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

 

From: Al Gietzen

Sent: Wednesday, September 29, 2010 2:42 PM

To: Rotary motors in aircraft

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

 

 

Rino

----- Original Message -----

From: Ed Anderson

To: Rotary motors in aircraft

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.

 

Ed

 

From: Bill Schertz

Sent: Wednesday, September 29, 2010 9:10 AM

To: Rotary motors in aircraft

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