastegate)
EGR External cooled exhaust gas
recirculation (EGR)
Emission level EPA final Tier 4/EU Stage V
Data take n from Ref. [17]. © S AE Inter nationa l
TABLE 3 Specification of instrumentation used in
experiments at Purdue.
Instrument
Measured
parameter Measurement range
AC dynamometer Speed 0–3000rpm
Torque 0–5000 Nm
Laminar flow
element
Air flow rate 0–2300 kg/h
K-type
thermocouple
Temperature −200–1260°C
Pressure transducer Pressure 0–5 bar/0–8 bar
Weighing balance Diesel consumption 36,300 g
John Deere NOx
sensor
NOx measurement 0–2000 ppm
AVL MSS 483 PM concentration 0–50 mg/m3
© SAE International
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400
FIGURE 2 Test cell schematic of the EGRP and high-eciency turbocharger configuration with sensor locations.
© SAE International
FIGURE 3 The normalized speed and torque for a crawler
tractor cycle and agricultural tractor cycle.
Adapted f rom Ref. [21]
FIGURE 4 An example of the constant speed–load
acceptance test specifically for the 1900rpm operating point.
© SAE International
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Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024 401
typica l low average load operation on engines , with aert reatment
systems, based on real-life scenarios [29]. With no cycle available
at the time, SwRI, in collaboration with John Deere, designed the
cycle based on 24 di erent application duty cycles [29]. e LLAC’s
average load of maximum power, at 15%, is considerably lower
compared to the NRTC at 35% [29]. Aer the LL AC wa s performed
on two separate eng ines, SwRI discovered that t he emission control
for NOx at lower loads was poor, resulting in more than three to
four times t he regulator y emission standard [29]. With thi s knowl-
edge, the LLAC was run on the 13.6L engine at Purdue with the
stock engine conguration and the EGRP and high-eciency
turbocharger engine conguration. is is not only to determine
if there was a f uel benet with the EGRP, but also if the B SNOx and
the exhaust throttle outlet temperature remained similar to the
baseline setup. Figure 6 shows the normalized speed and torque
for the LLAC.
Unlike the NRTC and LLAC, the RMC does not contain
drastic transient responses. e RMC is a continuous cycle
that star ts at idle and smoothly ramps to each required steady-
state operating point within a 20 s timeframe [24]. e steady-
state points in the RMC are intentionally arranged to alternate
between high and low torque to have consistent aertreatment
temperatures [24]. Tab le 4 lists the steady-state operating
points and transitions for the RMC.
Original engine manufacturers have the option to run
RMC, in contrast to steady-state discrete-mode tests, as a
method of steady-state certication within the U.S. EPA Tier
4 Emission Standard [30]. e RMC was run in this study to
evaluate the fuel savings with the EGRP conguration based
on a continuous cycle.
Literature Review
Several studies have examined the interaction between
advanced EGR systems and turbocharged diesel eng ines under
transient conditions. For example, Gu and Su [31] performed
a transient bench test on a two-stage turbocharged heav y-duty
diesel engine to optimize its performance during a load
increase from 20% to 100% in 1 s at a constant speed of
1200rpm. e results indicated that using a low-pressure EGR
system in the transient control scheme led to a 42.1% reduction
in peak soot emission, a 24.8% decrease in peak NOx emission,
a 9.14% reduction in indicated specic fuel consumption, and
a 30.6% increase in maximum IMEP achieved within 1 s,
FIGURE 5 Normalized speed and torque of the NRTC used
in Tier 4 and Stage IV regulatory testing to analyze fuel
eciency, BSNOx, and BSPM.
Data take n from Ref. [18]. © S AE Inter nationa l
FIGURE 6 Normalized speed and torque of the LLAC
developed by the Southwest Research Institute to analyze fuel
eciency, BSNOx, and BSPM for typical low load operations.
Data take n from Ref. [29]. © SAE I nternational
TABLE 4 The ramped modal cycle operating points.
RMC mode
number
Time in
mode
(s)
Engine speed
(%)
Engine brake
torque (%)
1a Steady-state 126 Idle 0
1b Transition 20 Linear transition Linear transition
2a Steady-state 159 Intermediate 100
2b Transition 20 Intermediate Linear transition
3a Steady-state 160 Intermediate 50
3b Transition 20 Intermediate Linear transition
4a Steady-state 162 Intermediate 75
4b Transition 20 Linear transition Linear transition
5a Steady-state 246 100% 100
5b Transition 20 100% Linear transition
6a Steady-state 164 100% 10
6b Transition 20 100% Linear transition
7a Steady-state 248 100% 75
7b Transition 20 100% Linear transition
8a Steady-state 247 100% 50
8b Transition 20 Linear transition Linear transition
9 Steady-state 128 Idle 0
Data take n from Ref. [18]. © S AE Inter nationa l
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402 Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024
compared to the steady-state optimization control scheme
without EGR [31].
