Al, is correct in that the EC does not directly
interface with the O2 sensor - however, because the autotune option does
requires the EM2/3 (at least I think I recall that being the case)
to which the O2 sensor is connected to, I suspect the following is
a likely description of how the autotune function works.
My understanding that - the EM2 is a component of the
Auto Tune system of the EC.
I suspect that the EM2 has a circuit to read the
O2 sensor voltage.
If the sensor is putting out around 0.450 volts
(450 millivolts), then the air/fuel ratio is close to stoichometric ratio of
14.7:1 air/fuel. If the EC triggers the injectors and they produce a
mixture that is richer than 14.7:1 then the O2 voltage increases. This
voltage swing is probably detected by the EM2 and a mixture correction signal
sent to the EC to reduce the pulse width being sent to trigger the injectors
thereby reducing the air/fuel ratio and bringing it back to
Stoichometric. Should the O2 voltage drop below 450 millivolts
(indicating leaner that 14.7:1), that deviation is sense by the EM2 and a
correction sent to the EC to richen the mixture by increasing pulse width of
signal sent to injectors.
So no EM2 - no autotune function, no Operational
O2 sensor also equals no AutoTune function.
But, just a SWAG on my part, Tracy may provide the
correct description if he gets back to the local Colorado Library
{:>).
Ed
Sent: Wednesday,
September 29, 2010 2:42 PM
Subject: [FlyRotary]
Re: Auto tune/oxygen sensor
Bill;
The EC is not a
closed loop system – does not use the O2 sensor output – unless something has
changed recently.
Al
-----Original
Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill
Bradburry
Sent: Wednesday, September 29, 2010 8:53
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Auto tune/oxygen
sensor
Bosch 11027 is the O2
sensor that Tracy recommends in the instructions. I think the controller
uses that input to maintain the mixture where you set it. I don’t think
it is only used for setting the map table. YMMV
Bill
B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Al
Gietzen
Sent: Wednesday, September 29, 2010 12:07
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Auto tune/oxygen
sensor
I have the
BOSCH sensor 11027 and it works fine.
That’s what I have
also; and I think mine has something close to 150 hrs and still going fine.
I seldom burn avgas, so that helps.
I think
one needs the O2 sensor for auto tune.
Yes, it does.
As I understand it; with the knobs centered the EM tunes to mid-range on the
O2 sensor; roughly stoichometric.
Al
-----
Original Message -----
Sent: Wednesday, September 29, 2010 11:05
AM
Subject: [FlyRotary] Re: Auto tune/oxygen
sensor
Bill, if
it’s a one wire sensor, then just about any of the "universal" 1 wire O2
sensors you find in your auto store will
work.
If
multiwire (I.e. has a heater element and a separate sensor ground wire),
then you need to get one with the same number of wires. If you get the
same make O2 sensor, then the wires should be the same
color.
Bosch has a wire chart which tells you which color wire is which -
this may help. I always get a Bosch unit - they might cost a few bucks
more, but they are generally good quality, available anywhere and you can
find the wire color code. Here's the wiring color code for the
"Universal" Bosch unit.
Cable
colour allocations for the Universal Oxygen Sensor are as
follows,
sensor
output signal wire = black, sensor heater element cables
=
White (
Note - heater is not polarity sensitive ) Sensor signal
ground
( where
used ) = Grey
Important:
The cable allocations must be assigned correctly.
Otherwise
the
Sensor could be destroyed
Don't
let them sell you a wide band O2 sensor which a novice parts guy might try
to do because they all have 5 -6 wires and might get confused with a Narrow
band O2 sensor with a heater.
Sent: Wednesday, September 29, 2010 9:10
AM
Subject: [FlyRotary] Auto tune/oxygen
sensor
Was
going to do some auto tune in the air yesterday, to get to some regions of
the performance map that can't be reached on the
ground.
Took off
and the O2 sensor indication completely disappeared from the EM-2 display.
Did one circuit of the airport and landed.
Discovered that the O2 sensor
had failed (physically -- the top fell off and separated from the body).
This caused me to raise the following questions.
1. I
believe that the oxygen sensor readout is only that, not used by the EC-2
for control purposes.
2. When
in auto tune, is the EM-2 looking at the sensor for indications of which way
to adjust the mixture? If not, what is the feedback
mechanism?
I went
to the Auto parts store for a replacement, and ran into the problem that
there are 100's of different oxygen sensors, and they need to know what car
it came from. Anyone have the specs on what this sensor
is?
Bill
Schertz
KIS Cruiser
#4045
N343BS
Phase I
testing