Comprehensive review of innovation in piston engine and low temperature combustion technologies

    Roland Allmägi Affiliation
    ; Risto Ilves Affiliation
    ; Jüri Olt Affiliation


Global transport today is mainly powered by the Internal Combustion Engine (ICE) and throughout its century and a half of development it has become considerably more efficient and cleaner. Future prospects of the ICE rely on the scientific work conducted today to keep this trend of higher efficiency and cleaner emissions in new engines going. The aim of this article is to give a comprehensive review of development directions in novel piston engine designs, which seek to overcome the drawbacks of the ubiquitous 4-stroke piston engine. One of the directions of development is devoted to improving the mechanisms and the general layout of the piston engine to reduce losses within the engine. Research teams working with alternative engine work cycles like the 5- and 6-stroke engine and technologies for extracting waste heat seek to reduce thermal losses while novel layouts of valve trains and crank assemblies claim to significantly improve the mechanical and Volumetric Efficiency (VE) of piston engines. These novel ideas include camless or Variable Valve Action (VVA) and engines with Variable Compression Ratio (VCR) or opposed pistons. One alternative approach could also be to totally redesign the reciprocating mechanism by replacing the piston with some other device or mechanism. Additional scientific work is investigating Low Temperature Combustion (LTC) technologies such as Turbulent Jet Ignition (TJI) and Homogeneous Charge Compression Ignition (HCCI) and its derivatives like Premixed Charge Compression Ignition (PCCI) and Reactivity Controlled Compression Ignition (RCCI) that have shown improvements in thermal and fuel conversion efficiency while also significantly reducing harmful emissions. These combustion strategies also open the path to alternative fuels. The contemporary work in the combustion engine fields of research entail technical solutions from the past that have received a modern approach or are a completely novel idea. Nonetheless, all research teams work with the common goal to make the piston engine a highly efficient and environmentally friendly device that will continue to power our transport and industry for years to come. For this, solutions must be found to overcome the mechanical limitations of the traditional layout of the piston engine. Similarly various improvements in combustion technology are needed that implement state of the art technology to improve combustion characteristics and reduce harmful emissions.

Keyword : piston engine, membrane engine, 5-stroke engine, 6-stroke engine, variable valve action, variable compression ratio, low temperature combustion

How to Cite
Allmägi, R., Ilves, R., & Olt, J. (2024). Comprehensive review of innovation in piston engine and low temperature combustion technologies. Transport, 39(1), 86–113.
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May 21, 2024
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Abani, N.; Nagar, N.; Zermeno, R.; Chiang, M.; Thomas, I. 2017. Developing a 55% BTE commercial heavy-duty opposed-piston engine without a waste heat recovery system, SAE Technical Paper 2017-01-0638.

Agarwal, A. K.; Singh, A. P.; Maurya, R. K. 2017. Evolution, challenges and path forward for low temperature combustion engines, Progress in Energy and Combustion Science 61: 1–56.

Alagumalai, A. 2014. Internal combustion engines: progress and prospects, Renewable and Sustainable Energy Reviews 38: 561–571.

Alvarez, C. E. C.; Couto, G. E.; Roso, V. R.; Thiriet, A. B.; Valle, R. M. 2018. A review of prechamber ignition systems as lean combustion technology for SI engines, Applied Thermal Engineering 128: 107–120.

Arabaci, E. 2021. Performance analysis of a novel six-stroke Otto cycle engine, Thermal Science 25(3A): 1719–1729.

Arabaci, E.; İçingür, Y.; Solmaz, H.; Uyumaz, A.; Yilmaz, E. 2015. Experimental investigation of the effects of direct water injection parameters on engine performance in a six-stroke engine, Energy Conversion and Management 98: 89–97.

Ashley, C. 1990. Variable compression pistons, SAE Technical Paper 901539.

