# Saab Variable Compression engine

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{{Short description|Saab engine technology concept}}
{{Refimprove|date=July 2019}}
thumb|right|300px|The Saab Variable Compression engine.
The '''Saab Variable Compression engine''' was a development project of [Saab Automobile](/source/Saab_Automobile), for which it won an award both in 2000 and 2001.<ref>{{cite web |url=http://www.saab.gr/main/GLOBAL/en/model/95_WAGON/awards.shtml |title=Saab Global, Saab 9-5 SportCombi, Awards |accessdate=2012-03-29 |url-status=dead |archiveurl=https://archive.today/20130217212619/http://www.saab.gr/main/GLOBAL/en/model/95_WAGON/awards.shtml |archivedate=2013-02-17 }}</ref>

In a normal internal combustion engine, because cylinder bore diameter, piston stroke length and combustion chamber volume are almost always constant, the [compression ratio](/source/compression_ratio) (CR) for a given engine is almost always constant.

One exception is the [experiment](/source/experiment)al Saab Variable Compression (SVC) engine, designed for the [Saab 9-5](/source/Saab_9-5). This engine uses a technique that dynamically alters the volume of the combustion chamber, thus changing the compression ratio.

To alter the combustion chamber volume, the SVC 'lowers' the [cylinder head](/source/cylinder_head) closer to the [crankshaft](/source/crankshaft). It does this by replacing the typical one-part engine block with a two-part block, with the crankshaft in the lower block and the cylinders in the upper portion. The two blocks are [hinge](/source/hinge)d together at one side. By pivoting the upper block around the hinge point, the volume of the combustion chamber can be modified. In practice, the SVC adjusts the upper block through a small range of motion, using a [hydraulic](/source/hydraulic) actuator.  This design was originally patented by Gregory J. Larsen of Lakeland, FL USA.<ref> {{US patent reference | number = 5025757 | y = 1991 | m = 06 | d = 25 | inventor = Gregory J. Larsen | title = Reciprocating piston engine with a varying compression ratio}} </ref>

thumb|right|300px|The Saab Variable Compression engine. The SVC project was shelved by [General Motors](/source/General_Motors_Corporation), when it took over Saab Automobile, due to cost.{{Citation needed|date=May 2012}}

== External links ==
*[http://www.fs.isy.liu.se/Lab/EngineLab/SVC/ SVC]
*[http://www.saabnet.com/tsn/press/000318.html SVC - The SAAB network]
*[https://web.archive.org/web/20010709095350/https://www.sae.org/automag/techbriefs/04-2001/techb4.htm SAE Tech Briefs]
*[http://www.autozine.org/technical_school/engine/tech_engine_4.htm SVC engine images]

== References ==
{{Reflist}}

Category:Engine technology
Category:Saab engines

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Adapted from the Wikipedia article [Saab Variable Compression engine](https://en.wikipedia.org/wiki/Saab_Variable_Compression_engine) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Saab_Variable_Compression_engine?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.