Paul, The impossible has happened, I actually left the ground
yesterday. Flew for 3 hours. Seems my prop is too big as cannot get
over 6500 revs. Currently discussing this with Lonnie Prince. The
EGT went to over 1800 and then I assume burnt away for I now have a
balmy 4-500 degrees. Is there a probe that will stand this temp??
The alternative is to strap them to the outside of the pipe. Not
ideal, but may be an alternative. Ran most of the time at 5000
revs, and wondered why I could only get 100 Kts, and then realised
that the prop was only turning at 1700. 5000 rpm and 21.5 MAP.
Temps were a little too cold. Water 135 and oil 145. What is the
thinking on a thermostat?? Oils pressure was 80 psi, never moved.
Had over 80 litres of fuel added for the second flight of 2 hours
and there is a lot remaining, so fuel consumption was low, as is
indicated by the speed. As you can see all very scientific, but
when you consider that I was just waiting for that moment of dead
silence to suddenly appear as it did twice with my Eggenfellner
monstrosity, I was not in the mood to do many calculations.

Neil.

Congratulations.

Better to use cowl flaps as it cuts the cooling drag when they are
closed. Well worth the trouble. It is worth 3 MPH on my 182.

Here are some pictures for the new guys.

What is the diameter of that prop? It could be too big as the prop
tips are running into the transonic wall.

Is 21.5" MAP the highest you have seen? Sounds like the air filters
are clogged.

Paul Lamar


Neil,

Way to go! Three hours on your first flight is fantastic.

I too saw 1800 EGT's when running a tangential muffler on my
3-rotor. It was reasonably quiet, but didn't perform very well. I
switched to a low-tech 3-into-1 runner manifold and my EGT's
dropped into the 1500-1600 range, and I picked up 20 mph on the top
end. If I were you, I would explore that possibility. Relocating
the EGT probes won't fix the root problem. High EGT's may damage
your o-rings, and/or rotor housings.

Mark S.

Neal try this low back pressure muffler.

Paul Lamar

Mark and Paul, Seems unbelievable that you can drop that much temp
by just putting on a straight pipe. In my ignorance I would have
thought that the temp will be what it is regardless of what happens
after. Can anyone explain this?? However I cannot ignore your
experience and will have to explore the "simpler' option. What
muffler did you use without the tangential? Paul I have looked at
your muffler and am very impressed with the simplicity therein. If
I go with the straight exit pipes then it is little more to alter
the rest while I go. More mods! ARGGGG.

Neil.

Mark S has done a lot of R&D. We all owe him. He is right out there
on the bleeding edge with a 3 rotor P-port. Take off is fine with
four people in a Lancair ES with half power :)

Brian Trubee is testing the new muffler on his 2 rotor side port
RV4.

Neil, Try moving the EGT sensors down stream first. That is the
cheapest mod. My guess is about a foot.

Paul Lamar


Neil,

Since the power also increased when switching exhaust systems, I
attribute the lower EGT's to less back pressure. I envision the
exhaust gasses getting caught in a tornado-like vortex within the
can. The rotary's exhaust is very powerful, so it will eventually
force the exhaust gasses out through the exit, but by then most of
the heat has already been dissipated into the tangential can. In my
mind I see a swirling white-hot fireball within the tangential
muffler. I hope yours is made of 625 inconel.

The idea of the 3-into-1 exhaust is to get the hot gassed away from
the exhaust port as soon as possible, and to streamline the flow,
thereby enhancing power. Our very experienced rotary guru's have
stated that rotaries really benefit from a free-flowing exhaust
system, preferably 105" long port to tip. We probably can't do the
105", but I bet we could do 52.5".

To answer your question about which muffler I changed to after the
tangential, it is called a DNA (Dynamic Noise Attenuation - likely
just a marketing gimmick). But the company doesn't make it any
longer, so that isn't an option. While it doesn't kill the noise
very well, it has been the only muffler I have tried that has lasted
more than a few dozen hours. I figure that's what ANR headsets are
for.

Mark