Ashok, A.; Gugulothu, S. K.; Venkat Reddy, R.; Burra, B.; Panda, J. K. 2022. A systematic study of the influence of 1-pentanol as the renewable fuel blended with Diesel on the reactivity controlled compression ignition engine characteristics and trade-off study with variable fuel injection pressure, Fuel 322: 124166.

Barba, D. 2018. Assessing the efficiency potential of future gasoline engines, in SAE 2018 High Efficiency IC Engine Symposium, 8–9 April 2018, Detroit, MI, US.

Bendu, H.; Murugan, S. 2014. Homogeneous charge compression ignition (HCCI) combustion: mixture preparation and control strategies in Diesel engines, Renewable and Sustainable Energy Reviews 38: 732–746.

Bianco, A.; Millo, F.; Piano, A. 2020. Modelling of combustion and knock onset risk in a high-performance turbulent jet ignition engine, Transportation Engineering 2: 100037.

Bobi, S.; Kashif, M.; Laoonual, Y. 2022. Combustion and emission control strategies for partially-premixed charge compression ignition engines: a review, Fuel 310: 122272.

Bombarda, P.; Invernizzi, C. M.; Pietra, C. 2010. Heat recovery from Diesel engines: a thermodynamic comparison between Kalina and ORC cycles, Applied Thermal Engineering 30(2–3): 212–219.

Boretti, A. 2020. A 480 kW/liter direct injection jet ignition rotary valve super-turbocharged positive ignition methanol engine, Case Studies in Thermal Engineering 21: 100676.

Borghi, M.; Mattarelli, E.; Muscoloni, J.; Rinaldini, C. A.; Savioli, T.; Zardin, B. 2017. Design and experimental development of a compact and efficient range extender engine, Applied Energy 202: 507–526.

Breitgraf, H. J. 1988. Kolbenloser Verbrennungsmotor (Membran-Motor). Patent No DE000008800034U1. Available from Internet: (in German).

Burch, I.; Gilchrist, J. 2020. Survey of Global Activity to Phase Out Internal Combustion Engine Vehicles. The Climate Center, Santa Rosa, CA, US. 18 p. Available from Internet:

Burnete, N. V.; Mariasiu, F.; Depcik, C.; Barabas, I.; Moldovanu, D. 2022. Review of thermoelectric generation for internal combustion engine waste heat recovery, Progress in Energy and Combustion Science 91: 101009.

Cao, J.; Ma, H. Y.; Li, G. 2014. Research on a new type of multi-link variable compression ratio by interpolation algorithm of Zadoff-Chu sequence, Applied Mechanics and Materials 602–605: 3392–3395.

Chakraborty, A.; Biswas, S.; Kakati, D.; Banerjee, R. 2022. Leveraging hydrogen as the low reactive component in the optimization of the PPCI-RCCI transition regimes in an existing diesel engine under varying injection phasing and reactivity stratification strategies, Energy 244: 122629.

Chen, H.; Guo, Q.; Yang, L.; Liu, S.; Xie, X.; Chen, Z.; Liu, Z. 2015. A new six stroke single cylinder Diesel engine referring Rankine cycle, Energy 87: 336–342.

Chumueang, R.; Laoonual, Y.; Chollacoop, N. 2015. Effects of injection timing and injection pressure on combustion characteristics and emissions of ethanol ED95 under partially premixed combustion condition, SAE Technical Paper 2015-32-0826.

Colonna, P.; Casati, E.; Trapp, C.; Mathijssen, T.; Larjola, J.; Turunen-Saaresti, T.; Uusitalo, A. 2015. Organic Rankine cycle power systems: from the concept to current technology, applications, and an outlook to the future, Journal of Engineering for Gas Turbines and Power 137(10): 100801.

Conklin, J. C.; Szybist, J. P. 2010. A highly efficient six-stroke internal combustion engine cycle with water injection for in-cylinder exhaust heat recovery, Energy 35(4): 1658–1664.

D’Amico, F.; Pallis, P.; Leontaritis, A. D.; Karellas, S.; Kakalis, N. M.; Rech, S.; Lazzaretto, A. 2018. Semi-empirical model of a multi-diaphragm pump in an organic Rankine cycle (ORC) experimental unit, Energy 143: 1056–1071.

