NREL/CP-540-39010. Posted with permission. 

Presented at the SAE 2006 World Congress, 

April 3-6, 2006, Detroit, Michigan 2006-01-0424 

Tier 2 Useful Life (120,000 miles) Exhaust Emission Results for 

a NOx Adsorber and Diesel Particle Filter Equipped Light-Duty 

Diesel Vehicle 

Marek Tatur, Dean Tomazic 

FEV Engine Technology 

Matthew Thornton 

National Renewable Energy Laboratory 

John Orban, Elizabeth Slone 

Battelle Memorial Institute 

Copyright © 2006 SAE International

ABSTRACT 

Due to its high efficiency and superior durability, the 

diesel engine is again becoming a prime candidate for 

future light-duty vehicle applications within the United 

States. While in Europe the overall diesel share exceeds 

40%, the current diesel share in the United States is 1%. 

Despite the current situation and the very stringent Tier 

2 emission standards, efforts are being made to 

introduce the diesel engine back into the U.S. market. In 

order to succeed, these vehicles have to comply with 

emissions standards over a 120,000 miles distance 

while maintaining their excellent fuel economy. The 

availability of technologies—such as high-pressure, 

common-rail fuel systems; low-sulfur diesel fuel; oxides 

of nitrogen (NOx) adsorber catalysts or NACs; and diesel 

particle filters (DPFs)—allow the development of 

powertrain systems that have the potential to comply 

with the light-duty Tier 2 emission requirements. In 

support of this, the U.S. Department of Energy (DOE) 

teamed with industry to engage in several testing 

projects under the Advanced Petroleum Based Fuels – 

Diesel Emission Controls (APBF-DEC) activity [1; 2; 5; 

6; 7; 8]. Three of the APBF-DEC projects evaluated the 

sulfur tolerance and durability of NAC/DPF systems on 

various platforms, and one evaluated the performance 

and durability of a selective catalytic reduction (SCR) 

system in heavy-duty engines. A fifth project 

investigated the effects of oil properties on the 

performance and durability of a NAC. 

This project investigated the performance of the 

emission control system and system desulfurization 

effects on regulated and unregulated emissions in a 

light-duty diesel engine. Emissions measurements were 

conducted over the Federal Test Procedure (FTP), the 

US06 [an aggressive chassis dynamometer emissions 

test procedure, part of the Supplemental Federal Test 

Procedure (SFTP)], and the Highway Fuel Economy 

Test (HFET). Testing was conducted after the 

accumulation of 150 hours of engine operation 

calculated to be the equivalent of approximately 8,200 

miles. For these evaluations, three out of six of the FTP 

test cycles were within the 50,000-mile Tier 2 bin 5 

emission standards [0.05 g/mi NOx and 0.01 g/mi 

particulate matter (PM)]. Emissions over the SC03 (airconditioning test) portion of the SFTP were within limits 

of the 4,000-mile SFTP standards. Emissions of 

NOx+NMHC (non-methane hydrocarbons) exceeded the 

4,000-mile SFTP standards over the US06 portion of the 

SFTP. Testing was also conducted after the 

accumulation of 1,000 hours of engine operation 

calculated to be the equivalent of approximately 50,000 

miles. The results were reported in [7] 2005-01-1755. 

Recalibrated drivability maps resulted in more 

repeatable NOx emissions from cycle to cycle. The NOx

level was below the Tier 2 emission limits for 50,000 and 

120,000 miles. NMHC emissions were found at a level 

outside the limit for 120,000 miles. 

INTRODUCTION 

The NAC/DPF concept has shown promising results on 

a light-duty platform with a new, but degreened emission 

control system. The platform development process and 

the control strategies were already discussed as part of 

an SAE paper published 2004 and 2005 [1; 7]. Following 

this development phase, an aging process with a target 

of 2,200 hours was initiated. The 2,200 hours represent 

the useful lifetime of the emission control system 

(equivalent to 120,000 miles). Details regarding the 

aging procedure and the emission control systems are 

provided in following sections. 
The aging process was interrupted by evaluation cycles 

to monitor system performance. Cold and hot UDDS 

(Urban Dynamometer Driving Schedule - the first two 

bags of the FTP-75) simulations as well as US06 and 

HFET cycle simulations, were tested repeatedly 

throughout the aging process to gain statistical 

confidence in the emission results. In addition to the 

engine dynamometer test cell transient cycles, the 

emission control system was tested on the vehicle at the 

U.S. Environmental Protection Agency National Vehicle 

and Fuel Emissions Laboratory (EPA-NVFEL) in Ann 

Arbor, Michigan, over the FTP, US06, HFET, and SC03. 

PROGRAM OBJECTIVES 

The main objective of the APBF-DEC activity is to 

investigate the sulfur tolerance and durability of different 

aftertreatment systems such as the NAC/DPF 

combination. An additional project has been initiated 

under this activity to evaluate SCR technologies. 

