Hello everybody i'm new here but I would like to give my .02 about intakes from a engineering prespective.. bare with me
The popular belief is that CAI performs better than SRI is because CAI suck in colder air but infact the difference in IAT are negligible. The advantage of the CAI lies in fluid dynamics. The best intake maximize both air flow velocity (under engine vacumm) and volumetric efficiency (cylinder filling).. that is done using the correct lenghts and cross sectional diameter of piping for a particular engine. For example a tube with a smaller cross sectional area would maximize air flow and volumetric efficency at lower RPMs but would cut out and starve the engine of air at higher RPMs. A larger tube would sacrafice air flow velocity at lower RPMs but maximize volumetric efficency at high RPMs. A longer tube would create a pressure differential meaning faster intake air velocity but you would always run the risk of maxing out the volumetric efficency at higher RPMs.
Companies like AEM understand this and employ different piping diameters in their CAIs, for example the Intergra LS run 2.5", GSR run 2.75" and Type-R runs 3" due to their difference in redline and volumetric efficiency ranges compared to the rev band. Also if you notice their dyno graphs most of their gain lie in the mid RPM range, otherwise the dyno graphs would look like carbon copies of running a much cheaper SRI.
Most of the people who knows me know what a big JDM whore I am.. I guess its the new fad. but back to intake dynamics.. ever notice how just about every CAI manufacturer out there are american companies? AEM, Injen, Weapon R, etc. JDM is all about individual throttle body w/ velocity stacks, weird shaped CF intakes, and ARC induction boxes, I guess they're not as worried about "sucking in warm air from under the hood" as we are (no offense/ not directed to anybody here, I am just trying to put down the popular belief). Have anybody ever seen the weird shaped Carbon Fiber J's racing intake on hondas? believe it or not it's not just pretty looking, it's functional! The weird shape is in fact a taper tube design that tapers in from 3.5" at filter to 2.75" at the TB, volumetric efficiency graphs shows that a smooth taper design generates a better flow velocity than a constant diameter and generates more low and midrange power when compared to a traditional SRI, and since it's not a long tube, it would not max out at high RPM's like traditional CAIs. The Japanese calls these types of tapered intakes Tsuchinoko chambers. Also since the walls are made from composite it does not conduct as much heat as metal walled intake tubes we are all used to seeing, smart huh?
I would go on but I think everyone would be too bored out of their minds by now
