George, et al,

 

I'm not a Skip, although on days like this I wish I were a Skip of some sort.

 

I will try to correct my errors (as pointed out by George) whilst Eating Crow, although typing with greasy fingers is difficult.

 

I went down the wrong path by visiting an United Kingdom Measurement Laboratory web site AND making an ASSumption about a "port" on the back of the VM MAP sensor while failing to talk to anyone at VM.  Gulp.... I have just now gotten off the phone with VM - with many of my questions answered.

 

George is absolutely correct. 

 

1.  The "port" on the back of the VM MAP sensor is used to seal the sensor at the proper setting.  The sensor does indeed read absolute manifold pressure. 

 

2.  To check the MAP indicator reading before engine start, turn the altimeter to zero MSL and read the pressure from the Kollsman window.  It should match the MAP readout within about 1%.

 

3.  The snubber valve can become contaminated (plugged) with effluent if it is mounted below the tap into the induction system.  Some "nose down" parked airplanes use a loop in the connecting tube to keep goop away from the snubber.  A plugged snubber can certainly lead to delayed MAP indications.  It can be cleaned with acetone.

 

It is still difficult to compare Ram Air induction systems.  Certainly it is difficult to measure the pressure rise against ambient pressure.

 

Utilizing effective Ram air systems does have an implication on injector fuel atomization with the current injector design.

 

I apologize for presenting misleading information and I would hope this is not like the movie "Groundhog Day" - If only I had used disappearing ink.