Energy Conversion Factor for Gasoline Engines in Real-World Driving Emission Cycle


A precise energy conversion factor is required to define the impact of greenhouse gas emissions by gasoline-powered vehicles and policies that will guide the application of future eco-innovations. The current energy conversion factor adopted by many countries is based on the Willans line approach, initially proposed in 1888 for steam engines, later adapted for internal combustion engines. The actual energy conversion factor, which defines the energy conversion for drivers in real traffic, is missing. In this article, eight world-class engines are tested in an engine bench for the acquisition of specific fuel consumption 3D maps. Then, their energy conversion factors, calculated by dividing the energy output by the energy input, are simulated in real and urban traffic, acquired according to the real driving emissions (RDE) cycle. In addition, a reference vehicle is instrumented to measure the energy input (fuel flow) and the energy output (mechanical energy in the half axles) under the same RDE cycle standards. The results of both procedures are very similar, respectively, 0.405 ± 0.04 L/kWh for the simulation based on eight benchmark engines, and 0.392 ± 0.04 L/kWh for the reference vehicle driven in RDE traffic conditions, with a 95% confidence interval. For turbocharged engines, the factor attained by the simulation is 0.395 ± 0.04 L/kWh. The values of the energy conversion factor for gasoline engines got in this research are higher than those obtained through the Willans line approach, suggesting a new standard value of 0.405 L/kWh, replacing the current 0.264 L/kWh. It could substantially change the greenhouse gas emissions in a tank-to-wheel approach for the entire vehicle and add-on eco-innovations.

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Brake mean effective pressure


Brake specific fuel consumption


Common access network


Coefficient of variation


Exhaust gas recirculation


Environmental Protection Agency


Greenhouse gas


Internal combustion engines


Intergovernmental Panel on Climate Changes


Life cycle assessment


Real driving emission








  1. 1.

    Crutzen, P.J.: Geology of mankind. Nature 415, 23 (2002).

    Article  Google Scholar 

  2. 2.

    Crutzen, P.J.: The anthropocene: the current human-dominated geological era. Pontifical Academy of Science. (2006). Accessed 10 Jan 2019

  3. 3.

    EPA. Global greenhouse gas emissions data. (2018). Accessed 20 May 2019

  4. 4.

    IPCC: Climate change 2014: mitigation of climate change. Contribution of working group III to the fifth assessment report of the intergovernmental panel on climate change. (2014). Accessed 10 Jan 2019

  5. 5.

    Fayçal-Siddikou, B., et al.: Comparative LCA of electric, hybrid, LPG and gasoline cars in Belgian context. World Electr. Veh. J. 3(3), 469–476 (2009).

    Article  Google Scholar 

  6. 6.

    Cavalett, O., Chagas, M.F., Seabra, J.E.A., et al.: Comparative LCA of ethanol versus gasoline in Brazil using different LCIA methods. Int. J. Life Cycle Assess. 18, 647 (2013).

    Article  Google Scholar 

  7. 7.

    Edwards, R., Hass, H., Larivé, J., et al.: Well-to-wheels analysis of future automotive fuels and powertrains in the European context well-to-wheels report version 4a. Jt. Res. Cent. (2014).

    Article  Google Scholar 

  8. 8.

    Willans, P.W.: Economy trials of a non-condensing steam engine: simple, compound and triple. Min. Proc. Inst. Civ. Eng. 93, 128–188 (1888).

    Article  Google Scholar 

  9. 9.

    Nam, E.K., Sorab, J.: Friction reduction trends in modern engines. SAE technical paper 2004-01-1456 (2004).

  10. 10.

    Pachernegg, S.J.: A closer look at the Willans-line. SAE technical paper 690182 (1969).

  11. 11.

    Noce, T., Silva, R.R., Morais, R., et al.: Energy factors for flexible fuel engines and vehicles operating with gasoline-ethanol blends. Transp. Res. D Transp. Environ. 65, 368–374 (2018).

    Article  Google Scholar 

  12. 12.

    Philips, P.: Analytic engine and transmission models for vehicle fuel consumption. SAE Int. J. Fuels Lubr. 8(2), 423–440 (2015).

    Article  Google Scholar 

  13. 13.

    EC: Regulation (EC) No 443/2009 setting emission performance standards for new passenger cars as part of the community’s integrated approach to reduce CO2 emissions from light-duty vehicles. EUR-Lex.!Xu63JC (2017). Accessed 10 Jan 2019

  14. 14.

    Rohde-Brancenburger, K., Obernolte, J.: Leichtbaustrategien, ein wesentlicher Beitrag zur Klimadebatte, DVM-Tag, Berlin. Accessed 23–25 Apr 2008

  15. 15.

    Rohde-Brandenburger, K., Koffler, C.: Reply to Kim et al.: commentary on “correction to: on the calculation of fuel savings through lightweight design in automotive life cycle assessments” by Koffler and Rohde-Brandenburger. Int. J. Life Cycle Assess. 24, 400–403 (2019).

    Article  Google Scholar 

  16. 16.

    Lodi, C., Seitsonen, A., Paffumi, E., et al.: Reducing CO2 emissions of conventional fuel cars by vehicle photovoltaic roofs. Transp. Res. D Transp. Environ. 59, 313–324 (2018).