An integral part of the program is to demonstrate the 

capability of a state-of-the-art engine and emission 

control system (ECS) combination to achieve the Tier 2 

Bin 5 emission levels. 

Figure 1 illustrates several different emission regulation 

limits, as well as the certification level for the base 

vehicle, along with the optimized engine-out emissions 

level for the project vehicle with the FEV prototype 

engine installed. With the improved engine-out 

calibration, the ECS requirements to achieve Tier 2 Bin 

5 levels correspond to 82% NOx conversion efficiency 

and 83% PM reduction. The ECS was aged up to 2,200 

hours with a fuel sulfur level of 15 ppm to allow an 

assessment of its impact on the durability of the 

systems. The detailed fuel specifications for this project 

are presented in Appendix A. PM [g mile] / 0.00

0.02

0.04

0.06

0.08

0.10

NOx [g/mile]

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

TIER 2

BIN 5 TIER 2

BIN 8

EU 4

EU 3

TIER 1

Audi A4 1.9 l TDI

Station Wagon

European 

Certification

Optimized engine-out 

emission calibration

Figure 1: Emissions Legislation and Initial Vehicle 

Results 

HARDWARE DEFINITION 

As the hardware definition was discussed in great detail 

in the preceding publications [1; 2; 7], the following 

chapters include the main specifications in tabular form. 

ENGINE HARDWARE 

The engine used in this project was designed to 

accommodate the increased demands of emission 

reduction development. The crankcase, crankshaft, and 

connecting rods are mass-production parts. The cylinder 

head and the pistons are proprietary components 

developed by FEV Engine Technology specifically for 

emission reduction applications. Table 1 shows relevant 

details of this engine configuration [1; 2; 7]. 

Table 1: Diesel Future II Engine Specifications 

Arrangement In-Line 4-Cylinder 

Displacement 1.9 L 

Rated Power 100 kW @ 4000 rpm 

Max. Torque 330 Nm @ 2000 rpm 

Bore/Stroke 79.5 mm / 95.5 mm 

Turbocharger Garrett GT 17 V 

Injection System Bosch Common Rail, 2nd Gen. 

Valves 2 x Intake / 2 x Exhaust 

Compression Ratio 18.2 : 1 

VEHICLE HARDWARE 

A model year 2001 Audi A4 Avant (station wagon) was 

selected as the project vehicle. This body style was 

readily available in the United States equipped with 

various gasoline engines. The OEM (original equipment 

manufacturer) engine was then removed and replaced 

with the Diesel Future II engine as described previously. 

Figure 2 shows a photograph of the project vehicle. 

Figure 2: Project Vehicle Audi A4 Avant 

More detailed vehicle data are listed in Table 2. 

Table 2: Project Vehicle Specifications 

Vehicle Mass 1540 kg 

Transmission 5-Speed Manual 

Total Length 4544 mm 

Total Height 1429 mm 

Total Width 1766 mm 

Air Drag Coefficient cD = 0.3 
EMISSION CONTROL SYSTEM SPECIFICATON 

The catalysts were designed and developed together 

with a MECA (Manufacturers of Emissions Controls 

Association) program participant. The catalyst system 

utilized an exhaust piping with dual wall insulation, which 

considerably decreased the thermal losses especially 

during cold-start and low-load operation. The dual wall 

insulating piping was also provided by a MECA program 

participant. 

Figure 3 illustrates the fully instrumented emission 

control system, which comprised a close-coupled precatalyst, underbody catalyst, and the DPF (arrangement 

described from left to right). 

Figure 3: Instrumented Emission Control System 

Table 3: Emission Control System Catalyst 

Specifications 

PreNAC 

t

UBNAC DPF 

Volume [l] 1.34 2.5 4.1 

Diameter [in] 4.16 5.66 5.66 

Length [in] 6.0 6.0 10.0 

Substrate 

Material 

[-] Cord Cord SiC 

Wall 

Thickness 

[mil] 4.5 4.5 14 

Cell Density [cpsi] 400 400 200 

TESTING AND AGING CYCLES 

ENGINE DYNAMOMETER TEST CELL AGING CYCLE 

This aging protocol was based on the simulated 

adaptation of the LA92 driving cycle, a higher speed and 

high-acceleration cycle, which is also referred to as the 

Unified Cycle. This cycle includes a high percentile of inuse driving conditions and is more aggressive than the 

FTP-75 with higher speed, higher acceleration, fewer 

stops, and less idle time. The second main goal was a 

10-minute cycle duration so that no single-speed load 

point was held for any extended period of time. The 

cycle was repeated until the accumulated time for the 

evaluation tests was reached. FEV proposed additional 

evaluation points during the aging procedure itself in 

order to allow continuous assessment of the catalyst 

performance. 

