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

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