LOP operation question

I have a little over 50 hours on my IO 540. How many hours should I have on it before I consider moving into the LOP envelope. I’m considering contacting Airflow Performance to get the engine dialed in, and to learn the correct method of leaning to LOP. The G3X touch seems straight forward with the leaning process, I have a quest to make it to TBO (as much as possible), so I do not want to pull the trigger to soon. Input appreciated.

Thanks...

I wouldn't worry about it after 50 hours. LOP is better for the engine temps (and fuel costs). There is plenty of information about LOP operation using the search here and google. On the Skyview, just hit the LEAN mode button, start leaning and it will detect the peak temps on each cylinder, show you the GPH spread, and then will give you a delta temp past peak. The engine will miss a bit if you get too lean, so just enrichen it a bit and look for 25-50 degrees LOP and enjoy the fuel savings.

There's a ton of good info out there about running LOP. Suffice it to say that after your engine is broken in (and after 50 hours, I'd think so!), with the exception of takeoff and landing, LOP is a good choice in the rest of the flight regimen. Check out John Deakin's articles on Pelicans Perch and the information at http://www.gami.com/articles/articles.php for more on LOP. Next, call Airflow Performance, talk to Don or Colleen and see if they have one of their Fuel Injection 101 classes planned. I attended this last year and thought it was well worth the time and money. If they offer it again, I'll try and go again just because I enjoyed the class, Colleen's cooking, and the people who attended. It really was outstanding and you learn a ton about how these engines and fuel injection really operates.

In addition to running LOP on my -8, I've run it on two Bonanzas and my Cirrus. It's SOP for the Cirrus. You do need reasonably balanced injector nozzles to run LOP smoothly and Don can help you with that.

You could and would have been just as well running LOP from the start. points to note, high mean effective pressure is what you need to break in the engine, you can achieve that ROP or LOP, but the LOP option is actually better.

We just did an RV8 with an IO375 that way, worked a treat and the cleanest oil I have seen

As for learning about LOP, www.advancedpilot.com plenty you can learn there.

WARNING: The lean find function is all engine monitors are great teaching tools, and for your education, but they are ineffective in obtaining optimum results in everyday flying. Hysteresis in probes and the algorithms in the software are never a good match for you, your brain and raw data.

Best way to do normal inflight leaning is to do the Big Mixture Pull, let things settle for a few minutes. Then slowly find the first one to peak from the lean side, take note of the raw data peak, and then lean back to the appropriate LOP amount. That could be 60-80dF at high powers, 40dF around 75%, 25dF at 70% or around 10-15dF at 65% or less.

WARNING #2: Most engine monitors %power displays are wrong, Dynon being an exception. How you tell is if the % power does not change when you go LOP, then it is just doing a ROP only calculation.

If you are at 75% power Rich of Peak, when you get appropriately LOP you will be around 10% less than that, in other words 67-68%. So you do not want to be 40dF LOP then, rather say 10-120dF LOP.

Get good at doing a BMP, and you will never use the "Lean Find" function ever again, unless you are teaching the concept to a newbie.

Useful links for you; Deakin articles and Red Box simulator.
https://www.advancedpilot.com/tech.html

Hope that helps

Balance your injector nozzles and enjoy.

David, I found the same thing on my GRT system, it had me much further LOP than I really was. Once I discovered manual LOP was more accurate I picked up 5-6 kts running the same 40 LOP that I thought I was running before.
Also agree the power indication only works on the ROP side with GRT.
Tim Andres

plus 1 for Deakien

Read through all the Pelican Brief articles by Deakin.

You could have been doing LOP after 3--5 hrs. But better start now!

Tim and David: You've got me wondering:

If I can't trust the %power display on the lean side, then after finding the 1st cylinder to peak egt from the lean side, how do I know whether I want to go 10dF lean or 80dF lean?

revenson said:

Tim and David: You've got me wondering:

If I can't trust the %power display on the lean side, then after finding the 1st cylinder to peak egt from the lean side, how do I know whether I want to go 10dF lean or 80dF lean?

Click to expand...

LOP will achieve the most out of each ounce of gas you put in the cylinder, and will lower CHTs. How far you go LOP is at your discretion. If looking strictly for miles per gallon (peak efficiency), I find 20 degrees about right. More LOP further reduces fuel flow, but power starts falling off faster than fuel flow. The other issue is how well you balanced your injectors and if using electronic ignition or not. My stock IO-540 was not happy much past 20 degrees LOP (rough engine) before balancing the injectors (GAMA spread was 1.5 gph). After balancing (GAMA spread 0.1 gph) I could go LOP way past the point of practicality.

So - go experiment and find out where you want to operate.

Carl

Carl Froehlich said:

...If looking strictly for miles per gallon (peak efficiency), I find 20 degrees about right. More LOP further reduces fuel flow, but power starts falling off faster than fuel flow...

Click to expand...

This rapid drop in power will always be true in the gross sense, but the sharpness of the slope is highly influenced by ignition timing. A fixed mag will really fall on its face while an optimized timing event will bring back a bunch of power at the same mixture. This is the other reason engine monitors cant predict power with any certainty when LOP. The ignition is simply too much of a wild card.

Carl, you miss my point. Deakin/Busch recommend greater lop leaning of at 80% power than say, 65% power to stay out of the 'red box'.

The previous posts suggest my GRT monitor is not displaying accurate %power once lean of peak, making it more difficult to know whether I want 10, 20, or 60dF lean of peak.

This is the first I've heard that %power calculated by my monitor is not accurate lop. Guess I'll go fly and pay attention to power% once lean of peak to see if it stays the same, as suggested above.

revenson said:

Carl, you miss my point. Deakin/Busch recommend greater lop leaning of at 80% power than say, 65% power to stay out of the 'red box'.

The previous posts suggest my GRT monitor is not displaying accurate %power once lean of peak, making it more difficult to know whether I want 10, 20, or 60dF lean of peak.

This is the first I've heard that %power calculated by my monitor is not accurate lop. Guess I'll go fly and pay attention to power% once lean of peak to see if it stays the same, as suggested above.

Click to expand...

Yep - did not address the ?what does my engine monitor do? question as I find such indication fun to watch, and once I know what it means it can be helpful to get repeated results, but not much more. Go experiment and take data on TAS vs Fuel Flow vs how far LOP. Try ignoring whatever % power readings you have and pay attention to the real engine parameters.

Unless you are doing something weird, normally aspirated engines at cruise power will be out of the ?red box?.

Facts and data will set you free,
Carl

revenson said:

...The previous posts suggest my GRT monitor is not displaying accurate %power once lean of peak, making it more difficult to know whether I want 10, 20, or 60dF lean of peak...

Click to expand...

I use the "mission at hand" to decide how far I want to go LOP. If I'm in a hurry or battling a headwind for example, I'll stay much closer to peak. OTOH, if I'm really trying to stretch the leg I'll be looking at the best MPG figure. Your TAS/FF calculation is your best real time measurement of engine output.

...This is the first I've heard that %power calculated by my monitor is not accurate lop. Guess I'll go fly and pay attention to power% once lean of peak to see if it stays the same, as suggested above...

Click to expand...

Thats because it is a derived number based on some often incorrect variables. In the days when the timing was fixed, you might have a fighting chance of calculating the approximate engine output, but not with variable timing and especially with timing that can be optimized for both the best power and LOP conditions. As an example, my ignition has a LOP function which allows me to add the needed timing advance on top of the existing best power mixture curve. In practice, I'll climb at best power mixture with the timing advancing as requred. At TOC I'll push over and accelerate to 205KTAS (typical). Once I come off best power mixture and go LOP I'll drop about 7 Knots indicating a significant and expected loss of power. The EFIS might be able to properly calculate this loss of power with enough magic in lookup tables, but not what happens next. Without moving mixture, RPM or MP, I simply activate the LOP advance shift and I get 3 knots back within 30 seconds. 3 additional knots at max cruise speed is a significant power % and the EFIS would have no idea what changed.

Once you are LOP, assuming 8.5:1 compression ratio, you can use the formulae 15.7 * Fuel flow / Rated HP= % power
So a 180 HP burning 8 GPH
15.7 * 8 = 125.6 HP /180 = 70%
Once you do the math it?s pretty easy to memorize 7.5 as 65%, 8 as 70% and 8.5 as 75%, rounded a bit, it?s close enough and doesn?t matter a whole lot anyway. With the throtttle wide open, adjust the power to balance your need for speed vs you how much you want to spend at the pump!
Tim Andres

Old test data indicates that best economy occurs at mixtures somewhat leaner than 25 LOP but I agree with Carl, it would be interesting to run controlled tests of a flying aircraft looking at FF vs. TAS at 25, 50, 75 and 100 LOP and graph the results to see what the magnitude is. Then add in timing to see how that affects the results.

tim2542 said:

Once you are LOP, assuming 8.5:1 compression ratio, you can use the formulae 15.7 * Fuel flow / Rated HP= % power...

