Reducing Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two Final Report (2020) / Chapter Skim
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3 Certification, Compliance, and Enforcement
3 Certification, Compliance, and Enforcement
Pages 46-63
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From page 46... ...
Section 3.4 addresses in-use compliance and enforcement. 3.2 SUMMARY OF CERTIFICATION APPROACHES IN PHASE I AND PHASE II RULES Perhaps the most anticipated aspects of the Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles -- Phase II rules (EPA and NHTSA, 2016)
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From page 47... ...
. The other is the use of the GEM, which simulates vehicle fuel efficiency and CO2 emissions over three distinct driving cycles for prescribed vehicle configurations and weights, resulting in a single output expressed in fuel consumed in gallons per 1,000 ton-miles and an equivalent CO2 output expressed as grams per ton-mile.
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From page 48... ...
EPA has always stipulated that engines or vehicles certified for criteria pollutant emissions would meet the standard through a "useful life" period, and that the technology required to meet those certified values cannot be disassembled from the certified engine configuration during the useful life period. The Phase I fuel economy regulations promulgated by NHTSA (EPA and NHTSA, 2011)
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From page 49... ...
For most of the dry box, refrigerator box trailers, and pup vans between 28 and 53 feet the agency was able to justify applying performance standards in the Phase II rule. Technologies to be applied to achieve these standards include a variety of aerodynamic features and low-rolling-resistance tires, primarily carried over from EPA's SmartWay program, and the California Air Resources Board's Greenhouse Gas Reduction Regulation.
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From page 50... ...
Vocational. 65 mph cruise with road grade and flat road effects; steady-state and transient cycle average fuel map optional.
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From page 51... ...
Ultimately the problem must be addressed as a system optimization of a society of interacting vehicles and control devices. 3.3.2 Engines 3.3.2.1 Engine Dynamometer Testing Adequacy At present, MHDV fuel efficiency is determined by simulation and is determined separately from criteria pollutant values, which are still engine based.1 However, the engine fuel efficiency is regulated in addition to the MHDV fuel efficiency and is determined using the same well-established test procedure that is used for criteria pollutant standards.
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From page 52... ...
. Therefore, there is difficulty in employing test cell instantaneous fuel economy data to verify models used to predict instantaneous efficiency of an engine or vehicle under transient operation.
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From page 53... ...
Whereas instantaneous fuel efficiency and instantaneous pre-aftertreatment criteria pollutants can be measured in a test cell, both urea SCR and the DPF to reduce PM make it difficult to associate tailpipe or stack criteria pollutant levels directly and repeatedly with engine operation. 3.3.2.3 Powertrain Measurement Integrated powertrain measurement has been presented as an important alternative to engine testing in cases where the engine and transmission have been closely integrated and are controlled as one unit.
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From page 54... ...
If fuel efficiency is determined using simulation and an engine model derived in the test cell, the test circumstances for fuel efficiency and criteria pollutants will differ. 3.3.3 Whole Vehicle Modeling 3.3.3.1 Adequacy and Possible Improvements Whole vehicle modeling offers substantial advantages over whole vehicle testing in that vehicle design changes and operational differences may be examined rapidly and inexpensively.
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From page 55... ...
Currently, simulations such as GEM provide an attractive opportunity to determine the fuel efficiency of a range of vehicle designs over different routes. However, the inputs to GEM are relatively simple, such as a single rolling resistance value for tires, and a wind-averaged drag coefficient that is not speed dependent.
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From page 56... ...
Furthermore, the method of measuring rolling resistance must yield values that represent real-world use on average pavement, and must be consistent between laboratories and of high quality. Recommendation 3-4: For certification against a standard using vehicle simulation, it is essential that the rolling diameter and rolling resistance tests are standardized to meet the same data quality level as engine tests, and that they yield results that are sufficiently representative for modeling average real-world performance.
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From page 57... ...
All merit the same level of attention and measurement accuracy in the quest to improve vehicle fuel efficiency. Finding: Regulation has focused more upon engine efficiency compliance than separate tire or aerodynamic compliance, even though all three systems are associated with the same order of magnitude of energy in truck operation.
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From page 58... ...
The fuel consumption of the complete vehicle in these larger truck classes is determined by the GEM simulation model, based on user inputs including characteristics of the vehicle such as the drag coefficient or rolling resistance, and, in the Phase II rule, on engine fuel maps and torque curves. No actual measurement of fuel consumption of the vehicle being certified is performed.
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From page 59... ...
Recommendation 3-6: NHTSA, in coordination with EPA, should develop an effective in-use compliance method that would allow the overall performance of the regulatory program to be quantified, identify whether groups of in-use trucks may not be in compliance, and provide insight into truck operating conditions where GHG emissions and fuel consumption of future trucks could be further reduced. 3.4.2 Approaches to Determine In-Use Compliance for MHDVs In general, the objective of an in-use compliance program should be to determine if real on-road emissions and fuel consumption match the results expected from the regulatory standards and requirements.
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From page 60... ...
It may be possible to develop OBD monitoring for MHDVs that is more closely tied to GHG emissions and fuel consumption, and is sufficiently comprehensive.5 If successful, the OBD data could be transmitted electronically from the truck to the truck manufacturer and/or NHTSA and EPA, to assess in-use performance of GHG emissions and fuel consumption, as well as criteria air pollutants, both for individual trucks and groups of trucks as a whole. Engine manufacturers are currently required to report warranty repairs to NHTSA and EPA, and these reports have been used to identify systemic defects in engines.
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From page 61... ...
A more significant change could be to require the truck builders to be responsible for the on-road GHG emissions and fuel consumption of the trucks they sell. Truck manufacturers could select a standard they will meet, subject to a regulatory maximum, with in-use compliance based on on-road data subsequently collected on their trucks.
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From page 62... ...
the importance of establishing baselines of fleet fuel consumption and GHG emissions to allow assessment of program effectiveness. When combined with an in-use compliance program more removed from actual on-road emissions, more of the objectives could be met.
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From page 63... ...
2011. Greenhouse gas emissions standards and fuel efficiency standards for medium- and heavy-duty engines and vehicles.
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