New pilot. Tried running LOP for the first time. Experts, critique!

[systemloc]

Hi!

I'm still very new, 75 hr pilot. 20 hrs in my plane, a PA-32-301T Saratoga Turbo. I'm starting IFR training with my CFII, while in cruise, I'm working on running LOP. I have read a ton of Mike Busch's stuff, and watched all the videos I could find. My CFII doesn't know anything about running LOP, though, so I'm on my own, and would love extra eyes checking my work.

In cruise today at 8000 feet, 65% power setting by the POH, as below, with the book ROP fuel flow. I have a G1 Insight engine monitor. It shows CHT in the green, EGT in the white. Reading the manual for the engine monitor, it records your max EGT and as you move away from that, it gives you the boxed number up top which tells you how far below max EGT you are for each cylinder. At 65% power, I pulled from ROP slowly through peak EGT until I was lean, and continued to lean till the engine started fishbiting (running rough), and I enrichened just enough to run smooth. The settings below are what I got.

Please note this is a TIO-540 Lycoming, so I am looking for CHT below 400 per Mike Busch's recommendations, so I believe all my CHTs were extremely conservative by Mike Busch's literature.

I have a really big spread on how far off peak I am for each cylinder. I haven't figured out what my GAMI spread is. I think the above settings are great, and very safe, as the cylinder closest to peak EGT is 23 degrees LOP. I also think at 65% power, I'm not murdering the engine to pull slowly through peak EGT, but obviously I wouldn't do this normally, I only did it because I'm still learning and watching what the monitor does.

I'm also not sure, would you call the above 25 LOP, or 73 LOP? Are you looking at best cylinder? Worst? Middle?

After awhile we got a descent or something and I changed all my settings. When I got back to the same RPM and MP settings, I tried the exact same procedure, but I couldn't get the same numbers on the engine monitor. My spread was basically 23 degrees LOP to 4 degrees LOP, so most of my cylinders were very close to peak (not in order, 4,7,12,13,15,23). I could maybe lean a bit more, but my lowest temp cylinder was 60 LOP, with the hottest around 20 and I kept getting fishbites. My cylinder temperatures were pretty similar to the above pics. I believe (4,7,12,13,15,23) was too close to peak EGT to be safe based on leaning by EGT, but if you take Mike Busch's advise and my worse CHT is 370, I should be just fine even that close to peak EGT.

I'm a bit confused why I couldn't lean better the second time around, may just need a finer touch on the knob. I'm also very unsure of whether running close to peak EGT was safe. If you look at the redfin pics from the Advanced Pilot Seminars lectures that Mike Busch throws out, at 65% power, there is still a red zone around peak EGT, but if you look only at CHT per what Mike Busch says, I should be just fine because my CHTs are all WAY below 400.

 

[AnthonyS1]

You need to figure out what your GAMI spread is. That is the difference in fuel flow from the first to peak to the last to peak. For example if the first cylinder peaks at 15GPH and the last cylinder peaks at 14.3 GPH you GAMI spread is .7. This would be a high spread and you would want to call GAMI to get adjusted injector sizes to lower the GAMI spread to at least below .5 GPH. If you don't already have GAMIs then order them.

To answer your other question in the above photo you are currently operating at 25LOP... this is actually a little too rich and your engine should be at least 50LOP at the current manifold pressure setting. If you can't run smooth LOP you need better balanced injectors.

I have a NA continental powered Bonanza which almost everyone operates LOP in them now. Lycomings are a lot more finicky to run LOP. Some just won't. Also I think someone with a turbo powered airplane could better answer this but usually when operating a turbocharged engine LOP you actually go by how far LOP the TIT is and not so much the cylinders. My turbocharged experience is limited.

 

[RyanB]

My CFII doesn't know anything about running LOP, though, so I'm on my own

Find a new instructor.

 

[Cedric31]

As a fellow Turbo Lycoming driver (TO-360 in my case) a couple things to be aware of:
Mike Busch's experience is mainly with Continental engines. All of his own aircraft are/were TCM powered and so are most of the aircraft his company manages. So, naturally, most of his publications are mostly based on data derived from TCM powerplants. But even though Lyco and TCM engines are fairly similar, there are distinct differences. TCM engines have more trouble with their cylinders, so keeping CHTs low makes a lot of sense. For Lycoming engines the problems are more about spalled lifters, cams and sticking valves. All of these things become worse when the CHT is too low. My personal target CHT is 380-400°F, I definitely would shy away from running a turbo Lycoming cooler than 350°F CHT for extended periods of time. An important thing to note is that despite all of the talk regarding LOP for the last 10+ years, Lycoming to this day does not authorize it for their engines, as far as I'm aware. Their leanest allowable setting is peak EGT (or in our case peak TIT), which according to them is "best economy". TCM on the other hand says "best economy" for their engines is 40-50 LOP and actually authorizes their engines to be run there.
Don't be afraid to run a little inside the "red fin" that Mike has drawn in his publications. That again is more in reference to TCM engines. He's completely right when he says at the end of the day it's all about cylinder pressures and the CHT is the best measurement of that available to us. So fly your aircraft in reference to that.
But if you take one thing away from my long mumbling response it's this: in the last few years more and more Lycoming engines suffered pre-mature damage from spalled lifter/cam interfaces and sticking valves than ever before. These engines don't like to run as cool as TCMs.