Liu etal. [32] studied the impacts of dierent intervention
speeds and timings of an electric supercharger on the tra nsient
performance of a turbocharged diesel engine. To develop an
optimized control strategy, simulation was used to analyze
the combined impact of the electric supercharger and turbo-
charger. e optimized slope control strategy enhanced tran-
sient responsiveness and stability, reducing the intake pressure
rise time by 52.5% compared to the base engine and signi-
cantly minimizing f luctuations in intake pressure and
engine torque.
To evaluate the replacement of the EGR valve with a
turbine and quantify the potential benets of increased EGR
rates and improved brake specic fuel consumption (BSFC)
in a heavy-duty engine, a simulation-based assessment was
conducted by Serrano etal. [33]. e results, based on eight
engine running conditions, show that twin-turbocharging
with compressors in series and the EGR turbine discharging
after the first stage allows for approximately 5% higher
maximum EGR rates and up to 7% fuel savings compared to
a single-stage turbocharging layout.
Zhang etal. [34] conducted an experiment on a two-stage
series turbocharged heavy-duty diesel engine with a high-
pressure common rail. During the transient process, the speed
was maintained at 1650 rpm, and the load was linearly
increased from 10% to 100% within 5 s. e results showed
that the optimized EGR valve open-loop control strategy
signicantly improved air–fuel mixing quality and reduced
the smoke opacity peak by over 64%. With the EGR valve
closed-loop control strategy, the smoke opacity peak was lower
than with the open-loop control strategy but higher than
without EGR.
Gumus and Otkur [35] evaluated the feasibility of using
a high-eciency compact microchannel heat exchanger as an
EGR cooler to meet EURO 7 emission standards for heavy-
duty diesel engines. e implementation of the newly designed
microchannel heat exchanger resulted in a 6.75% reduction
in NOx emissions, an 11.30% reduction in PM emissions, and
a 0.65% decrease in specic fuel consumption at the analyzed
rated power operating point. ese results align well with the
goals for reducing NOx and PM emissions to meet Euro 7
diesel emission regulations.
With the increase in the stringency in emission regula-
tions, it is expedient to continue to study the performance of
new technologies during transient operations, commonly
experienced in actual driving conditions. Researchers have
investigated and published enhancements in BSFC, brake
specic nitrogen oxides (BSNOx), and brake specic carbon
dioxide (BSCO2) using Eaton’s electric EGRP in conjunction
with a high-efficiency turbocharger for on-road engines
[11, 36].
Johnson etal. [11] explored the advantages of integrating
a high-efficiency turbocharger with an electric EGRP to
optimize the air handling system. is combination improved
engine fuel eciency without increasing engine-out NOx
emissions. e study employed a variable geometry turbine
(VGT) turbocharger and focused on 13 modes of the SET cycle
in a steady state. e results, obtained from testing a 13L 2019
model year engine on a dynamometer, demonstrated the
potential for a 3.5% reduction in engine BSFC under highway
cruising conditions.
Bagal and Bhardwaj [10] examined the development and
performance of the EGRP, which enhances engine fuel e-
ciency without increasing engine-out NOx emissions. ey
utilized computational uid dynamics to optimize Eaton’s
EGRP design, leading to a reduction in the pump’s uid-borne
noise. is optimized design was then evaluated for fuel
benets using a calibrated GT-POWER engine model, repre-
senting a current production 13-L HD diesel engine. e
newly optimized engine architecture with an Eaton EGRP
demonstrated a maximum BSFC improvement of 6.2% at a
1500rpm full load operating condition and a 4.35% fuel
benet for the 13-mode ESC engine dyno cycle.
Bistis etal. [36] demonstrated an improved CO2 impact
by utilizing high-eciency turbochargers and an EGRP. ey
developed two high-eciency turbochargers to replace the
VGT turbocharger, along with an EGRP to drive the required
amounts of EGR. Both turbochargers are xed geometry
without a wastegate device and were designed to reduce CO2
emissions. e FTP and beverage transient cycles were consid-
ered in this test. However, for the FTP evaluation, the engine
required a slight derate due to the engine controller limiting
fuel. e rst high-eciency turbocharger achieved a 1.7%
reduction in CO2 while maintaining tailpipe NOx slightly
below 0.02 g/hp-h in the federal test procedure (FTP) cycle
and a 25.7% reduction in CO2 while NOx decreased from 0.014
g/hp-h to 0.013 g/hp-h. e second high-eciency turbo-
charger enabled a larger 3.6% reduction in CO2 while keeping
tailpipe NOx slightly below 0.015 g/hp-h for the FTP cycle and
a 27.6% reduction in CO2 while NOx increased from 0.014 g/
hp-h to 0.020 g/hp-h for the beverage cycle.