This driving cycle was transformed into 14 steady-state 

points that were operated consecutively for 43 seconds, 

each resulting in the desired 10-minute cycle. During the 

evaluation tests of this cycle, it became apparent that 

the temperature profile that the ECS was exposed to 

was much higher than during the driving cycle itself. 

Therefore, the points with temperatures above 450°C 

were moved towards higher engine speed and lower 

load to decrease the catalyst inlet temperature while 

maintaining the same fuel flow. Table 4 shows the 

resulting operating points that are used in the aging 

cycle. 

Table 4: Steady-State Aging Operating Points 

Point Engine Speed 

[rpm] 

BMEP

[bar] 

Effective 

Power [kW] 

1 1000 1.0 1.6 

2 1230 1.8 3.5 

3 1510 0.8 1.9 

4 1570 2.8 7.0 

5 1650 4.3 11.2 

6 2850 4.6 20.8 

7 2400 6.6 25.1 

8 3100 6.5 31.9 

9 3050 6.9 33.3 

10 3050 4.9 23.7 

11 2100 4.5 15.0 

12 2000 2.0 6.3 

13 1500 6.0 14.3 

14 1200 4.3 8.2 

Based on the effective power output of the engine and 

the vehicle specific data the respective calculated 

vehicle speed during each operating condition could be 

calculated from the following equation: 

gmfvAc

P v

Dair

Engine

⋅⋅+⋅⋅⋅⋅ = 2

2

1 ρ

 (1) 

As the residence time during each of the operating 

points was known as well as the time spent during the 

evaluation cycles, an accurate assessment of the overall 

distance could be calculated. With the aging time of 

2,200 hours the distance was approximately 120,000 

miles. 

VEHICLE CHASSIS DYNAMOMETER TEST CELL 

CYCLES 

During the evaluations on the vehicle chassis 

dynamometer, four cycles were tested: 

1. UDDS/LA4 (Bag 1 and Bag 2 of the FTP-75 Cycle) 

2. US06 

3. HFET 

4. SC03. 
Table 5 lists the details regarding length, average speed, 

and maximum speed for each cycle. 

Table 5: Test Cycle Details 

Cycle Length Average 

Speed 

Maximum 

Speed 

Remarks 

UDDS 12.07 km 

7.5 mi 

31.6 km/h 

19.6 mi/h 

91.8 km/h 

56.7 mi/h 

Urban driving 

US06 12.9 km 

8.01 mi 

77.9 km/h 

48.4 mi/h 

129.3 

km/h 

80.3 mi/h 

Aggressive 

high-speed 

driving 

HFET 16.52 km 

10.26 mi 

77.8 km/h 

48.3 mi/h 

96.4 km/h 

59.9 mi/h 

Highway driving, 

fuel economy 

SC03 5.8 km 

3.6 mi 

34.8 km/h 

21.6 mi/h 

88.2 km/h 

54.8 mi/h 

Additional load 

due to AC and 

high ambient 

temperature 

TEST ENVIRONMENT 

AGING AND EVALUATION TEST CELL 

The aging and evaluation test cell was equipped with the 

following equipment: 

 Horiba 7100 XGR for gaseous emissions 

 [NOx, hydrocarbon (HC), carbon monoxide 

(CO), carbon dioxide (CO2) and oxygen (O2)] 

 ADAPT 4.5 test cell controls 

 FEV CVS with tunnel 

 2 Horiba CFV with 330 cfm (provides ability to 

run 330 and 660 cfm tests) 

 Pierburg PS2000 particulate sampling system 

 UUT (Unit Under Test) transient cycle controller. 

VEHICLE CHASSIS DYNAMOMETER TEST CELL 

Vehicle testing was conducted at the EPA-NVFEL in 

Ann Arbor, Michigan. The vehicle was tested using a 

48"-diameter single-roll, electric chassis dynamometer. 

Table 6 contains a summary of the analytical systems 

used for the vehicle tests. 

Table 6: Summary of Laboratory Analytical Equipment 

Category Analytical Equipment 

CO/ CO2 Horiba AIA-210/220 NDIR

HC Horiba FIA-220 FID 

CH4 Horiba GFA-220 GC/FID 

THC Horiba FIA-220 HFID 

NOx Horiba CLA-220 HCLD 

PM EPA sampling system 

CVS Horiba VETS 9000 subsonic venturi 

TEST RESULTS 

ENGINE DYNAMOMETER TEST CELL 

During the course of aging, the catalyst system was 

evaluated frequently in order to assess its degradation in 

performance due to sulfur poisoning and thermal aging. 

The initial tests were performed at 0 hours with fresh 

catalysts. The subsequent test series were performed 

before and after the desulfurization events at 150 and 

300 hours of aging. After the 300-hour mark the 

desulfurization/evaluation cycle frequency was 

increased to every 100 hours up to 1600 hours of aging. 

