Two- and four-stroke engines: Difference between revisions

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''' The M4+2 engine''', also known as the double-piston internal [[combustion]] engine, is a type of [[internal combustion engine]] invented by Polish patent holder Piotr Mężyk.<ref name="Piotr Mężyk">[http://izoling.beep.pl/www.izoling.pl/badania/czytaj/engine.html Double pistons internal combustion engine], Official site of the city of [[Myszków]], Poland. {{in lang|pl}} {{webarchive |url=https://web.archive.org/web/20170109041809/http://izoling.beep.pl/www.izoling.pl/badania/czytaj/engine.html |date=2017-01-09}}</ref>

The M4+2 engine took its name from a combination of [[two-stroke engine]]s and [[four-stroke engine]]s. The two-stroke combustion engine is characterized by a simple construction and system of air load change, as well as a bigger index of power output. However, its filling ratio is worse than in a four-stroke engine. The ecological index of a two-stroke engine is also unfavorable. The system of valves of the four-stroke engine is its disadvantage. The cylinders of both modules of the double-pistons engine have been joined along one axis with a common cylinder head – in the form of a ring. The pistons are moved at different speeds and with appropriate stage displacement. The two crankshafts are connected with a special transmission that rotates the four-stroke crankshaft at twice the speed of the two stroke crankshaft. The engine is named double-piston because of its construction – double pistons and crankshafts. In the M4+2, the advantages of both engines being connected are obvious; the [[piston]]s of the engine working in one [[combustion]] [[Cylinder (engine)|cylinder]] are set opposite to each other but in different modes. Although[[opposed-piston theengine|Opposed-piston projectsengines]] ofhave connectingbeen two-stroketried modesbefore in oneboth cylinder2 werestroke attemptedand a4 long time ago in the [[opposed-piston engine]]stroke, the combination of the two different cycles had never been tried before. It turned out that the engine is not only ableunique to workthis but also the effects are very promisingengine. The engine has a far greater efficiency over the break-even value known to combustion engines (about 35%) and closer to the one associated with [[steam turbines]] or [[electric engines]] (about 70%).{{Citation needed|reason=this should be in one of the already cited refs|date=April 2010}}

[[File:proto.jpg|thumb|200px|The M4+2 [[prototype]] constructed at the [[Silesian University of Technology]], [[Poland]]]]

Advantages:

Other advantages:

* More efficient [[power (physics)|power]] production (150 [[horsepower]] from 1000 cc of volume in the basic version)

* Ability to use different [[fuel]] types (natural plant oils as well as petroleum)

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The idea was developed at the [[Silesian University of Technology]], Poland, under the leadership of Adam Ciesiołkiewicz.<ref>Journal of KONES Internal Combustion Engines 2002 No. 1-2 {{ISSN|1231-4005}}, the official Polish educational site{{dead link|date=October 2021}}</ref> It was granted the [[patent]] number 195052 by the Polish [[Patent Office]].<ref name="patent">[http://www.uprp.pl/wydawnictwa/wyd/bup_03/bup09_03/bup09_2003.pdf The Polish Patent Office newsletter] {{in lang|pl}} {{Webarchive|url=https://web.archive.org/web/20070125181513/http://www.uprp.pl/wydawnictwa/wyd/bup_03/bup09_03/bup09_2003.pdf |date=2007-01-25}}</ref> The work with the new combustion engine has been done by IZOLING P.W. Company in cooperation with the Silesian University of Technology in Gliwice. Consultations with researchers from Technical University of Kraków were also held. So far, two working engine models have been made. The preliminary model is based on two existing engines (a two-stroke motorbike engine and a four-stroke small machine engine). This model confirms the concept of two- and four-stroke engines' connection. The second model is the functional model.<!-- It realizes the elaborated engine work conception. --> The new solution for a combustion engine was presented during scientific conferences (KONES '2002, Seminary of biofuels 2003, etc.) and in mass media (journals, newspapers, TVP, radio).

The hope to build a modern and universal ecological engine with good technical parameters and low fuel consumption is connected to the double-piston internal combustion engine.

=== The M4+2 engine working cycle ===

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The engine is characterized by:

* Extended gas expansion and limited [[exhaust gas]] temperature on the outlet,;

* The variability of the compression ratio and the possibility of changing the compression ratio during the engine work depending on the temporary load,.

* A beneficial changing of working space during the mixture compression with different crankshafts' polar locations. That makes the pressure forming in the cylinder possible (within reasonable limits).

* An almost constant characteristic of volume increasing during the expansion stage at different piston positions (it influences the steady power transport).

Calculations prove the new engine has more favorable parameters and work indicators:

* The increase of engine [[thermal efficiency]] (Although the mechanical efficiency is lesser than a conventional engine)

* Higher total efficiency – efficiency characteristic is more favorable at medium load. It is comparable with the diesel engine efficiency, so the exploitation of fuel consumption is relatively smaller.

* The higher torque and the higher power output compared to the four-stroke SI engine with the same stroke volume

<!--

<!-- Preliminary research shows that the combustion engine has possibility of lean-mixtures combustion (lambda>1). The properties and the possibility of compression ratio change during normal work forecast the possibility of different fuels combustion (like vegetable oils, low-octane petrol, bio – fuels with high stage of vegetable components). The properties and features of new engine show that it can work as SI or diesel engine.

-->

=== Ricardo 2x4 engine ===

The two-cycle modes are currently being researched at [[Ricardo Consulting Engineers]] in the [[United Kingdom|UK]]. The concept consists in switching from one mode to the other depending on the [[Revolutions per minute|rpm]] value. The four-stroke engine is more efficient when running at full throttle, while the opposite is the case for the two-stroke engine. When a small car under heavy load runs at half speed, the engine automatically switches to the two-cycle mode, which is then more efficient. The research on this showed a 27% reduction in fuel consumption.<ref name="genius">[http://www.theengineer.co.uk/Articles/305434/Stroke+of+genius.htm Engineer Online] Stroke of genius [[The Engineer (UK magazine)]]{{dead link|date=October 2021}}</ref><ref name="mit">[http://www.technologyreview.com/Energy/20494/ Nonelectric Hybrid Engines] [[Technology Review]]/[[MIT]] A novel hybrid engine could slash fuel consumption{{dead link|date=October 2021}}</ref>