Warning gross over simplification ahead !
The four stroke internal combustion engine.. it has been around for a while and has been likend to an air pump.
The lower engine is more or less the same in all engines, conceptually at least. Cylinders, Pistons, Crankshaft go whirlywhirl.. power comes out. Of course it is not that simple but only the top of the piston has anything to do with generating power, all the other bits just need to stay in one piece and dictate the capacity. At this junction I’m not too interested in the bottom end yet. Partly because there is not all that much you can do about it.. so it is kind of dull-isch, like a foundation of a building.. you need a good one but you’re not going to buy the house because of it’s nice foundations.
Back to the airpump bit. I don’t know about that, yes it pumps sort of, but the thing that makes it pump is the chemical reaction between air and fuel.
One could thus argue that an engine is a self propagating mechano chemical reactor.
The more air mass you can put in, the more petrol you can burn completely in a way that allows optimum transfer of the heat energy into the mechanical whirly bits and thus powerrrrr.
The upper engine part or head is the interesting bit, it governs the air intake, valve opening and closing, as well as fuel mixing. All in all it dictates the conditions of the chemical reaction for a large part
As thay say in Germany : Einfach kan Jeder.
As putting in more fuel is quite easy, the limiting factor is getting the air& fuel mixture in to the cylinder in a state that is nice to set fire to. You can imagine that this can get quite complicated, quite rapidly.
Simply increasing the bulk flow capacity of a cylinder head will reduce losses due to drag ( good-isch) but that in itself does not ensure that more air mass+ fuel is present in the right place , time and state to go whoosh.
I say whoosh, not bang..it is called an internal combustion engine, not an internal explosion engine.
Bulk airflow is not hard to achieve.. huge ports, large valves in large bores with a cam that will keep the valves as far open for a long as possible. Only one problem: it does not work.
It might work well in an engine that only needs to turn at one particular tempo, it might even put out prodigous amounts of power, but will not accelerate quickly ”through” a load. And that is what is needed for a engine to pull from idle to say 7000 rpm.
Just to cut it short: the goal is to:
1: maximise air mass intake per intake cycle
# reduce air drag
The air has to go into the carb, though the port, take a 90 degree turn and squeeze through a small gap that varies with valve lift then flow into the cylinder. All this changing of direction and squeezing and unsqueezing costs energy. The objective is to make this whole process as energy efficient as possible while
# maximise inertial ramming
Air has mass, quite a bit actualy, and as such it likes to keep going in a straight line. The effect of this is that you can push in a bit more mass in as the molecules in the back will push on a bit.
#maximise air flow quality
How, when and where the air -fuel combo is mixed
# maximise pressure wave tuning
a can of worms to be adressed later
2: create an efficient burning space
luckily it comes with one standard
3: create an efficient burning mixture