Starting at 1,600 hours, desulfurizations and evaluations 

were performed every 50 hours. 

The average NOx emission results are displayed in 

Figure 5. Tier 2 Bin 5 useful life standards are included 

for reference and appear as a horizontal lines 

(intermediate and useful life standards). 

Cold- and hot-start UDDS (or LA4) cycles were 

performed at the aging marks depicted in Figure 5. Due 

to the steep increase in pre-desulfurization NOx, the 

desulfurization frequency was increased after the 1,600-

hour mark to every 50 hours. 

The composite FTP emissions, which comprised 43% 

cold-start emissions and 57% hot-start emissions, are 

illustrated in Figure 6. Note that some of the evaluations 

consisted only of replicate hot UDDS cycles. 

With the increased desulfurization frequency the 

composite FTP tailpipe NOx emissions post 

desulfurization after 2,200 hours could be maintained 

below the emission standard for 120,000 miles of 0.07 

g/mile. A detailed statistical analysis of NOx emissions 

results from the test cell is discussed in the 

‘STATISTICAL ANALYSIS’ chapter. 

The bars represent the average NOx numbers while the 

circles above and in the bars show the maximum and 

minimum numbers for the associated procedure. Figure 

4 shows an example of the setup of each emissions 

graph. Emission [g/mile] 0.000

0.025

0.050

0.075

0.100

0.125

0.150

0.175

0.200

0.225

0.250

0.275

0.300

0

100200300400500600700800900

1000

Emission species

Maximum number 

in test sequence Average number of 

corresponding procedure

Minimum number 

in test sequence

Pre-desulfurization

evaluation

Post-desulfurization

evaluation Aging time

Figure 4: Emissions graph setup 

Three average bars during one evaluation period 

indicate one additional evaluation procedure capturing 

unregulated emissions, not subject of discussion in this 

paper. 
During the evaluation procedure at 1,300 hours the NOx 

adsorber regeneration failed to operate, therefore the 

tailpipe emissions should not be considered in the 

efficiency processing. NOx [g/mi] 0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

110012001300140015001600170018001900200021002200

NOx

Aging Hours

NOx [g/mi] 0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0

100200300400500600700800900

1000

NOx

Cold UDDS

NOx [g/mi] 0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

110012001300140015001600170018001900200021002200

NOx

Aging Hours

No Regenerations

NOx [g/mi] 0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0

100200300400500600700800900

1000

NOx

Hot UDDS

Figure 5: Cold and Hot UDDS NOx Emissions 

FTP Composite NOx Emissions

0.00

0.05

0.10

0.15

0.20

0.25

0 250 500 750 1000 1250 1500 1750 2000 2250

Age (hours)

NOx (g/mi)

Figure 6: Composite FTP Emissions 

As illustrated by the data in Figure 7, the PM emissions 

were low through out most of the 2200 hours of aging of 

the ECS. There were two instances where the 

composite PM emissions were above the emission 

standard of 0.01 g/mi. These higher emission numbers 

were a result of a high-soluble organic fraction on the 

cold UDDS filters. After a DPF failure during the 1,000-

hour vehicle tests, the DPF was replaced, and the aging 

was continued. The performance of the new DPF 

remained at the high level as observed with the first 

DPF. 

The remaining UDDS-regulated emissions and fuel 

economy results, as well as the results for the US06 and 

HFET simulation cycles, are presented in Appendix B. 

FTP Composite PM Emissions

0.000

0.003

0.006

0.009

0.012

0.015

0 250 500 750 1000 1250 1500 1750 2000 2250

Age (hours)

PM (g/mi)

Figure 7: Composite PM Emissions 

VEHICLE CHASSIS DYNAMOMETER 

After 150, 1,000, and 2,200 hours (equivalent to roughly 

8,200, 50,000, and 120,000 odometer miles, 

respectively) of aging the ECS was installed on the 

project vehicle and tested at the EPA-NVFEL in Ann 

Arbor, Michigan. The matrix of tests performed on the 

chassis dynamometer is shown in Table 7. 

Table 7: Vehicle Emissions Test Matrix 

Day Test and Test Order Æ

1 CUDDS HUDDS HFET HFET US06 HUDDS 

2 CUDDS HUDDS HFET HFET US06 HUDDS 

3 CUDDS HUDDS HFET HFET US06 HUDDS 

4 CUDDS HUDDS HFET HFET US06 HUDDS 

5 CUDDS HUDDS SC03 SC03 SC03 HUDDS 

6 CUDDS HUDDS SC03 SC03 SC03 HUDDS 

Overall, engine dynamometer test cells were consistent 

with the vehicle chassis dynamometer results. 
For the 120,000-mile emission test, day 5 and 6 were 

omitted as the SFTP results for 120,000 miles were of 

lower priority for the project, furthermore useful life 

requirements over the SFTP do not exist. 