De Bortoli Cassiani, M.; Bittencourt, M.; Galli, L.; Villalva, S. 2009. Variable compression ratio engines, SAE Technical Paper 2009-36-0245.

Dilber, V.; Sjerić, M.; Tomić, R.; Krajnović, J.; Ugrinić, S.; Kozarac, D. 2022. Optimization of pre-chamber geometry and operating parameters in a turbulent jet ignition engine, Energies 15(13): 4758.

Dong, G.; Morgan, R.; Heikal, M. 2015. A novel split cycle internal combustion engine with integral waste heat recovery, Applied Energy 157: 744–753.

Duan, X.; Lai, M.-C.; Jansons, M.; Guo, G.; Liu, J. 2021. A review of controlling strategies of the ignition timing and combustion phase in homogeneous charge compression ignition (HCCI) engine, Fuel 285: 119142.

Elbanna, A. M.; Xiaobei, C.; Can, Y.; Elkelawy, M.; Bastawissi, H. A.-E.; Panchal, H. 2022. Fuel reactivity controlled compression ignition engine and potential strategies to extend the engine operating range: a comprehensive review, Energy Conversion and Management: X: 13: 100133.

Envera LLC. 2018. High-Efficiency VCR Engine with Variable Valve Actuation and New Supercharging Technology. Final Report. NETL Contract No DE-EE0005981. Envera LLC, Mill Valley, CA, US. 149 p. Available from Internet:

Ershov, M. A.; Grigorieva, E. V.; Abdellatief, T. M. M.; Kapustin, V. M.; Abdelkareem, M. A.; Kamil, M.; Olabi, A. G. 2021. Hybrid low-carbon high-octane oxygenated gasoline based on low-octane hydrocarbon fractions, Science of the Total Environment 756: 142715.

Feng, H.; Zhang, Z.; Jia, B.; Zuo, Z.; Smallbone, A.; Roskilly, A. P. 2021. Investigation of the optimum operating condition of a dual piston type free piston engine generator during engine cold start-up process, Applied Thermal Engineering 182: 116124.

Fraidl, G.; Kapus, P.; Melde, H.; Losch, S.; Schoffmann, W.; Sorger, H.; Weißback; M.; Wolkerstorfer, J. 2016. Variable compression ratio – in a technology competition?, in 37th International Vienna Motor Symposium, 28–29 April 2016, Vienna, Austria. Available from Internet:

Fromm, L. 2022. Near-Zero Heavy-Duty Diesel Engine Enters Fleet Service: Already Compliant with 2027 NOx Emission Levels. Achates Power Inc., San Diego, CA, US. 2 p. Available from Internet:

Gargate, S.; Aher, R.; Jacob, R.; Dambhare, S. 2014. Estimation of blow-by in diesel engine: case study of a heavy duty Diesel engine, International Journal of Emerging Engineering Research and Technology 2(2): 165–170. Available from Internet:

George, S.; Balla, S.; Gautam, M. 2007. Effect of diesel soot contaminated oil on engine wear, Wear 262(9–10): 1113–1122.

Gregório, J. P.; Brójo, F. M. 2018. Development of a 4 stroke spark ignition opposed piston engine, Open Engineering 8(1): 337–343.

Guan, J.; Liu, J.; Duan, X.; Jia, D.; Li, Y.; Yuan, Z.; Shen, D. 2021. Effect of the novel continuous variable compression ratio (CVCR) configuration coupled with spark assisted induced ignition (SAII) combustion mode on the performance behavior of the spark ignition engine, Applied Thermal Engineering 197: 117410.

Guo, C.; Zuo, Z.; Feng, H.; Roskilly, T. 2021. Advances in free-piston internal combustion engines: a comprehensive review, Applied Thermal Engineering 189: 116679.

