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From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: [FlyRotary] Re: turbo wastegate requirements
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Date: Thu, 11 Sep 2003 23:14:11 -0400
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Jim Sower <canarder@frontiernet.net> wrote:

>>><... That ambient pressure outside certainly needs to be accounted for ...>
OTOH, the back-and-forth between Rusty and I and others seems to indicate that 
5 or
6 psi (or 10-12 in Hg) is all the boost anyone will reasonably need.  So a 
popoff
valve set for 5 psi and forgotten would allow us to take off with 35" (in the
unlikely event we needed that much power) and turbo normalize to 15 k ft so it
would seem that a really dumb popoff valve would work OK.<<<

That's true provided you don't have a problem with the potential 40" MAP you 
could get on a std sea level day... the popoff's whole purpose is to limit MAP 
to some reasonable MAP redline.  If the possibility of hitting 40" is 
acceptable to you I suppose it would be ok.  Alternatively, I also like the 
idea of using a simple pressure switch to sense MAP, set to go off an inch or 
two MAP less than your redline... hooked to big red light on the panel when 
you see it you ease back on the throttle.  The set-and-forget throttles we 
have on the big Continentals and Lycomings incur all the expense and 
complication of a slope controller and an oil-pressure-driven wastegate 
actuator.  If you're willing to live with a little more workload and the 
responsibility of maintaining MAP below redline through diligent piloting, you 
could probably do away with the wastegate and popoff entirely.  Run all the 
exhaust through the turbo, be gentle with the throttle, pay attention during 
descents to maintain your chosen MAP and you would be just fine.  Just another 
thought.

      <Marv>