Mailing List flyrotary@lancaironline.net Message #22117
From: WALTER B KERR <jbker@juno.com>
Subject: Re: [FlyRotary] Re: More MAP measurement questions(Ram pressure)
Date: Wed, 18 May 2005 17:12:06 -0400
To: <flyrotary@lancaironline.net>
Thanks for the comments.  What are the inside diameters of your tubes (assuming primary and secondary are different)?  Also, what RPM are you seeing static, when you said you measured essentially 30"?   Do you think you could be getting any ram-air effect in your MAP port with the open end pointing somewhat into the air stream?
 
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I do not understand your question Rusty. A good pitot pressure measures almost 100% ram pressure. This is exactly what plenum static pressure is equal to. There is nothing adding work or pressure ratio to the air between the plenum or T/B and the runner. You can not measure a pressure higher than what is in large plenum, ie very low average velocity through it. Apparently some think there is a magic here that the ram pressure is higher than the stopped air pressure. If you put a static probe, a pitot probe, and a downstream pitot probe in a system they will all read the same number (ignoring  frictional losses)
 
Bernie
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