You need to shorten the intake runners to 18" to 20" engines for
more power with a 2.85:1 PSRU. Take off RPM will be 6500 to 7500
engine RPM.
Also you will need my cooling book.
Shield the lower left motor mount bushing with ss from the 1500 F
exhaust pipe.
Paul Lamar
Jake, thanks for the pics. It is sad to see such potential in a
project go unfinished. Let's hope you get a good deal on the FWF
package, and get another rotary in the air.
Steve Carlisle
Thanks for the info, what is your cooling book? How would you
shorten the intake runners with the air intake on the right side
like it is? How much power difference would there be? I was
planning on wrapping the exhaust pipes and will plan on a sheild for
the motor mount.
Jake
The plenum is unnecessarily large. Move it to the top of the engine
something like this. You will save weight too :)
This is a P port but an optimized side port will work too only
about 50 HP less.
With the intake runners as long as they are now you will be about
165 to 180 HP. You should get 200 HP with an optimized side port
engine, 2.85:1 PSRU and 18" runners at 6500 to 7500 take off RPM.
With a P-port you would get 250 HP.
There are now better mufflers than that shown in these pictures and
3D's.
http://www.rotaryeng.net/cooling.html
I also sell the book direct for cash $30 + $5 shipping in the US.
More shipping over seas.
Paul Lamar
HI Jake, With all respect to Paul's opinion on what you should do, I
would like to share my opinion. Paul is correct that you will get
more power from shorter intake runners. But the difference in power
is not nearly worth the vast amount of work it would take you at
this point to accomplish the change. It would require changes to
the cowl, building a new plenum, relocating the injectors and
throttle body, changing the cold air intake system, and possibly
building a new engine mount. It is much better to be flying an
airplane with adequate power (while not as much as its potential)
than it is to spend years not flying. Paul is also correct that the
engine mount needs shielding. However, I would discourage you from
wrapping the exhaust. I used to do it but don't anymore. The
problem is the high duty cycle and extra hot rotary exhaust. First
problem is that there is no wrapping material that will hold up for
very long. Standard exhaust wrap with start coming apart on the first
or second flight. The really expensive stuff wont last much past 100
hrs. It stinks as it burns. It is a pain in the arss whenever you
have to do maintenance or inspections of your exhaust system (and you
will want to be inspecting it frequently). Further, it retains the
heat in the pipe. That makes it oxidize away much faster. Also,
because the metal is running at a significantly higher temperature
the metal will warp and fatigue much faster. Welds in particular
will not last long. Trust me, I learned all this the hard way. You
see a lot of pictures of installations with pretty exhaust wrap, but
those are the 'before' pictures, taken before putting a ton of hours
on the plane or race car. Wrapping works fine for a street vehicle,
and in race cars they just replace it after every other race. You
don't want it in your airplane. Ceramic coatings are better. They
prevent oxidation and allow inspection. They do still raise the
operating temperature of the metal and they don't last forever. In
my opinion they are not worth the hassle and expense but not an
unreasonable choice. The shielding you use need not be exclusively
stainless steel. If closer than about 1" to the exhaust pipe it
should probably be steel, but aluminum works fine further away,
especially if there is decent air flow in the area. At that point
you are just fighting radiant heat. In fact, you will find that a
layer of aluminum foil bonded to the inside of your cowl on the hot
side of the engine is indispensable in keeping the fiberglass from
getting too hot.
Good Luck,
David Leonard Turbo Rotary RV-6
To add to what Dave said wrapped exhaust can and has caused a
crash. Also make sure the flanges are correctly welded to the exhaust
pipe. The RX8 engine is less critical as the exhaust is 100 to 200 F
cooler.
Paul Lamar
Thanks for the info Dave and Paul, Is there exhaust systems that
are out there already made. It would be nice to have it go straight
into a muffler and out. the system that it has now plans on an elbow
and then the muffler attached under the airplane and out in the
airflow.
Jake -------------------------------------------- On Mon,
We have gone around on this for the last 16 years and nothing short
of very expensive Inconel will work under the cowl. And then you must
deal with the
extra heat. No off the shelf automotive muffler will work.
They are not designed for a rotary running at 75% full power
hour after hour. In fact some of them are dangerous and at least one
caused a crash.
It is absolutely mandatory to be able to easily visually inspect the inside
of the muffler on a regular basis.
Here are some pictures of failed mufflers.
And here is an easily visually inspected, external muffler that works a
little bit like
a ram jet engine to off set the drag. Brian Trubee in Seattle is flying
one.
http://www.rotaryeng.net/exhaust.html
http://www.rotaryeng.net/coax.html
Paul Lamar
The Rotary Engine News Letter. Powered by Linux. ACRE NL web site.
http://www.rotaryeng.net You Tube
http://tinyurl.com/beqqxas
Copyright 1998-2014 All world wide rights reserved.
