Hi
Bill,
I could be wrong,
but, I’m fairly certain that the position of the Ec2 manual mixture
control does not necessarily have any deterministic relationship to air/fuel
ratio of the EC2. The resulting air/fuel ratio is a combination of (among
other things) the MCT bin (pointed to by manifold pressure) in which
the engine is operating plus the effect of the manual mixture control
knob.
The narrow band O2
sensor response curve is pretty crappy for any sort of linear interpolation
– but, most have a range of from a few 10 millivolts to approx 1.1
volt. With the higher voltage 1.0 representing higher air/fuel ratios
– somewhere in the vicinity of 12 – 10 :1 air/fuel ratio. Stioch
(14.7:1) voltage is normally around 0.45 volts (or 450 millvolts) and
that is generally the only value that is really rather accurate on a narrow
band O2 sensor.
So with my EFISM if
the air/fuel ratio indictor is in the middle of its range on the display, it
should be yellow in color. I also have a feature that when looking at
the air/fuel indicator screen (the one with fuel flow and fuel used values
displayed), if you press button b3 and b4 together you will get displayed in
the air/fuel ratio window of the actual voltage being read from the O2
sensor. So if the EFISM indicator is yellow and in the middle the
voltage should read somewhere close to 450 mv. IF it is green
and near the right hand limit the voltage will probably be reading around
900 mv indicating an higher air/fuel ratio. If red and to the left
side then it will be reading less than 450 mv.
However, remember
that the curve for the narrow band O2 sensor is not very suitable for
interpolation. The wide band O2 sensor is much better and therefore
you can get more accurate indication of air/fuel
ratio.
So almost all
narrow band O2 air/fuel ratio indictors are only useful in giving you a
relative indication of leaner or richer.
In fact, I am
considering a future modification/option/user selectable Narrow band or wide
band O2 sensor for the EFISM. Initially the wide band O2 sensors were
in the $250 -$300 range, but now have dropped down to around $80 for the
borsch model which makes them more cost
feasible.
I probably did not
answer your question, but that is as close as I could
come.
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Bradburry
Sent: Friday, October 16, 2009 8:57
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Stoich A/F
Ratio?? : [FlyRotary] Re: where's the missing
power?
Good point, Ed.
How much change does the mixture knob on the EC-2/3
allow? Say for instance, if Mike was at 14.7 at full throttle with the
mixture knob at the center position, how far would he have to turn the knob
to the right to achieve 12.65 AFR? I ask this because the A/F gage
will not read that mixture. It will be topped out well before that
mixture ratio occurs. How do you determine best power
mixture?
Bill B
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Friday, October 16, 2009 8:35
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Stoich A/F Ratio??
: [FlyRotary] Re: where's the missing power?
Hi
Mike,
I guess I’m missing
something - If your mixture monitor shows stoich at full throttle, then it’s
not solely an airflow problem – it appears to me that it’s the lack of
sufficient fuel. IF you are at stoich 14.7:1 A/F ratio then that means you
have more oxygen available in your system to support burning more fuel =
more power. You should be able to enrich the mixture
particularly at full throttle (assuming you are wanting full power at full
throttle) to around 12.65:1 air/fuel ratio for best power. I know you
know all of this - that is why I am puzzled by your statement that you feel
it’s an airflow problem when on the surface with the Stoich ratio it would
appear it’s a lack of sufficient fuel.
Ed.
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mike Wills
Sent: Thursday, October 15, 2009 11:22
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: where's the
missing power?
Sorry for my absence on a
topic I started. My nephew had a skateboarding accident last weekend
and is in the hospital in a chemically induced coma until his brain swelling
is under control. And I thought car powered airplanes were dangerous. Stay
away from skateboards.
Tracy - My
mixture monitor shows stoich at full throttle. I suspect an airflow issue
rather than fuel.
Al - my vacuum gauge is located
in the plenum directly behind the throttle
plates.
Lynn - I
agree that the TB inlet is horrible and needs a bell mouth. The inlet is
also pretty obstructed by the cowl which isnt visible in the pics I sent. I
think I'll make an attempt to clean this up some and see if it gets me
anywhere. If not I'll live with it for a
while.
Kelly - always tough to
determine if the problem is an engine issue or if the load is simply too
much for the engine to overcome. I'm going to experiment with the shallow
dive several have suggested and see what
happens.
----- Original Message -----
Sent:
Tuesday, October 13, 2009 4:21 PM
Subject:
[FlyRotary] Re: where's the missing
power?
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Al Gietzen
Sent: Tuesday, October 13, 2009 7:22
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: where's the
missing power?
I dont have a
regular manifold pressure gauge, just an industrial type vacuum gauge ( I
really gotta get an MP gauge). Anyway, the vacuum gauge was indicating 4"
of vacuum.
Where are you
measuring the 4” vacuum? If it is near the ports it is no unusual;
if it is out before the runners; something is
wrong.
Al
__________ Information from ESET NOD32
Antivirus, version of virus signature database 3267 (20080714)
__________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com
__________ Information from ESET NOD32
Antivirus, version of virus signature database 3267 (20080714)
__________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com