I went up to work on my plane and missed the dreamliner takeoff by 15
minutes. Damn!

I'm working on getting the fuel injection map tuned. The engine runs very
strong at some
manifold pressures, but then I advance the throttle, and it starts
surging. It could be
several things- too lean at the new setting, too rich, it could be that
the injectors are
staging, I could have the secondary injectors running too rich,( the
primarys are 28 lb,
the secondary are 40 lb injectors) or some combination thereof. I'm off to
work a bit more
on getting this thing tuned.

Brian Trubee

Try my manifold pressure taps that screw into the oil injector holes.
If your engine does not run better you can send the taps back for a
refund.

Paul Lamar


Brian,
Look at the MAP table values between the low RPM and High RMP tables. At
just above idle, I found that advancing the throttle slowly (slowly
twisting
a vernier control), the engine would be smooth and accelerate slowly. If I
pushed the throttle forward manually, it would surge and then eventually
smooth out. What was happening is that at low manifold pressure, there is
no
way to access the high RPM (low pressure) values to tune these entries.
When
you suddenly advance the throttle, the manifold pressure changes quicker
than the RPM, putting you in a bin that may be richer or leaner than
desired.

By manually changing those values to be similar, the problem went away.

Bill Schertz
KIS Cruiser #4045
N343BS
Phase I testing

That makes sense but there is something else going on.
We don't know when or how often Tracy is reading the
manifold pressure but it only takes a few microseconds at most
to do so with a computer. Lets assume for the moment it takes
1000 micro seconds or 1 ms to do that. There is a reason for
this but I won't go into that yet.

By using our HyTek data acq system and measuring the pressure in the
intake 1000 times a second or every 1 ms we found the pressure
changing rapidly depending on when in the intake cycle you
measure it. AKA e-shaft position.

This is with the engine running at a constant RPM.

At another RPM the pressure wave shape in the intake
manifold is entirely different. This would be true for
any intake manifold regardless of the design. P-port, side port, four
port, six port regardless. Air is bouncing around inside the intake
manifold and plenum in a highly un-predictable fashion.

Each rotary engine installed in an aircraft so far has a unique
design of intake manifold. Since there is also no standard way of
connecting the pressure tap to the manifold it could be located
anywhere south of the throttle. The bottom line is; the pressure
is constantly changing with RPM, e-shaft position and throttle
opening and position of the pressure tap. No two engine installations
are alike. IMHO this is the reason it is so hard to tune Tracy
EFI system.


Paul Lamar

I've got a vacuum leak. I can't get the MAP to go below 15"
hg.  I took an old bicycle inner tube and fastened it over
the air intake in such a way that I could introduce air
through the valve and then sprayed soapy water over the
intake manifold.  It turns out that the leak was around the
primary injectors.  I'll fix that and then do another
check.  I only used the bike inner tube because my shop vac
does not have provision to use the hose as a blower.
Tomorrow I'll go up with a vacuum cleaner that can provide
a high volume of air to do antoher leak check after I fix
the leak around the primaries.

What was happening was that the EC2 was jumping back and
forth between the two Map tables

 More progress tomorrow.

Brian Trubee

Paul, I have a few thoughts on pressure taps generating  MAP sensing. The
success of your injector hole mounted taps is likely due to the signal hole
in the adapter being much smaler than the ID of the conecting hose which
dampens the rate of change of pressure in the hose, and also the length of
hose providing a resavoir of volume. Connecting two rotors which are
mechanically 180 degrees out of phase with a tee close to the pressure taps
allows the rising and falling pressures to cancil out much of the pressure
changees. The location in the rotor housing would seem to have much larger
pressure change rate than along the manifold runner, which is probably true,
however it is located where turbulemt flow surrounds the end of the pressure
tap.

A pressure tap in the manifold runner would be subjected to airflow
across the orifice which would lower the pressure sensed acording to the
speed of the air, making the signal nonlinear. On a three rotor engine IMHO
there should be only two pressure taps on the two rotor housings on the
flywheel end so the rising and falling pressure signals could self cancil. A
third signal would skew the signal higher in amplitude, and possibly promote
harmonics along the tube to the sensor at some value of RPM making it
difficult to use a look up table with the MAP signal changing while
everything else was constant. Additionally judging only from photograps of
the parts, it looks like a 3 rotor is a 180 degree  firing order like the
lemans engine without the flywheel end extra rotor, with 1 and 3 in phase
and 2 180 degrees from them rather than the 120 degree separation some posts
indicate reguarding ignition systems.

Question------is the cosmo engine 120 degrees or 180 degrees.

george grimes

120

Paul Lamar