Life of the sensor is 1-10% when operating on 100LL vs. unleaded fuel.
According to Robert Paisley installing it much closer to the cylinder will keep the lead deposit off the sensor:
https://vansairforce.com/community/showthread.php?t=173975&page=2
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I had read that wide band sensors would not last with 100LL. Instructions said to mount the sensor at an angle in the pipe and a minimum distance from the head. The readings it shows appear to be the same now as when installed 400 hrs ago. I do lean aggressively on the ground and in the air. My mixture lever always ends up in the same position on the quadrant showing the same numbers (which bounce around, I guess since only 2 cyls are being monitored) on the A/F gauge, fuel flow, richness and power on the Dynon at my usual cruise settings.
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No smart guy here.
Instructions said to mount the sensor at an angle in the pipe and a minimum distance from the head..
Additionally, I think others have noted that the way O2 sensors are powered up in aircraft applications is different than in automotives, where the sensor is allowed adequate time to heat up before the engine is fired. That can contribute to short lifetimes for sensors.
I've heard this but it doesn't make sense. In my race car I have dual FAST O2 sensors. I always turn the system on for a bit prior to cranking. However, this is a race car and represents probably 0.01% or less of the automobiles using O2 sensors. Most cars/trucks you open the door, sit down, & crank. The only time the vehicle knows it is being cranked is when the key is turned or button pressed and then an almost instant fire; unless it is a diesel. In my diesel truck I do turn on the key and make sure the glow plug light is out then fire. How do most cars heat the sensors prior to being fired if they don't know they are being fired until they are fired?
I am wiring up my O2 sensor soon in my plane, plan on putting it on a switch (like autopilot or EFIS) that gets powered prior to cranking to give it some time to heat.
When modern engines are first cranked, they are operating in "open loop" mode, where there is no feedback from sensors and the engine is simply dumping X amount of fuel in to mix with Y amount of air. At some point steady engine operation and temperatures results in a change to "closed loop" mode where it starts paying attention to things like the oxygen sensor, catalytic temps, etc. For the first few minutes those are ignored.
The oxygen sensor, if it's hot prior to start, can get damaged by water vapor from the combustion chamber condensing on a cool valve/head/port/exhaust pipe and then droplets hit the hot ceramic sensor. For this reason most OEM's leave the sensor unpowered for the first 30 seconds to a minute after engine start, until the exhaust temperatures are well above the point that would allow for water condensation, and then power up the oxygen sensor. During this time period the engine is operating in open-loop mode.
When I installed the SDS system on my 9A this spring, I put an electronic timer circuit in place to be triggered by the starter solenoid current and wait 30 seconds before applying power to my oxygen sensor.
When I installed the SDS system on my 9A this spring, I put an electronic timer circuit in place to be triggered by the starter solenoid current and wait 30 seconds before applying power to my oxygen sensor.
When modern engines are first cranked, they are operating in "open loop" mode, where there is no feedback from sensors and the engine is simply dumping X amount of fuel in to mix with Y amount of air. At some point steady engine operation and temperatures results in a change to "closed loop" mode where it starts paying attention to things like the oxygen sensor, catalytic temps, etc. For the first few minutes those are ignored.
The oxygen sensor, if it's hot prior to start, can get damaged by water vapor from the combustion chamber condensing on a cool valve/head/port/exhaust pipe and then droplets hit the hot ceramic sensor. For this reason most OEM's leave the sensor unpowered for the first 30 seconds to a minute after engine start, until the exhaust temperatures are well above the point that would allow for water condensation, and then power up the oxygen sensor. During this time period the engine is operating in open-loop mode.
When I installed the SDS system on my 9A this spring, I put an electronic timer circuit in place to be triggered by the starter solenoid current and wait 30 seconds before applying power to my oxygen sensor.
Has this approach worked for you in extending the sensor life, compared to the numbers Ross is suggesting?
Greg - Can you please post details on your delay timer circuit? I have a Ballenger AFR gauge with NTK wideband sensor in my plane, but it is wired to come on with the master. I'd like to change to your approach of delaying the sensor start.
Thanks!
"I thought about installing a lambda gauge in my airplane many years ago, but I was told they wouldn’t work with leaded avgas, so I didn’t question it, and I didn’t try. Finally, I decided to see for myself. I’ve been flying with lambda gauges in my two airplanes now for a combined 800 hours. I only had one probe go bad and that happened early, when there was a lot of rich operation."
the lead fouling caused his first lambda probe to fail. But that problem hasn’t recurred, primarily because the information the gauge provides allows him to run his engine far leaner—and that keeps lead deposits from building up.
