Sport Pilot wrote:

You can only get so much speed when you inject the fuel through the
combustion or expansion cycle. High speed diesels get more speed by
injecting more of the fuel early. But an aircraft engine doesn't need
to turn more than 2500 RPM so we should be able to get the benifit of
the longer burn time.


True, but even 2500 rpm is a high speed Diesel. When we speak of low
speed Diesels, those are like the big ship and stationary engines that
run maybe 800 rpm max.