Although there are publications on the implementation
of the EGRP and high-eciency turbocharger for on-road
heavy-duty diesel engine cycles, there are no studies exploring
their application to o-road diesel engine cycles such as the
NRTC, LLAC, or RMC. While the FTP for heavy-duty vehicles
features a greater ma ximum load increase (from 0% to 78.5%)
compared to the NRTC (which increases from 0% to 44%),
the NRTC is more dynamic [25]. e FTP heavy-duty tran-
sient cycle has 11.9 load increases per minute, while the NRTC
has 23.1 [25]. Other heavy-duty drive cycles, such as the ETC
(18.9 load increases per minute) and the WHTC (16.3 load
increases per minute), still fall below the NRTC in terms of
load increase frequency [25]. e NRTC also has the highest
average normalized speed and average torque compared to
other legislated heavy-duty engine cycles [25].
Hence, this work contributes to existing literature by
investigating how the electric EGRP and high-efficiency
turbocharger perform under various transient drive cycles
that apply to o-road engines. It also seeks to demonstrate the
capabilities and shortcomings of the prototype EGRP and
high-eciency turbocharger across the drive cycles on a very
relevant o-road engine. For comparison purposes, the NRTC
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Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024 403
and LLAC cycles were modied to beless aggressive, aer the
EGRP and high-eciency turbocharger were found to have
transient response shortcomings. is helps to demonstrate
the benefits of EGRP and turbocharging amid transient
response challenges of the original NRTC and LLAC cycles.
In this work, hydrocarbon emission was not measured, as they
are not problematic in modern diesel engines.
Methodology
Design of Experiments
Before any testing with the EGRP and high-eciency turbo-
charger could commence, the ECU control logic had to
bedeveloped. e John Deere Team eectively developed
transient capable controls integrating the EGRP into existing
production model-based air and EGR controls. e EGR valve
position was set fully open during engine testing with the
EGRP and high-eciency turbocharger. A design of experi-
ments (DOEs) were conducted using these controls to optimi ze
fuel eciency at specic operating points, while maintaining
BSNOx to bewithin 25% of baseline values. Additional limits
included maintaining engine-out temperatures similar to
baseline va lues, staying below specic peak cylinder pressures,
and other design limit requirements.
e various DOE operating points, shown in Figure 7,
were tested in an open loop. e selected operating points
primarily consist of points within the NRTC. e operating
points were chosen for their eectiveness in developing models
that dene the design space and improve fuel eciency for
steady-state testing and the NRTC.
To address the concern of not incorporating a n aertreat-
ment system into the setup, measures were taken to ensure
that, when the engine was equipped with the EGRP and high-
eciency turbocharger, it performed comparably to the stock
engine. Specifically, the engine exhaust throttle outlet
temperature and exhaust mass ow rate were maintained at
levels similar to the stock engine, ensuring that the thermal
management of the aertreatment was not inferior to the
baseline case. Additionally, the engine-out BSNOx a nd BSPM
were found to beeither similar to or lower than those of the
stock engine, which, in conjunction with the previous
measure, indicated that the tailpipe emissions would not
beexpected to beworse than the baseline case.
e DOEs entailed constraining one parameter while
modifying another. For operating points below 712 Nm, the
EGRP speed and the exhaust throttle area were altered to
investigate the improvements in fuel economy while main-
taining similar exhaust throttle outlet temperatures as the
stock engine. For operating points above 712 Nm, the EGRP
speed and the BCS current were primarily constrained to
analyze the eects engine delta pressure and air-to-fuel ratio
have on BSFC improvement and brake thermal eciency. In
certain DOEs where higher cylinder temperature and pressure
were permissible, a third variable, main injection timing, was
introduced. Main injection timing was advanced in eorts to
enhance the combustion process and improve closed-cycle
eciency. e drawback to advancing the main timing is the
increase in NOx emissions. However, one advantage of the
EGRP is the ability to reduce NOx emissions by increasing the
EGRP speed, thereby increasing the EGR ow rate. e green
circles in Figure 7 represent where advanced main timing was
tested. e blue circles represent operating points where
advanced main timing improved fuel eciency while BSNOx
was maintained.
One of the challenges encountered in optimizing fuel
eciency at lower power operating points was the need to
maintain the exhaust throttle outlet temperature similar to
that of the stock engine, while ensuring that BSNOx measure-
ments remained within acceptable limits. At specic operating
points such as 1900rpm– 647 Nm and 2100rpm– 580 Nm,
the best fuel eciency was achieved by increasing the exhaust
throttle area and by increasing the EGRP speed. is combi-
nation eectively reduced engine delta pressure, thereby
enhancing open-cycle eciency. However, increasing the
exhaust throttle area led to two dierent trade-os: (1) the
exhaust throttle outlet temperature decreased and (2) higher
BSNOx. To maintain BSNOx levels and improve the exhaust
throttle outlet temperature, indexes with slightly more
restricted exhaust throttle areas were chosen as the
optimal points.
For the operating points above 1550rpm lying on the
torque curve, the best fuel eciency, disregarding the pump’s
power consumption, was observed at pump speeds ranging
from 7500rpm to 10,000rpm. ese high pump speeds eec-
tively reduced the engine delta pressure, resu lting in improved
open-cycle eciency. However, the higher EGRP speeds led
to increased power consumption by the pump. In real-life
applications, this pump power would beconnected to a 48V
bus on a vehicle, reducing the tota l output power of the engine
and resulting in a higher corrected BSFC.