Figures 8 through 12 show the composite FTP results. 

The average result is represented by the bar height, and 

the minimum and maximum results are represented by 

the error bars. 

At the 150-hour test, the vehicle performance over the 

cold UDDS cycle resulted in highly variable NOx 

emissions. Consequently some effort was subsequently 

undertaken to improve the drivability of the vehicle on 

the chassis dynamometer; this resulted in more stable 

NOx emissions during the 1,000-hour evaluation. As a 

result of a DPF failure after the first day of testing, the 

PM numbers increased steadily throughout the test 

series. In order to assess the emission control 

performance for the remaining emissions the DPF was 

not replaced after the failure became apparent. NMHC 

as well as CO show an increase between 150 and 1,000 

hours of aging. The emission level for the 2,200-hour 

testing was found on a slightly higher level as during the 

1,000-hour testing. 

The composite test results show the NOx reduction 

potential for the developed concept. Throughout the 

aging it was possible to keep the NOx emissions on a 

level below the Tier 2 Bin 5 emission standard. The 

average of the FTP composite NOx emissions was found 

at 0.07 g/mi after 120,000 miles of aging. The THC 

emissions are the only species that exceed the emission 

standard of Tier 2 Bin 5 but remains below the Bin 8 

standard. 

FTP Composite Vehicle and Engine Dyno

NOx Observed Means and Ranges

0.00

0.07

0.14

0.21

0.28

0.35

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

EO 150 1000 2200

Engine Out NOx (g/mi)

0.00

0.07

0.14

0.21

0.28

0.35

Tailpipe NOx (g/mi)

Figure 8: Composite FTP NOx Emission Results 

FTP Composite Vehicle and Engine Dyno

THC Observed Means and Ranges

0.0

1.0

2.0

3.0

4.0

5.0

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

EO 150 1000 2200

Enigine Out THC (g/mi)

0.0

0.1

0.2

0.3

0.4

0.5

Tailpipe THC (g/mi)

Figure 9: Composite FTP THC Emission Results 

FTP Composite Vehicle and Engine Dyno

CO Observed Means and Ranges

0.0

2.0

4.0

6.0

8.0

10.0

12.0

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

EO 150 1000 2200

Engine Out CO (g/mi)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Tailpipe CO (g/mi)

 Figure 10: Composite FTP CO Emission Results 

FTP Composite Vehicle and Engine Dyno

Particulate Matter Observed Means and Ranges

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

EO 150 1000 2200

Engine Out PM (g/mi)

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

Tailpipe PM (g/mi)

Figure 11: Composite FTP Particulate Matter Emission 

Results
FTP Composite Vehicle and Engine Dyno

Fuel Economy Observed Means and Ranges

25

27

29

31

33

35

37

39

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

Engine

Dyno

Vehicle

Dyno 

EO 150 1000 2200

Engine Out FE (mi/gal)

25

27

29

31

33

35

37

39

Tailpipe FE (mi/gal)

Figure 12: Composite FTP Fuel Economy Results 

STATISTICAL ANALYSIS 

Statistical analyses were performed to characterize 

trends in emissions levels over the 2,200 hours of 

testing. Two sets of data were used in this analysis: (1) 

Data collected between 300 and 1,600 hours when 

desulfurizations were performed every 100 hours, and 

(2) data collected after 1,600 hours when 

desulfurizations were performed every 50 hours. The 

limited data collected prior to 300 hours, based on 150-

hour cycles, were not included in the trend analysis. To 

account for the evaluations consisting of only the hot 

UDDS cycles, an imputation method was developed to 

estimate the cold UDDS and resulting FTP composite 

NOx emissions results. The statistical analysis is based 

on a combination of imputed and actual FTP composite 

results. 

Figure 13 illustrates the degradation in catalyst 

performance between desulfurizations and the 

effectiveness of the desulfurization process at restoring 

performance. A log-linear model was fit to estimate 

average trends and evaluate statistical significance. The 

upper graph demonstrates that the average loss in NOx

reduction efficiency (FTP composite) between 

desulfurizations varies 15% to 35% prior to 1,600 hours. 

After the desulfurization strategy changed at 1,600 

hours, the loss in NOx reduction efficiency was generally 

10%. There was a slight drop between 1,800 and 2,000 

hours that could not be explained. 

The lower graph demonstrates that prior to 1600 hours 

there is an increase in average NOx reduction efficiency 

of 10% to 35% at each desulfurization event. After 

1,600 hours, there is on average a 10% improvement in 

NOx reduction efficiency at each desulfurization event, 

with a higher trend between 1,800 and 2,000 hours. 

