Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two First Report (2014) / Chapter Skim
Currently Skimming:
3 Certification and Compliance Procedures Using GEM
3 Certification and Compliance Procedures Using GEM
Pages 29-39
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 29... ...
already addressed the units to be employed for measuring • Fuel efficiency or greenhouse gases versus criteria engine efficiency, vehicle efficiency, and the associated car- pollutants. Although reducing engine power output bon dioxide emissions levels, for both gasoline and diesel.
|
From page 30... ...
; they included compliance with the vehicle standard will typically be de • Maximum reusability, termined based on a customized vehicle simulation model, • Maximum flexibility, called the Greenhouse gas Emissions Model (GEM) , which • Selectable complexity, is consistent with the NAS Report recommendations to • Code neutrality, require compliance testing for combination tractors using • Graphical user interface vehicle simulation rather than chassis dynamometer testing.
|
From page 31... ...
(a) The "annual production period" for all models within an engine family of light-duty motor vehicles, heavy-duty motor vehicles and engines, and on-highway motorcycles begins either: when any vehicle or engine within the engine family is first pro duced; or on January 2 of the calendar year preceding the year for which the model year is designated, whichever date is later.
|
From page 32... ...
; for modeling and simulation in engineering. The user has • Fixed axle ratios; five main inputs to the model: • Fixed tire sizes and a rolling resistance that is invariant with respect to speed and torque, though user supplied; • Aerodynamic drag coefficient value by bin, • Fixed electrical load; • Steer and drive tire rolling resistance by value, • Fixed mechanical accessory power; • Vehicle speed limiter presence and value, • Three fixed cycles (California Air Resources Board • Vehicle mass reduction (lb)
|
From page 33... ...
Idle reduction input to the model is limited namic drag is not considered for those vehicles. Exception is to a yes/no type answer, whereas idle reduction strategies in granted for a limited number of vocational tractors, which are actual use can be much more sophisticated, especially as the treated as vocational vehicles, as detailed in the following: latter relates to safety of the driver in hot and cold weather.
|
From page 34... ...
offers sufficiently efficient vehicles and that the purchasers, OEMs have, therefore, developed automated techniques, for economic or external reasons, elect to purchase these including obtaining source code to allow better implementasufficiently efficient vehicles, then the GEM computations tion within their order entry system. may not be time-sensitive, because compliance is assured.
|
From page 35... ...
(These are discussed in road, load, bridge, and safety requirements. Weight reduction the Section "Development of the Greenhouse Gas Emissions credit might better be focused on achieving a total vehicle Model.")
|
From page 36... ...
vehicle manufacturer with benefits of using a potentially superior engine or transmission. Several presenters have sugFinding: For tire rolling resistance, there needs to be high gested that full vehicle simulation or simulation of a power confidence in input values to GEM, because fuel efficiency pack that includes the aftertreatment system and the transimprovement rests on incremental changes in technology mission should be used, rather than only the engine.
|
From page 37... ...
real-world operation, nor would GEM deprive a purchaser of performance features that are truly necessary for ser Similarly, GEM, in having a fixed test weight, does not vice but that may be atypical of current GEM cycles. For differentiate between lighter duty Class 8 tractors that may example, engine downsizing or lighter, lower friction, less pull volume-limited loads and heavier duty tractors that robust transmissions might yield fuel savings but might not typically pull combined gross vehicle weights approaching be appropriate for certain duty cycles.
|
From page 38... ...
Recommendation 3.11: NHTSA and EPA should modify the Greenhouse Gas Emissions Model (GEM) to employ Information on Fuel Consumption cycles or vehicle activities that cover as large a fraction of over-the-road tractor operation as possible without becom- Other methods of obtaining fuel economy information ing overly cumbersome.
|
From page 39... ...
2012. "Volvo trucks earn 2014 greenhouse gas certifica trucks, aide says.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.