[peterrr]

well it is olny a model for your thoughts and in the beginning when a little fiery balloon is floating through the combustion chamber a rather accurate one.
But I have explain somehow how small changes in the beginning lead to large changes at the end. It is best to read the explanation in the changed pdf file.
Combustion is almost like building a fire. There is a series of survivalists on TV where the always find some moss that will really burn well. Lets suppose they found a lot of it and also made a funnel shaped basket an filled it with the moss. They hang it from a branch and lite the piece of moss with a tinder.
Then they fan it and it gets going- first slowly and then with a great whoosh.
In engines this is the same you lite the mixture with a spark then fan it by compressing it. An example of things going bad is late ignition. You are not only late but you also don't fan enough so you become even later. Then when the fire gets going the piston goes down so it you cannot build up pressure and finally when the piston decelerates you build up pressure and heat but there is no way to expand it. The good thing is you burned all the gasoline in one whoosh, but the bad thing is you cannot use it. It only heats the engine