Since Mazda is thinking of running the engine up side
   down in the new car soon to be introduced I was thinking
   of the best rotation for use in an aircraft.

   That has to be with the exhaust port pointing down.
   That gets the exhaust heat out of the cowl as soon
   as possible. The problem with the stock center housing
   is rotor cooling oil drain back in that orientation. In early days
   I fought against it for that reason.

   Also an off the shelf dual throat Webber 52 mm down draft carb
   can be used with a p-port in a very simple manor. That allows
   moving the engine up 2 inches.  More on this shortly.

   Here is a cut away center housing showing the cooling
   oil drain backs from the rotors. That is the main factor
   the orientation of the engine.

   If we are building our own aluminum center housing
   that should be the way to go. No oil pan is necessary
   just an after market dry sump pump system. One
   AN line from the bottom of the center housing can
   scavenge all rotor cooling oil.

   An AN dash 16 is shown in the TTC engine oil plumbing but
   a dash 8 would be plenty big enough for 250 HP.

   All that breather and oil filler part can be done away with
   in the center housing. Greatly simplifying it.

   Paul Lamar

   Hi Paul, what is the history on engine pic Eng1A.JPG ?

   Steve Carlisle

   That goes back about 17 or 18 years. In those days they called it plugs
   up. The oil pan and rotor cooling oil drain backs were big problems.

   Lew Ross original Moony installation in 1973 used that orientation
   because the crank
   angle sensor or distributor  stuck way up over the top of the rotor
   housing. Later
   engines did away with that crank angle sensor and the distributor of
   course.

   Here are a couple of 3D's with the exhaust down and the dry sump
   oil system with direct oil scavenging. That was Jim Mederer's idea on
   the TTC engine. The dry sump is not drawn in yet. This depends
   on a new center housing designed to allow the cooling oil
   to go straight down.

   It gives a much cleaner installation with lots of room for a cooling
   system on the right side of the engine. What I am most pleased
   with is the possibility of using a 52 mm down draft  Webber carb or
   Webber copy.
   This is going to make the installation much much quicker as
   no messing around with a $1000  EFI. Very straight forward
   and reliable just like an aircraft engine almost.

   This the ball jointed universal motor mount that fits all aircraft.
   Totally adjustable so the prop shaft always comes out of the
   center of the hole in the cowl. Much cheaper to ship as it fits
   in a mailing tube. A traditional welded motor mount requires
   a 3 foot cube box which shipping on that can b several hundred
   dollars.

   Another draw back to the stock plugs up or exhaust down is the
   stock oil pump is raised making it more problematic to prime
   itself. That is another reason for the dry sump system. One
   of the pumps can be used as the pressure pump as done
   on the TTC engine.


     With exhaust down there is no room for an oil pan and a
   down draft air craft or automotive carb or EFI will work.


   Paul Lamar

   Paul,

   I like the exhaust down and out the cowl bottom fast option for all the reasons you suggest.

   But what about exhausts on top and out the upper cowl side(s)? that would minimize convection off the exhausts coming up past the engine and leave the bottom portion of the cowl for cooling (water, oil) virtually unaffected by the exhausts. And certain installations might prefer the side exhausts even if for nothing more than some sort of emotional/looks appeal.

   What would the consequences of that option be?

   Regards,
   Brad Chubb

   The aircraft industry avoids that because there is a history of getting
   carbon monoxide in the cockpit.

   Paul Lamar

Comment to Brad,
Paul I don't think Brad has heard a Rotary unmuffled! Just saying I would rather stand next to a Merlin without hearing protection. The quick opening of the rotary exhaust makes it killer loud.

Bill Jepson



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