A few posts back you criticized my hypothetical but relatively conventional 1.0 litre engine as "noisy" and "hot" compared to the engine you are proposing. Perhaps, but it can also be described as "compact" and "lightweight", and with half the cylinders (and each cylinder being smaller) it has less friction and much, much less surface area. The BSFC map of such an engine, if it were done per usual principles, will have a best efficiency point at probably three-quarters of rated torque, and half of rated speed but will be relatively insensitive to the RPM. You compare this to your own engine, which you describe as quiet and cool. BE CAREFUL - Be objective and don't jump to conclusions about unproven concepts. It's fine to use intuition as a design tool, but it's equally important to not be blinded by it.
By the way, in MY world, 60 horsepower from a 1.0 litre engine is extremely under-tuned. In my world, a 1.0 litre displacement engine makes 160-ish horsepower, and that's with OEM-level reliability, excellent driveability, and emissions-legal operation (typical 1000cc sports motorcycle engine). Admittedly, this type of tuning does not give the best BSFC numbers ...
Back to topic, if you are using 20:1 effective compression ratio, the end of compression pressure will be around 66 times the end of intake pressure. It's plausible that the peak pressure could reach 200 bar, depending on the increase in temperature from combustion. To expand 200 bar down to 1 bar adiabatically requires a 44:1 mechanical expansion ratio (assuming ratio of specific heats is 1.4; if you use 1.3 it changes things a bit). If you work backwards from reaching 1 bar at the end of the power stroke, you will find that you should be using a little less than half the intake stroke - not a quarter of it. Obviously this is back-of-notepad calculations here but I hope you get the idea.
BUT, we are still talking idealism here. In reality, pressure drop through the intake port will mean the pressure in the cylinder is less than expected (translation, valve has to stay open longer than the ideal world predicts to let the same amount of air in). The other thing is that there will inherently be back pressure from pushing the exhaust out the port and down the exhaust pipe. This is not necessarily "friction" loss - in fact the pressure will most likely be dominated by pressure wave effects. And, due to inherent mechanical friction, it's not worth utilizing the last little bit of expansion (the extra friction and losses from having to make the engine bigger to utilize it outweigh the possible gain). Translation, the target pressure at end of power stroke should probably be more like 1.2 - 1.5 bar (guesstimate) not 1 bar. Working backwards, that means you can let more air into the engine on the intake stroke (in the interest of downsizing the engine and reducing friction and heat-transfer area).
