Why not just have a small compressed air pump driven by gears from
crankshaft or camshaft, with a tank to store a few "starts" full of
compressed air? Seems like an easier fix than an electric driven
compressor.

Max Kallio wrote:
2-stroke diesels need compressed air for starting the engine, so the
turbo (exhaust driven centrifugal supercharger) is out of a guestion
and it produces very little boost at low rpm anyhow.

How about supplementing a centrifugal turbocharger with a high speed
electric motor to create boost needed for starting and to enhance
boost at low rpm?

This would pretty much eliminate the turbo lag and actually help suck
the exhaust out of the cylinder at low rpm.

When the rpm rises, the electric motor could disengage or perhaps even
work as an auxilary generator.

Also, if the turbo has some problems, the electric motor could be used
at full power to help the turbo to spin and create boost at least for
the time it takes to land safely. Of course, the engine should be
able to have enough power to stay airborne at least at low altitudes
(if the load is not exeeded) even when the turbo fails completely.

Links...

www.turbodyne.com