The Saab Variable Compression engine was a development project of Saab Automobile
Saab Automobile AB () was a automotive industry, car manufacturer that was founded in Sweden in 1945 when its parent company, Saab AB, began a project to design a small automobile. The first production model, the Saab 92, was launched in 1949. ...
, for which it won an award both in 2000 and 2001.
In a normal internal combustion engine, because cylinder bore diameter, piston stroke length and combustion chamber volume are almost always constant, the compression ratio
The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine.
A fundamental specification for such engines, it can be measured in two different ways. Th ...
(CR) for a given engine is almost always constant.
One exception is the experiment
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...
al Saab Variable Compression (SVC) engine, designed for the Saab 9-5
The Saab 9-5 is an executive car, manufactured and marketed by Saab from 1997 to 2012, across two generations.
The first generation 9-5 was introduced in 1997 for the 1998 model year, as the replacement of the Saab 9000. At the time, the car ...
. 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
In a piston engine, the cylinder head sits above the cylinders, forming the roof of the combustion chamber. In sidevalve engines the head is a simple plate of metal containing the spark plugs and possibly heat dissipation fins. In more modern ...
closer to the crankshaft
A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...
. 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
A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation, with all ...
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
Hydraulics () is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concer ...
actuator. This design was originally patented by Gregory J. Larsen of Lakeland, FL USA.
The SVC project was shelved by General Motors
General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. The company is most known for owning and manufacturing f ...
, when it took over Saab Automobile, due to cost.
External links
SVC
References
{{Reflist Engine technology Saab engines