Assessment of Fuel Economy Technologies for Light-Duty Vehicles (2011) / Chapter Skim
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8 Modeling Improvements in Vehicle Fuel Consumption
8 Modeling Improvements in Vehicle Fuel Consumption
Pages 118-137
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From page 118... ...
in its for reducing light-duty vehicle fuel consumption over a time rulemaking analyses, and the EPA's OMEGA model, used horizon on the order of 10 years. by the EPA in its rulemaking analysis (EPA and NHTSA, 118
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From page 119... ...
utes less to reducing fuel consumption, in this case) , or might be positively There are at least six sources of error in estimating the synergistic, meaning that the sum of the technologies' effects is greater than potential to reduce vehicle fuel consumption: the impact of the individual technologies (in this case, contributes more to reducing fuel consumption)
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From page 120... ...
. In addition, the 2002 The second critique covered a variety of points including committee judged that the potential for diesels to meet tighter the degree of optimism in studies cited to support the comemissions standards was highly uncertain and also excluded mittee's estimates and inadequate attention to the depenhybrids from its quantitative assessment due to uncertainty dence of fuel consumption impacts on the characteristics of about their future potential.
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From page 121... ...
2-3 35 140 X X X X X X X X X X X X Variable valve lift and timing 1-2 70 210 X X X X X X X X Cylinder deactivation 3-6 112 252 X Engine accessory improvement 1-2 84 112 X X X X X X X X X X X X Engine supercharging and downsizing 5-7 350 560 X X Production-intent transmission technology Five-speed automatic transmission 2-3 70 154 X X X X X X Continuously variable transmission 4-8 140 350 X X X X X X Automatic transmission w/aggressive shift logic 1-3 70 X X X X -- Six-speed automatic transmission 1-2 140 280 X X X MODELING IMPROVEMENTS IN VEHICLE FUEL CONSUMPTION Production-intent vehicle technology Aero drag reduction 1-2 140 X X X X X X -- Improved rolling resistance 1-1.5 14 56 X X X X X X X X X X X X Safety technology Safety weight increase −3 to −4 0 0 X X X X X X X X X X X X Emerging engine technology Intake valve throttling 3-6 210 420 X X X X Camless valve actuation 5-10 280 560 X X X X Variable compression ratio 2-6 210 490 X X X X Emerging transmission technology Automatic shift/manual transmission (AST/AMT) 3-5 70 280 X X Advanced CVTs -- allows high torque 0-2 350 840 X X Emerging vehicle technology 42-V electrical system 1-2 70 280 X X X X X X Integrated starter/generator (idle off-restart)
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From page 122... ...
Similarly, 4.0 to 6.0 percent of the committee's committee's costs estimates. The costs of fuel consumption estimated 5.0 to 7.0 percent benefits of engine boosting and technologies in the 2002 NRC report were the same for all downsizing was attributed to reduced pumping losses.
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From page 123... ...
Multivalve OHC 2-5 3.5 1-2.6 1.8 NA NA Variable valve timing 2-3 2.5 3-5 4 2-4 3 Variable valve lift and timing 1-2 1.5 1.5-3.5 2.5 3-4 3.5 Cylinder deactivation 3-6 4.5 0.0-0.5 0.25 6 6 Subtotal 12 8.5 12.5 3-6 4.5 1.5-3.5 2.5 1-2 1.5 Intake valve throttlingb Total 16.5 11 14 5-10 7.5 NA NA 5-15 10 Camless valvesc aNHTSA's fuel consumption benefits are path dependent. The path shown here is for dual overhead camshaft engines.
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From page 124... ...
consumption impact estimates for individual technologies. It In general, studies of fuel consumption potential intended is a method of aggregating the fuel consumption impacts of to inform the regulatory process and using the PDA method various technologies and must obtain the individual technol ogy benefit estimates from other sources.
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From page 125... ...
Comparing the actual fuel consumption performance of these Recently, FSS models have been extensively used to vehicles to an estimate based on the sum of their individual estimate the fuel economy impacts of individual technolo- effects can provide an estimate of the degree of synergy. gies and combinations of technologies (e.g., Ricardo, Inc., Second, simplified lumped parameter models of vehicle 2008a,b; Sierra Research, Inc., 2008)
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From page 126... ...
44) combined fuel consumption impacts of multiple technologies by requiring that the laws of physics controlling energy FIGURE 8.2 EPA's comparison of full vehicle simulation model (Ricardo, Inc.)
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From page 127... ...
This an externally provided representation of the physics of a is typically a narrow window of three to five model years, device in order to estimate its impact on fuel consumption. beginning 2 years in the future.
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From page 128... ...
Like the Volpe model, of each technology vary by vehicle class. Previously the OMEGA is based on the PDA method and although the logic 10 vehicle classes of the 2002 NRC report were used, but of the two models is fundamentally the same, there are some the 2011 rule is based on 12 vehicle classes that include 4 notable differences.
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From page 129... ...
129 MODELING IMPROVEMENTS IN VEHICLE FUEL CONSUMPTION FIGURE 8.3 Volpe model engine technology decision tree. Figure 8-3.eps bitmap
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From page 130... ...
Likewise, multiplying the terms in equation 2 will the EPA test car database for all relevant combinations of produce a smaller estimated change in fuel consumption than technologies. Using the PDA method, a manufacturer's fuel adding the δi, which could erroneously lead to negative fuel economy potential can be calculated using data on individual consumption.
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From page 131... ...
FSS modeling has been used by the estimating the fuel consumption impacts of novel vehicle automotive industry since the 1970s, and is a proven method systems for which there are no actual test data (Greene and of estimating the impacts of existing and new technologies DeCicco, 2000)
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From page 132... ...
There is always a difference between the simula- for a predicted change are likely to be greater. The accuracy tion and actual subsystem operation, known as the modeling of FSS models in predicting fuel consumption changes in error.
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From page 133... ...
In many provides brake-specific fuel consumption as a function of endynamic system models, the characteristics of both the gine speed and load. Numerous other modules are necessary turbocharger compressor and turbine are simulated based to represent the many interacting components of the engine on steady-state maps.
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From page 134... ...
SOURCE: Reprinted with permission from John J Moskwa, Powertrain Control Research Laboratory, University of Wisconsin, Madison, Wisc.
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From page 135... ...
The PDA method explicitly recognizes this kind of interaction by ordering technologies for interaction and using only incremental impacts, given that ordering, to estimate the total fuel consumption impact. But incremental effects, as defined in the Ricardo ANOVA, also include true synergistic effects, such as when a 42-volt electrical system is implemented together with electric ac cessories (e.g., electric power steering)
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From page 136... ...
Unlike FSS, the PDA to better assess the contributory effects of technologies applied method cannot be used to generate estimates of the impacts for the reduction of vehicle energy losses and to better couple of individual technologies on vehicle fuel consumption. the modeling of fuel economy technologies to the testing of Thus, the PDA method by itself, unlike FSS, is not suitable such technologies on production vehicles.
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From page 137... ...
SAE Paper 2006-01-0664. ing technologies for reduced fuel consumption: A review of the technical SAE International, Warrendale, Pa.
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