Ed,
That was mentioned before by someone (Tracy?). They said that is why
the addresses above and below 31 that have the same manifold pressure should be
the same or very close. The EC-2 could begin to “hunt” moving back
and forth between the upper and lower addresses and if they were not close to
the same, there would be a problem.
Also, reading both Steven and Bob on the injector disable… I don’t
think either of them is correct. I think Tracy
said or implied that if you shut down the primaries, the EC-2 would turn on the
secondaries, period. Not to do this would mean that you would be a fool to try
it if you were staging because the engine would shut down. You also do not
have to turn on the cold start switch because that is done automatically when you
flip the disable switch. If you are staging, the cold start switch should have
no effect because you are just looking for 2 injectors. If you have different
size injectors, you would have to mess with the mixture. Above staging, the
cold start would be effective, but you would still have to mess with the
mixture if you have different size injectors.
I sounds like Steven is actually doing this with his engine and
reporting what happens. If that is true, then theory be dammed, we are staring
at facts unless he used a different wiring scheme.
When will Tracy
be back to tell us what really should happen. You cant make proper decisions
about operating the engine if you don’t know what it is supposed to do
under certain circumstances.
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Monday, July 06, 2009 10:25
AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Potential Low
range MCT (MAP) Problem on EC3/Ec2
I happened to be reading the EC3 operating manual –
doesn’t everyone do this for pleasure reading{:>)? When I came across
something that may explain something that Joe and I observed (and may have
played a role in the hard to start problem we initially encountered (after the
CAS wiring problem was fixed)
Joe has the later version of the EC2 where the lower rpm
operating of the fuel MAP (or more correctly the MCT - Map Correction
Table), where the common assumption/understanding is that the operating point below 2300 rpm is based solely on rpm.
Turn’s out that assumption is not quite correct per this extract
from the EC3 manual.
EC3 Mixture
Correction Table addressing is illustrated on the following page. Note that
below
2300 rpm and 13” manifold pressure (absolute), the MCT address is a function
of rpm as opposed to manifold pressure. If you have an EM2 engine
monitor to display the data, you can use a copy of this chart to record your
table data after the engine is tuned
Not that there are two conditions that must be met before
the EC3/EC2 uses only rpm to determine the lower operating point. The
engine rpm must be below 2300 AND the manifold pressure must be below 13”
Hg. So that implies that if you are operating at 2000 rpm, but your
manifold pressure is at 13.5 or 14 or higher then the EC2 is using the manifold
pressure to determine the operating point and not the rpm.
So lets say you are trying to start your engine – rpm
< 2300 but manifold pressure > 13. Therefore the MCT pointer may be
pointing to the bin corresponding to a manifold pressure that is close to
ambient (29.92” Hg). That is also the point for WOT throttle (Lots
of fuel). So its safe to say that on the first turn of the prop that is
where your Ec3/2 is at. The instance the engine fires, the manifold
pressure immediately begins to drop – how fast it drops will depend in
part on what throttle setting you have. If you throttle is closed, the
manifold pressure will almost immediately drop to low values (presumably below
13” hg) and all is well. If however, your throttle is set at ¼ or
more open, then the manifold pressure is not as likely to drop below 13”
hg. If this is the case, then the operating point is going to be based on
manifold pressure which may be considerably above 13” Hg. That
point in turn may be overly rich for idle conditions and your engine fails to
sustain operation do to excess fuel and floods.
Tracy, of course,
may have algorithms to deal with this, but based solely on the comments in the
manual – looks like this could happen. Particularly in the early
stages, before you get the MCT tuned.
Thought I would pass this on – my older EC2 only
uses manifold pressure across the entire range.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm