The compression RATIO stays the same, the compression psi is reduced. This is an important point. A lot of energy is wasted in a conventional as heat because the expansion rate of the engine is to small ( lower compression ratio). But to high a compression ratio causes to high a compression psi and you get uncontrolled ignition. The Atkinson/Miller cycle reduces compression psi while maintaining a high compression ratio.

Ducit Amour Hybridae
Mark Smith
Master Certifited Technician
Tempus non reparabilis fugit
"It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it."

Best Tank 35.0 MPG