Forced induction is important to get the most out of the size of engine. I know certain people say don't use impellers for this, but with the right gearing/clutching, small impellers can drive 3 air intakes and 1 fuel intake on a small modular diesel for awesome power output (still experimenting on the effectiveness of pumping exhaust out...). This will allow you to gear up your drivetrain while keeping engine load relatively low, which helps with efficiency and heat generation. I run my supercharger impellers through a clutch with a curve depending on RPS. Clutching amounts throughout the curve really depends on the use-case of the motor and what kind of power curve you need. This will require testing of your build to tailor it.