Editing Opposed-piston engine (section)

== Design ==
[[File:Opposite piston engine.gif|framed|right|Schematic of a supercharged opposed-piston engine<br>
1. Intake for fuel-air mixture<br>
2. Supercharger <br>
3. Airbox <br>
4. Boost relief valve<br>
5. Outlet crankshaft <br>
6. Inlet crank mechanism<br>
7. Cylinder with inlet and outlet slots<br>
8. Exhaust<br>
9. Water cooling jacket<br>
10. Spark plug]]

Compared to contemporary [[Two-stroke engine|two-stroke engines]], which use a conventional design of one piston per cylinder, the advantages of the opposed-piston engine are:
* Eliminating the [[cylinder head]] and valve-train, which reduces weight, complexity, cost, heat loss, and friction loss of the engine.<ref>{{cite book |last1=Pirault |first1=Jean-Pierre |last2=Flint |first2=Martin |title=Opposed Piston Engines: Evolution, Use, and Future Applications |date=2010 |publisher=[[SAE International]]|isbn=9780768018004 |url=https://books.google.com/books?id=vVQIQgAACAAJ |access-date=20 November 2019 }}</ref><ref>{{cite book|last=Foster|first=D.|chapter=Thermodynamic Benefits of Opposed-Piston Two-Stroke Engines|year=2011|publisher=SAE International|location=PA|chapter-url=http://papers.sae.org/2011-01-2216/|author2=Herold, R. |author3=Lemke, J. |author4=Regner, G. |author5= Wahl, M. |doi=10.4271/2011-01-2216|title=SAE Technical Paper Series|volume=1}}</ref><ref>{{cite web |title=Start-Ups Work to Reinvent the Internal Combustion Engine |url=https://www.nytimes.com/2011/03/31/business/energy-environment/31ENGINE.html |website=[[New York Times]]|access-date=29 November 2019 |date=30 March 2011 }}</ref>
* Creating a [[Two-stroke engine#Uniflow-scavenged|uniflow-scavenged]] movement of gas through the combustion chamber,<ref>{{cite web |title=Opposed-Piston |url=http://achatespower.com/our-formula/opposed-piston/ |website=AchatesPower.com |date=22 July 2018 |access-date=29 November 2019 }}</ref><ref>{{cite web |title=TROPE : Toroidal Opposed Piston Engine |url=https://www.youtube.com/watch?v=AM335uWoYBQ  |archive-url=https://ghostarchive.org/varchive/youtube/20211221/AM335uWoYBQ |archive-date=21 December 2021 |url-status=live |website=YouTube.com | date=19 December 2010 |publisher=frankydevaere |access-date=29 November 2019 }}{{cbignore}}</ref> which avoided the drawbacks originally associated with the [[Two-stroke engine#Cross-flow-scavenged|crossflow-scavenged]] designs of early piston-engines.
* A reduced height of the engine

The main drawback was that the two opposing pistons had to be geared together. This added weight and complexity when compared to conventional piston engines, which use a single [[crankshaft]] as the power output.

The most common layout was two crankshafts, with the crankshafts geared together (in either the same direction or opposing directions).<ref>{{cite web |title=OPRE: Opposed piston Pulling Rod Engine |url=http://www.pattakon.com/pattakonOPRE.htm |website=Pattakon.com |access-date=29 November 2019 }}</ref> The Koreyvo, Jumo, and [[Napier Deltic]] engines used one piston per cylinder to expose an intake port, and the other to expose an exhaust port. Each piston is referred to as either an intake piston or an exhaust piston, depending on its function in this regard. This layout gives superior scavenging, as gas flow through the cylinder is axial rather than radial, and simplifies design of the piston crowns. In the Jumo 205 and its variants, the upper crankshaft serves the exhaust pistons, and the lower crankshaft the intake pistons. In designs using multiple cylinder banks, each big end bearing serves one inlet and one exhaust piston, using a forked connecting rod for the exhaust piston.