The upper deck pressure on the nozzles must be higher than the MP;
preferably by about 3 psi.  There are several ways to achieve this.  If the
upper deck pressure gets lower than the MP, the fuel can go backwards OUT of
the nozzle screens into the hot engine compartment.

You must devise a method to have the pressure higher at the nozzle screen
than the MP.  A set of turbo nozzles with ram air of it's own--specifically
to these nozzles--would do it.  I'm thinking turbo nozzles with an upper
deck reference line fed to the front of the cowl with a bell ram-air duct.

As the upper deck reference pressure approaches MP, the fuel is no longer
atomized as well.  This results in poor vaporization and roughness when LOP.
The reason it still runs smooth ROP is that the poor vaporization isn't as
noticeable.  It's there, just not noticeable to the pilot.

Walter Atkinson
Advanced Pilot Seminars
(225) 925-2066
<www.advancedpilot.com>