LOP Climbing

[rocketman1988]

I put a timer on my PLX system that's set for 2 mins after the engine is started. That seems to help improve the life of a sensor when using 100LL. Without the timer was getting about 25 hours or one oil change. Now get 100 to 150 hrs. Others I know have clipped the power lead to the sensor. No data on that method. As riseric states the O2 sensor not really needed nut nice to have as confirmation of the lean assist.

The life of the sensor appears to be highly variable; I have had them last 5 hours or up to 20 hours. As has been said, its really info only.

As a data point, the sensor is installed in the #6 pipe, EFII, Custom Aircraft exhaust, WOT climb, LOP cruise.

 

[David Carter]

I put a timer on my PLX system that's set for 2 mins after the engine is started. That seems to help improve the life of a sensor when using 100LL. Without the timer was getting about 25 hours or one oil change. Now get 100 to 150 hrs.

I have 150 hours on my O2 sensor, which is always running 100LL. When yours failed, what were the symptoms? Complete failure, creeping inaccuracy? I'm wondering if I'm lucky or perhaps just oblivious to a creeping failure mode.

Regarding the 2-minute timer delay, page 1 of the Ballenger manual says the following under the heading "Critical Product Notes":

Do not leave the sensor in the exhaust stream while disconnected from the controller or unpowered. This will foul an oxygen sensor rapidly.

I realize you are running a different system, but I think all the sensors work on similar principles, and therefore, running the engine with the sensor powered off would not be advisable. The sensors have heating elements in them, which perhaps helps prevent fouling.

 

[rocketman1988]

I have 150 hours on my O2 sensor, which is always running 100LL. When yours failed, what were the symptoms? Complete failure, creeping inaccuracy? I'm wondering if I'm lucky or perhaps just oblivious to a creeping failure mode.

Regarding the 2-minute timer delay, page 1 of the Ballenger manual says the following under the heading "Critical Product Notes":



I realize you are running a different system, but I think all the sensors work on similar principles, and therefore, running the engine with the sensor powered off would not be advisable. The sensors have heating elements in them, which perhaps helps prevent fouling.

The symptom is that the sensor starts o read 14.7-14.8 all of the time, regardless of the mixture setting. It is detailed in the plx manual.

 

[David Carter]

The symptom is that the sensor starts o read 14.7-14.8 all of the time, regardless of the mixture setting. It is detailed in the plx manual.

Thank you! Mine still gives full-scale readings & seems to behave as it did when new.

Are you running a Bosch or NTK sensor? Mine is NTK, which is said to be more resistant to lead fouling.

 

[rocketman1988]

Thank you! Mine still gives full-scale readings & seems to behave as it did when new.

Are you running a Bosch or NTK sensor? Mine is NTK, which is said to be more resistant to lead fouling.

I have used both. What is you AFR at takeoff and LOP cruise?

 

[riseric]

The symptom is that the sensor starts o read 14.7-14.8 all of the time, regardless of the mixture setting. It is detailed in the plx manual.

Same here, 14,7 steady. Bosch. 2 sensors. 15 - 20 hours each. 100LL. Never tried another brand.
Vettermann exhaust, #4 header, ROP climb, ~50LOP cruise.

 

[hevansrv7a]

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Good advice!
If you read their stuff carefully you will find a method for determining the "Target EGT" which is safe and effective. Since LOP, done correctly is actually easier on the engine than other settings, it makes sense to use it within safe limits. This is how. My "12" can't be leaned but when I flew my "7A" I had a note on the panel for the target EGT that I had determined using their instructions.. Any other target EGT is guesswork and IMO, should be avoided.

 

[dmattmul]

Same here, 14,7 steady. Bosch. 2 sensors. 15 - 20 hours each. 100LL. Never tried another brand.
Vettermann exhaust, #4 header, ROP climb, ~50LOP cruise.

PLX sells a gauge that gives the "relative health" of your O2 sensor which I installed (In my glove box) several years ago. (See attached pic) It's showing it has failed (100LL contaminates the sensor) recently. Next oil change I will replace and post pics. Using LL I think we are doomed to having an unreliable O2 sensor, but the fight goes on!

 

[Bicyclops]

Air fuel ratio and EGTs aren't, I my opinion, the best way to keep from damaging and engine when leaning, whether climbing or cruising. EGT is just a measure of the burnt gasses in the pipe at some unknown amount lower temperature than the burn in the cylinder. AFR, if accurate (uncontaminated sender), would be a good measure of where the the burn is in relation to stoichiometric mixture. Great, but doesn't necessarily keep you out of the "red box".

I think of the CHTs as being the primary indicator. If your CHTs are under control, you aren't hurting the cylinders, whether you are ROP or LOP.

Ed

 

[rv8ch]

I think of the CHTs as being the primary indicator. If your CHTs are under control, you aren't hurting the cylinders, whether you are ROP or LOP.

I've read this in other places as well, but one thing that is not clear to me is that it seems like detonation could cause some damage quicker than a CHT probe could react.

 

[David Carter]

I have used both. What is you AFR at takeoff and LOP cruise?

Takeoff between 10 & 12.5. 10 if the CHTs are running too hot, 12 - 12.5 otherwise. LOP cruise typically around 16.

 

[lr172]

Takeoff between 10 & 12.5. 10 if the CHTs are running too hot, 12 - 12.5 otherwise. LOP cruise typically around 16.

Unless you are using a shot of nitrous or pushing 15 PSI of boost, 10:1 is WAY richer than necessary. Best to address baffling issues if unable to keep chts in check.

 

[dmattmul]

Thank you! Mine still gives full-scale readings & seems to behave as it did when new.