Careful consideration was given to selecting the optimal
index to achieve the highest possible fuel eciency while still
maintai ning acceptable levels of BSNOx. In Zar Nigar Ahmad ’s
FIGURE 7 Operating points for the design of experiments.
© SAE International
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404 Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024
FIGURE 8 Actual pump speed of the best DOE operating points maintaining NOx levels, and improving fuel economy.
© SAE International
thesis [37] titled “Optimizing Fuel Economy and Emissions
for O-Road Diesel Engine Using Electric EGR Pump and
High Eciency Turbo,” and Ahmad etal. [38] “Impact of
O-Road Engine Electrication through EGR Pumping on
CO2, Soot, and NOx Emissions Reductions During Steady-
State Operating Conditions,” the control strategy used is
described in greater detail along with all of the parameters
analyzed determining the most optimal index.
Figures 8 and 9 display the pump speed and pump power
for the DOE-optimized points. e best index from each oper-
ating point in the DOEs was utilized in creating a calibration
map for steady-state testing and transient testing in closed
loop. e indices chosen for the calibration had engine-out
NOx and engine-out PM below 25% of the stock engine perfor-
mance, and engine-out temperatures similar to the stock
engine performance. Other engine limits—including peak
cylinder pressure, exhaust throttle outlet temperature—and
other design constraints were maintained.
For BSFC calculations, the electrical energy from the
EGRP was considered. When the pump was consuming power,
the corrected power was calculated using Equation 1. A 90%
electrical conversion eciency was used for the pump.
FIGURE 9 Pump power of the best DOE operating points maintaining NOx levels, and improving fuel economy.
© SAE International
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Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024 405
= −
corrected
Pump power
Power Engine power 0.9
Eq. (1)
In the case of power generation by the pump, Equation 2
was used.
( )
=−×
corrected
Power Engine power Pump power 0.9
Eq. (2)
The BSFC was determined by dividing the total fuel
consumed by the engi ne’s energ y output, as shown in E quation 3.
=
Fuel consumed g
BSFC
Energy kWh Eq. (3)
where
=
∫
end of cycle
corrected
start of cycle
1
Energy kWh Power
3600 s dt E q. (4)
In the stock conguration, the pump’s power consump-
tion was zero because the EGRP was not incorporated into
the setup. e cycle energy for the stock engine was deter-
mined by integrating the engine power.
A comprehensive analysis of steady-state results was
conducted by Zar Nigar Ahmad in her thesis [37], and also
explained in Ahmad etal. [38]. ese works provide a detailed
explanation on the steady-state DOE strategy used, the
resulting calibration map, and the steady-state characteriza-
tion of the engine, with the same EGRP and high-eciency
turbocharger. Hence, this article does not describe the
detailed eort to calibrate the engine operation. However,
the BSFC, BSNOx, and BSPM results from the steady-state
testing are presented in Figu res 10, 11, and 12, respectively.
Further information about this is discussed in-depth in the
work of Ahmad etal. [38].
Results
e initial optimized calibration map was slightly modied
for mid–high engine speeds at low engine loads to increase
the pressure ratio across the pump. is improved the motor’s
capability to maintain the commanded pump speed and
function accordingly. With these modications the NRTC,
LLAC, CSLA tests, and RMC were performed.
e NRTC and CSLA tests were each performed twice to
ensure consistency and repeatability since the NRTC is
utilized in the U.S. EPA Tier 4 regulations, and the CSLA is
crucial for determining time response. Repeatability was seen
among the NRTC and with the CSLA test for time response.
An additional measure was implemented to verify consistent
results. After each cycle, a repeat point was executed to
conrm that boundary conditions were maintained and to
ensure the reliability of the presented data.
FIGURE 10 Brake specific fuel consumption plot for steady state.
Reprin ted with pe rmission from Re f. [38]. © SAGE
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406
FIGURE 11 Brake specific nitrogen oxide plot for steady state.
Reprin ted with pe rmission from Re f. [38]. © SAGE
FIGURE 12 Brake specific particulate matter plot for steady state.
Reprin ted with pe rmission from Re f. [38]. © SAGE
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Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024 407
Using 12 repeat point data collected over a period of 2
weeks, the typical uncertainty values for key measured
parameters were calculated, and presented in Ta ble 5. is
follows the method described in the work of Starnes etal.
[39], with 95% confidence and ±2σ limits using the
t-distribution.
To compare the stock turbocharger to the high-eciency
turbocharger, using Equation 5, the eciency of both turbo-
chargers was calculated. e method explained in “CIMAC’s
‘Turbocharging Eciencies—Denitions and Guidelines for
Measurement and Calculation’” [40] was used. Figure 13
displays a segment of the high-pressure turbochargers’ e-
ciency for both congurations during the NRTC transient
test, showing performance across low to high speeds w ith high
torque. Since the goal of a turbocharger is to enhance engine
power, its eciency at operating points with high torque is
important. In this section, the eciency of the high-eciency
turbocharger (in red) is consistently higher than the
stock turbocharger.
