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Rusty, interesting theory, but I would be inclined to discount fuel droplets as a factor in your rich indicator readings. You say you can hear the engine as it leans and richens indicating that your mixture knob is working. Generally full rich readings indicate a voltage of near 1.0 volts from the O2 sensor. If you really want to check out the O2 sensor, hook a high impedance volt/ohm meter into its out put and see what the voltage swing is as you vary the mixture control.

On mine max rich is around 1.0 volts, mids scale gives me around 0.45-0.6 volts, low end drops off around 0.1.5 - 0.2 volts.

Is the O2 sensor you are using a heated 3/4 wire unit? If so I am wondering whether you might possibly have a ground loop feeding heater voltage onto your sensor lead?

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC

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

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Thursday, April 01, 2004 7:40 AM

Subject: [FlyRotary] Re: Rusty's O2 / EM2 problems.

Greetings,

I haven't had a chance to do anything else with my O2 testing, but I've had an odd thought.

The full story, is that I originally had erratic O2 readings with the rev-2 configuration. Primarily, this was staying on the mid, to low end of the scale, but would then just go away completely, as if it was way too lean.   I had used the same sensor I used before, but now had the EM-2, rather than my old mixture gauge. It didn't take long before I noticed that the O2 sensor was falling apart, so it was replaced with the Bosch 11027 sensor that several of you are using. On the next run, the EM-2 read almost full scale, and I couldn't do much to change it with the mixture knob. I could hear the engine getting richer and leaner, but the reading stayed near full scale. The only time it would change was when I leaned so much that the engine was starting to cut out, then it would plunge to nearly zero.

I'll be testing the reading with my old mixture gauge very shortly, so we'll see what that shows, but by all rights, the EM-2 should be giving me a valid reading. If we assume it's correct, then I'm running so rich, that the O2 reading is maxed through the whole usable mixture range required to run.

Here's the wild question-   Is it possible that the fuel is not atomizing completely due to the 30" distance from my injectors to the engine, and some of it is making it through the engine as "droplets". It's hard for me to believe that could really happen, but it would explain the overly rich O2 reading.

Thanks,

Rusty (shouldn't ask questions so early)