Jim Mederer used a interesting technique to tune the turbo for
            aircraft use. Most turbos are designed for automotive use where
            fast spool up is necessary. The probelm with this is at high
            continuous aircraft power the turbine will over heat and or over
            speed and fail.

            What Jim did was use a controlled leak in the exhaust manifold to
            get just enough boost.

            Works better than a waste gate with low A/R turbos.

            This has a side benefit of reducing the exhaust back pressure. Less
            back pressure more power.

            Paul Lamar

            Hi Paul. I don’t understand! I thought a waist gate was a controlled
            leak in the exhaust manifold.

            Steve Izett

           Yes it is but it is a bit heavy and problematic.
           This  is much simpler and and lighter weight.

           The waste gate only measures the back pressure.
           This device respons to the ratio of back pressure to atmosperica pressure.
           I think it does a better job of keeping the HP matched to the altitude change.

           Of course the jury is still out until we fly it.



           Paul Lamar





           Paul,
              Is the rectangular tube in photos the "Controlled Exhaust Leak" ??................


            Kelly Troyer

       Yes but it is but not that big. Up stream of that there is a one inch orifice.
       To get more boost you go to 3/4 inch. Less boost 1.5 inch.
       Simple, cheap and it works great.

       A waste gate gives you more boost at low RPM. Not what you
       need in an aircraft engine.


       Paul Lamar

   Paul, I like the pictures. sturdy reduction drive! what is the ratio. what would it take to get two of them?

   james whitehurst

   Those are Bell 47 helicopter final drives at $35,000 apiece.
   We did not pay that much as we inherited it from Dave Garber.

   I am working on a much cheaper version using Allison truck transmission
   parts.  We are thinking of a turbo 3 rotor powered Lancair for the Sports
   Class at Reno. We need to come up with 200K $$$$$


   Paul Lamar


Paul, I will follow the net for the updates. I need 2.
 2700 max rpm on the prop I will be using.

james whitehurst

I forgot to mention the Bell is 3:1.

The Allison version will be in the same ball park.

BTW rumour has it the new RXx will be 3.2 litres equivalent
so at the same level of tune as the current 13B  TTC engine we are
looking at 800 HP for a two rotor. It is all aluminium
stock as well.


Paul Lamar


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