When Paul was visiting, I was in the process of attacking two issues on the single
rotor engine.

The first issue one was mixture setting on the Rotec TB40 . The problem is with the
reference pressure to the pressure regulator. My mixture was to rich at WOT to the
point where the engine would just barely run. I emailed the guy at Rotec asking what
to do adjust the pressure regulator to my needs. The answer was that I should find a
place in the intake system for the reference pressure pick up where the mixture turns
out to be right.
To make a long story short, I ended up calculating the pressure situation in the TB40
and determined that the reference pressure was way too high. The second position I
tested resulted in a mixture setting I can live with. In addition, I now have also an
18” tuned intake tube.

The second issue is a persistent oil spill through the crank case breather tube. I
have observed this on the test stand engine as well as on the engine in the airplane.
I just could not believe it was rotor seal blow by, because the two engines are not
totally identical as far a rotor sealing is concerned.
One possible cause I found is two holes in the 12A housings exhaust port are more or
less open into the oil pan. I never payed any attention to those.
Today I did a test on the test stand measuring crank case pressure under different
conditions. At 5500 RPM the pressure in the crank case is 1.5psi, this is with the
crank case breather open.
The next test with the crank case breather closed resulted in the same pressure
reading. The pressure I saw can not result from blow-by because it should have been
higher with the crank case breather closed.
The next step is engine tear down a see what I can find. Hopefully closing off the
two holes will solve the problem.


Richard Sohn
N2071U

http://www.fairpoint.net/~res12/home.html

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