Fuel plumbing for an FE

[Anthony]

Dan,

as cross sectional area determines max flow capabilities, the cross sectional area of a circle is pie*r*r, or pie*d*d/4. So, if I have a 2" ID pipe, the cross sectional area would be 3.141 sq inches. If I have a pipe twice in diameter, 4 inches, then the cross sectional area is 12.564 sq inches, 4 X as much. Therefore a 6AN hose has a 3/8" ID, and a 12AN hose, twice the diameter, has a 3/4" ID, the 12AN hose has 4X the cross sectional area, more area for fluid to flow, and should flow about 4X as much as a single 6AN. So, it would take 4 6AN lines to flow about as much as a single 12AN line. However, what you said before is correct as well, in that wall resistance does come into play, and if the cross sectional areas of 4 6AN lines and a single 12AN line are exactly the same, the 12 AN line would flow a little more than the 4 6AN lines due to wall resistance, and would be variable from 1% to 10, 20, 30% dependent upon on the flow rate and viscosity of the fluid, with higher flow rates and higher viscosity fluids having a greater loss to resistance in the 4 6AN lines, and a greater diofference comparing it to the single 12AN line.

Not to open another can of worms, but this also has ramifications in cylinder port design, not that I'm any expert on the subject, but I do like the theory. With an exhaust port, which is purely hot gas, I would think you would want round exhaust ports as an optimal design, with less wall-gas injterface not only for flow resistance , but also less heat transfer. However, you also don;t want a sharp bend in the short side radius, so you may want to raise the floor alittle, blunting the bottom of the circle, to enhance flow in the bottom of the port. With the intake port, it is more complex, as you have a mixture of air and liquid/vapor fuel. You may want more of a square port than a round port, utilizing a flat bottom, for more wall space for fuel to be vaporized, so a round port on the intake side may not be optimal even though a round port is optimal for flow alone, with again taking in consifderation of the short side radius of the port.

As I have found out many times, things are usually alot more complicated than what they appear to be in the first place.