[SEL] Fuel Intake Compensating Valve Theory/Question

[FRM8198 at aol.com]

Hi List,
On the Fairbanks Morse ZD, there is a compensating valve mounted on  the 
intake of the mixer.  The International LB also has a compensating  valve in the 
air intake circuit.  Both are similar in construction.   They look like a large 
check valve with a few holes in the movable  spring loaded plate.  
I know that the Fairbanks Morse ZD will NOT run with the valve  removed.  At 
least, that is my experience.  I removed the compensating  valve assembly as 
the engine was running and it quit on me.
What is the theory in the use of this compensating valve?  It  seems that 
this device acts as a partial choke to increase fuel flow into the  mixer.  The 
other thing that I wonder about is how the original engine  designer/builder 
discovered that this device was needed.  Does anyone  have any thoughts on this 
subject?  

Francis Maciel
Santa Maria, CA