06 gxp custom cai

[f3racer]

I replaced the accordian tube, if I go with the bigger filter I get close to the ground, I don't care what it looks like I wanted cold as possibe air. 4 inch tubing might be nice but this is basically a research project. Also what good does 4 inch tubing do when the opening to the throttle body is only 3 inches.

[starscream5000]

Also what good does 4 inch tubing do when the opening to the throttle body is only 3 inches.

This is how I always looked at it as well.

[mechguy]

Also what good does 4 inch tubing do when the opening to the throttle body is only 3 inches.

Well, not too too much of a difference for short sections. But to realize the difference, consider this exploitation:

The water tap outside of your house has the same outlet as a garden hose. Compare flow of turning the tap on without any garden hose attached. Now turn the tap on with as many garden hoses attached as you can. Pretty big difference.

[SlowNA06]

what good does 4 inch tubing do when the opening to the throttle body is only 3 inches.

The bigger the tube, the slower that same volume of air will have to move through the tube, and the slower the air, the lower the restriction will be through that tube.
Show your work

3" Diameter x 10" tube:
Volume = pi * radius^2 * height
Volume = 3.14 * 1.5^2 * 10
Volume = 3.14 * 2.25 * 10
Volume = 3.14 * 22.5
Volume = 70.65 in^3

4" Diameter x 10" tube:
Volume = pi * radius^2 * height
Volume = 3.14 * 2^2 * 10
Volume = 3.14 * 4 * 10
Volume = 3.14 * 40
Volume = 125.6 in^3

Difference: 77.78% increase in volume from 3" to 4" tube.

The longer the tube, the more air is restricted. This is something that, alone, I suspect would make a noticeable difference only with an exceptional length, such as more than three feet. It's something like a 3% increase in restriction per foot.

Bends add a considerable amount of restriction, though. A 90* bend (or two 45* bends) would be somewhere along the lines of a 17% increase in restriction in a 4 inch tube.

So a 4" x 10" tube with a 90* bend is still ~5% (or shall we say, negligibly) less restrictive than a straight 3" x 10" tube with no bends.