Gussak, L.; Turkish, M.; Siegla, D. 1975. High chemical activity of incomplete combustion products and a method of prechamber torch ignition for avalanche activation of combustion in internal combustion engines, SAE Technical Paper 750890.

Hannibal, W.; Flierl, R.; Stiegler, L.; Meyer, R. 2004. Overview of current continuously variable valve lift systems for four-stroke spark-ignition engines and the criteria for their design ratings, SAE Technical Paper 2004-01-1263.

Hasan, M. M.; Rahman, M. M. 2016. Homogeneous charge compression ignition combustion: Advantages over compression ignition combustion, challenges and solutions, Renewable and Sustainable Energy Reviews 57: 282–291.

Heywood, J. B. 2018. Internal Combustion Engine Fundamentals. 2nd Edition. McGraw-Hill Education. 1056 p.

Hiyoshi, R.; Aoyama, S.; Takemura, S.; Ushijima, K.; Sugiyama, T. 2006. A study of a multiple-link variable compression ratio system for improving engine performance, SAE Technical Paper 2006-01-0616.

Hoeltgebaum, T.; Simoni, R.; Martins, D. 2016. Reconfigurability of engines: a kinematic approach to variable compression ratio engines, Mechanism and Machine Theory 96: 308–322.

Hua, J.; Zhou, L.; Gao, Q.; Feng, Z.; Wei, H. 2021. Influence of pre-chamber structure and injection parameters on engine performance and combustion characteristics in a turbulent jet ignition (TJI) engine, Fuel 283: 119236.

Hupkens, J. 1986. Verbrandingsmotor. Patent No NL8603054A. (in Dutch).

Izadi Najafabadi, M.; Tanov, S.; Wang, H.; Somers, B.; Johansson, B.; Dam, N. 2017. Effects of injection timing on fluid flow characteristics of partially premixed combustion based on high-speed particle image velocimetry, SAE International Journal of Engines 10(4): 1443–1453.

Jia, B.; Mikalsen, R.; Smallbone, A.; Roskilly, A. P. 2018. A study and comparison of frictional losses in free-piston engine and crankshaft engines, Applied Thermal Engineering 140: 217–224.

Jia, X.; Zhao, Y.; Chen, J.; Peng, X. 2016. Research on the flowrate and diaphragm movement in a diaphragm compressor for a hydrogen refueling station, International Journal of Hydrogen Energy 41(33): 14842–14851.

Johnson, T.; Joshi, A. 2018. Review of vehicle engine efficiency and emissions, SAE International Journal of Engines 11(6): 1307–1330.

Kalghatgi, G. T. 2005. Auto-ignition quality of practical fuels and implications for fuel requirements of future SI and HCCI engines, SAE Technical Paper 2005-01-0239.

Kalghatgi, G. T. 2018. Is it really the end of internal combustion engines and petroleum in transport?, Applied Energy 225: 965–974.

Karvonen, M.; Kapoor, R.; Uusitalo, A.; Ojanen, V. 2016. Technology competition in the internal combustion engine waste heat recovery: a patent landscape analysis, Journal of Cleaner Production 112: 3735–3743.

Kéromnès, A.; Delaporte, B.; Schmitz, G.; Le Moyne, L. 2014. Development and validation of a 5 stroke engine for range extenders application, Energy Conversion and Management 82: 259–267.

Khandal, S. V.; Banapurmath, N. R.; Gaitonde, V. N.; Hiremath, S. S. 2017. Paradigm shift from mechanical direct injection diesel engines to advanced injection strategies of diesel homogeneous charge compression ignition (HCCI) engines – a comprehensive review, Renewable and Sustainable Energy Reviews 70: 369–384.

Kim, D.; Ito, A.; Ishikawa, Y.; Osawa, K.; Iwasaki, Y. 2012. Friction characteristics of steel pistons for Diesel engines, Journal of Materials Research and Technology 1(2): 96–102.

