A clearer question might result in a more useful answer.
I will take a GUESS at what you were asking. If my guess is wrong then please explain what you really want to ask.
HCCI operation is hard to do outside of laboratory conditions. A spark is a fairly robust way of starting a fire in a mixture of fuel and air that is otherwise below its self-ignition temperature (gasoline engine). Squirting fuel into plain air that has just been compressed to well beyond ignition temperature of that fuel is another one (diesel engine).
What happens when you compress your premix to a few degrees short of ignition temperature, what happens if it goes well above ignition temperature before TDC because the ambient temperature went up, what happens when the owner fills up with fuel that came from a different refinery and has slightly different self-ignition properties.
