Intake air flow modification

[MetroMPG]

Originally Posted by SVOboy

Anyway, I would like to think that this is just the opposite effect of sticking a big *** 4" CAI, except with a small *** 1.5" HAI. So it'd follow basically the same principles, and as kickflipjr was saying, it would increase velocity as there is less cross-sectional area.

but the HAI feeds the engine less dense air, that's why the throttle has to open further. it needs a higher volume to do the same amount of work.

if you don't change the density of the air, then forcing the throttle to open further because airflow is being starved by an upstream restriction offers you no advantage.

analogy:

1. you're drinking a thick milkshake through a straw with the "mouth" end 75% closed (squished).

2. you squish the "cup" end of the straw 75% closed, which permits you to open up the "mouth" end fully.

have you experienced a change in the amount of effort to drink through that straw? any effeciency gains from the perspective of pumping/throttling losses? i don't see any.