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min size of port [message #34035] Wed, 10 October 2001 03:14 Go to next message
Observator is currently offline  Observator
Messages: 19
Registered: May 2009
Chancellor
Hi Wayne,

I would ask you about port dimensions of Pi Align
model: back to my PiAfterburner Eminence Beta12LTA:
Fs=45,Qts=0.51,Vas=2,4548cuft,
PiAlign give me
Ve 2,454828132 cuft
Fre 33,08823529 Hz
Qe 1,388888889 -

to achieve exact Fre and Qe for this box, the optimal port
Diameter is 2.408" and Length is 2.515" (calculated in excel).

Use of a larger port cause rise of the Qe/Fre.

Using this port dimensions in other software (WinISD for example)
show me the red numbers for this port: 0,41 mach in Vent, that
means noise or Doppler distortion risk.

Have I to consider this risk or is it something different
for the Pi align approach ?

Thanks in advance,

O'Tor

Re: min size of port [message #34039 is a reply to message #34035] Wed, 10 October 2001 09:33 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18738
Registered: January 2001
Illuminati (33rd Degree)
Depends on the displacement. The Beta LT has peak displacement volume of 42cc, which is only 2.5 cubic inches. That's not very much to push through a 2" diameter port, so airspeed won't get anywhere near 40% mach, which is 300mph and 480kph. By the way, maximum airspeed is at fb, and falls off above that.
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