<...Do you think you could be getting any ram-air effect in your MAP port ...>
Not sure what difference it would make.  Dynamic pressure at 120 kias is a little over 7" of WATER (that's about 0.55" Hg or 0.27 psi.  At 150 kias q is 0.87" Hg (0.43 psi).  That's if you recover it ALL with NO losses at all.  For takeoff purposes, at 60 kias it's 0.068' Hg or 0.137 psi
Don't use it all in one place ... Jim S.

Russell Duffy wrote:

Yes , I measure in the runner and do not have a plenum down stream of the T/B. But Tracy and I have had this very discussion, my MAP attempts to measure the stagnation or total pressure. My comment to Tracy is that if he has a plenum after the T/B , that he is measuring the stagnation pressure. My tube sticking into the runner has a 45 degree slant cut on it and the opening faces toward the average flow. Tracy says that the runner sees all kinds of pressures as the rotor inlet opens and closes. I agree with that, but think you want the average stagnation pressure which is what his plenum measures. I added a lawnmower fuel filter in the MAP line to attempt to dampen any pulses out.

 

 

Hi Bernie,

 

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?  

 

Thanks,

Rusty (more questions, since you're not flying)