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