Evaluation of the Heavy-Duty In-Use Testing (HDIUT) Program:

Not-to Exceed (NTE) vs. Work-Average Window (WAW) Concepts

In-Use Testing Workgroup Meeting

February 22, 2017

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Outline

• Rulemaking Timeline• Purpose of the Workgroups• Current Heavy-Duty In-Use Testing (HDIUT) Program

(NTE Method)– Requirements– Program Effectiveness

• NTE Modification Data Analysis• European WAW Method• WAW Modification Data Analysis• Related Research• Open Discussion/Questions• Action Items/Next Steps

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Heavy-Duty Truck Rulemakings

Scheduled Board Dates

Rulemaking Scheduled

Board Hearing Date

Revisions to Periodic Smoke Inspection Program

September 2017

California Phase 2 GHG Standards October 2017

Revisions to the Warranty Period and Recall Authority Requirements

December 2017

New HD Engines: - Low NOx Standard and Test Procedures - Revised HDIUT Program - Revised Durability/Useful Life

2019

Heavy-duty Inspection and Maintenance 2020

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Purpose of Workgroups

• Provide stakeholders the opportunity toprovide suggestions and comments

• Answer questions that CARB has during therulemaking process

• Data and idea exchange between CARB staffand stakeholders during the rulemakingprocess

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Purpose of the In-Use Testing

Workgroup

• Objective: Develop in-use requirements to ensure thecertified NOx reductions are enforced in real-worldoperation

• Considerations:– Update HDIUT program– Analyze/compare NTE and European WAW methods– Potential NTE modifications: event duration, control

area/definition of region, temperature exclusions– Determine recommended method, new agency in-use

compliance method– PEMS measurement accuracy– Alternative emissions metrics– Pass/Fail protocol

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Current HDIUT Program

• HDIUT program adopted in 2005 by U.S. EPA and in2006 by CARB

• In-use testing helps assure that engines meetapplicable emission standards throughout their usefullife

• CARB and U.S. EPA jointly select engine families to betested (25%/year, 4-yr rolling average)

• Manufacturers recruit fleets, conduct testing usingPortable Emissions Measurement Systems (PEMS)

• Test data and results submitted to CARB and U.S. EPA

• Data is analyzed under the NTE requirements

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Number of Vehicles to Test Per Engine

Family under HDIUT Program

• Phase 1 Testing:– 5 vehicles – If all pass, then testing complete– If 1 vehicle fails, then one more tested. If it passes, then

testing complete.– If only 4 of 6 vehicles pass, then test 4 more vehicles, for a

total of 10 vehicles. If 8 of 10 vehicles pass, then testingcomplete.

• Phase 2 Testing:– If fewer than 8 of 10 vehicles pass in Phase 1, Phase 2 may

be required. 10 more vehicles need to be tested.– CARB/U.S. EPA control how vehicles are tested

• Information can be found in 40 CFR 86.1915

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Determining Pass/Fail of a Test

• Under NTE, 1-Hz emission data is gatheredwith PEMS over 1 shift day of driving

• Data points evaluated to determine NTEevents according to set criteria (next slide)

• Emissions evaluated for each NTE event; eventemissions compared to NTE threshold todetermine whether event passes or fails

• Test is considered passing if time in all passingevents over total time in all events is > 0.90

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1. Inside NTE control area• > 30% max power• > 30% max torque• > 15% European Stationary Cycle

speed (rpm)

2. Temperature conditions• > 250oC (for SCR aftertreatment)• Meet minimum intake

manifold/engine coolanttemperatures

3. At least 30 consecutiveseconds meeting abovecriteria

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Current Criteria for Valid NTE Events

Points excluded by reason:

Emissions value: work-specific average of 1 Hz data within each NTE event

HDIUT Program So Far

• Data from 565 tests show:– Average data in NTE events included:

• Mean: 5.4%

• Median: 3.2%

• 105 tests with 0 NTE events

– Average duration of tests (mean): 8.9 hours

– 12 tests failed (6 prompted one more test for itsrespective family, all of which passed)

– Most tests passed with Pass Ratio of 1.0

– Only one manufacture has initiated a recall

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• Potential changes to NTE to reduce dataexclusion and increase data evaluated

– Expand NTE control area

• Reduce minimum torque

• Reduce minimum power

– Lower aftertreatment-out temperature minimum

– Reduce minimum duration of NTE event

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Under Current Program Most Data

