There are 3 factors to consider when designing a CAI.

1) CFM
2) temp of the air source
3) Turbulant or vertex flow

The CFM is controlled by 2 factors; pipe diameter and pressure/vacuum. Since we are talkng about an s/c motor pressure vacuum is controlled by the thrust generated with the combination of the impellars and pully diameter. The correct amount of CFM will change if you modify the pulley and possibly changing the ECU. Pipe diamter therefore for this conversation is what we will discuss. Pipe diamter from origin to insertion at the front of ithe ntake should be the same if not only slightly larger than the diamter of the intake itself. Funnelled, or cone shaped mouths at the beginning of the intake often hinder not help air flow. I will discuss that further when I explain vertex flow.

Temp of the air source has less of an impact with a s/c due to the large amount of heat generated during the compression process. Obviously extremely hot air entering the intake will have an effect but 5 deg differance not have as much. The amount of warming of the air inside the the intake tube is rarely significant and for a s/c motor almost irrelevant. Summer to winter changes would be considered an extreme change. Where I live the temp in summer can be upper 90's and winter well below zero. a 100deg spread will effect air density sufficiently. Air temp plays a more significant role with normally aspirated engines.

Now for the part you have all been waiting for...


Vertex flow. Vertex flow is any airflow not parrallel and directional to the main flow of air. Think of eddy currents. Contra or vertex flow can cause overall cfm calculated by volume and speed/rate of travel. In my 2004 Dodge Ram with a Hemi, the factory air box and intake tube created vertex flow that was so detrimental it was measurable. The intake tube was constructed of high impact plastic and a decent insulator from the heat in the egine compartment. The problem was that the tube was constructed like accordian bellows, ribbed inside and out. These ribs along with a few too many beds caused the air not to travel smoothly through the tube. The test I performed is as follows: I removed the tube from the truck and ran air through it. With a CFM gauge/meter I measured the CFM out the other end as well as wind speed. Also using a fog machine at the source I could visually see the flow of air. I purchased an AFE brute force CAI. I repeated the same test. The results were amazing. There was a 22% differance in air speed and CFM. Tube diamter was alomost identical. The main differacne between the 2 was the smoothness of the ID and fewer smoother bends. The brute force produced a smooth non vertice flow out the end. Also sharp bends in the tube or restrictions any where along the tube will also cause vertex flow. So having a flare at the mouth of the tube is not recommended and using a mandrel to bend is most beneficial.

I have a degree in flow dynamics. We use water, smoke,fog, air and other malleable solutions to check CFM, pressures and the like. The aforementioned commentary is not to insult anyone but to help you in your endeavors when creating some of the fine craftsmanship I have seen displayed here. In summary the optimal air in take would be best constructed following these general rules.

1) Keep the tube as short and as straight as possible.
2) when beds are needed use a madrel and keep the bend radius as big as feasable.
3) Using tubing that is the same size from one end to the other.
4) Use tubing that has a completely smooth ID.
5) Do not flare the end.
6) Try to gather the air from outside the engine compartment but not at the expense of many tight bends.
7) To determine which is worse more bends or pullng air from within the compartment you will need to perform dynos with both configurations and measure CFM with both configurations.


Sorry for the long dissertation but knowledge is power!!!



Leadfoot

Keep the rubber side down.