Saab Variable Compression engine

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 closer to the crankshaft.

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 actuator.

[2] The SVC project was shelved by General Motors, when it took over Saab Automobile, due to cost.