Excluded from Emissions Evaluation

• 3 sets of data chosen from HDIUT program– HDIUT data tends to be more over-the-road rather than

vocational

• Data were from passing tests• Data verified to consist of a valid test under the work-

average window method (for next set of analyses)• Data evaluated under 4 variations of NTE:

A. Current (base) B. Min NTE event duration reduced from 30 to 10 sec C. Min torque and power both set to 10% of max, aftertreatment temperature requirement removed D. Both B and C modifications applied

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Data Chosen for Analysis

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

NO

x Em

issi

on

s (g

/bh

p-h

r)

2 Events 28 sec

1 Event 39 sec

13 Events 253 sec

Effect of Modifying NTE Criteria,

Example 1 (HDIUT Data)

Pass Ratio: NTE Time (sec): Events: Med. Event Time:

Test Details: Total Duration: 44774 sec Total Non-idle: 30455 sec Vehicle: Delivery Engine year: 2010 Month of test: FebruaryOverall: 0.18 g/bhp-hr

0.75* g/bhp-hr Threshold

0.20 g/bhp-hr

Base 1.0 4837 (10.8%) 71 53 sec

10 sec 0.99674 8405 (18.8%) 292 18 sec

10%T/P,Temp 0.9967 11972 (26.7%) 167 50 sec

10%T/P,Temp,10sec 0.9843 16101 (40.0%) 411 24 sec

*FEL: 0.33 g/ bhp-hr13

0

0.5

1

1.5

2

2.5

NO

x Em

issi

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s (g

/bh

p-h

r)

10%P/T,Temp 0.9907 9816 (30.0%) 79 68 sec

10%P/T,Temp,10sec 0.9868 11438 (35.0%) 174 26 sec

Effect of Modifying NTE Criteria,

Example 2 (HDIUT Data)

Pass Ratio: NTE Time (sec): Events: Med. Event Time:

Test Details: Total Duration: 32722 sec Total Non-idle: 17735 sec Vehicle: Tractor Engine year: 2011 Month of test: MayOverall: 0.35 g/bhp-hr

0.65 g/bhp-hr Threshold

0.20 g/bhp-hr

1 Event 87 sec

Base 0.9813 4640 (14.2%) 55 56 sec

10 sec 0.9831 6160 (18.8%) 152 19 sec

2 Events 104 sec

1 Event 87 sec

5 Events 145 sec

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Effect of Modifying NTE Criteria,

Example 3 (HDIUT Data)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

NO

x Em

issi

on

s (g

/bh

p-h

r)

Base 0.9124 5490 (13.2%) 76 55 sec

10 sec 0.8783 6876 (16.6%) 161 27 sec

10% T/P,Temp 0.8096 8363 (20.2%) 87 63 sec

10% T/P,Temp, 10 sec 0.756 10613 (25.6%) 220 23 sec

8 Events 481 sec

30 Events 837 sec

30 Events 1592 sec

89 Events 2590 sec

Pass Ratio: NTE Time (sec): Events: Med. Event Time:

Test Details: Total Duration: 41444 sec Total Non-idle: 26520 sec Vehicle: Tractor Engine year: 2011 Month of test: JulyOverall: 0.98 g/bhp-hr

0.65 g/bhp-hr Threshold

0.20 g/bhp-hr

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Observations from NTE Cases

• Pass ratio generally lower with modified cases, but notalways

• Amount of additional data varies by test– Certain tests with no NTE events may still not have NTE events

with modified criteria

• Shortening minimum event duration generally resulted inmore, but shorter events

• Reducing the torque and power thresholds and removingthe minimum aftertreatment temperature criteriongenerally resulted in slightly more events, and slightlylonger event durations

• Combining both cases results in more events with longerdurations

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• Adopted in the European Union as part of Euro VI• Emissions evaluated over segments of data (windows)

– Windows consist of consecutive 1 Hz data points that addup to defined quantity of work, windows overlap

– Average power over window meet set percentage of maxpower

– Brake-specific emissions: Total emissions emitted inwindow divided by total work done in window

– Window emissions ranked and emissions at 90th percentileused to determine compliance

– Does not have separate temperature-based exclusions– No measurement margin (conformity = 1.5 x standard)

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Work- Average Window Method

• Work done each second is added until the cycle work isaccumulated (FTP work in this example)

• Average Power = Window work / window duration

• Window is valid if average power > 10% max power

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Determining Valid Windows

Snippet of data from a test conducted on PEMS: A valid window is shown in green and an invalid one in red.