 

[Arnold]

As a fellow Turbo Lycoming driver (TO-360 in my case) a couple things to be aware of:
Mike Busch's experience is mainly with Continental engines. <SNIP> For Lycoming engines the problems are more about spalled lifters, cams and sticking valves. All of these things become worse when the CHT is too low. My personal target CHT is 380-400°F, I definitely would shy away from running a turbo Lycoming cooler than 350°F CHT for extended periods of time. An important thing to note is that despite all of the talk regarding LOP for the last 10+ years, Lycoming to this day does not authorize it for their engines,(emphasis added) as far as I'm aware. Their leanest allowable setting is peak EGT (or in our case peak TIT), which according to them is "best economy". TCM on the other hand says "best economy" for their engines is 40-50 LOP and actually authorizes their engines to be run there.<SNIP>

I'm not sure if this is your engine. I would follow Lycoming's recommendations. https://www.lycoming.com/sites/default/files/TIO-540-AE2A Operator Manual 60297-27.pdf

[Edit] Kudos for posting the question and seeking advice.

 

[David Megginson]

Hi!

I'm still very new, 75 hr pilot. 20 hrs in my plane, a PA-32-301T Saratoga Turbo. I'm starting IFR training with my CFII, while in cruise, I'm working on running LOP. I have read a ton of Mike Busch's stuff, and watched all the videos I could find. My CFII doesn't know anything about running LOP, though, so I'm on my own, and would love extra eyes checking my work.

In cruise today at 8000 feet, 65% power setting by the POH, as below, with the book ROP fuel flow. I have a G1 Insight engine monitor. It shows CHT in the green, EGT in the white. Reading the manual for the engine monitor, it records your max EGT and as you move away from that, it gives you the boxed number up top which tells you how far below max EGT you are for each cylinder. At 65% power, I pulled from ROP slowly through peak EGT until I was lean, and continued to lean till the engine started fishbiting (running rough), and I enrichened just enough to run smooth. The settings below are what I got.

Please note this is a TIO-540 Lycoming, so I am looking for CHT below 400 per Mike Busch's recommendations, so I believe all my CHTs were extremely conservative by Mike Busch's literature.

I have a really big spread on how far off peak I am for each cylinder. I haven't figured out what my GAMI spread is. I think the above settings are great, and very safe, as the cylinder closest to peak EGT is 23 degrees LOP. I also think at 65% power, I'm not murdering the engine to pull slowly through peak EGT, but obviously I wouldn't do this normally, I only did it because I'm still learning and watching what the monitor does.

I'm also not sure, would you call the above 25 LOP, or 73 LOP? Are you looking at best cylinder? Worst? Middle?

After awhile we got a descent or something and I changed all my settings. When I got back to the same RPM and MP settings, I tried the exact same procedure, but I couldn't get the same numbers on the engine monitor. My spread was basically 23 degrees LOP to 4 degrees LOP, so most of my cylinders were very close to peak (not in order, 4,7,12,13,15,23). I could maybe lean a bit more, but my lowest temp cylinder was 60 LOP, with the hottest around 20 and I kept getting fishbites. My cylinder temperatures were pretty similar to the above pics. I believe (4,7,12,13,15,23) was too close to peak EGT to be safe based on leaning by EGT, but if you take Mike Busch's advise and my worse CHT is 370, I should be just fine even that close to peak EGT.

I'm a bit confused why I couldn't lean better the second time around, may just need a finer touch on the knob. I'm also very unsure of whether running close to peak EGT was safe. If you look at the redfin pics from the Advanced Pilot Seminars lectures that Mike Busch throws out, at 65% power, there is still a red zone around peak EGT, but if you look only at CHT per what Mike Busch says, I should be just fine because my CHTs are all WAY below 400.

As long as (a) all the cylinders are well lean of peak EGT and (b) your engine isn't running excessively roughly, you're fine. If they're available for your engine, you could smooth out the spread by installing GAMIjectors, but it looks like you're managing OK without them.