Are you running a Bosch or NTK sensor? Mine is NTK, which is said to be more resistant to lead fouling.

Can you point me to a part number for the NTK? Did you have to modify the connector? I can't seem to find a NTK (Or Denso) that fits the connector supplied with the PLX equipment. Yes, when fails reads ~14.7 all the time, ROP or LOP.

 

[dmattmul]

Regarding the 2-minute timer delay, page 1 of the Ballenger manual says the following under the heading "Critical Product Notes":

Do not leave the sensor in the exhaust stream while disconnected from the controller or unpowered. This will foul an oxygen sensor rapidly.

The issue with obtaining data from sources automobile related info (Including the one I'm posting below) is the location for their O2 sensors are located far from the heat source. EFII recommends positioning the one O2 sensor we use (Most automotive applications use 2 one before and one after the catalyst) in the direct flame output of the exhaust. Mine is located about 5 inches downstream and angled slightly into the exhaust stream. My theory (I'm a Chem E not an Automotive engineer) was heating the sensor slightly (How much can the heater really heat the sensor) when condensation was present was a negative to the sensor vs "blasting" it with heat from the exhaust. Seems no one really understands what is best for our O2 sensors, so we continue to struggle keeping them alive. Eventually we will, have unleaded fuel options and then we can truly have a O2 sensor that lives. (Hopefully)

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[Bicyclops]

Detonation isn't immediately fatal. Mild detonation can exist for hours without damage. Moderate to severe detonation will cause the CHT to rise rapidly and will damage the ring lands. It can also lead to pre-ignition which will be very damaging very fast. CHT rise during pre-ignition will be very fast indeed and the piston may be damaged and fail in a minute or less. Thus we want to avoid detonation because it's hard to tell when it is severe. It is relatively easy to tell that it is not happening. If CHT is not rising rapidly, it isn't detonating to any great degree. Detonation is not only a function of manifold pressure, RPM, mixture, and timing. It is a function of those and, most especially, high cylinder temperature. So the trick is to not spend any significant amount of time with a power setting which could lead to high temps and potential detonation. Thus the "big pull". It needs to be smooth but not slow, say on a count of 3 similar to what you would do when going to full throttle on the takeoff roll or pulling to idle cut off. What you don't want to do is slowly pull mixture while whatching for the EGTs to peak and drop. Screw the EGTs. The best and highest use of EGT gauges, once the injectors have been balanced, is to diagnose fouled spark plugs during runup.

How to avoid detonation if you have well calibrated injector nozzles? Take off full throttle and full rich unless at a high density altitude. Your fuel flow should be high enough to ensure that you are well ROP and this should keep your CHTs under control during initial climb. At some point, pattern altitude or cruise altitude - your choice, reduce RPM if you have a constant speed prop and do a big pull on the mixture. Pull right through the "red box" until you feel a decrease in power and are still running smooth. You are now lean of peak and are at a reduced power level. Detonation is unlikely. If you want, you could even pull some throttle, but I don't think it's necessary or beneficial. The engine is going to be the most efficient with wide open throttle - less pumping losses. Let everything settle for a bit and check fuel flow for a number that you expect from experience and check and monitor your CHTs - all of them. If CHT is say 380 and rising, lean more - as long as it's running smoothly -, increase airspeed, reduce RPM and/or MAP, open cowl flaps etc. If none of that will control CHT, your injectors might not be as well balanced as they could be or your ignition might be too far advanced. Good baffle seal is also necessary for CHT control ROP or LOP. Experiment with this at higher altitudes where manifold pressures are lower and work your way down.

If the CHTs are rising rapidly through say 380 and you can't stop the rise with any of the above procedures, you need to push the mixture to way ROP and reassess why. CHT control has to be ahead of anything except aircraft control. Also, don't run into anything. ;-) Keep in mind that conditions change and what worked yesterday might not work as well today especially if the OAT is higher.

With a carbureted engine, it's a little tougher but not necessarily impossible to get far enough LOP with a smooth running engine to protect from detonation at low altitudes and high manifold pressure. On our O-320 powered fixed pitch 6A I used to pull about a tenth inch of MAP and lean to rough and then back a touch. I was able to cruise at 3000' like that with happy CHTs even on hot SoCal summer days. The slightly cocked throttle plate helps to swirl the mixture and helps with distribution to all the cylinders. Another trick is to add a just little bit of carb heat and then lean some more. Don't try any of this down low the first time and always monitor CHTs.

My 10:1 IO-360 works well with this method, though on very hot days I sometimes need to use my cowl flaps. Your mileage may vary. Sneak up on it and don't blindly take my word for it.

Ed
RV-6

I've read this in other places as well, but one thing that is not clear to me is that it seems like detonation could cause some damage quicker than a CHT probe could react.

 

[David Carter]

Can you point me to a part number for the NTK? Did you have to modify the connector? I can't seem to find a NTK (Or Denso) that fits the connector supplied with the PLX equipment. Yes, when fails reads ~14.7 all the time, ROP or LOP.

I'm using the Ballenger controller, which has built-in support for both the Bosch and the NTK sensors. It's a jumper setting. Ballenger's product listing for the NTK sensor says this in the compatible controllers section:

• PLX Devices M-300, SM-AFR, R-300, R-500 with some modifications

Here's the link to that listing: https://www.bmotorsports.com/shop/product_info.php/products_id/352

 

[David Carter]

Unless you are using a shot of nitrous or pushing 15 PSI of boost, 10:1 is WAY richer than necessary. Best to address baffling issues if unable to keep chts in check.

I agree. I do need to replace my baffle seals and then probably get the AFP servo re-jetted to reduce the maximum fuel flow.