• Same data used as in NTE analysis earlier

• Min window power: 10% of max engine power

• 3 work window sizes, based on:

– World Harmonized Transient Cycle

– Federal Test Procedure

– Custom work window size: 30 seconds at 30% ofmaximum power to approximate work in lowestpossible work NTE event

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Work-Average Window Analysis

0

0.5

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Effect of Different Work Windows

Sizes, Example 1 (HDIUT Data)

0.5* g/bhp-hr (CF = 1.5)

90th Percentile 0.37 g/bhp-hr (CF = 1.13)

90th Percentile 0.39 g/bhp-hr (CF = 1.20)

90th Percentile 0.54 g/bhp-hr (CF = 1.64)

WHTC

Valid 22.81%

88.1%

Invalid 8.24%

FTP

Valid 24.08%

85.5%

Invalid 7.96%

Custom

Valid 30.68%

68.8%

Invalid 5.15% Med. % Power

% Valid Windows

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> 0.5 g/bhp-hr: 12% Med. HP: 16.2%

> 0.5 g/bhp-hr: 0.1% Med. HP: 31.8%

> 0.5 g/bhp-hr: 2.3% Med. HP: 26.0%

*FEL: 0.33 g/ bhp-hr

0

1

2

3

4

5

6

7

NO

x Em

issi

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s (g

/bh

p-h

r)

Effect of Different Work Windows

Sizes, Example 2 (HDIUT Data)

0.3 g/bhp-hr (CF = 1.5)

90th Percentile 0.84 g/bhp-hr

90th Percentile 0.76 g/bhp-hr

90th Percentile 0.47g/bhp-hr

WHTC

Valid 26.05%

71.1%

Invalid 5.65%

FTP

Valid 26.83%

65.9%

Invalid 5.00%

Custom

Valid 32.29%

51.3%

Invalid 2.00%

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Med. % Power % Valid Windows

(CF = 4.21) > 0.3 g/bhp-hr: 34.5%Med. HP: 21.4%

(CF = 3.79) > 0.3 g/bhp-hr: 30.5%Med. HP: 18.7%

(CF = 2.35) > 0.3 g/bhp-hr: 18.1%Med. HP: 36.5%

0

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NO

x Em

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s (g

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Effect of Different Work Windows

Sizes, Example 3 (HDIUT Data)

0.3 g/bhp-hr (CF = 1.5)

90th Percentile 1.88 g/bhp-hr

90th Percentile 2.33 g/bhp-hr

90th Percentile 2.80 g/bhp-hr

WHTC

Valid 25.58%

83.6%

Invalid 7.39%

FTP

Valid 28.90%

76.2%

Invalid 6.52%

Custom

Valid 34.93%

65.3%

Invalid 2.03%

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Med. % Power % Valid Windows

(CF = 11.64) > 0.3 g/bhp-hr: 97.5%Med. HP: 28.3%

(CF = 9.41) > 0.3 g/bhp-hr: 99.2%Med. HP: 25.3%

(CF = 14.00) > 0.3 g/bhp-hr: 89.6%Med. HP: 32.9%

Observations from Work-Average

Window Cases

• Generally more challenging than NTE• Impact of different window sizes varied with each

test– WHTC work > FTP work > Custom work– Percentage of windows valid appears to decrease with

window work

WHTC FTP Custom Current NTE

CF %valid CF %valid CF %valid % Time

Example 1 1.13 88.1 1.20 85.5 1.64 68.8 10.8

Example 2 4.21 71.1 3.79 65.9 2.35 51.3 14.2

Example 3 9.41 83.6 11.64 76.2 14.00 65.3 13.2 23

Related Research

• CARB’s contract with Southwest Research Institute will evaluate alternative metrics

– Grams of NOX per unit fuel consumed

– Grams of NOX per unit CO2 emitted

• Will allow for better characterization of emissions at very low loads

• Results expected Summer 2018

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Next Steps

• Continue analysis with vocational data as currently ongoing data collection project with the University of California, Riverside completes

• Consider methods of accounting for emissions from operations below 10% of maximum power, including switching to a separate set of metrics

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Discussion

• Comments or questions about the data analysis or the possible strategies for increasing data inclusion?

• Concerns with NTE modifications approach (e.g. shorter events, lowering requirement to 10% of torque and power, removing or lowering minimum aftertreatment out temperature)?

• Concerns with work-Average window approach (window size based on FTP, WHTC, or another amount, power threshold)?

• Suggestions for other options? Further analyses that you would like to see completed? Other PEMS data that you would wish to contribute, such as data from vocational vehicles?

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