Editing Variable displacement (section)

==Present==
There are currently two main types of cylinder deactivation mechanizations used today, depending on the type of the engine's valvetrain. The first is for [[Valvetrain#Pushrod|pushrod]] designs which uses solenoids to alter oil pressure delivered to lock pins in the lifters. With lock pin out of place, the lifters are collapsed and unable to elevate their companion pushrods under the valve rocker arms, resulting in valves that remain closed when the cam pushes on the part in lost motion.

The second type is for overhead cam engines, and uses a pair of locked-together rocker arms that are employed for each valve. One rocker follows the cam profile, while the other actuates the valve. When a cylinder is deactivated, solenoid-controlled oil pressure releases a locking pin between the two rocker arms. While one arm still follows the camshaft, the unlocked arm remains motionless and doesn't move the valve.<ref name="type">[http://alternativefuels.about.com/od/researchdevelopment/a/cylinderdeact.htm "Cylinder Deactivation"], About.com, Christine & Scott Gable</ref> With computer control, fast cylinder deactivation and reactivation occur almost instantly.<ref name="greencar2">{{cite web|url=http://www.greencar.com:80/articles/variable-displacement-better-mpg.php|archive-url=https://web.archive.org/web/20120508210702/http://www.greencar.com/articles/variable-displacement-better-mpg.php|url-status=dead|archive-date=2012-05-08|title=Variable Displacement for Better MPG|website=www.greencar.com|first=Bill|last=Siuru|access-date=2009-11-30}}</ref>

Several automotive manufacturers have engines with cylinder deactivation in current production.

Daimler AG's ''[[Active Cylinder Control]]'' (ACC) variable displacement technology debuted in 2001 on the 5.8 L V12 in the CL600 and S600.

[[Mercedes-Benz]] developed their ''[[Multi-Displacement System]]'' [[V12 engine|V12]] in the late 1990s, which shuts off every other cylinder in the firing order. It was widely deployed on pushrod V8 engines starting with the 2004 [[DaimlerChrysler]] [[Chrysler Hemi engine#5.7 / 345|Hemi]].

Starting in 2003, [[Honda]] introduced ''[[Variable Cylinder Management]]'' on the [[Honda J engine|J family]] engines. Honda's system works by deactivating banks of cylinders, switching from 6 to 4 to 3 cylinders.

In 2005, [[General Motors Corporation|GM]] introduced their ''[[Active Fuel Management]]'' cylinder deactivation system (in the [[GM LS engine|Generation IV small-block]]) which, similar to Chrysler's MDS, switched off half of the cylinders. In 2018 GM introduced an improved system called ''Dynamic Fuel Management''<ref>{{Cite web|url=https://media.gm.com/content/media/us/en/chevrolet/home.detail.html/content/Pages/news/us/en/2018/may/0518--silverado-dfm.html|title=2019 Silverado Leads Industry With Dynamic Fuel Management|date=2018-05-18|website=media.gm.com|language=en|access-date=2019-02-26}}</ref> that shuts off any number of cylinders, in a variety of combinations, depending on immediate needs. The system is based on ''Dynamic Skip Fire,''<ref>{{Cite journal|last1=Tripathi|first1=Adya|last2=Shost|first2=Mark|last3=Switkes|first3=Joshua|last4=Wilcutts|first4=Mark|date=2013-04-08|title=Design and Benefits of Dynamic Skip Fire Strategies for Cylinder Deactivated Engines|url=https://www.sae.org/publications/technical-papers/content/2013-01-0359/|journal=SAE International Journal of Engines|language=en|volume=6|issue=1|pages=278–288|doi=10.4271/2013-01-0359|s2cid=110333295 |url-access=subscription}}</ref> a technology developed by California company Tula Technology<ref>{{Cite web|url=https://www.sae.org/news/2018/05/gm-2019-v8s-with-dfm-system|title=GM adopts advanced cylinder deactivation for 2019 Chevy Silverado V8s|website=www.sae.org|language=en|access-date=2019-02-26}}</ref> and the 6.2L engine incorporating it was named one of [[Ward's 10 Best Engines]] for 2019.

In 2012 [[Volkswagen]] introduced ''Active Cylinder Technology'' (ACT), the first manufacturer to do so in four-cylinder engines.<ref>{{cite web | url=http://www.volkswagen.co.uk/technology/petrol/active-cylinder-technology-act | title=Active Cylinder Technology (ACT) | access-date=2018-01-21 | archive-url=https://web.archive.org/web/20170621192104/http://www.volkswagen.co.uk/technology/petrol/active-cylinder-technology-act | archive-date=2017-06-21 | url-status=dead }}</ref>

In 2015 [[Alfa Romeo]] implemented cylinder bank deactivation in the Giulia and Stelvio Quadrifoglio [[Alfa Romeo 690T engine|V6 engine]], allowing it to operate as an inline-three under light loads.<ref name="AutoTecnica">{{Cite web |last=Daudo |first=Franco |date=March 23, 2019 |title=Alfa Romeo: la tecnica del V6 di Giulia e Stelvio Quadrifoglio |url=https://www.autotecnica.org/alfa-romeo-tecnica-v6-510-cv/ |website=Auto Tecnica |language=it}}</ref>

In November 2016 [[Ford Motor Company|Ford]] announced its compact three-cylinder [[Ford EcoBoost engine|Ecoboost]] engine with deactivation on one of the cylinders. This is the smallest engine so far to use deactivation, and will allow the benefits to be applied in small cars.<ref>{{Cite web|url=https://newatlas.com/ford-ecoboost-cylinder-deactivation/46700/|title=Three cylinders become two to improve EcoBoost engine efficiency|website=newatlas.com|date=30 November 2016|language=en|access-date=2017-10-25}}</ref>

In November 2017, [[Mazda]] announced standard cylinder deactivation in all 2018 [[Mazda CX-5|CX-5]] models, and availability on [[Mazda6]] models.<ref>{{cite web | url=http://www.motortrend.com/news/2018-mazda-cx-5-adds-cylinder-deactivation/ | title=2018 Mazda CX-5 Adds Cylinder Deactivation| work=MotorTrend| date=22 November 2017}}</ref><ref>{{cite web | url=https://insidemazda.mazdausa.com/the-mazda-way/technology/mazdas-new-cylinder-deactivation/ | title = Mazda's New Cylinder-Deactivation Offers Improved Fuel-Efficiency Without Sacrificing Driving Performance| date = 20 December 2017}}</ref>

As of the 2020 model year, about 15% of light-duty vehicles sold in the United States used cylinder deactivation, predominantly used by Mazda (64%), GM (44%), Honda (24%), and FCA (23%).<ref>{{Cite web|url=https://www.epa.gov/automotive-trends/highlights-automotive-trends-report|title = Highlights of the Automotive Trends Report|date = November 2021}}</ref>