Combined these graphs indicate that the performance of 

the desulfurization process was relatively unstable with 

the 100-hour desulfurization strategy, but was quite 

consistent with the 50-hour desulfurization strategy. 

Change in NOX Reduction Efficiency (% of Engine Out NOX) Between 

Desulfations

-80%

-70%

-60%

-50%

-40%

-30%

-20%

-10%

0%

10%

300 600 900 1200 1500 1800 2100

Age (hours)

NOX Reduction Efficiency

Difference Difference Trend

Increase in NOX Reduction Efficiency (% of Engine Out NOX) at Each 

Desulfation

0%

10%

20%

30%

40%

50%

60%

70%

300 600 900 1200 1500 1800 2100

Age (hours)

NOX Reduction Efficiency

Difference (Post-Pre) Difference Trend

Figure 13: NOx Reduction Efficiency Behavior over Time 

Figure 14 shows the trends in FTP composite NOx

reduction efficiency relative to engine-out emissions 

using two sets of data: Data collected between 300 and 

1,600 hours under the 100-hour aging cycle and data 

collected between 1,600 and 2,200 hours under the 50-

hour aging cycle. To account for the effects of the 

desulfurization process, separate log-linear models were 

fit to three subsets of NOx emissions data: (1) 

measurements made before a desulfurization event, (2) 

measurements made after a desulfurization event, and 

(3) the average of measurements made at the beginning 

(post-desulfurization) and end (pre-desulfurization) of 

each aging period. The latter results plotted at the 

midpoint of the aging period represent the best estimate 

of the average emissions over time; however, we could 

not verify that the increase in NOx emissions within an 

aging period is linear. 
0.00

0.06

0.12

0.18

0.24

0.30

300 600 900 1200 1500 1800 2100

Age (hours)

NOx (g/mi)

Pre-Desulf at ion Average Post -Desulf at ion

Pre-Desulf at ion Trend - Pre 1650 Average Trend - Pre 1650 Post -Desulf at ion Trend - Pre 1650

Pre-Desulf at ion Trend - Post 1650 Average Trend - Post 1650 Post -Desulf at ion Trend - Post 1650

0%

20%

40%

60%

80%

100%

300 600 900 1200 1500 1800 2100

Age (hours)

NOx Reduction Efficiency

Pre Desulf at ion Average Post Desulf at ion

Pre-Desulf at ion Trend - Pre 1650 Average Trend - Pre 1650 Post -Desulf at ion Trend - Pre 1650

Pre-Desulf at ion Trend - Post 1650 Average Trend - Post 1650 Post -Desulf at ion Trend - Post 1650

Figure 14: NOx Emission and Reduction Efficiency 

Trends over Time 

The trend in post-desulfurization emissions was not 

found to be statistically significant. However, the loglinear regression analyses demonstrated that there were 

statistically significant trends in both the average and 

pre-desulferization NOx emissions when the 

desulfurization strategy is based on 100-hour aging 

cycles. Because of the curvature in the trends, we 

performed additional analyses to determine if there were 

any persistent trends in the emissions results over time. 

This was accomplished by iteratively truncating the leftmost data from each of the three data sets, then refitting 

the regression model, and evaluating the significance of 

the regression slope parameter. Through this process, 

we determined that when the analysis is applied to data 

collected between 700 and 1600 hours, we cannot 

demonstrate that the average and pre-desulfurization 

trends were statistically significant. None of the 

regression lines shown in Figure 14, based on the 50-

hour desulfurization data, were found to have statistically 

significant trends. 

A similar analysis strategy was applied to the observed 

fuel efficiency and CO, PM, HC emissions results; 

however; because there were no statistically significant 

differences between pre- and post-desulfurization results 

for these parameters, there was no advantage to using 

the imputation method to characterize trends. Fuel 

efficiency trends were found to be statistically significant; 

however when the analysis is restricted to data collected 

after 400 hours, the trend is no longer significant. There 

were no observed trends in the pre- and postdesulfurization results for any of the observed 

emissions. 

CONCLUSION 

The developed integrated concept, which incorporates 

software and hardware solutions, shows considerable 

potential meeting future emission standards. Important 

aspects during the development were the modifications 

of the test engine and the engine-out emissions 

optimization. With the adjusted engine-out emissions 

level, the exhaust aftertreatment interventions were 

defined, developed, and refined. Due to the large portion 

of cold-start emissions, the rapid warm-up strategy, 

allowing fast catalyst light-off, was optimized. DPF and 

desulfurization regeneration strategies were developed 

focusing on catalyst lifetime durability and fuel 

consumption. 