    Article  Google Scholar 

  17. 17.

    Abdelhamid, M., Pilla, S., Singh, R., et al.: A comprehensive optimized model for on-board solar photovoltaic system for plug-in electric vehicles: energy and economic impacts. Int. J. Energy Res. 40, 1489–1508 (2016).

    Article  Google Scholar 

  18. 18.

    Jung, H., Song, M.: A development of energy management system with semi-transparent solar roof and off-cycle credit test methodology for solar power assisted automobile. SAE Int. J. Commer. Veh. 10(1), 170–177 (2017).

    Article  Google Scholar 

  19. 19.

    Heywood, J.B.: Internal Combustion Engine Fundamentals. McGraw-Hill, New York (1988)

    Google Scholar 

  20. 20.

    Iliev, S.P.: A comparison of ethanol and methanol blending with gasoline using a 1-D engine model. In: Katalinic, B. (ed.) Proceedings of the 29th DAAAM International Symposium, vol. 100, pp. 1013–1022. DAAAM International, Vienna (2015)

  21. 21.

    Bozza, F., De Bellis, V., Teodosio, L.: Potentials of cooled EGR and water injection for knock resistance and fuel consumption improvements of gasoline engines. Appl. Energy 169, 112–125 (2016).

    Article  Google Scholar 

  22. 22.

    Zhu, S., Bo, H., Akehurst, S., et al.: A review of water injection applied on the internal combustion engine. Energy Convers. Manag. 184, 139–158 (2019).

    Article  Google Scholar 

  23. 23.

    Wittek, K., Geiger, F., Andert, J., et al.: Experimental investigation of a variable compression ratio system applied to a gasoline passenger car engine. Energy Convers. Manag. 183, 753–763 (2019).

    Article  Google Scholar 

  24. 24.

    Baêta, J.G.C., Pontoppidan, M., Silva, T.R.V.: Exploring the limits of a down-sized ethanol direct injection spark ignited engine in different configurations in order to replace high-displacement gasoline engines. Energy Convers. Manag. 105, 858–871 (2015).

    Article  Google Scholar 

  25. 25.

    INMETRO Instituto Nacional de Metrologia, Qualidade e Tecnologia: Portaria no 377, de 29 de setembro de 2011. Anexo D. (2011). Accessed 15 Jan 2019

  26. 26.

    Machado, G.A.A.: Eficiência de uma transmissão automotiva e do comportamento tribológico em regimes de lubrificação aplicadas à engrenagens automotivas. (Automotive transmission efficiency and tribological behavior in lubrication regimes applied to automotive gears) Dissertation, Escola Politécnica da USP, São Paulo (2018)

  27. 27.

    ICCT International Council on Clean Transportation: Real-driving emissions test procedure for exhaust gas pollutant emissions of cars and light commercial vehicles in Europe. The International Council on Clean Transportation. (2017). Accessed 15 Jan 2018

  28. 28.

    EC: Commission Implementing Regulation (EU) No 2014/427 establishing a procedure for the approval and certification of innovative technologies for reducing CO2 emissions from light commercial vehicles pursuant to Regulation (EU) No 510/2011 of the European Parliament and of the Council. EUR-Lex.!nY68hV (2014). Accessed 16 Jan 2018

  29. 29.

    EC: Commission Implementing Regulation (EU) 2017/646 amending Implementing Regulation (EU) 2015/378 laying down rules for the application of Regulation (EU) No 514/2014 of the European Parliament and of the Council with regard to the implementation of the annual clearance of accounts procedure and the implementation of the conformity clearance passenger and commercial vehicles (Euro 6). EUR-Lex. (2017). Accessed 16 Jan 2018

  30. 30.

    ABNT (Brazilian Association of Technical Standards). NBR 6601: Veículos rodoviários automotores leves—determinação de hidrocarbonetos, monóxido de carbono, óxidos de nitrogênio, dióxido de carbono e material particulado no gás de escapamento. (Light motor vehicles—determination of hydrocarbons, carbon monoxide, nitrogen oxides, carbon dioxide and particulate matter in the exhaust gas). Rio de Janeiro (2012)

  31. 31.

    ABNT (Brazilian Association of Technical Standards). NBR 7024:Veículos Rodoviários Automotores Leves—Medição do Consumo de Combustível—Método de Ensaio (Light automotive road vehicles—measurement of fuel consumption—test method). Rio de Janeiro (2017)

  32. 32.

    Cuenot, F.: Real world fuel economy measurements. Technical Insights from 400 tests of Peugeot, Citroën and DS cars. Transport & Environment. (2017). Accessed 10 Feb 2018

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The authors thank Brazilian Development BNDES for the economic support, the Joint Research Centre JRC for the technical assistance to this project and to Mr. Adam Aslam/Gabriel Santos for the grammar revision.

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Correspondence to Toshizaemom Noce.

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Noce, T., de Morais Hanriot, S., Sales, L.C.M. et al. Energy Conversion Factor for Gasoline Engines in Real-World Driving Emission Cycle. Automot. Innov. 3, 169–180 (2020).

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  • Energy conversion factor
  • Willans line
  • EC443
  • Eco-innovation
  • CO2 emission