Editing Variable displacement (section)

==Related technologies==
[[Variable compression ratio]]. The best known such system was the experimental [[Saab Variable Compression engine]], which used a hinged block to move the pistons closer to or further from the head, thus changing the size of the combustion chambers. Other experimental systems include the Hefley engine, which uses a sliding crank race on an eccentric shaft,<ref name="hefley">{{cite web|url=http://www.hefleyengine.com|title=乐天娱乐_乐天国际娱乐平台注册㊣24小时在线服务*注册送彩金*》入口|website=www.hefleyengine.com}}</ref> and the Scalzo Piston Deactivation Engine, which uses a four-bar linkage, and has the distinction of being able to stop individual pistons entirely.<ref name="scalzo">{{cite web|url=http://www.scalzoautomotiveresearch.com/technology|title=The Piston Deactivation Engine|website=www.scalzoautomotiveresearch.com}}</ref> There are currently no production vehicles that use any of these designs.

Additionally, some engines such as Cadillac's [[Northstar engine series]] and Ford's [[Ford Modular engine|Modular]] and [[Ford Duratec engine|Duratec]] engines feature a fail-safe mode where if the engine overheats or loses coolant, the engine controller would cut fuel and spark to half of the cylinders.  With valve operation left unaltered, the noncombustive cylinders would air-cool the engine.<ref>{{cite web |last1=Allison |first1=Wesley |title=1997 Ford F-150 - Road Test |url=https://www.motortrend.com/reviews/1997-ford-f150-2 |website=Motor Trend |publisher=MotorTrend Group |access-date=28 May 2025}}</ref>