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From: n295vv@aol.com

Brent, your good analysis of the heater parameters has added more questions!

Firstly, I do not have a pressurized IV, and during the last northern Illinois
winter, my door seal was in need  of repair, so the heater system didn't have
to push against any high cabin ambient pressure.

Next, when I mention not having any heat flow at <31" MP, I mean, I didn't
have ANY heat flow--none, zippo!  Elevated airspeed made no difference, but
the minute I raised my MP above 31" , I got loads of heat and air flow. (and
noise)

Now the plot thickens--at Redmond, I saw a factory assembled engine on a
stand, and the sonic nozzles were different--they weren't nozzles with 5/16"
orifices like mine--they were just 1-1/4" tubes welded on in the same place.
Did they change them because the 5/16" nozzles were restricting air flow at
<31" MP, and they didn't tell anyone about the change?

There is the possiblility that they changed from the thick nozzles to tubes
because of noise--I can't even talk to to the tower when my heat is on at
31"+, the background noise isn't even cancelled out by my Bose headset-- must
be 150 DB or more.

Well, I am changing to the new axial control valve, but I don't expect to
resolve the pressure vs flow question.  Has anyone else out there experienced
this problem?

david jones