Overview:

In the past decade the development of advanced electronically controlled heavy duty diesel engines

has led to significant improvements in performance, fuel economy and longevity. The flexibility and

sophistication of these engine control programs has made it possible to significantly alter the engine

calibration based on a range of operating conditions. The ability to dynamically switch between a

certification mode to an off FTP mode forms the basis of the recent EPA consent decree settlement. In

response to this agreement, engine manufacturers have agreed to develop low NOx Rebuild Kits including

electronic calibration programs. These recalibration programs can effectively reduce the emission rate and

limit the impact of the off cycle operation.

The advances in diesel technology are not limited to electronic controls alone. The use of advanced

materials and manufacturing has further extended the useful service life well beyond a million miles for many

applications. In the absence of exhaust after treatment, the deterioration factor for engine out emissions

remains low when compared to light duty gasoline powered vehicles. The combined impact of these

technological improvements on the mobile source emission inventory is not well understood.

In effort to characterize the deterioration factor of HDDs and explore the effectiveness of restorative

maintenance including Low NOx engine control programs, the California Air Resources Board established

Measure 17 (M17). The purpose of M17 is to evaluate the viability of chassis dynamometer HDD I/M program

to supplement existing I/M efforts. The program goal is to reduce NOx emissions by 10 tons per day and ROG

emissions by 1 ton per day within the Southern California Air Basin by 2010.

The results from the initial phase of testing of 100+ HDD trucks suggest the NOx emission rates are

higher than the certification values and the dispersion of the population has increased in recent years, Figure

1. The initial information suggests the reduction potential for mechanical repairs alone is approximately 4% at

a repair threshold of 10 gram/wheel horsepower-hour. Progressively lower reductions are achieved when the

repair threshold is decreased. In some instances the mechanical repairs have resulted in an increase of NOx

emissions, Figure 2.

A subset of these test vehicles were subjected to both mechanical repair and Low NOx

reprogramming. The results indicate that a 24% reduction in NOx emissions on average can be achieved with

only modest reduction in fuel economy for most trucks. The average cost of the repair and reprogramming is

$753 per truck with a cost benefit of $0.68/ lb of NOx reduced.

CARB Stockton HDD Test Facilities:

• Superflow Model 602 tandem roll 36” hydrokinetic dynamometer

• California Analytical Instruments emissions bench measuring raw exhaust

• Total flow is determined using a Superflow Air Turbine attached to the intake.

Evaluation of the Effectiveness of Low NOx ECM Reprogramming to

In Service Heavy-Duty Vehicles

Matthew R. Smith, Ted Younglove and Wayne Miller – UC Riverside CE-CERT

Donald Chernich, Robert Ianni, Tullie Flower, Mark Burnitzki, Mike Bernard and Roelof Riemersma – CARB

Program Sponsor: California Air Resources Board

www.cert.ucr.edu

Figure 3. Typical Stockton HDD Lab Power Curve

Typical Test Profile

0

50

100

150

200

250

300

350

1 8 15

22

29

36

43

50

57

64

71

78

85

92

99

106

113

120

127

134

141

148

155

162

169

Time in Seconds

Co

rre

cte

d V

ehic

le H

p

-

2

4

6

8

10

12

14

16

18

20

NO

x (

g/w

hp

-hr)

CV Hp

Measured NOx

Ramp Lug down

100 hp line

Analysis Region

Model Year

2000

1998

1996

1994

1992

1990

1988

1986

1984

1982

1980

NO

X (g

/whe

el-h

orse

pow

er-h

r)

14

12

10

8

6

4

2

Mfr

6.00

5.00

4.00

3.00

2.00

1.00

Model Year

2000

1998

1996

1994

1992

1990

1988

1986

1984

1982

1980

NO

X (g

/whe

el-h

orse

pow

er-h

r)

14

12

10

8

6

4

2

Mfr

6.00

5.00

4.00

3.00

2.00

1.00

NOx Standards (g/bhp-hr)

Figure 1. M17 NOx Emission Rates for HDD Trucks Tested at Stockton Lab

2

4

6

8

10

12

14

16

NO

x (g

/wh

p-h

r) P

re a

nd

Po

st

0284

0529

0757

1388

1429

3622

3990

4635

5594

5756

6184

7182

8165

8866

9051

9707

VEH_SER_NO

(2) Post-repair

(1) Pre-repair

Figure 2. M17 NOx Reductions for Mechanical Repair Only

Test Cycle Development:

• Candidate cycles must provide sufficient dynamic load to accurately characterize the vehicle emission behavior.

