According to
Adept Airmotive :: FAQ's
Question: Why is the ADEPT Airmotive not a compression ignition (diesel) engine?
Answer: Although diesel has certain advantages with regards to fuel consumption and economy, we don’t believe that compression ignition technology is best suited to GA applications. Among the reasons for this are:
Poor relationship between torque and power
Diesel engines have to be heavier to contain higher bearing loads
Diesel engines have poor power to weight ratios
Vibration
Satisfactory power generation generally requires high turbo boost with related reliability problems
Diesel fuel weighs more than gasoline
We can meet the fuel consumption targets by using an efficient gasoline engine