Koenigsegg. 2023. Gemera. Koenigsegg Automotive AB, Ängelholm, Sweden. Available from Internet:

Konstantinou, G.; Kyratsi, T.; Louca, L. S. 2022. Design of a thermoelectric device for power generation through waste heat recovery from marine internal combustion engines, Energies 15(11): 4075.

Lajunen, A.; Suomela, J.; Pippuri, J.; Tammi, K.; Lehmuspelto, T.; Sainio P. 2016. Electric and hybrid electric non-road mobile machinery – present situation and future trends, in 29th International Electric Vehicle Symposium 2016 (EVS29), 19–22 June 2016, Montréal, QC, Canada, 2334–2345.

Leach, F.; Kalghatgi, G.; Stone, R.; Miles, P. 2020. The scope for improving the efficiency and environmental impact of internal combustion engines, Transportation Engineering 1: 100005.

Lee, Su.; Kim, C.; Lee, Se.; Lee, J.; Kim, J. 2022. Experimental investigation on combustion and particulate emissions of the high compressed natural gas reactivity controlled compression ignition over wide ranges of intake conditions in a multi-cylinder engine using a two-stage intake boost system, Fuel Processing Technology 228: 107161.

Li, J.; Yang, W.; Zhou, D. 2017. Review on the management of RCCI engines, Renewable and Sustainable Energy Reviews 69: 65–79.

Li, J.; Zuo, Z.; Jia, B.; Feng, H.; Wei, Y.; Zhang, Z.; Smallbone, A.; Roskilly, A. P. 2021. Comparative analysis on friction characteristics between free-piston engine generator and traditional crankshaft engine, Energy Conversion and Management 245: 114630.

Li, T.; Wang, B.; Zheng, B. 2016. A comparison between Miller and five-stroke cycles for enabling deeply downsized, highly boosted, spark-ignition engines with ultra expansion, Energy Conversion and Management 123: 140–152.

Li, T.; Zheng, B.; Yin, T. 2015. Fuel conversion efficiency improvements in a highly boosted spark-ignition engine with ultra-expansion cycle, Energy Conversion and Management 103: 448–458.

Li, W.; McKeown, A.; Yu, Z. 2020. Correction of cavitation with thermodynamic effect for a diaphragm pump in organic Rankine cycle systems, Energy Reports 6: 2956–2972.

López, J. J.; García, A.; Monsalve-Serrano, J.; Cogo, V.; Wittek, K. 2020. Potential of a two-stage variable compression ratio downsized spark ignition engine for passenger cars under different driving conditions, Energy Conversion and Management 203: 112251.

Lu, Y.; Pei, P.-C. 2015. Performance evaluation of 4-cylinder 5-stroke internal combustion engine, Chinese Internal Combustion Engine Engineering (2): 18–24. (in Chinese).

Ma, F.; Yang, W.; Xu, J.; Li, Y.; Zhao, Z.; Zhang, Z.; Wang, Y. 2021. Experimental investigation of combustion characteristics on opposed piston two-stroke gasoline direct injection engine, Energies 14(8): 2105.

Mali, B.; Shrestha, A.; Chapagain, A.; Biswokarma, R.; Kumar, P.; Gonzalez-Longatt, F. 2022. Challenges in the penetration of electric vehicles in developing countries with a focus on Nepal, Renewable Energy Focus 40: 1–12.

Meschendörfer, K. 1989. Membran-Verbrennungsmotor. Patent No DE000008909481U1. Available from Internet: (in German).

Milojević, S.; Pešić, R.; Davinić, A.; Taranović, D.; Petković, S.; Hnatko, E.; Stefanović, R.; Veinović, S. 2018. Influence of variable compression ratio on emission and vibe function parameters of experimental engine, in International Congress Motor Vehicles & Motors 2018, 4–5 October 2018, Kragujevac, Serbia, 227–244. Available from Internet:

Mofijur, M.; Hasan, M. M.; Mahlia, T. M. I.; Rahman, S. M. A.; Silitonga, A. S.; Ong, H. C. 2019. Performance and emission parameters of homogeneous charge compression ignition (HCCI) engine: a review, Energies 12(18): 3557.

