"The Natural Philosopher" wrote in message
...
To the best of my knowledge, diesel engines have "always" (*) used
injectors to define the timing of the ignition.


Nope. Tractors often use(d) manifold injection.

Irrespective of *where* the fuel is injected (manifold, pre-combustion
chamber or direct into cylinder) it is the injection of a dose of fuel as a
spray of tiny droplets which determines the moment of combustion - isn't it?

Or are you saying that some engines injected fuel into cool air during the
induction stroke, then compressed the fuel-and-air mixture (as opposed to
just the air) and let combustion occur when the air had been compressed to a
high enough temperature? Didn't that make the timing of combustion extremely
variable, without any control over the duration of combustion, whereas
injection into the pre-heated air allows a long period of injection to give
prolonged burn.