 

[David Megginson]

As a fellow Turbo Lycoming driver (TO-360 in my case) a couple things to be aware of:
Lycoming to this day does not authorize it for their engines, as far as I'm aware. Their leanest allowable setting is peak EGT (or in our case peak TIT), which according to them is "best economy".

The diagram in the Operator's Manual for my Lycoming O-320 shows "Best Economy Range" centered around 50°F LOP, though the narrative text doesn't reflect that.

 

[EdFred]

You might as well have posted stats for the Toronto Maple Leafs because that is about as relevant. They are talking about operations in a turbo 540, not a carb'd 320.

 

[oskrypuch]

You might as well have posted stats for the Toronto Maple Leafs because that is about as relevant. They are talking about operations in a turbo 540, not a carb'd 320.

In terms of general operation, for sure very different.

But a power engine curve showing the relative ranges of EGT (or TIT), CHT & BSFC, is much the same for any Lyc or Conti engine.

* Orest

 

[David Megginson]

My advice would be to operate a new Lycoming engine well rich of peak (preferably 150°F ROP or higher to avoid the red zone) while it's under warranty, then operate it either <= 50°F LOP or >=150° ROP (as you prefer) once the warranty has expired. Just stay well clear of 50°F ROP — both 100°F ROP and peak EGT are cutting it close, especially if your cylinders have a wide spread.

 

[Capt. Geoffrey Thorpe]

You might as well have posted stats for the Toronto Maple Leafs because that is about as relevant. They are talking about operations in a turbo 540, not a carb'd 320.

Well, ummm, not so much.
The right side (of peak) is pretty much just chemistry - not much variation.
The left side is a bit more engine specific, particularly the location of the minimum point. But aircraft engines in general are kinda suckey for several reasons.
Big reason is that they were designed in the days of cheap fuel. Just run rich, get best power, and that's the end of it. So, they have open chambers with minimal charge motion (swirl, tumble or squish), easy and good for power. Generally the cylinder to cylinder air and fuel distribution is somewhere between poor and abysmal, but, hey, if you are running rich, it really doesn't matter. Fixed spark timing falls in the minus side, but given the limited lean tolerance of the engine, not that much of a difference.
On the plus side, two plugs help. Low surface/volume ratio helps economy in general, but the large chambers do not help the lean tolerance.

And, that's the way it is.

 

[David Megginson]

Well, ummm, not so much.
The right side (of peak) is pretty much just chemistry - not much variation.
The left side is a bit more engine specific, particularly the location of the minimum point.

Just so. The power curve is much steeper on the left side, so uneven fuel/air distribution that gets masked by the shallow slope on the ROP side will become noticeable roughness due to the steep slope on the LOP side.

But it's still not that complicated. If you can run smoothly at 50°F LOP, go for it! If you can't, then you need to run on the rich side of 100°F ROP (preferably 150° ROP).

And if you're operating at 60% power or below, it doesn't matter where you lean, because you're not likely going to produce enough internal cylinder pressure to cause predetonation even at peak CHT.

 

[benyflyguy]

I can’t help but think seeing a couple more pics of the plane inside and out won’t help.

 

[systemloc]

I got additional data to try and calculate a GAMI spread. My engine monitor is an Insight G1, so unfortunately, no data recording. I set the autopilot, reduced power to 65% power cruise, set the engine generously rich, then leaned and snapped a pic of the monitor every 0.5 GPH steps. I plotted the data for the CHT and EGT above. The "Series" is the cylinder. Each data point is 0.5 GPH from the next. Unfortunately, I think the data is too course to be of much help given the numbers for GAMI spread suggested in a prior post. My GAMI spread is probably between 1 and 0.5 GPH. I see now that I need to make a finer plot. It's a bit difficult as I have the original fuel flow gauge and not a digital to get more precise readings, but I will try next time I'm out. One thing I notice is that Cylinder 2 and 4 run HOT!!! That's really weird since they are on the same side? 6 is the coldest and it's on that side too. Wondering if I need to check the baffling, maybe too much air is going around 6 and robbing air from 2 and 4.

Also, passed my check ride!!! This was my first solo flight in my own plane.

 

[Clip4]

From the horse’s mouth.

https://www.lycoming.com/content/leaning-lycoming-engines

 

[AnthonyS1]

From the horse’s mouth.

https://www.lycoming.com/content/leaning-lycoming-engines

Just read the whole thing. Honestly the suggestions for best power and best economy are crap recommendations for engine longevity. They are good recommendations for the objective listed "best power" "best economy" it says to run the turbocharged engines at peak TIT for economy. Good luck getting even half the TBO life out of your cylinders operating like that.

 

[WillFly4Food]

Cylinder temps are a result of both air/fuel ratio, and airflow around the cylinder. Check your baffling and also the overall cooling air routes in and out of the cowling. Keep us posted.