Morfeldt, J.; Davidsson Kurland, S.; Johansson, D. J. A. 2021. Carbon footprint impacts of banning cars with internal combustion engines, Transportation Research Part D: Transport and Environment 95: 102807.

Möller, A. A. 2019. Cam-less valve train opportunities – implementing a Freevalve valve train in an automotive application, in VDI Wissensforum GmbH (Ed.), Ventiltrieb und Zylinderkopf 2019 – im Kontext von Euro VII und E-Mobilität.

Naresh, P.; Babu, A. V. H. 2015. Concept of six stroke engine, Journal of Advancement in Engineering and Technology 3(4): 1–3.

Noga, M. 2018. Five-stroke internal combustion engine – yesterday, today and tomorrow, IOP Conference Series: Materials Science and Engineering 421(4): 042058.

Noga, M. 2017. Selected issues of the indicating measurements in a spark ignition engine with an additional expansion process, Applied Sciences 7(3): 295.

Noga, M.; Sendyka, B. 2014. Increase of efficiency of SI engine through the implementation of thermodynamic cycle with additional expansion, Bulletin of the Polish Academy of Sciences Technical Sciences 62(2): 349–355.

Noga, M.; Sendyka, B. 2013. New design of the five-stroke SI engine, Journal of KONES Powertrain and Transport 20(1): 239–246.

Noh, H. K.; No, S.-Y. 2017. Effect of bioethanol on combustion and emissions in advanced CI engines: HCCI, PPC and GCI mode – a review, Applied Energy 208: 782–802.

Nuccio, P.; Marzano, M. R. 2008. Historical review of variable valve actuation systems, in 13th International Conference on Applied Mechanics and Mechanical Engineering: AMME-13, 27–29 May 2008, Cairo, Egypt, 12–38.

Ochieng, A. O.; Megahed, T. F.; Ookawara, S.; Hassan, H. 2022. Comprehensive review in waste heat recovery in different thermal energy-consuming processes using thermoelectric generators for electrical power generation, Process Safety and Environmental Protection 162: 134–154.

Palanivendhan, M.; Modi, H.; Bansal, G. 2016. Five stroke internal combustion engine, International Journal of Control Theory and Applications 9(13): 5855–5862. Available from Internet:

Pan, J.; Khajepour, A.; Li, Y.; Yang, J.; Liu, W. 2021. Performance and power consumption optimization of a hydraulic variable valve actuation system, Mechatronics 73: 102479.

Pandey, J. K.; Kumar, G. N. 2022. Effect of variable compression ratio and equivalence ratio on performance, combustion and emission of hydrogen port injection SI engine, Energy 239: 122468.

Paykani, A.; Garcia, A.; Shahbakhti, M.; Rahnama, P.; Reitz, R. D. 2021. Reactivity controlled compression ignition engine: pathways towards commercial viability, Applied Energy 282: 116174.

Pfeffer, V.; Wirbeleit, F. 1988. Arrangement for Controlling the Oil Feed to a Control Chamber of a Piston with Variable Compression Height. Patent No US4784093. Available from Internet:

Pillai, A.; Curtis, J.; Tovar Reaños, M. A. 2022. Spatial scenarios of potential electric vehicle adopters in Ireland, Case Studies on Transport Policy 10(1): 93–104.

Pirault, J.-P.; Flint, M. 2010. Opposed-Piston Engine Renaissance: Power for the Future. Achates Power, Inc. 17 p. Available from Internet:

Polat, S.; Yücesu, H. S.; Uyumaz, A.; Kannan, K.; Shahbakhti, M. 2020. An experimental investigation on combustion and performance characteristics of supercharged HCCI operation in low compression ratio engine setting, Applied Thermal Engineering 180: 115858.