The AFR500v2 is widely fuel compatible. Many are listed below:
Gasoline / Petrol (leaded or unleaded)
Alcohol (Methanol)
Ethanol
Compressed Natural Gas (CNG)
Liquefied Petroleum Gas (LPG)
Propane
Many other combustible fuels
Top causes for an error:
1. Bad Sensor due to rich misfiring or backfiring (tuning far too
rich and/or raw fuel hitting the sensor possibly leading to a
cracked ceramic or contaminated ceramic element).
2. Bad Sensor due to having the sensor in the exhaust stream
with no control and no heating which almost immediately foul
a sensor.
3. Bad Sensor due to bad manufacturing or damage in transit or
improper installation (sensor is at the bottom of the pipe, etc).
4. Bad Sensor due to mechanical damage (dropped or hit).
5. Sensor not reading within range due to being too hot or cold
(ie right next to the port or far down the exhaust stream).
How to maximize sensor life
1. Get a baseline tune before installing a sensor. You don’t need the sensor in most cases to get your baseline timing and fuel settings.
2. NEVER leave a sensor in an exhaust unheated (disconnected).
3. Don’t leave the sensor in continuously, only use for tuning and specific monitoring periods.
4. Limit your use of the sensor with leaded, race, or oil mixed fuels. NTK sensors are significantly more durable than Bosch sensors in such environments.
5. Limit time in water cooled exhausts and avoid this where possible.
6. Handle the sensor with extreme care. The sensing element is a delicate ceramic. Rough handling or drops may destroy the sensor.
7. Never exceed 1700F (930C) EGT at the sensor. In high EGT environments, extended bungs such as SNSR-01064/SNSR- 01054 or Heat Sink Bung Extenders such as SNSR-01065 are strongly recommended.
Sensor Installation
Oxygen sensors are sensitive to temperature, pressure and contaminants. A non-ideal sensor installation may dramatically reduce your sensor life.
Ensure that there are no leaks in the exhaust system as this will falsely indicate lean or high air fuel ratio values. The sensor should be installed upstream of any air-injection equipment.
The sensor should not be installed in a pressurized environment and therefore should be installed downstream of any turbochargers or similar systems causing exhaust pressure.
The sensor should be installed upstream of any emissions systems and catalytic converters.
Typically, the oxygen sensor should be installed 1ft to 4ft from the exhaust ports. A sensor that is too close will receive frequent thermal variations, leading to a reduced sensor life. A sensor that is too far away may run too cold and risk condensate leading to reduced sensor life.
The sensor should be installed at least 10˚ above horizontal to avoid condensation and water pooling in the sensing element. Ideally the sensor is installed off vertical between the 10 and 2 clock positions (see Fig 4).
Anyone know if the NTK and Bosch (PLX) sensors are directly interchangeable? My question focuses on the cable connector the PLX units have.
The first option is Bosch LSU 4.9 sensor capability. As shipped (unless otherwise specified), this is set for the Bosch LSU 4.2 & NTK Sensors. You must install a red jumper to enable LSU 4.9 ONLY mode.
Greg - Can you please post details on your delay timer circuit? I have a Ballenger AFR gauge with NTK wideband sensor in my plane, but it is wired to come on with the master. I'd like to change to your approach of delaying the sensor start.
Thanks!
I'd do the same thing in the airplane, I'll bet the SDS has exactly that circuit for its use in autos. If not, then I'd use a Hobbes switch to provide a ground for the relay when your oil pressure comes up.
Either would work - I have mine looking for +12 volts on the starter solenoid to indicate cranking, then starting a timer for power.
I got interested in A/F monitoring for my plane a while ago, and installed a system that has been working flawlessly for a couple hundred hours now. Wrote an extensive article for KitPlanes on it:
https://www.kitplanes.com/adding-direct-air-fuel-ratio-monitoring/
The key to making this work without the sensor failing prematurely is the right sensor. The one I found is made by NGK and is specifically rated to tolerate some lead. I used the Ballenger system, and modified the display to make it compatible with my panel space.
There are two things to say about this, IMO:
1) After all the back and forth about short sensor life, it CAN be made to work with the right sensor.
2) Having flown with A/F for some time now, let me tell you, it makes setting mixture SO much easier. None of the back and forth with finding the peak EGT, etc. Just remember your two chosen A/F numbers: One for rich of peak operation, one for lean of peak operation, and set your mixture to the number. Glance at your EGT and/or fuel flow to make sure something hasn't gone nuts, and you are all set. It's so nice, I'm reconciled to the possible cost of sensor replacement if and when, but so far still going strong.
Reinhard Metz
N49EX
Then turbo normalization bwahahahahaha
I got interested in A/F monitoring for my plane a while ago, and installed a system that has been working flawlessly for a couple hundred hours now. Wrote an extensive article for KitPlanes on it:
https://www.kitplanes.com/adding-direct-air-fuel-ratio-monitoring/
The key to making this work without the sensor failing prematurely is the right sensor. The one I found is made by NGK and is specifically rated to tolerate some lead. I used the Ballenger system, and modified the display to make it compatible with my panel space.