The development of the concept was concluded by a 

useful lifetime aging process. As expected the tailpipe 

NOx emissions continuously increased. The 

desulfurization procedure reversed the sulfur poisoning 

to an extent that allowed meeting the emission 

standards throughout the aging duration. It was found 

that the desulfurization frequency needed to be 

increased throughout the useful life, while the first 250 

hours did not indicate significant sulfur poisoning, 

considerable emissions performance degradation was 

observed towards the end of the useful life aging 

process. The frequency of the desulfurization was 

increased and the tailpipe NOx emissions remained 

below the emissions standard after this procedure. 

There are remaining challenges that need to be 

addressed, such as the increase in HC emissions over 

catalyst life. 

ACKNOWLEDGMENTS 

The authors would like to thank the members of the 

APBF-DEC Steering Committee, the ABPF-DEC NOx

adsorber Workgroup, the National Renewable Energy 

Laboratory, Oak Ridge National Laboratory, EPA, and 

DOE for their support and guidance. This project and all 

of the ABPF-DEC activities are being conducted with the 

cooperation of engine and vehicle manufacturers, 

emission control device manufacturers, energy and 

additive companies, California State agencies, and the 

EPA. Representatives from all of these organizations 

and their member companies are represented on the 

steering committee and the workgroups. In particular, 

the authors thank Kevin Stork and Steve Goguen in the 

DOE FreedomCAR and Vehicle Technologies Program 

for their financial support of this activity. This project 

would not be possible without their help and technical 

support. 
REFERENCES 

1. Tomazic D., Tatur M., Thornton M. “Development of 

a Diesel Passenger Car Meeting Tier 2 Emissions 

Levels,” SAE Paper 2004-01-0581, March 2004, 

Detroit, Michigan. 

2. Tomazic D., Tatur M., Thornton M. “APBF-DEC NOx

Adsorber/DPF Project: Light-Duty Passenger Car 

Platform,” DEER Paper, August 2003, Newport, 

Rhode Island. 

3. Geckler S., Tomazic D., et al. “Development of a 

Desulfurization Strategy for a NOx Adsorber Catalyst 

System,” SAE Paper 2001-01-0510, March 2001, 

Detroit, Michigan. 

4. McDonald, J. “Progress in the Development of Tier 2 

Light-Duty Diesel Vehicles,” SAE Paper 2004-01-

1791, March 2004, Detroit, Michigan. 

5. Webb, C., et al. “Achieving Tier 2 Bin 5 Emission 

Levels With a Medium-Duty Diesel Pick-Up and a 

NoDx Adsorber, Diesel Particulate Filter Emissions 

System-Exhaust Gas Temperature Management” 

SAE Paper 2004-01-0584. 

6. Whitacre, S., et al. “Systems Approach to Meeting 

EPA 2010 Heavy-Duty Emission Standards Using a 

NoDx Adsorber Catalyst and Diesel Particle Filter on 

a 15l Engine” SAE Paper 2004-01-0587. 

7. Tatur M., Tyrer H., Tomazic D., Thornton M., 

McDonald, J. “Tier 2 Intermediate Useful Life 

(50,000 miles) and 4000 Mile Supplemental Federal 

Test Procedure (SFTP) Exhaust Emission Results 

for a NOx Adsorber and Diesel Particle Filter 

Equipped Light-Duty Diesel Vehicle,” SAE Paper 

2005-01-1755. 

8. Thornton M., Tatur M., Tyrer H., Tomazic D. “Full 

Useful Life (120,000 miles) Exhaust Emission 

Performance of a NOx Adsorber and Diesel Particle 

Filter Equipped Passenger Car and Medium-Duty 

Engine in Conjunction with Ultra Low Sulfur Fuel,” 

DEER 2005. 

CONTACT 

Marek Tatur, FEV Engine Technology, Senior Engineer 

Diesel Combustion Systems. E-Mail: tatur@fev-et.com

Matthew Thornton, National Renewable Energy 

Laboratory. E-Mail: matthew_thornton@nrel.gov

DEFINITIONS, ACRONYMS, ABBREVIATIONS 

APBF-DEC Advanced Petroleum-Based Fuels – 

Diesel Emissions Control 

BTDC: Before Top Dead Center 

CA: Crank Angle 

CO: Carbon Monoxide 

CO2: Carbon Dioxide 

DOE U.S. Department of Energy 

DPF: Diesel Particle Filter 

ECM: Electronic Control Module 

ECS: Emission Control System 

ECU: Engine Control Unit 

EGR: Exhaust Gas Recirculation 

EPA: Environmental Protection Agency 

ETK: Emulator Task Kopf 

FSN: Filter Smoke Number 

FTP Federal Test Procedure 

FTP-75: Light-Duty Federal Test Procedure 

HC Hydrocarbon 

HFET: Highway Fuel Economy Test 

HSDI: High-Speed Direct Injection 

LA-4: Bag 1 and Bag 2 of the FTP-75 Cycle 

MECA Manufacturers of Emissions Controls 

Association 

lpm: liters per minute 

NAC: NOx Adsorber Catalyst 

NMHC Non-Methane Hydrocarbon 

NO: Nitric Oxide 

NO2: Nitrogen Dioxide 

NOx: Oxides of Nitrogen 

O2 Oxygen 

OEM: Original Equipment Manufacturer 

PM: Particulate Matter 

RPM: Revolutions per Minute (engine speed) 