γ
γ
γ
γ
η
−
−
−
=
−
a
a
exh
exh
i
1
Co
air p,air Ci
Ci
TC 1
To
exh p,exh T
Ti
1
1
P
mC T P
P
mC T P
Eq. (5)
where ṁair is the fresh air ow rate, ṁfuel is the fuel ow rate,
Cp,air is the specic heat constant of fresh air, Cp,exh is the
specic heat constant of exhaust gas, TCi is the low-pressure
compressor inlet temperature, TCo is the high-pressure
compressor outlet temperature, PTi is the high-pressure
turbine inlet pressure, PTo is the low-pressure turbine outlet
pressure, PCi is the low-pressure compressor inlet pressure,
PCo is the high-pressure compressor outlet pressure, ηTC is the
overall turbocharger eciency, γa is the specic heat of air,
γexh is the specic heat of exhaust gas.
Nonroad Transient Cycle
e hot NRTC was executed on both the stock engine and the
EGRP-equipped engine, but with the EGRP and high-e-
ciency turbocharger conguration not all of the desired torque
setpoints were achieved. e green segments represented in
Figure 14 highlight instances where the EGRP conguration
did not match the baseline engine load. To assess the dier-
ences among the reference cycle, the baseline NRTC, and the
EGRP NRTC, three distinct regions were magnied in Figure
14. As a result, not all the statistical criteria required to validate
the NRTC duty cycle under the U.S. EPA Tier 4 emission
standards were met.
TABLE 5 Uncertainty of key parameters at repeat point.
Measured parameters Uncertainty
Speed (rpm) ±0.11%
Torque (Nm) ±0.1%
Air flow rate (kg/h) ±0.5%
Diesel flow rate (kg/h) ±0.06%
Engine-out exhaust temperature (°C) ±0.34%
Nitric oxide (g/kWh) ±1.75%
PM ±6.95%
© SAE International
FIGURE 13 Comparison between the eciency of stock turbocharger and high-eciency turbocharger at high engine speed–
load section of NRTC.
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408 Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024
FIGURE 14 Comparison of engine load between the EGRP and high-eciency turbocharger engine vs. the baseline engine.
© SAE International
e EGRP-equipped engine’s inability to meet the refer-
ence torque values is due to insucient fresh airow. In Figure
15, regions where the engine fell short of reaching the refer-
ence torque setpoints are highlighted by orange circles. An
analysis between the commanded speed and the actual pump
speed was conducted. In Figure 15, the commanded pump
speed (blue) signies the speed requested by the ECU, while
the actual pump speed (red) reects the pump’s operational
speed. Orange arrows indicate the regions where the actual
pump speed exceeded the commanded pump speed. In this
gure, the actual pump speed decelerates at approximately
2000 r pm/s. is ramp rate is attributed to the motor controller
soware protecting the motor from electrical and mechanical
overstress. Unfortunately, this ramp rate permits more EGR
than intended, displacing the fresh air required to produce
torque. e baseline EGR valve position (magenta) is also
plotted in Figure 15. In regions indicated by the orange arrow,
the EGR valve is shut, blocking exhaust gas from entering the
intake manifold. Without EGR, the stock engine achieves
higher torque values compared to the engine equipped with
the EGRP and high-eciency turbocharger.
e total cycle work calculated from the NRTC baseline
was 64.8kWh. Factoring in the pump power, the cycle work
from the rst and second runs with the EGRP-equipped
engine was 62.3kWh and 62.4kWh, resulting in a 3.9% and
3.7% reduction in cycle work from the stock engine. Without
taking into account the pump power, the cycle work was
62.7kWh and 62.8kWh, accounting for a 3.2% and 3.1%
reduction in cycle work compared to the stock engine, as indi-
cated in Table 6.
e 3kW continuous power rating of the EGRP did
contribute to the loss of cycle work. e motor did not have
the power to retard the torque required to maintain the
commanded pump speed, so the pump dropped speed linearly
to safeguard the motor. e motor controller soware included
a ramp rate to protect the motor. Due to the lack of fresh
airow with the EGRP-equipped engine, the engine ECU was
hitting the smoke map limit, necessitating a reduction in
fueling. e smoke map limit is modeled within the ECU to
reduce fueling when there is insufficient fresh air f low,
ensuring there is no excessive soot generation. is led to a
reduction in cycle work.
To accurately evaluate the new technology, the measured
engine speed and measured engine torque from the engine
with the EGRP and high-eciency turbocharger were utilized
to develop a modied NRTC pattern to run on the stock
engine. is helps to ensure that there is a direct and fair
comparison between both congurations. Also, the electrical
energy of the electric motor in the EGRP is accounted for in
the fuel consumption calculations. With the EGRP and high-
efficiency turbocharger configuration, there was a 1.3%
improvement in BSFC and a 33.1% improvement in BSPM
compared to the modified NRTC on the stock engine.
