Actually, Dave that is not a good indication of back pressure due to a
turbo.  Without the turbine in the housing, the results just really don't
mean much.  All turbo's produce considerably more back pressure than a open
exhaust.  The good installations produce less and the not so good ones can
produce so much back pressure it significantly reduces the benefit of the
turbo and increases the heat load on the engine considerably.  So all for a
turbo - POWER and more POWER!  but reduced back-pressure is not one of the
benefits.

Ed A


----- Original Message -----
From: "DaveLeonard" <daveleonard@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, March 21, 2005 10:44 PM
Subject: [FlyRotary] Back pressure test results


> I did an experiment today to see what effect back pressure from a turbine
> housing has on performance.  My engine is currently set up using an empty
> stock turbine housing as my manifold/muffler.  First I ran the engine with
> the housing and exhaust pipe in place, then I removed the housing and ran
it
> with just the manifold in place.  Here are the results given in static
RPM:
>
>                           MAP 20     MAP 25   MAP 28.5 (WOT)
> With Turbine Housing      2700        3350      4700
> With Manifold only        2790        3450      4790
>
>
> The sound was notably louder without the housing (neighbor came out to see
> what was going on), but not as much of a difference as I was expecting.
>
> These results have convinced me to stick with a turbo (not as much
detriment
> from back pressure as I thought), still working on the installing the
TO4B,
> but it probably won't be done until the Fall (working too hard, and I
don't
> want to interrupt my IFR training schedule).
>
> Dave Leonard
>
>
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