SC03: Air Conditioning Test 

SCR: Selective Catalytic Reduction 

THC: Total Hydrocarbon 

UDDS: Urban Dynamometer Driving Schedule 

US06: An aggressive chassis dynamometer 

emissions test procedure, part of the 

Supplemental FTP 

UUT Unit Under Test 
APPENDIX 

APPENDIX A: FUEL PROPERTIES 

The base fuel used in this study is an ultra-low sulfur (0.6-ppm) fuel with properties that are representative of diesel fuels 

used in the United States, except for its sulfur content. Table A-1 summarizes the properties of the fuel. To achieve higher 

sulfur levels, without otherwise impacting other fuel properties, a mixture of the sulfur containing compounds (listed in 

Table A-2) typically found in diesel fuel is doped into the base fuel. The dopant mixture contains a variety of classes of 

sulfur containing molecules that are in the same boiling range as diesel fuel, with an emphasis on thiophenes. Careful 

addition of this dopant mixture yields fuels containing 8- and 15-ppm sulfur for use in the catalyst aging experiments that 

follow this development activity. 

Table A-1: Test Fuel Properties 

Fuel Property ASTM 

Method 

Base Fuel BP15 

Density (kg/m3) D4052 826.2 837.1 

Viscosity @40oC (mm2/s) D445 2.3 2.5 

Distillation 

IBP (oC) D86 180 164 

10% recovery (oC) D86 203 201 

20% recovery (oC) D86 219 218 

30% recovery (oC) D86 233 233 

40% recovery (oC) D86 244 246 

50% recovery (oC) D86 251 259 

60% recovery (oC) D86 257 272 

70% recovery (oC) D86 265 286 

80% recovery (oC) D86 279 302 

90% recovery (oC) D86 312 322 

FBP (oC) D86 352 346 

Cloud point (oC) D2500 -26 -12 

Pour point (oC) D97 -23 -18 

Flash point, PMCC (oC) D93 69 64 

Sulfur (ppm) D5453 0.6 13.3 

Aromatics (vol. %) D1319 23.9 29 

Olefins (vol. %) D1319 4.6 

Saturates (vol. %) D1319 71.4 

Aromatics (vol. %) D5186 26.9 25 

Polyaromatics (vol. %) D5186 8.4 4.2 

Non-aromatics (vol. %) D5186 64.7 70.8 

Cetane number D613 42.5 51.1 

Cetane index D976 51.5 48.8 

Table A-2: Properties of Sulfur Doping Compounds 

Concentration 

(mass %) 

Compound Chemical Formula Boiling Point 

(

o

C) 

50 Dibenzo[b,d]thiophene C12H8S 333 

30 Benzo[b]thiophene C8H6S 222 

10 Di-t-butyl disulfide C8H18S2 200 

10 Ethyl phenyl sulfide CH10S 206 
APPENDIX B: TEST CELL EMISSION RESULTS 

NOx Emissions

0.000.150.300.450.600.75

0 250 500 750 1000 1250 1500 1750 

Age (hours)

NOx (g/mi)

Cold UDDS Hot UDDS US 06 HFET

PM Emissions

0.0000.0050.0100.0150.0200.025

0 250 500 750 1000 1250 1500 1750 

Age (hours)

PM (g/mi)

Cold UDDS US 06 HFET Hot UDDS
HC Emissions

0.000.130.260.390.520.65

0 250 500 750 1000 1250 1500 1750 

Age (hours)

HC (g/mi)

Cold UDDS Hot UDDS US 06 HFET

FTP Composite HC Emissions

0.00.10.20.30.40.5

0 250 500 750 1000 1250 1500 1750 

Age (hours)

HC (g/mi)
CO Emissions

0.01.22.43.64.86.0

0 250 500 750 1000 1250 1500 1750 

Age (hours)

CO (g/mi)

Cold UDDS Hot UDDS US 06 HFET

FTP Composite CO Emissions

0.00.51.01.52.02.5

0 250 500 750 1000 1250 1500 1750 

Age (hours)

CO (g/mi)
Fuel Economy

203040506070

0 250 500 750 1000 1250 1500 1750 

Age (hours)

FE (mi/gal)

Cold LA4 (D15) Hot LA4 (D15) US 06 (D15) HWFET (D15)

FTP Composite Fuel Economy

283032343638

0 250 500 750 1000 1250 1500 1750 

Age (hours)

FE (mi/gal)