A long time ago l needed to know how effiicient a petrol engine would be with normal aspiration.
It centred around how much fluid could pass the inlet valves.
I`ll put it another way.
If you take a five gallon can and turn it upside down, with airways in the bottom/top - stay with me - and take the cap away altogether it will empty in x seconds.
How close would you need to hold the top to slow the flow?
l reckon slightly under one quarter of the diameter of the opening.
Which is bad news for boy racers.