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From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: [FlyRotary] Re: Intake questions
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Date: Thu, 18 Sep 2003 00:39:18 -0400
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>>>  Also it turns out there is no one magic runner length for the DIE effect and 
the length for this effect depends not only on the rpm point you select for 
  this effect to occur but also on your particular engine specifications - 
there that sounds mysterious enough, I think.<<<


Lots of really great information showing up as a result of this thread... this 
has to be one of the longest running discussions we've enjoyed here.  But 
that's not what I wanted to say....

Considering how the DIE works (could the Dynamic Intake Effect possibly have 
resulted in a worse acronym?) I'm really anxious to see the results with the 
turbo.  It seems to me that in a NA engine the DIE is functioning in a low 
pressure system (at least until you get to WOT and the MAP equals the baro 
setting).  I'm wondering if the positive pressure provided by the turbo's 
compressor is going to change how it works.  If we were to liken the intake 
system to an organ pipe, as you lengthen the pipe its resonant frequency goes 
down (and is the same reason you need to tune the runner length for maximum 
DIE at a given RPM).  At a fixed length that pipe will always sound the same 
note when a volume of air causes the column of air in the pipe to resonate. 
 If you increase the pressure, the pitch (frequency) of the note remains the 
same but the volume increases.  Given this phenomenon, I wonder if the intake 
tubes set to the same length as those that are providing an actual DIE in a NA 
application (at a given RPM, of course) will show an increase in DIE with the 
positive turbo pressure, or if the runners will need to be shortened 
(lengthened???) to account for the DIE wave being slowed by the higher 
pressure intake charge opposing it?  OR..., it could be that the DIE is 
negligible in the pressurized turboed system and the best results are to be 
gained by the shortest runner length possible to minimize friction losses on 
the incoming air stream.  Lots to think about.........

        <Marv>