Click to expand...

That doesnt account for the significant change in actual power output with a simple timing change though. In my ROP/LOP example cited earlier the throttle position, RPM, EGT and FF remaned the same yet my speed increased 3 knots with the advanced timing. Considering drag increases at the square of the speed, a 3 knot punch further into the drag wall is not an insignificant amount of power.

LOP

rv6ejguy said:

Old test data indicates that best economy occurs at mixtures somewhat leaner than 25 LOP but I agree with Carl, it would be interesting to run controlled tests of a flying aircraft looking at FF vs. TAS at 25, 50, 75 and 100 LOP and graph the results to see what the magnitude is. Then add in timing to see how that affects the results.

Click to expand...

This exact test is in my future. Last week I did tests to look at optimum ROP ignition settings. The curve is very flat for an IO-390. I need to do a couple of retests for verification. After the ROP results I tested LOP at 25*, the curve did increase speed noticibly and then went flat, I ran out of time to find where the advance began to drop speed. Each flight leg (ROP and LOP) took over two hours by the time I let each ignition advance stabilize for 5 minutes. I suspect it will take me weeks to get a good baseline before I even get to comparing different levels of LOP. This may take me into the fall.

Lean Test

Hey Rich, give me a call or email. Barry
23nine-73eight-295three
blmarzaa(at)gmail(dot)com

Another source on LOP...

I found this to be pretty good info...
https://www.youtube.com/watch?v=h3bATVXMHQg

M McGraw said:

This exact test is in my future. Last week I did tests to look at optimum ROP ignition settings. The curve is very flat for an IO-390. I need to do a couple of retests for verification. After the ROP results I tested LOP at 25*, the curve did increase speed noticibly and then went flat, I ran out of time to find where the advance began to drop speed. Each flight leg (ROP and LOP) took over two hours by the time I let each ignition advance stabilize for 5 minutes. I suspect it will take me weeks to get a good baseline before I even get to comparing different levels of LOP. This may take me into the fall.

Click to expand...

Excellent. Good data takes a while to accumulate. Look forward to seeing it Marvin.

tim2542 said:

David, I found the same thing on my GRT system, it had me much further LOP than I really was. Once I discovered manual LOP was more accurate I picked up 5-6 kts running the same 40 LOP that I thought I was running before.
Also agree the power indication only works on the ROP side with GRT.
Tim Andres

Click to expand...

Indeed, there are several reasons why people end up further LOP than they think they are;

1. The hysteresis in the probe and the algorithm detecting the peak can miss it, depending on how you operate the knob.
2. Once LOP the cylinders cool off and volumetric efficiency improves, thus you flow more air and now you can flow more fuel.
3. Some are running 50dF LOP because they think that is where to run, when the best BSFC is not always at 50dF, at low powers, it is 10dF and at 80+% it is more like 60-80dF LOP.

I have posted this many times, but if you want a quick reference use this table below.

Also remember, if you have a ROP power based on MAP and RPM of say 80% power, your actual LOP power will be the ROP % x 0.9, or basically like the old radial guys did, 10% BMEP drop. So that would be 72%. So set your LOP number based on around 70-75% or 25-40dF LOP. I would use 30, but lets not be too picky.

Outside the Box
? At 65% power, use richer than 100 ROP, or leaner than peak EGT.
? At 70%, use richer than 125?F ROP, or leaner than 25?F LOP.
? At 75%, use richer than 180?F ROP, or leaner than 40?F LOP.
? At 80%, use richer than 200?F ROP, or leaner than 60?F LOP.

My good friend and partner in APS activities John deakin simply says, get good at doing the BMP, and thats it. but if you want to squeeze every last ounce out of it, let it cool off, find peak from the lean side and be happy.

Remember Lean Find functions are great teaching tools, but sub-optimal in flight tools.

For those who want to play with the red box simulator, go here...> https://www.advancedpilot.com/redbox.html

An aggressively rich mixture is beneficial for the first hour of break in with older honing methods (no benefit with modern plateau honing). A very rich mixture also helps keep the intense heat of the first hour at bay for air cooled engines. After that, there is no need for running rich. LOP will create no adverse affects nor eliminate any benefit.

Larry