However, there was a 12.9% increase in BSNOx. ese results
can beobserved in Table 7.
Improvements in BSFC may beattributed to the improve-
ment in open-cycle eciency. In Figure 16, the blue circles
represent all the collected operating points in the modied
NRTC at 5Hz sampling frequency. e light blue-shaded
regions highlight improvements in BSFC and brake thermal
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Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024 409
eciency due to an improvement in open-cycle eciency
determined in steady-state testing [37]. Although the engine
spends a considerable amount of time at near-idle and lighter
load conditions, as indicated in Fig ure 16, these are not loca-
tions where the EGRP technology was used to attempt to
improve fuel eciency. erefore, this study did not focus on
conditions at idle. e green-shaded region indicates where
open and closed-cycle eciency improved the brake thermal
eciency and BSFC. No operating points were within the
green-shaded region, suggesting that the BSFC improvement
is projected to come from improved open-cycle eciency.
Low Load Application Cycle
In the LLAC, the engine with the EGRP and high-eciency
turbocharger also undershoots torque set points due to insuf-
cient fresh airow.
e cycle work of the stock engine was 106.9kWh. For
the EGRP-equipped engine, the cycle work was 105.8kWh
without accounting for the pump power and 105.2kWh when
accounting for the pump power.
Although the percentage change of cycle work between
the stock engine and EGRP-equipped engine was below 2%,
to ensure fair comparisons between the EGRP-equipped
engine and the stock engine, a modied LLAC was developed.
Like the modied NRTC, the measured engine speed and
engine load from the LLAC with the EGRP and high-eciency
turbocharger were used to construct the modied LLAC. e
modied LLAC was run on the stock engine. e results from
the LLAC baseline, the LLAC with the EGRP and
FIGURE 15 Top: The comparison of engine load between the dierent configurations from 540 s to 650 s in the NRTC. Bottom:
The commanded and actual pump speed of the EGRP plotted with the baseline EGR valve from 540 s to 650 s in the NRTC.
© SAE International
TABLE 6 Results of the NRTC.
Classified run
Cycle work
g/kWh
BSFC
g/kWh
Engine-out
BSNOx
g/kWh
Engine-out
BSPM
g/kWh
NRTC baseline 64.8 214.8 4.86 0.0232
NRTC baseline 64.8 216.9 4.83 0.0283
NRTC EGRP +
HET
62.3* 212.6* 5.08* 0.0195*
NRTC EGRP +
HET
62.4* 213.3* 5.08* 0.0200*
Modified NRTC 63.0 216.1 4.50 0.0299
Modified NRTC 62.8 215.8 4.50 N /A
* Accounting for pump power
© SAE International
TABLE 7 Percentage dierence between modified NRTC
cycle on stock engine and the engine with high-eciency
turbocharger and EGRP.
NRTC EGRP
+ HET
Modified
NRTC
Percentage
dierence (%)
Drive shaft energy
(kWh)
62.8 63.0
Pump energy (kWh) 0.4 0
Output energy (kWh) 62.4*63.0
Fuel consumed (g) 13,321.6 13,616.6
BSFC (g/kWh) 213.3* 216.1 1.3%
BSNOx (g/kWh) 5.08* 4.50 12.9%
BSPM (g/kWh) 0.0200*0.0299 33.1%
Pump energy—Energy consumed by the pump
Drive shaft energy—Energy converted from the drive shaft
Output energy = Drive shaft energy– Pump power
* Accounting for pump power
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410 Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024
TABLE 8 LLAC results.
Classified
run
Cycle work
(kWh)
BSFC
(g/kWh)
Engine-out
BSNOx
(g/kWh)
Engine-out
BSPM
(g/kWh)
LLAC
baseline
106.9 236.8 6.54 0.0182
LLAC EGRP
+ HET
105.2* 230.5* 5.67*0.0255*
Modified
LLAC
105.4 236.5 6.38 0.0190
* Accounting for pump power
© SAE International
high-eciency turbocharger, and the modied LLAC on the
stock engine are shown in Tabl e 8.
Aer comparing the results of the modied LLAC on the
stock engine to the LLAC with the EGRP and high-eciency
turbocharger, a 2.5% improvement in BSFC and an 11.1%
improvement in BSNOx were observed. e BSPM increased
by 34.2%, as shown in Tab le 9.
Similar to the modied NRTC, operating points from the
modied LLAC are located within the area where enhanced
open-cycle eciency improved both BSFC and brake thermal
eciency, as depicted in Figure 17.
Given that the modied LLAC primarily operates at low
loads, the exhaust throttle outlet temperature was analyzed
for both congurations to ensure the exhaust throttle outlet
temperature was above 250°C for adequate thermal manage-
ment. Figure 18 shows the EGRP and high-eciency turbo-
charger remain above 250°C for the majority of the cycle.
