Thank you for answers. Does anybody know, how about noise, vibration, maintenence? I spoke by e-mail with president and chief operating officer for Finch Aircraft and he said that noise and vibration are heavier and maintenence is costlyer than avgas piston engine. In my opinion, the maintenence should be cheaper, because in diesel engine is less parts to worry about (except cooling issue and gearbox of course). But then again other companies tell otherwise; for example:
SMA
What do you think?