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Internal Combustion Engines
Published in D. Yogi Goswami, Frank Kreith, Energy Conversion, 2017
David E. Klett, Elsayed M. Afify, Kalyan K. Srinivasan, Timothy J. Jacobs
Because two-stroke engines produce twice the power impulses of four-stroke engines for the same rpm, a two-stroke engine generally has a higher power density and is thus smaller and lighter than a four-stroke engine of equal output. The disadvantages of some two-stroke engines have historically been lower fuel conversion efficiency and higher exhaust emissions because of overlapping intake and exhaust processes and the loss of some fresh intake mixture with the exhaust products. For this reason, two-stroke SI engines have largely been confined to either small-displacement applications, such as small motorcycles, outboard marine engines, and small equipment, or large-displacement, stationary applications such as those used in oil and gas industry. Several manufacturers have addressed these shortcomings in recent years and have achieved significant improvements in two-stroke engine fuel economy and emissions (Blair 1988).
Automotive Trends in Asia
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
While two-stroke engines have definite advantages, such as reduced weight and size, higher power to weight ratio and fuel efficiency, fewer parts and lower cost to manufacture, compared with four-stroke engines, their main disadvantage is higher emissions. While a large number of Japanese engine manufacturers, notably Mazda, Subaru, Nissan, and Toyota, were very interested in developing low emission two-stroke engines in the late 1980s, this interest has declined markedly in recent years, due to the problem of overcoming the high emissions levels. However, the work to lower two-stroke emissions lead to the development of direct gasoline injection for four-stroke engines, so the research has had a positive outcome.
Internal Combustion Engines
Published in Don M. Pirro, Martin Webster, Ekkehard Daschner, Lubrication Fundamentals, 2017
Don M. Pirro, Martin Webster, Ekkehard Daschner
Two-stroke cycle gasoline engines are used in applications such as outboard motors, snowmobiles, chainsaws, lawn and garden equipment, and utility purposes such as pumps and lighting plants. These engines are typically lubricated by oil mixed with the fuel with a fuel/oil ratio ranging from 16:1 to 50:1, so some oil is always present in the charge. Under low-speed, low-load conditions (such as trolling a boat), poor combustion can result in a heavy buildup of port and piston crown deposits. Ashless and low ash oils tend to help control the level of deposit formation that is attributable to the ash-containing additives in the formulation.
Numerical analysis of modified crossbreed engine cycle under BS VI norms
Published in International Journal of Ambient Energy, 2022
P. V. Elumalai, M. Parathasarathy, S. Sathishkumar, M. Murugan, A. Saravanan, M. Sreenivasa Reddy, Keerty Venkata Sri Ramachandra Murthy
Here, the two-stroke engine can produce twice the torque and speed as the four-stroke engine because of its ability to complete the full cycle within two strokes of the engine operation (Choi et al. 2002). But the faster rate of operation of a two-stroke engine leads to incomplete combustion of fuel, which results in high fuel consumption with the emission of harmful gases, such as HC, NOx, CO and Sox into the atmosphere (Mavrelos and Theotokatos 2018; Ojapah et al. 2011). This reduces the overall efficiency of the engine.