I believe you played with some soft toys in your childhood. I have been told that I would try to stuff a huge teddy bear into a smallish box.
what i was doing was checking the compression ratio.. lol
meaning if the cylinder capacity is 400cc - and the combustion chamber capacity is 40cc you have a static compression ratio of 10:1 - meaning you are packing 400 cc of air mix into a 40cc space. This is usually lower in forced induction engines as the dynamic ratio is different - we can spend days on this over cups of tea and biscuits calculating the mean airflow into the cylinder of a 4 valve/cyl engine with short run intake and above atm pressure.
I think what you are trying to understand is how to lower the fuel consumption - in very short words - get a smaller engine. Leaning out the fuel is not all "aalaa, zabardast, magic, wah wah" it ends in tears along with holed pockets.