There are two things to say about this, IMO:
1) After all the back and forth about short sensor life, it CAN be made to work with the right sensor.
2) Having flown with A/F for some time now, let me tell you, it makes setting mixture SO much easier. None of the back and forth with finding the peak EGT, etc. Just remember your two chosen A/F numbers: One for rich of peak operation, one for lean of peak operation, and set your mixture to the number. Glance at your EGT and/or fuel flow to make sure something hasn't gone nuts, and you are all set. It's so nice, I'm reconciled to the possible cost of sensor replacement if and when, but so far still going strong.
Reinhard Metz
N49EX
SWEEEET!
After doing an extensive Porsche 930 mod over the last 3 years (its now SCARY fast definitely a Widow Maker) and having learned a TON, I've been thinking about doing a dual-Microsquirt setup with essentially a toggle switch (best power, best economy) with concomitant mixture and timing settings (essentially the switch changes between two ignition and mixture tables).
s/b very doable.
Then turbo normalization bwahahahahaha
If running at 65% power, will there ever be a reason to run in "best power"- mode (i.e. rich of peak)? Why not run LOP by default at lower power settings and ROP at higher ones?
Only pitfall I could think of would be the interpolation that the ECU is doing when between two data points. Right around the step-up point, this could prove problematic, when it interpolates between LOP and ROP and thus ends up right at peak EGT.
Could you provide more details on the "external smaller and auto-dimming display"? I would really like that. Also how is it mounted? I don't see any screws in your panel near the display.
Yes, the Ballenger display is rather big. I took mine apart and figured out the type of LEDs and how they were driving them (very straight forward) and tied into their circuitry with a cable that connects to my smaller 7 segment LED display. They are multiplexed in a way that I added a photoresistor that controls LED drive pulse width to do dimming. Works quite well. The assembly is press fit into the panel from the back. The display is one a circuit board, which I surrounded with a piece of black bent plastic strip, to create essentially a custom packaging. So - now, if you want to do the same thing, I will need to send you the schematic (sketches) for what I did, won't fit well in line here, so send me an email address if interested:
[email protected]
Reinhard
Most of these units provide a 0-5 volt, analog linear output for data logging. Just connect that to a GP input on your Dynon/Garmin and calibrate accordingly. You then get AFR data on your EFIS/EMS (including logs) with no need to mount the display on the panel.
Larry
I like your idea of using the ECU between best power and best economy, however wonder: Why build in that choice? Genuine questions: If running at 65% power, will there ever be a reason to run in "best power"- mode (i.e. rich of peak)? Why not run LOP by default at lower power settings and ROP at higher ones? Implementation would really just be a matter of introducing a step up in your fuel tables.
Only pitfall I could think of would be the interpolation that the ECU is doing when between two data points. Right around the step-up point, this could prove problematic, when it interpolates between LOP and ROP and thus ends up right at peak EGT.
Seems like I've answered my own question
I'm rebuilding my RV3 and had two Elektromotive ECUs left over from a previous project. I've put both of them in the -3 now, however use one for the left tank (with left fuel pump, left return line, replacement of the left magneto), and one for the right side. Run both of them at the same time (for ignition on both sides) and switch the 12V source to the injectors to effectively switch between tanks.
Interesting choice. My thought was running full EFI, both auto-style injectors on a rail and ignition. With dual sensors for everything I could have one run the top plugs and one run the bottom plugs, but only one could run the injectors at a time. So it would be easier to simply wire in parallel and have a change over switch in case either a sensor (crank position for ex) or an ECU failed.
Could you provide more details on the "external smaller and auto-dimming display"? I would really like that. Also how is it mounted? I don't see any screws in your panel near the display.
Yes, the Ballenger display is rather big. I took mine apart and figured out the type of LEDs and how they were driving them (very straight forward) and tied into their circuitry with a cable that connects to my smaller 7 segment LED display. They are multiplexed in a way that I added a photoresistor that controls LED drive pulse width to do dimming. Works quite well. The assembly is press fit into the panel from the back. The display is one a circuit board, which I surrounded with a piece of black bent plastic strip, to create essentially a custom packaging. So - now, if you want to do the same thing, I will need to send you the schematic (sketches) for what I did, won't fit well in line here, so send me an email address if interested:
[email protected]
Reinhard
While it can be integrated into the EFIS/EMS/MFD, I find that this a fairly primary piece of info and like it dedicated, rather than one more item on the display that looks like all the others and needs more mental focus to access. Also, the Garmin GDU470 I have makes decisions of how many items it has room to display, and that often makes for difficulty getting your GP I/O TO Display.
Do you have a part# and what's distance from the cylinder?