Mailing List flyrotary@lancaironline.net Message #22105
From: Russell Duffy <13brv3@bellsouth.net>
Subject: More MAP measurement questions
Date: Wed, 18 May 2005 14:04:55 -0500
To: Flyrotary List <flyrotary@lancaironline.net>
Message
Greetings,
 
I'm working on a new theory about my low MAP reading.  The theory is that this isn't a problem at all, but rather a difference in the way it's being measured. 
 
The TWM TB has a MAP port about 4 inches past the entrance of the TB throat.   That means I'm measuring the air pressure on the suction side of the largest restriction in the system (from wide open space, to 41mm tube).   Since there's no significant restriction downstream from the TB, I would guess that I could measure the MAP at the inlet of the side housing, and wouldn't find it significantly lower than what I'm seeing in the TWM TB.  In other words, I'm measuring the worst possible MAP, which is the suction side.    
 
From what I understand, the typical (if there is such a thing) intake has a large TB, feeding into an open plenum, then into the smaller runners that go to the engine.  If I'm not mistaken, virtually everyone is measuring their MAP in the open plenum, before the air has to enter the smaller runners to go to the engine.  In other words, the people who are reading 30" are doing it on the pressure side of the largest restriction.  
 
I could babble on about this, but my point is to ask where others are measuring their MAP (turbo folks need not apply).  You'll also have to give a general description of your intake layout.   I already know that Ed and Tracy are using the "typical" situation.  Is anyone measuring MAP in the runner to the engine?  
 
Cheers,
Rusty (duty calls...)
 
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