Pournazeri, M. 2012. Development of a New Fully Flexible Hydraulic Variable Valve Actuation System. PhD Thesis. University of Waterloo, Waterloo, ON, Canada. 168 p. Available from Internet:

Pournazeri, M.; Khajepour, A.; Huang, Y. 2017. Development of a new fully flexible hydraulic variable valve actuation system for engines using rotary spool valves, Mechatronics 46: 1–20.

Pournazeri, M.; Khajepour, A.; Huang, Y. 2018. Improving energy efficiency and robustness of a novel variable valve actuation system for engines, Mechatronics 50: 121–133.

Ragupathi, P.; Barik, D. 2023. Investigation on the heat-to-power generation efficiency of thermoelectric generators (TEGs) by harvesting waste heat from a combustion engine for energy storage, International Journal of Energy Research 2023: 3693308.

Raheem, A. T.; Aziz, A. R. A.; Zulkifli, S. A. M.; Rahem, A. T.; Ayandotun, W. B. 2022. A review of free piston engine control literature – taxonomy and techniques, Alexandria Engineering Journal 61(10): 7877–7916.

Raide, V.; Ilves, R.; Küüt, A.; Küüt, K.; Olt, J. 2017. Existing state of art of free-piston engines, Agronomy Research 15(S1): 1204–1222. Available from Internet:

Redon, F.; Kalebjian, C.; Kessler, J.; Rakovec, N.; Headley, J.; Regner, G.; Koszewnik, J. 2014. Meeting stringent 2025 emissions and fuel efficiency regulations with an opposed-piston, light-duty Diesel engine, SAE Technical Paper 2014-01-1187.

Reitz, R. D. 2013. Directions in internal combustion engine research, Combustion and Flame 160(1): 1–8.

Ryan, T.; Matheaus, A. 2003. Fuel requirements for HCCI engine operation, SAE Technical Paper 2003-01-1813.

Salvi, A.; Hanson, R.; Zermeno, R.; Regner, G.; Sellnau, M.; Redon, F. 2022. Initial results on a new light-duty 2.7-l opposed-piston gasoline compression ignition multi-cylinder engine, Journal of Energy Resources Technology 144(9): 092302.

Santos, N. D. S. A.; Roso, V. R.; Malaquias, A. C. T.; Baêta, J. G. C. 2021. Internal combustion engines and biofuels: examining why this robust combination should not be ignored for future sustainable transportation, Renewable and Sustainable Energy Reviews 148: 111292.

Schmitz, G. 2003. Five-Stroke Internal Combustion Engine. Patent No US-6553977-B2. Available from Internet:

Sellnau, M.; Foster, M.; Moore, W.; Sinnamon, J.; Hoyer, K.; Klemm, W. 2016. Second generation GDCI multi-cylinder engine for high fuel efficiency and US tier 3 emissions, SAE International Journal of Engines 9(2): 1002–1020.

Senecal, P. K.; Leach, F. 2019. Diversity in transportation: why a mix of propulsion technologies is the way forward for the future fleet, Results in Engineering 4: 100060.

Shaik, A.; Moorthi, N. S. V.; Rudramoorthy, R. 2007. Variable compression ratio engine: a future power plant for automobiles – an overview, Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 221(9): 1159–1168.

Siadkowska, K.; Majczak, A.; Barański, G. 2017. Studying a construction of pistons for the aircraft CI engine, Combustion Engines 168(1): 161–167.

Singh, A. P.; Kumar, V.; Agarwal, A. K. 2021. Evaluation of reactivity controlled compression ignition mode combustion engine using mineral diesel/gasoline fuel pair, Fuel 301: 120986.

Solouk, A.; Shakiba-Herfeh, M.; Shahbakhti, M. 2017a. Analysis and control of a torque blended hybrid electric powertrain with a multi-mode LTC-SI engine, SAE International Journal of Alternative Powertrains 6(1): 54–67.

Solouk, A.; Tripp, J.; Shakiba-Herfeh, M.; Shahbakhti, M. 2017b. Fuel consumption assessment of a multi-mode low temperature combustion engine as range extender for an electric vehicle, Energy Conversion and Management 148: 1478–1496.