• Cycle length should be minimized to reduce overall vehicle downtime and maximize vehicle throughput.

• Test must be repeatable for a broad range of vehicles.

• Replicate testing is required to provide a solid foundation for inventory and enforcement purposes.

• Combine two separate cycles, a power curve and a series steady state sampling modes.

Test Methodology:

Power curve Test -

• Vehicle is tested in direct drive, engine operating at the governed maximum rpm.

• Load is gradually applied while the engine RPM remains essentially constant until the peak power is reached.

• Lug down occurs as engine RPM drops and torque rises to Lug point usually between 1100 and 1400 rpm.

• The load is then removed at the conclusion of each test.

• Repeat sequence three replicate tests are obtained.

Steady States Test -

• Steady state test replicate freeway driving under three load conditions, 25, 50 and 75% of peak power.

• The vehicle is operated at 60 mph in direct gear for a period of 3-5 minutes at each load point.

• Duration is sufficient in many cases to capture engine switching to an off FTP control strategy.

11.22

3.09

0

20

40

60

80

100

120

140

160

180

200

500

520

540

560

580

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660

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940

960

980

1000

Test Duration Seconds

CV

Hp

0123456789101112131415

CV Hp

NOx g/whp-hr

Figure 4. Off FTP Switching During Steady State Operations

Nox (g

/whp-h

r)

Data Reduction and Analysis:

• Compare incremental ramp and lug down segments on a range of low, medium and high horsepower trucks.

• Combine those regions with the lowest test to test variability.

• Analysis region is between 100 hp and extends to the power peak.

• Analysis of mass emission rates in terms of g/mile, g/gallon and g/whp-hr.

• Least variability found in g/whp-hr.

• Primary standard in terms of “brake” horsepower hour however wheel horsepower is measured directly.

• Dynamometer is a power absorber only – no way to determine the drive train losses by motoring.

Processing the Data

• Test data analyzed using a binned integrated modal approach in terms of g/wheel horsepower hour.

• Values are higher than the certification, due to transmission and driveline losses – 15%-25%.

• Replicate sequence of 3-4 power curve tests are collected for each vehicle.

• Individual and triplicate tests are validated using a comprehensive quality assurance algorithm.

• QA for CO, CO2, THC, NOx and fuel economy.

• Acceptance criteria requires the integrated coefficient of variation, (COV =stdev/Average) <5%

Steady State vs Triplicate Comparision

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

100 125 150 175 200 225 250 275 300 325

CV HP

NO

x (g

/wh

p-h

r)

939

940

941

Steady State

Figure 5. Replicate Power Curve Test Repeatability

Binned Modal Data

100

125

150

175

200

225

250

275

300

325

350

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

113

Elapsed Time (seconds)

Co

rrec

ted

Veh

icle

HP

0

2

4

6

8

10

12

14

16

18

NO

x (g

/wh

p-h

r)

CV HP

Binned CV Hp

Measured NOx

Binned Nox

CV HPNOx

(g/whp-hr)Binned CV HP

NOx (g/whp-hr)

216 12.3 215 12.3219 12.3 220 12.2223 12.0225 12.0 225 12.0229 11.8231 11.6 230 11.7233 11.5236 11.4 235 11.4239 11.2 240 11.2242 11.1244 11.1246 10.9 245 11.0249 10.8 250 10.7254 10.7 255 10.7257 10.6259 10.6261 10.6 260 10.6264 10.5266 10.4 265 10.4269 10.3 270 10.3273 10.1276 10.1 275 10.1

Cycle ProcessedData Points 87 43

Average Mass Emission Rate 12.4 g/whp-hr

Figure 6. Binned Power Curve Test Data

Test, Repair and Reprogram Results:

• 5 candidate vehicles were tested, (4) power curve and (1) steady state test.

• All vehicles were subjected to basic tune up, injector flush, check injection timing set factory settings

and minor equipment repair, cost $200-$1031/truck, average $752/truck.

