Actually, the intake hose diameter doesn't play into the equation as much as you might think. more air coming in (as being pulled by the engine) will increase the velocity of the air. Is there a loss as you increase the speed of the air? sure there is, but it's not as much as you might think. What's going to be important in your intake piping is to have no sharp bends or rough surfaces. The sharp bends and rough edges cause turbulance, which WILL slow down the intake air.

 

I work in ventilation design... I can say that i agree with most of that too.

The only thing a smaller diameter will cause is increased velocity, and some presure drop. (think of more air rubbing the side of the duct)

I agree with bobec... i don't know if 100+ more dollars is going to make me want 18% (my number) to 22% (bobec's number) more air flow when i have a turbo pulling it in anyways...

Now if they had hard lines that aren't accordion like for the air to flow thru... ohh now we'd be talking.

 

Yeah the accordion lines were the first thing to go on my car. That's part of the "rough surfaces" thing that I was getting at.