Two slightly weird questions about WBO2 sensors
 

This question relates to the use of WBO2 sensors in piston aircraft for leaning. I'm posting here because no-one in my aircraft group has the level of knowledge that exists around here.

The engine is a normally aspirated, fuel injected, 6 litre, twin plugged boxer 4-cylinder. I run 100LL exclusively. 100 octane "low lead". The "low" is misleading, it has 20 TIMES the amount of lead of the old automotive pump gas. :eek:

However, apparently the NGK WBO2 sensor is lead tolerant. My question does not related to lead.

In certain ops I want to operate at "best power", in others, particularly cruise, I operate Lean of Peak. Currently I leak by finding peak EGT then lean or richen from there.

It's fiddly, requires at least some time operating in the "red box" (risk of detonation), and a few other issue. I want to start using AFR for leaning ops.

I have two specific questions:

1) I frequently use smoke. Smoke is generated by spraying a moderate viscosity mineral oil (similar to former oil for concrete work) into the hot exhaust - this would be upstream of the sensor.

I don't care about accuracy of the sensor while "smoke on" - I'm looking for input on use of smoke oil on the lifespan of the sensor and/or any impact on accuracy (while "smoke off")

2) My exhaust system is a 2-into-1 on each side, they don't join. So, I have to pick which side to monitor. Does anyone have any recommendation on which would be the best side to pick (if I have a choice)? Side that peaks EGT first? Last? Widest EGT spread? Something else?

I know, quite OT, but running out of places to ask

:D

Can't you spray after the sensor? and also why not add another for the other side?

I can't answer your Q directly, but I have an NGK WB unit, with a Bosch sensor. I have avoided Avgas because I was told it kills the sensor in a few hrs. I have had the same sensor for the last 17 yrs. However, at a track meet a week or so ago another 911 driver told me they are tolerant to Avgas. He is a 911 tech, runs a 911 business, and has WBO2 in his 76 911, and runs Avgas. So they may be more tolerant than we think. You would also think the heat of the exhaust (900 Deg C?) would cook any oil residue off the sensor, although it may be erroneous with the oil passing over it at the time?
Alan

If you have one side unmeasured and that side has an issue and goes lean, you may not know until you burn a hole in the piston. An expensive repair with 4 wheels on the ground. A little more concerning at 9000 ft.
I have gone through 2 WB02 sensors on my 930. I think the heat is killing mine, but they do not seem very good long term to me. And mine were both Bosch. Id want one on each side just so if one goes you still have something until you can replace it.

there are so many counter fit bosch sensors and pumps out there . i went through two in a year just trying to dial my motor in . The third one i purchased was from a local auto parts store . it came with a huge registration/serial # and i had to register it with bosch. The other two did not, i was told the ones without the registration #s are counterfeit . so far so good with this one.

The smoke is installed on both sides, and needs to be fairly close to the exhaust port for proper vaporization. It's already installed and I'm not changing it, it works perfectly.

I found a warning about reduced sensor life if the car burns over 1 qt per 1,000 km

I burn 1 gpm of oil when smoke ok.

I think by virtue of that alone it won't work. Although I'm still exploring if that's true if the sensor is powered off (ie heater is off) during smoke.

The NTK/NGK wide bands are more tolerant of leaded fuel. And yes, there are a lot of counterfeit bosch sensors out there. Would a lifespan of 300-400 hours be acceptable?

And you could always take the wide bands out and install the plugs when you know you're gonna be running the smoke oil through the AEIO-360.

A question:
How much exhaust length do you have past the sensor? if too close to the exhaust outlet, there can be inaccuracy from ambient air intrusion.

And opinion: If it were my aircraft, and I were operating it, I'd stay Rich of Peak, or invest in individual cyl CHT and EGT before O2 sensor. To me not worth the risk of burning a piston. And my experience is the bladder is a primary determining factor of range more than fuel so we never were hyper-miling to stretch range.

I mean the sensor. Two, one for each side.

Ah I see. I do have significant space constraints, but I'll see if there's room.

I can't install the sensors before the smoke injector for a variety of reasons, but after reading some other material it may be ok to smoke if the sensor is turned off, ie its heater is off, when I'm smoking.

Nice idea but I smoke a lot, and pulling the cowling between flights is more work than I want to deal with.

300-400 hours would be totally acceptable, as long as I know when it fails. If it just starts to slowly degrade accuracy it will be hard to tell when it fails, if it's a binary thing then I'm cool with that.