What is a better intake diameter? 3, or 3.5 in? And what is the differance in the .5in

from what i know about physics, in general, the bigger the opening, the more air u can get into it, but the less momentum and speed that air will have going into the opening and vice versa

I always thought if you keep it kind of small, the air gets packed in more, causing a higher velocity.

/not a physics major

Yes, it will have a higher velocity, but there won't be any more air coming in, actually probably less air, so the car isn't going to make more power. Thats like having an M62 running 15psi boost and an M90 running 15psi boost. The M90 is going to be moving a LOT more air, but its going to be the same pressure. The 3.5" is what you want.

Shawn

The key to air intake on our cars isn't highest CFM, it'* laminar air flow. 3" is the same diameter of the entrance to the upper intake/Supercharger from the throttle body. 3" has been dyno proven to provide more power, because the air doesn't have turbulence added from going to a smaller diameter later on.

I would agree with BonneMeMN, the best would be the same size as the TB. It is more laminar, and that .5 won't be a big difference for a simple CAI. If we had a FWI, or a real hood scoop, then that might be different, but as it stands, there is none.

The throttle body opening, as well as the intake opening measures 2 3/4" to be exact. At the opening to the throttle body it is 3 1/4" ID (3 1/2" OD) and then there is a very gradual transition within the throttle body.
The key to reducing turbulence is smooth walls and smooth gradual transition.
3 1/2" is still best IMO for minimal pressure drop and while maximizing flow....the bigger the better and then a smooth transition down to the 3 1/2" OD connection to the throttle body.

i'd say either way better than STOCK RESTRICTIVE AIRBOX

The series II L67 is much bigger then any others.

The L36 is the same size.

ADTR tested different diameters, and had the best performance response from 3". I belive it was due to the more laminar flow. This is more critical if you run with no MAF screen.