Soltic, P.; Hilfiker, T.; Hänggi, S. 2021. Efficient light-duty engine using turbulent jet ignition of lean methane mixtures, International Journal of Engine Research 22(4): 1301–1311.

Sprouse, C.; Depcik, C. 2013. Review of organic Rankine cycles for internal combustion engine exhaust waste heat recovery, Applied Thermal Engineering 51(1–2): 711–722.

Taylor, A. M. K. P. 2008. Science review of internal combustion engines, Energy Policy 36(12): 4657–4667.

Tolou, S. 2019. Experiments and Model Development of a Dual Mode, Turbulent Jet Ignition Engine. PhD Dissertation. Michigan State University, East Lansing, MI, US. 156 p.

Tripathy, S.; Das, A.; Sahu, B.; Srivastava, D. K. 2020a. Electro-pneumatic variable valve actuation system for camless engine: part I – development and characterization, Energy 193: 116740.

Tripathy, S.; Das, A.; Srivastava, D. K. 2020b. Electro-pneumatic variable valve actuation system for camless engine: part II – fuel consumption improvement through un-throttled operation, Energy 193: 116741.

Uusitalo, A.; Honkatukia, J.; Turunen-Saaresti, T.; Larjola, J. 2014. A thermodynamic analysis of waste heat recovery from reciprocating engine power plants by means of organic Rankine cycles, Applied Thermal Engineering 70(1): 33–41.

Vaja, I.; Gambarotta, A. 2010. Internal combustion engine (ICE) bottoming with organic Rankine cycles (ORCs), Energy 35(2): 1084–1093.

Veza, I.; Roslan, M. F.; Said, M. F. M.; Latiff, Z. A. 2020. Potential of range extender electric vehicles (REEVS), IOP Conference Series: Materials Science and Engineering 884: 012093.

Wang, J.; Duan, X.; Wang, W.; Guan, J.; Li, Y.; Liu, J. 2021. Effects of the continuous variable valve lift system and Miller cycle strategy on the performance behavior of the lean-burn natural gas spark ignition engine, Fuel 297: 120762.

Werding, H. 2007. Scheibenmotor. Patent No DE102007009350A1. Available from Internet: (in German).

Wittek, K. 2006. Variables Verdichtungsverhältnis beim Verbrennungsmotor durch Ausnutzung der im Triebwerk wirksamen Kräfte. Doktors Dissertation. Die Rheinisch-Westfälische Technische Hochschule Aachen, Deutschland. 134 S. (in German).

Wittek, K.; Geiger, F.; Andert, J.; Martins, M.; Cogo, V.; Lanzanova, T. 2019. Experimental investigation of a variable compression ratio system applied to a gasoline passenger car engine, Energy Conversion and Management 183: 753–763.

Wu, Z.; Wu, J.; Kang, Z.; Deng, J.; Hu, Z.; Li, L. 2021. A review of water-steam-assist technology in modern internal combustion engines, Energy Reports 7: 5100–5118.

Yin, L.; Turesson, G.; Yang, T.; Johansson, R.; Tunestål, P. 2018. Partially premixed combustion (PPC) stratification control to achieve high engine efficiency, IFAC-PapersOnLine 51(31): 694–699.

Young, A. G.; Costall, A. W.; Coren, D.; Turner, J. W. G. 2021. The effect of crankshaft phasing and port timing asymmetry on opposed-piston engine thermal efficiency, Energies 14(20): 6696.

Zhang, Z.; Zhang, P. 2018. Cross-impingement and combustion of sprays in high-pressure chamber and opposed-piston compression ignition engine, Applied Thermal Engineering 144: 137–146.

Zhu, S.; Akehurst, S.; Lewis, A.; Yuan, H. 2022. A review of the pre-chamber ignition system applied on future low-carbon spark ignition engines, Renewable and Sustainable Energy Reviews 154: 111872.