4. Conclusion

The main advantages of variable compression ratio engines are presented in this article. The various technologies that have led to prototypes, as well as "realistic" or innovative projects, have also been mentioned.

Some engines enable the Miller-Atkinson cycle to be run, and sometimes allow a different compression ratio for each cylinder. Other specific features are or can be applied to these engines, such as supercharging, variable valve timing and direct fuel injection.

On the other hand, the means for controlling and/or regulating the compression ratio have not been addressed, even though in the case of an automobile engine, this parameter is of prime importance due to the sudden variations in speed and load to which it can be subjected.

Fuel savings of 35% or more are claimed for partial loads. However, these...