The Saab Variable Compression engine was a development project of Saab Automobile
Saab Automobile AB () is a defunct 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. In 1968 th ...
, 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 volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values.
A fundamental specification for such engines, it is measured two ways: the stat ...
(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 wh ...
al Saab Variable Compression (SVC) engine, designed for the Saab 9-5
The Saab 9-5 is an executive car that was produced by the Swedish automobile maker Saab from 1997 to 2012.
The first generation 9-5 was introduced in 1997 for the 1998 model year, as the replacement to the Saab 9000. At the time, the car repr ...
. 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 an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinder (engine), cylinders and forms the roof of the combustion chamber.
In sidevalve engines, the head is a simple sheet of metal; whereas ...
closer to the 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 hinged 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 (from Greek: Υδραυλική) 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 counter ...
actuator. This design was originally patented by Gregory J. Larsen of Lakeland, FL USA.
The SVC project was shelved by General Motors, when it took over Saab Automobile, due to cost.
External links
SVC
References
{{Reflist Engine technology Saab engines