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Dave,
Thanks for doing such a great post and for that matter keeping me on my toes. I had never calculated the pressure drop for a laminar to turbulent situation in a typical port but had assumed it was about half to one inch of water depression. Just shows how far out I was on that one! One and all - I want you to note here that any time you see a comment concerning porting that says (in so many words) that the porting was done to get rid of turbulence rest assured that the writer had no idea what they were talking about. Because the Reynolds number is in excess of 2300 the flow in a port is turbulent no matter what. What Dave’s calculations have shown here is that it is deep into the turbulence as well - not just marginally. That means there is nothing we can do porting wise to make in not turbulent!
All that said reading your post Dave also brought to mind (inspired might be a better word) that I forgot one important factor here that will account for some of the correction error seen and I just flat overlooked it (tut tut). When air goes around a tight short side turn it separates but the lower the pressure drop the less it separates and visa versa. When a port is flowed at a high pressure drop the break away is bigger and ‘plugs’ the port more. The result here is that, at say 28 inches, we see a regular SB Chevy exhaust port flow numbers almost as big as a trick Cup Car port. The reality here is that if these two ports were flowed at say 100 inches there would be a far bigger difference between them because the regular port would had a large amount of flow separation on the short side where as the cup car port, having a huge inside turn radius and about a 65 degree angle, would not. So what might only be a small difference as measured at a low pressure drop would be a much bigger one at a high pressure drop.
Other than to reiterate my thanks for a great post and for keeping me on my toes the only question that I still have is – will we see a ‘Baker Plate’?
DV
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