To be a Diesel engine it must operate at a constant pressure during the power stroke. To do that you must inject fuel into the engine at a constant rate during the power stroke.
All of the fuel in most diesels is injected before TDC. The constant pressure part of the ideal diesel cycle is combustion. The power stroke is expansion.
http://www.ac.wwu.edu/~vawter/Physic...leEngines.html
I call them diesels because that what they were called when I started modeling. I don't intend to change what they are called. They work well enough for me to enjoy.
Diesel injections systems exist which inject multiple times during combustion. With electromechanical injectors it seems that injector control isn't an issue, yet there are no high RPM diesel engines.
There was also a note about an expansion rate limit for diesel fuel engines, meaning that above a certain RPM you simply get no more power because the volume in the cylinder is expanding too quickly to extract it. I've also read that fuel burn rate is slow, and this also limits RPM. It would take a bit of reasearch to validate some of these things.
Could we build a model size injected diesel fourstroke that would run at 8-10kRPM?
On a side note, I ran a cross a fresh article from Germany that talked about synthetic diesel fuel for vehicles. The goal is reduced emisions. The fuel has a cetane rating greater than 75. Reading about the new low sulphur diesel becoming available int he US now, it has a cetane rating of 55-60. This is interesting by itself as kerosene is much lower than that.
Greg