Problem with custom definition compression ratio in ANSYS IC Engine (Fluent)

I have a problem with the custom definition of the compression ratio in ANSYS IC Engine (Fluent). I'm using ANSYS 19.2.
Specifically, it is about a diesel engine full model, which is to simulate the compression phase and the combustion phase in the range of 700 to 760 crank angle (IVC and EVO).
The engine to be simulated has a calculated compression ratio of 15.5, the real being about 14.7.
Because the cylinder pressure and the temperature in the combustion chamber were always too high and the mass in the cylinder was too low, it was concluded that the compression ratio was too high. It was finally set to 13.8 for the simulation, but the same cylinder pressure as well as the temperature and mass profile result when the compression ratio changes.
It seems that the custom compression ratio is not inherited from the DesignModeler.
Curiously, a recalculation from the volumes of the * OUT files and CFD-Post volumes both gives a compression ratio of 16.0. The volume at top dead center is here about 2 cm³ smaller than the calculated volume (compression ratio 15.5).

Is this problem known and is there a solution for this? I am grateful for every tip and solution.

Thank you!

Best regards,

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