square tubing exhaust

[dieseldummy]

Hi,
Last night I helped a friend put 3" square tubing on his pickup for exhaust. It has a distintive deep tone that I have never heard from a 6.5. We didn't put a muffler on it, and it has a different turbo on it, but it definately sounds different than my pickup which is similar, but has 3" round pipe. It was easy to put on, and only cost $35 for the pipe and another $25 for band clamps. Just an interesting thought. Why don't more people do this?

[whatnot]

If you look at an HVAC CFM flow chart for ducts, you would see. Round is much better.

[JoeyD]

I have seen oval pipes on cars with low clearance, looks odd but makes it possible to have 4in pipe under a car with out hitting the ground

[rjschoolcraft]

As whatnot said, the square doesn't flow as well. The effective flow area will be less than the three inch round due to separation and turbulence in the corners.

[dieseldummy]

The flow thing makes since, but what if larger tubing was used? How big would it have to be to equal the flow of a round tube? We did the sqaure tube because it was cheap, not for performance.

[DmaxMaverick]

3" round tubing has an area of about 7.07 square inches. 3" square tubing has an area of 9 square inches, or 29% more. It is about 1/2 square inch less than 3 1/2" round tubing. Effectively, the area of 3" square tubing is about the same as 3 1/2" round tubing.

I don't know if the additional area of the square tubing would be enough to offset any resistance created by the "corners" of the tubing bends. If it were straight, end to end, there would be an advantage. We are able to easily bend the round tubing. Not so easy to bend square tubing. It would seem to me the only area of concern is the way you "bend" the tubing.

My guess is the square tubing will perform as well as the same size round tubing as long as the angles are not too extreme.

Good luck