“At the end of the day a engine can only consume as much air as it is capable of, having a bigger hole to let the air in doesn’t mean that it will be able to actually to consume more air.”
Volume flow rate is different to pressure. Meaning you can have the same volume flow rate but much higher pressure (the extreme case would be forced induction) which would relate to an increase in power, as it “crams” the additional oxygen in the cylinders. The same is true with naturally aspirated engines however they have only atmospheric pressure to play with (around 101.3kPa absolute pressure) therefore one of the ways to improve power in naturally aspirated vehicle is to reduce the pressure drop across the entire inlet tract (including throttle body). In the case of a boosted car it’s much easier to overcome this inherent pressure drop by simply running more boost.
As for reducing
air speed in the inlet tract it’s not as bad as people make it out to be as slowing
air speed does
decrease the pressure drop across the induction system.
In saying this though if this was to occur around the injector/cylinder port area it’s not good, as it would result in poor fuel atomization, wet-walling etc. Anything before and I wouldn’t be worried to much about speed. It’s only when fuel is involved that speed is important. Speed is important in the
intake manifold but that’s when you start playing around with runner diameter and lengths, to achieve desired savaging etc. Yes savaging does occur in the inlet tract but is quite weak relative to that occurs in the manifold itself.
Basically putting a larger throttle body is the same reason why larger inlet piping, higher flowing filter works!
For more info check out the following links
Boost Part 1
Boost Part 2
