AFR install (AFR=Air Fuel Ratio)

[miyu1975]

Hello,

I am considering adding an AFR sensor to my panel, although not entirely sure how or what I would looking for in the AFR numbers. More to learn.

I have an IO 360 with mechanical fuel injection (bendix) and dual (legacy) EFII electronic ignition. I have been running this setup for years and it has been great. I have read a little about using AFR to better lean and set max power, etc....using AFR.

Does anyone have experience and the PLX system, or recommend another, for a AFR sensor?

https://www.amazon.com/PLX-Devices-S.../dp/B00U1J1MCK

[RV6_flyer]

Never knew anything like this existed.

Reading the description on the Amazon link you posted, it says "O2 sensor harness 10ft." My concern would be how does the O2 sensor work with leaded fuel that we use in our airplanes?

I am under the impression that the leaded fuel will ruin the O2 sensor.

[Isaac]

See ?Kitplanes March 2019?. Article on how to add AFR to your airplane. It?s definitely doable with today?s sensors.

[622BH]

The PLX sensors are designed to work in an un-leaded fuel environment - auto gas.
If you install the sensors according to PLX instructions you will get maybe 50 hours (some get much less) of operation out of them before they stop working in our leaded av-gas world.
But, I'm told that if you mount the sensor up in the exhaust flame (about 18 inches or so) it keeps the lead from depositing on the sensor and you get a very long life from them.

I'll not get into the technical details of the Stoic... sensing and the benefit, as that has been discussed in other threads here. I'll simply say that if you want to get the most accurate efficiency from your fuel burn, using AFR would be greatly encouraged.
Also, strongly encourage you to chat with Robert Paisley - since you have the EFII ignition, he will be an excellent source of technical advice.

[Ralph Inkster]

Each engine / sensor installation will give different readings. What you should do is operate your engine as you normally do & see what your indicator values are at each power setting. Full Rich, Best Power, Peak, your Lean of peak setting. From that you can develop leaning guide lines referring AFR as an additional reference to your RPM, EGT, F/Flow tools you already have.

As a (rough) example 10.5 to 1 might be Rich, 11.5 thru 13 might be Best Power, Stoik around 14.7 (which means nothing), your Lean might be anywhere between 14 to 18, what ever your comfort level.

Would be interesting to know what YOUR numbers would be.

[David Carter]

Originally Posted by Isaac

See ?Kitplanes March 2019?. Article on how to add AFR to your airplane. It?s definitely doable with today?s sensors.

I have installed the Ballenger AFR500v2 unit detailed in this article, with the NTK sensor which is said to be more tolerant of leaded fuel than the older Bosch sensors. It's still early in my testing, and I'm currently working on a couple of enhancements.

https://www.bmotorsports.com/shop/pr...oducts_id/2337

Simplest is a smaller remote-mount, dimmable display. As mentioned in the Kitplanes article the built-in LED display is large, very bright, and non-dimmable. Note that if you have an EFIS (Garmin, Dynon, etc.) that accepts a 0-5v analog input, you can have the AFR (or lambda) value displayed & logged by the EFIS, and can mount the AFR box out of sight behind the panel without the need for a separate remote display.

Second & slightly more ambitious is a closed-loop mixture controller using a linear servo connected to the mixture knob with the same quick-disconnect linkage used in this product: http://flightenhancements.com/auto-lean.html This is ready for flight testing, likely starting this weekend. Set a target lambda/AFR value, and the controller will maintain it throughout climb, cruise, and descent. You can enter the target manually, or use preset targets for different phases of flight.

[rdrcrmatt]

If you do this, aside from the lead concerns, try to find a wide-band O2 sensor. The narrow band commonly available sensors are actually only sensitive to a not very useful window of A:F Ratios.

Wide band sensors are commonly found on "lean burn" cars, older Honda Civics and such. Maybe more cars these days than when I was into cars.

[jacoby]

Originally Posted by rdrcrmatt

If you do this, aside from the lead concerns, try to find a wide-band O2 sensor. The narrow band commonly available sensors are actually only sensitive to a not very useful window of A:F Ratios.

Wide band sensors are commonly found on "lean burn" cars, older Honda Civics and such. Maybe more cars these days than when I was into cars.

You would be hard pressed to find a narrow band aftermarket O2 setup. They've all moved to the wideband. Most use the Bosch LSU 4.2 or 4.9 and a couple use the NTK.


The NTK is said to be more lead compatible but they also want it to be recalibrated every hour with lead.

FWIW, Bosch recommends moving the sensor away from the exhaust port when using leaded fuel. They recommend 36".

[DanH]

Recalibrated every hour eh?

So when they die from lead poisoning, they drift out of calibration over a period of operating hours?

[jacoby]

Originally Posted by DanH

Recalibrated every hour eh?

So when they die from lead poisoning, they drift out of calibration over a period of operating hours?

Honestly that's just what I read in the instructions (page 11). I haven't used the NTK sensor.

I do have experience with the AEM UEGO running the Bosch LSU4.2. It survived a tank or two of 100LL and 120 race gas but mostly lived on pump gas + NOx. It was in the middle of the collector on long tube headers. It never had to be recalibrated.

These sensors are invaluable street tuning a car, especially with a carb. On an airplane? I don't know. EGT gives you a lot of info but you don't get the actual AFR. EGT is also slower to react but again does it matter?

With the LSU4.2 I've read numbers of something like 80k km service life with pump gas and 10k km with 0.60g/l lead. Which is like 10% more than 100LL has. You could maybe extrapolate that out at like 80km/h average and call that ~125 hours on lead?