Yes I am aware of the "effective sweep volume " of the piston however the standard takes the entire stroke into account for displacement calculation. In a running Engine, even while the exhaust port is open there is still transfer taking place and cylinder charging taking place whilst the port is uncovered.
Comparing on the same measurement basis - sure makes the DLE 20 appear to be a significantly better desing than the others doesn't it - it uses 20cc of total displacement - including the port open volume.
Sorry guys - ya walked right into that one.
Back to the original programming.
And Kudos to BP for taking care of Roberts shaft.