GTUs

so what you are saying is that, in a high over-lap engine, when the first apex seal opens the exhaust port but not close yet, the exhaust scavenge effect from the supersonic-pulls (reminded me of my thermodynamic class, supersonic flow in a convergeing diverging nozzle) the remain exhaust dilution and some fresh intake charge from preceding cycle. Is that the reason you said a low pressure exhaust helps, or more specificly should I say, you mean a highly scavenged/collected exhaust helps?



more questions:

what do you mean by "over scavenge that face to a lower pressure..." ? Do you smooth the top radius and bottom radius differently? (different vena contracta angles)? from you picture provided, it looks to me that the bottom of exhaust port and top of exhaust port has diiferent radius, is it true? or just me?



How would you use this trick, for a S5 n/a with a medim street port(more over-lap on secondary and aux ports only)

BDC

Here's a new linkon how to swap exhaust port sleeves in my gallery:



http://bdc.cyberosity.com/v/Technical/RollPin-Removal/



B



Btw, here's a link to some pictures of the closing-edge bevelling that Judge Ito stressed so highly...



http://bdc.cyberosity.com/v/Porting/JasonK...veled1.jpg.html



I personally haven't had any adverse effects from not doing the closing-edge bevel, but I am concerned about whether or not it's a good idea if making an exhaust port much wider than stock, thereby leaving less area for the seal to be supported by, resulting in a seal that might banana-shape itself outwards... I've been making it a mandatory part of my exhaust porting ever since the subject became a hot one as I figure it can't hurt, but I wonder if it's necessary for stock applications or not.



Any ideas? Any other experiences?



B