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Date: Mon, 24 Aug 2009 15:40:42 -0400
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From: Tim Olson <Tim@5000feet.com>
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Subject: Plenum pressure and Injector performance LOP
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Hey guys, I am remembering a long time ago reading about
how the air pressure surrounding the injector can affect how
well the injector works.  If I'm not mistaken, turbocharged
engines even use some pressure manifold around the injector
to accommodate for the increased Manifold Pressure.

What gets me curious is that I'm having a discussion with some
folks right now who are all having problems running Lean of Peak
and their engines stumble before they get to peak EGT. Between
the group, there are a variety of ignitions such as 2 mags
or 1 lightspeed and one mag, and varieties such as 8.5:1,
9:1, and 10:1 compression ratios, but the one constant is that
they all have what is purported to be a more effective cowl...
the Sam James cowl with a plenum.  So I'm wondering if the
knowledge base some of you have would provide any insight
to the issue. I originally was worried that the 10:1 pistons
might make LOP operation harder to accomplish, but perhaps
there is just too much air pressure on the outside of the
injector?  The cowl is known to often have too little exit
area, so it could be that the pressure differential is
even too high between the top and bottom half of the
cowl.

Any insight you can give?
Thanks,
Tim