• All vehicles were reprogrammed using OEM updated Low NOx calibration.

• Trucks were retested using a similar sequence to baseline.

• Emission reduction for NOx ranges from 5% - 40%, average 24% reduction.

• Comparable mechanical repairs alone result in a 4% reduction at 10 g/whp-hr and $935/truck.

• Cost effective alternative to more expensive repairs at $1,354/ton of NOx.

• Comparable mechanical repairs alone result in a $6,940/ton of NOx.

Conclusion:

The improvements in diesel technology have increased the useful service life of HDD trucks beyond 1M

miles in many applications. These advancements in durability and electronic engine calibration will

have a significant impact on the emission inventory for many years. The costs of alternative emission

reduction strategies, scrappage, after treatment, engine repower and mechanical repair are significant.

Updating engine control programming represents a quick and cost effective alternative emission

reduction strategy which can be applied to current and future generations of HDD trucks.

CO CO2 THC

(g

/wh

p-h

r)

(gra

m/g

al)

(g

ram

/mi)

(g

/wh

p-h

r)

(g

/wh

p-h

r)

(g

/wh

p-h

r)

Fuel Economy

(mpg)

Test Vehicle M 1 1998 Sn 6565Pre Repair 4.7 71.4 19.5 0.76 739.2 0.18 3.7 Lbs Nox at 100K 523 Post Repair 3.8 62.0 17.1 0.73 718.9 0.21 3.6 Cost / ton 765$ % Reduction -20% -13% -12% -5% -3% 21% -1% Cost / lb 0.38$

Test Vehicle M 3 1995 Sn 7649Pre Repair 13.7 192.8 50.8 0.84 788.8 0.07 3.8 Lbs Nox at 100K 2,872 Post Repair 9.7 136.9 37.7 0.68 780.1 0.08 3.6 Cost / ton 579$ % Reduction -29% -29% -26% -19% -1% 11% -5% Cost / lb 0.29$

Test Vehicle M 4 1996 Sn 8592Pre Repair 12.3 262.6 45.1 0.09 503.8 0.07 5.8 Lbs Nox at 100K 524 Post Repair 11.7 262.2 42.7 0.10 485.5 0.05 6.1 Cost / ton 3,597$ % Reduction -5% 0% -5% 11% -4% -22% 5% Cost / lb 1.80$

Test Vehicle M 4 1997 Sn 7982Pre Repair 11.6 223.0 41.4 0.18 562.6 0.15 8.5 Lbs Nox at 100K 1,444 Post Repair 9.3 198.6 34.9 0.14 513.1 0.09 5.7 Cost / ton 1,429$ % Reduction -19% -11% -16% -21% -9% -38% -33% Cost / lb 0.71$

Test Vehicle M 3 1998 Sn 0284 Pre Repair 14.1 230.5 51.7 0.31 629.8 0.06 4.5 Lbs Nox at 100K 3,775 Post Repair 8.4 151.0 34.5 0.32 626.8 0.05 4.4 Cost / ton 402$ % Reduction -40% -35% -33% 2% 0% -16% -2% Cost / lb 0.20$

All VehiclesAverage Pre 11.3 196.1 41.7 0.44 644.8 0.10 5.3 Lbs Nox at 100K 1,828 Average Post 8.6 162.1 33.4 0.40 624.9 0.10 4.7 Cost / ton 1,354$ % Reduction -24% -17% -20% -10% -3% -7% -11% Cost / lb 0.68$

Emission Reduction

NOx

Figure 7. Reprogramming Test Matrix and Results

M4 7982

14.5 g/whp-hr @ 80 hp

12.7 g/whp-hr @ 160 hp

11.1 g/whp-hr @ 230 hp

11.9 g/whp-hr @ 80 hp

10.1 g/whp-hr @ 160 hp

8.6 g/whp-hr @ 230 hp

6

7

8

9

10

11

12

13

14

15

16

0 20 40 60 80 100 120

NOx

(g/w

hp-h

r)

Pre Reflash

Lo NOx Reflash

18% Reduction

20% Reduction

23% Reduction

Figure 8. Pre and Post Steady State NOx Emissions

Seconds