In the modied LLAC stock conguration, a discernible
drop in exhaust throttle outlet temperature is observed in
regions where the torque is sustained below 220 Nm, including
1120 s to 1378 s, 3075 s to 3420 s, and from 3700 s to 4045 s.
During these intervals, the exhaust mass ow rate is higher
for the stock engine. is dierence in exhaust mass ow rate
is attributed to the exhaust throttle area being fully open on
the stock engi ne, but nearly closed with the EGR P conguration.
CSLA Test
e CSLA test was performed on six dierent operating points
listed in Ta ble 10 two separate times with both the stock and
EGRP congurations.
e engine equipped with the EGRP and high-eciency
turbocha rger demonstrated slower response ti mes to reach 90%
load compared to the stock engine during t he CSLA tests. Figure
19 provides a comparison of the average response time to 90%
load for both the baseline and EGRP conguration, revealing
disparities ranging from 0.1 s at 800rpm to 1.6 s at 1900rpm.
FIGURE 16 Improvement in BSFC for the NRTC can
beattributed to enhanced open-cycle eciency at lower
engine torques, shaded in light blue, identified from
steady-state testing.
© SAE International
FIGURE 17 Modified LLAC operating points lying within the
light blue-shaded region suggests improved
open-cycle eciency.
© SAE International
TABLE 9 Percentage dierence between modified LLAC
cycle on stock engine and the engine with high-eciency
turbocharger and EGRP.
LLAC EGRP
+ HET
Modified
LLAC
Percentage
dierence (%)
Drive shaft energy
(kWh)
105.8 105.4
Pump energy (kWh) 0.5 0
Output energy
(kWh)
105.2* 105.4
Fuel consumed (g) 24,256.2 24,923.2
BSFC (g/kWh) 230.5* 236.5 2.5%
BSNOx (g/kWh) 5.67* 6.38 11.1%
BSPM (g/kWh) 0.0255*0.0190 34.2%
Pump energy—Energy consumed by the pump
Drive shaft energy—Energy converted from the drive shaft
Output energy = Drive shaft energy– Pump power
* Accounting for pump power
© SAE International
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Figure 20 overlays both congurations at the point of the
throttle snap for the 1900rpm operating point. e dierence
in time response is evident by the EGRP-equipped engine load
(green) deviating from the baseline engine load (black).
During the transient response, the EGR valve on the stock
engine closes, preventing exhaust gases from entering the
intake manifold. However, with the EGRP conguration, the
actual pump speed decelerates at approximately 2000 rpm/s
during the transient response, leading to more exhaust gas
recirculation than intended. In the EGRP conguration, the
EGR valve remains fully open during the transient responses,
so the pump speed is the only way to reduce EGR ow. As a
result, the engine experiences a slower time response to reach
90% load. is pattern was consistent across all operating
points except the 800rpm operating point.
Fig ure 21 displays the average peak soot measurement for
both congurations. e EGRP conguration shows signi-
cantly lower peak soot measurements at operating points of
800 rpm, 1000 rpm, and 1200rpm compared to the baseline
conguration. is could bedue to the advancement in main
timing with the EGRP configuration, a more complete
combustion process with the additional time to reach load,
less fuel being injected at the start of the throttle snap, or a
combination of the different factors mentioned. For the
remaining 1550 rpm, 1900 rpm, and 2100rpm operating
points, the EGRP and high-eciency turbocharger setup
displayed higher peak soot measurements compared to the
baseline setup. e slower changes in EGRP speed during t ran-
sients caused higher soot emissions at elevated speeds, since
EGR ow was higher than desired, as indicated in Figure 20.
RMC
To stay below the advertised dynamometer limits, the RMC
cycle was modied from a maximum power of 510kW to
500kW. Tabl e 11 compares the RMC baseline results to the
RMC EGRP and high-eciency turbocharger results.
FIGURE 18 The exhaust throttle outlet temperature
primarily stays above 250°C for the EGRP-equipped engine.
© SAE International
TABLE 10 List of CSLA operating points executed in
this study.
CSLA operating points
800rpm– 2504 Nm
1000rpm– 2275 Nm
1200rpm– 2848 Nm
1550rpm– 3050 Nm
1900rpm– 2588 Nm
2100rpm– 2319 Nm
© SAE International
FIGURE 19 The average time response to 90% load for the
CSLA tests.
© SAE International
FIGURE 20 Comparison of the 1900rpm CSLA test
between the stock hardware configuration and the EGRP and
high-eciency turbocharger configuration.
© SAE International
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412 Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024
Overall, a 1.3% improvement in BSFC was observed with
the EGRP and high-eciency turbocharger. e increase in
BSNOx was merely 2.8% as can beseen in Table 12.
BSFC and engine-out BSNOx were calculated for the
operating points at intermediate speeds and rated speeds in
the RMC. e percentage change in BSFC and BSNOx between
the EGRP-equipped engine and the stock engine for the seven
dierent operating points is displayed in Figures 22 and 23.
e negative sign represents an improvement in BSFC and a
reduction in BSNOx. PM data was not collected during the
RMC test. However, since the RMC is a relatively slow tran-
sient representation of the steady-state operating points, the
steady-state data in Figure 12 provides a rough estimate of the
expected BSPM values for RMC.
