Where, VSE: swept volume of the displacer piston, VSC: swept volume of the power piston, : phase angle between the displacer piston and the power piston, VDC: dead volume of the compression volume and VD: the overlap volume.
When the minimized value of VC becomes VDC, the overlap volume, VD is able to be lead. Eq. 1 changes to a next equation (part is omitted).
So, when , the minimized value of VC is becomes VDC.
The dead volume of the compression volume, VDC is the minimized volume of the compression space, and a clearance volume when the displacer piston comes the nearest to the power piston.
You must take care the real engine design when the engine is used a normal crank mechanism, because above equations do not hold good when the movements of th epistons are not the sine waves.