Originally Posted by GuitsBoy

Yes, yes, yes, i definately agree with you. I doubt the surface area to volume would make any kind of detectable difference. The bigger problem is when you transition fromthe 3" to 4" are you going to flatten the reducer cone or expand to round 4" then flatten in the problem areas. The first choice would be difficult to get the pipes to butt togather nicely once you start squashing, so break out the cutoff wheel, BFH and get ready for big messy welds. The second way would compromise ground clearance where there's full 4" round sections.

Originally Posted by GuitsBoy

HAHAHAHAH!!!!! you cant possibly be serious?!? the 2x2 square has a circumfrence of 8, the 1x4 has a circumfrence of 10. It wouldnt even be the same tubing!

Anyway, yes, as you flatten the round pipe, the cross sectional area lessens. Imagine if you continues to crush it till it was completely flat. How much area would that be? Probably wouldnt flow as well as the original pipe, huh?

That being said, most of our exhausts are way overkill for our applications. You can easily get away with crushing some areas for added clearance.

Here's the formula for fiuring out the cross sectional area of a floval pipe (flat oval)

Original 3" tubing has an area of 7.065 (radius x radius x pi) and a circumference of 9.42 (diameter x pi)

Now lets crush it to 2 inches high. Now the easiest way to think about a floval pipe is to break it into easier shapes. Lets picture it as a rectangle with a half circle on each side. First lets figure out the area of the two half cirlcles (equal to one whole circle) on each side. 1 x 1 x 3.14 = 3.14. So the two half circles have an area of 3.14 sq. inches. Now lets find the circumference. dia x pi gives us 6.28. The circumference of the pipe wont change when you flatten it, so lets take the original 9.42 and subtract 6.28. This gives us 3.14 inches of circumference left over. Half of this will be the flat spot on the top, and half on the bottom, so lets divide by 2. (3.14 / 2 = 1.57) Now lets figure out the rectangular area between the two half circles. We know the pipe is 2" high now, and that we've got 1.57" of flat on the top and bottom, so 1.57 x 2 = 3.14. Now all we have to do is add the area of the two half circle sections to the area of the center rectangular section. 3.14 + 3.14 gives us 6.28 cross sectional area of our crushed pipe, where as the original has 7.065. See the difference?

Of course this example does not take tubing wall thickness into consideration, but you get the idea.

Originally Posted by BitViper

I sure was at the time....


Its not a circumfrence problem its an area problem.....
Area of a square is the square of one side..if that side was 2 then the area would be 4 ..The area of a rectangle is base * height....so 1*4 is four..So I was correct there BUT...

Your calculation of 7.065 Vs 6.28 still right the formula for an elipse = PI*R1*R2.... gives the same results

Bravo!

Originally Posted by JustAnIlluzion

a 20 ton press should do this no problem right?