ConclusionandFuture
Work
e primary focus of this study was to compare the fuel e-
ciency and engine-out emissions of the EGRP-equipped
engine with the stock engine for various drive cycles including
the NRTC, LLAC, and RMC and to evaluate the time response
to 90% load for the CSLA tests between both congurations.
is study specically demonstrates the shortcomings and
benets of the prototype EGRP, when paired with a high-
eciency turbocharger, in an o-road diesel engine.
During NRTC, LLAC, and CSLA testing with the EGRP
and high-eciency turbocharger conguration, the setup was
unable to produce the required torque due to shortcomings
of the EGRP. A modied version of the NRTC and LLAC was
developed and run on the stock engine to accurately compare
engine performance between the engine with the EGRP and
high-eciency turbocharger and the stock engine. For the
modied NRTC, a 1.3% improvement in BSFC was seen with
the EGRP and high-efficiency turbocharger hardware.
Whereas for the modied LLAC a 2.5% improvement in BSFC
was observed with the EGRP and high-eciency turbocharger
hardware. e RMC, requiring no modications because of
the EGRP, showed a 1.3% improvement in BSFC.
FIGURE 21 Average peak soot measurements for the
CSLA tests.
© SAE International
TABLE 11 RMC results.
Classified run
Cycle work
(kWh) BSFC (g/kWh)
Engine-out
BSNOx (g/
kWh)
RMC baseline 141.0 208.8 5.28
RMC EGRP+
HET
141.0* 206.1* 5.43*
* Accounting for pump power
© SAE International
TABLE 12 Percentage dierence between RMC cycle on stock
engine and the engine with high-eciency turbocharger
and EGRP.
RMC EGRP
+ HET RMC stock
Percentage
dierence (%)
Drive shaft energy
(kWh)
141.2 141.0
Pump energy (kWh) 0.2 0
Output energy (kWh) 141.0*141.0
Fuel consumed (g) 29,056.9 29,102.6
BSFC (g/kWh) 206.1* 208.8 1.3%
BSNOx (g/kWh) 5.43* 5.28 2.8%
Pump energy—Energy consumed by the pump
Drive shaft energy—Energy converted from the drive shaft
Output energy = Drive shaft energy– Pump power
* Accounting for pump power
© SAE International
FIGURE 22 Percent change in BSFC comparing the EGRP-
equipped engine with stock engine.
© SAE International
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Willoughby et al. / SAE Int. J. Commer. Veh. / Volume 17, Issue 4, 2024 413
Overall, the results of this study show that implementing
the EGRP and high-eciency turbocharger improves BSFC
at similar NOx levels. However, while the impact is meaning-
fully advantageous, it was limited by the EGRP design
constraints, which were EGRP speed and power. e require-
ment to deliver adequate airow in the cylinder was not met
due to excess EGR. Higher EGR ow results in lower airow.
is study does not focus on resolving this issue, but demon-
strates benets and limitations of the EGRP. Future eorts
should address this shortcoming.
Examining the fuel benets of the NRTC and LLAC with
a higher-power motor would provide valuable insights. With
a higher-power motor, the deceleration ramp rate would
beincreased, facilitating sucient fresh airow for the engine
to produce torque. Hence, it would beadvantageous to develop
an EGRP with a more powerful electric motor that is able to
accelerate and decelerate the EGRP more quickly. An alterna-
tive approach could include rening the control logic to have
the EGR valve vary positions with the EGRP and high-e-
ciency turbocharger hardware. is would restrict the amount
of exhaust gas recirculating back into the engine.
O-road engines are critical for everyday use in various
industries. Exploring innovative technologies to reduce emis-
sions and improve fuel economy helps economically and envi-
ronmentally. is study shows that the EGRP has the potential
to reduce emissions and improve fuel economy on o-road
diesel engines. However, to meet future emissions regulations
using the EGRP, the automotive industry must address
concerns such as the lack of fresh airow. is can beachieved
by designing an EGRP with a high-power motor or by modi-
fying the control strategy to adjust EGR valve positions with
the EGRP, ensuring the EGR valve is not completely open.
Once the shortcomings are addressed, the authors anticipate
fuel savings for the original regulatory drive cycles. Also,
future studies can focus on exploring the long-term durability
of EGR systems and turbochargers in o-road diesel engines.
Acknowledgements
e authors would like to express gratitude and appreciation to
the Herrick engineering tech nicians, Frank Lee and Jose Lopez
Romero, for their support and assistance. e authors also wish
to thank Lakshmi Prasad, Nathan ial Bergland, and Dav id Arntz
from John Deere, as well as Nam Do, Michael Ellinger, and Jim
Malone from Eaton, for their guidance and contributions.
ContactInformation
Gregory Shaver, corresponding author
gshaver@purdue.edu
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