Saab Variable Compression engine
The Saab Variable Compression engine was a development project of Saab Automobile, 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 (CR) for a given engine is almost always constant.
Source: Wikipedia — Saab Variable Compression engine (CC BY-SA 4.0)