"NY" wrote in message
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"The Natural Philosopher" wrote in message
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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.

Also, you don't want the chance that detonation could occur *before* TDC
otherwise the increased pressure of the combustion gases would try to turn
the engine backwards - which at the very least if it only happened
occasionally would result in dramatic loss of power as the engine has to
"fight against" the rogue pre-TDC explosion.

It only needs the engine to get a bit hotter than normal and
ignition-by-compression could occur before TDC.

Anyway, all modern diesels have one injector (at least) per cylinder and it
is the moment of injection which determines the moment of combustion. I've
never seen a diesel engine (turbo or non-turbo, direct or indirect
injection) which didn't have one injector per cylinder.