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From: "Bill Bradburry" <bbradburry@bellsouth.net>
To: "'Rotary motors in aircraft'" <flyrotary@lancaironline.net>
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Subject: RE: [FlyRotary] Re: progress report #347c
Date: Tue, 23 Jun 2009 14:04:50 -0400
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Jeff,
I think Al is saying that the baro setting you get from ATC is the pressure
at sea level and that the altimeter then takes the ambient pressure and
indicates the altitude above sea level.  So if you set the altimeter to
field elevation, it gives you a reading in the window of what the sea level
pressure should be.
Bill 

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Jeff Whaley
Sent: Tuesday, June 23, 2009 1:57 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: progress report #347c

I agree with Bill ... If you set field elevation the barometric pressure
will be displayed in the window.
Conversely when you get the ATIS, they give you barometric pressure (BP) -
when you set to BP the correct altitude will be displayed by the altimeter
... that is why it's called altimeter setting. That is the manifold pressure
you should read if engine is off. Your altimeter is affected by both
altitude and local barometric pressure.
Jeff

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Bradburry
Sent: Tuesday, June 23, 2009 11:48 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: progress report #347c

Al,
Hmmmm, Further explanation would be helpful here.  I thought that the
altimeter was actually reading the air column weight or pressure at its
location.  If you set the altimeter to the field elevation, it seems it
should read the barometric pressure in the window.  Since the EM-2 and the
altimeter are reading the same pressure, they should be the same??
Are you saying that there is some calibration table that should be applied?
Why would ATC keep giving you the barometric pressure if that didn't
correlate to the field elevation?
Hep me! Hep me!

But yeah, my main point was that the indication should not be moving around
in the closed hangar.  Orfices and volume are to smooth out pressure pulses
coming from the engine.  If the engine is not running, there are no pulses.
(unless Don is really excited about his plane and his heart is beating
really hard and those pulses are being picked up by the EM-2!  :>) But he
still should see that in the altimeter as well!  )

Bill B 

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Al Gietzen
Sent: Tuesday, June 23, 2009 11:25 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: progress report #347c

Your MP in the closed hangar should read the same as your altimeter.  Set
the altimeter to the field elevation and read the pressure in the Kollsman
window.  If they don't match, one or the other is incorrect. 
-----------------
Don, Bill;

I'm quite certain that is not entirely correct.  There is a correction that
must be applied depending on field elevation.  For example; if the field
elevation is 1500'; you'd multiply the altimeter setting by 0.947.  I have a
table of corrections; give me your field elevation, and I'll give you the
correction.

The best 'filter' for smoothing MAP pulses is not just an orifice
(resistor); but a combination of some volume (capacitance) and an orifice.
You might consider adding some volume (a fuel filter works good) between the
port and your orifice.  Bill is right; it should not jump around when the
engine is not running.

Al G


 The pressure
should also be solid.  It should not jump around in the closed hangar.  If
you are outside, wind on the static source can make it move, but not in the
hangar.

Bill B 

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Don Wallker
Sent: Tuesday, June 23, 2009 12:11 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] progress report #347c

List,
    Thanks for all the great suggestions from my "Not getting full power"
post.  Concerning the RPM dropping out above 6000 RPM.  This weekend I
dropped by my local FBO.  They didn't have any #12 aircraft wire, but after
describing what I was trying to do (eliminate electrical
noise) he suggested #16-2 with shield.  I installed it by tying both #16s
together and running it from the battery to a 5 amp breaker and then onto
the EM-2 and EC-2.  Grounded the shielding near the battery and not on the
other end.  I also moved my high power wires to the injectors and coils away
from other things.  I know that is bad engineering, doing 2 changes at once,
but it was easy to move the wires at that time.  Fired it up, ran it at a
fast idle, and turned injectors on and off.  The RPM stayed on with the
secondaries off, and got squirrelly with the primaries off.  Similar
situation at full throttle, 5880 RPM or so, so I think I have that licked.
The proof will be in the air.  Thanks Tracy and all the rest of you. 
    Sunday I got thinking about the MP pressure being all over the place.
The local RV guru told be that he couldn't get his analog MP gauge to be
steady until he drilled a 1/16th inch hole in a rivet, and put it in the
line as a dampener.  I thought, that's easy to do!  I noticed that the spout
on my oiler is a small diameter, so sticking a drill bit in it, found it was
1/16 inch.  I cut off 2 inches and inserted a piece in each manifold line,
Tightened it down and fired it up.  6080 RPM!  When a wind came up, it read
6150 for a short time.  
More than I have ever gotten on the ground.  HP display ever read 147 HP!
And the MP had settled down.  Exhaust gas temps are not as high, they are
closer together, but still about 150 f  different..  My theory is that with
the MP being all over the place.  The EC-2 computer, doesn't know what to
do, so is switching back and forth to different MAP addresses as they come
up, trying to do it's best.  With the MP, much steadier, the EC-2 can do a
much better job.  This also seems to explain why the auto-tune never worked.
I'll give that a try soon.  I am working on dampening the pulses down
further.  Tonight, I installed 5 inches of the 1/16th inch tubing.  Still
bouncing around some.  I made a dampener consisting of a green scrub pad,
rolled up very tight, stuffed in a 5/8 inch plastic tube with barbs on both
ends and installed between the 1/16 inch tube and EM-2.  At 2000 RPM it
bounces around between 10.1 and 10.4.  At full throttle, it bounces around a
little more 24.5 to 25.1.  One other thing I noticed, is that with the
engine off, all other electrical off and only the EM-2 and EC-2 on, in a
closed hanger, a cold beer in hand, the MP bounces around from 24.5 to 24.8.
Oh, and my true airspeed reads 14 MPH on the EM-2 when every thing else is
turned off.  
Is all this normal?  Sorry, but I no longer know normal.  What are the rest
of you getting? Is it possible to get the MP rock steady?  5000ft elev, 75 F
    In reference to the guy who was asking about fuel pressure, I set mine
for 38 PSI.  Recently, I hooked up a Vacuum line from the manifold to the
pressure regulator.  As Idle, the pressure is now about 34 and a full power,
about 39 psi.  This has messed with my mixtures, but I will go back and
remap, and will try auto-tune.  The Rotory gods are almost smiling.

Don Walker
N113BR RV-8
Renesis, EC-2 EM-2,  2.85 PSRU
Electric seatcovers, Power ashtray

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