Quote:
Originally Posted by freebeard
This all sounds reasonable, 4-2-1 would definitely be the way to go. Except I would think the exhaust port should be matched. A round pipe on an oval port will induce turbulence.
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Agreed, and I found an excellent series of how-to videos on the actual header fabrication on the
youtube channel of
stainless headers mfg. inc. - the fourth video in particular covers dollying out the primary tube to match the ports for a smooth transition.
The 'fun' part though - the PipeMax program is predicting optimal primary sizes of 1.25" OD at the outside (28.6mm ID), with 'possible torque loss' at around 1.375" OD (31.7mm ID). The ports themselves (inner measurements) are 28mm x 39mm. If I had a converging taper there, it would have to fit within about 75mm length, which seems like a bit much when going down from 39mm to 28.6mm in one dimension (the other dimension would stay the same). On the other hand, using the 1.375" OD means I won't choke the engine too much (for street use) even with the VTEC wild cam, and a 'double length' design may reclaim lost torque.
Quote:
Originally Posted by freebeard
Ceramic coating would be a preservative. It may/may not be more effective for heat than wrapping with a thermal tape.
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I've seen good reports, relatively low measured surface temperatures (below WOT crazy-turbo-boost scenarios) in particular are quite convincing as to the effectiveness - if the heat isn't coming
out thermodynamics says it must be staying
in 
it will depend somewhat on how much it costs, of course.
"For after your catalystic converter:"
LOL ... mind you, a logarithmic horn
does have very good atmospheric coupling
... "cataclysmic converter" perhaps?
Quote:
Originally Posted by freebeard
If you look at vascular structures like capillaries, you see structures like this:
[...]
The 'pipes' don't have a constant cross-section in the vicinity of the branch. At the very least, the branches should be a lower case y not an upper case Y.
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I'd be very cautious about extrapolating across scales that much - the flow regimes will be very, very different. Analogies can definitely be drawn from nature, but only if the
Reynolds Number is very similar. For example, a supersonic aeroplane wing, a bird wing and a fruit-fly wing are operating across wildly different flow regimes, and therefore have to obey completely different 'design rules'. On the other hand, bird wings, model aircraft wings, and light aircraft are in a similar regime and follow common 'rules', or various insect wings are operating in a similar regime and so follow common 'rules'.
In design generally, "Form follows function". In fluid dynamics, "Form follows Reynolds Number".