# Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles(2015)

## Chapter: Appendix G: Friction Reduction in Downsized Engines

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Page 383
Suggested Citation:"Appendix G: Friction Reduction in Downsized Engines." National Research Council. 2015. Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/21744.
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Appendix G

Friction Reduction in Downsized Engines

Downsizing has a significant effect on friction reduction potential. This effect can be explained as follows with the calculation of brake specific fuel consumption (BSFC) at a typical Federal Test Procedure (FTP) cycle operating condition, assuming a constant indicated specific fuel consumption (ISFC).

 BSFC = ISFC × IMEP/BMEP = ISFC × (BMEP + FMEP)/BMEP (1)

The BSFC that would result with a typical baseline friction level at a typical FTP cycle operating condition would be as follows, using Equation 1:

BSFC = ISFC (38 + 11)/38 = 1.289 ISFC

Where: BMEP (brake mean effective pressure) = 38 psi (typical FTP cycle operating condition)
FMEP (friction mean effective pressure) = 11 psi (typical baseline friction at FTP operating condition)

Achieving a 10 percent reduction in friction would provide the following improvement in BSFC:

BSFC = ISFC (38 + 0.9 × 11)/38 = 1.261 ISFC

Therefore, a 10 percent reduction in friction will provide a 2.2 percent reduction in fuel consumption. Consequently, a 25 percent reduction in friction will provide a 5.6 percent reduction in fuel consumption, as discussed in the SI Efficiency Fundamentals section of Chapter 2.

For a 50 percent downsized, high BMEP engine, a BMEP level twice that of the naturally aspirated engine would be required for the same operating condition of the vehicle. The BSFC for this engine with the baseline friction is as follows:

BSFC = ISFC (2 × 38 + 11)/(2 × 38) = 1.145 ISFC

Applying the same 10 percent reduction in friction would provide the following improvement in BSFC:

BSFC = ISFC (2 × 38 + 0 .9 × 11)/2 × 38 = 1.130 ISFC

Therefore, a 10 percent reduction in friction in the downsized engine will provide only a 1.3 percent reduction in fuel consumption, which is approximately half the reduction in fuel consumption shown for the naturally aspirated engine. Consequently, a 50 percent downsized engine will require nearly twice the reduction in friction relative to that required in a naturally aspirated engine to achieve the same reduction in fuel consumption.

Even though friction reductions are not as effective in the downsized engine, the downsizing itself provides a significant reduction in friction. Friction power is calculated as follows:

 Friction Power = K × RPM × Displacement × FMEP (2)

Equation 2 indicates that friction power would be reduced by 50 percent when the engine displacement is reduced by 50 percent, assuming constant FMEP (although FMEP would be expected to show a moderate increase due to the engine redesign to withstand higher BMEP levels).

The effect of 50 percent downsizing can be calculated by comparing the baseline conditions shown previously for both the naturally aspirated and downsized, high BMEP engines as follows:

Naturally Aspirated Engine: BSFC = 1.289 ISFC
Downsized Engine: BSFC = 1.145 ISFC

This comparison indicates that 50 percent downsizing could potentially provide a 11 percent reduction in fuel consumption, with the simplifying assuming of constant FMEP in both engines.

Page 383
Suggested Citation:"Appendix G: Friction Reduction in Downsized Engines." National Research Council. 2015. Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/21744.
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Next: Appendix H: Variable Valve Timing Systems »
Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles Get This Book
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The light-duty vehicle fleet is expected to undergo substantial technological changes over the next several decades. New powertrain designs, alternative fuels, advanced materials and significant changes to the vehicle body are being driven by increasingly stringent fuel economy and greenhouse gas emission standards. By the end of the next decade, cars and light-duty trucks will be more fuel efficient, weigh less, emit less air pollutants, have more safety features, and will be more expensive to purchase relative to current vehicles. Though the gasoline-powered spark ignition engine will continue to be the dominant powertrain configuration even through 2030, such vehicles will be equipped with advanced technologies, materials, electronics and controls, and aerodynamics. And by 2030, the deployment of alternative methods to propel and fuel vehicles and alternative modes of transportation, including autonomous vehicles, will be well underway. What are these new technologies - how will they work, and will some technologies be more effective than others?

Written to inform The United States Department of Transportation's National Highway Traffic Safety Administration (NHTSA) and Environmental Protection Agency (EPA) Corporate Average Fuel Economy (CAFE) and greenhouse gas (GHG) emission standards, this new report from the National Research Council is a technical evaluation of costs, benefits, and implementation issues of fuel reduction technologies for next-generation light-duty vehicles. Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles estimates the cost, potential efficiency improvements, and barriers to commercial deployment of technologies that might be employed from 2020 to 2030. This report describes these promising technologies and makes recommendations for their inclusion on the list of technologies applicable for the 2017-2025 CAFE standards.

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