Lycoming vs Continental operation lean of peak (LOP)

[wdeninger]

Shopping for a plane and considering engine variants.

I've heard some aviation enthusiasts state that it is possible to safely run Continental engines LOP whereas Lycoming should be kept ROP.  Is this an engine cooling issue with Lycoming, or is there a more significant difference with operating mixtures between the TIO-540-AF1B vs the 210HP Continental TSIO-550?

-W

 

 

[Mooney Dog]

I dont think it matters either way so long as everything else is good with the engine. Though ive always been told if you want to fly fast, its ROP. LOP is for going far. 

I normally run ROP in planes that dont have proper CHT monitoring though. 

[KSMooniac]

Physics are the same in both engines.

My Lyc IO-360 is very happy running LOP and I fly out that way in cruise, descent, and landing. Only TO/climb is ROP for me. Stock injectors, 0.0 GAMI spread.

Anecdotally, the TIO-540 is difficult to run LOP... some will, some won't, and I don't think the puzzle has been definitely solved as to why.

I believe the Continental engines will all run LOP but might need GAMIjectors. The few I've flown all would.

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[PilotX]

My Bravo runs beautifully LOP without GAMI injectors. My buddy’s Bravo runs beautifully LOP with GAMI injectors. YMMV

[PT20J]

Both can run LOP if fuel injected. Lycomings generally have better mixture distribution and can often run LOP with stock injectors. Continentals usually require GAMIjectors. 

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[Niko182]

The M20 E, F, J, K, S, R, TN, U, and V will all run LOP usually out of the box. They might need gamis but for the most part the engines on these planes are happy to easily run LOP.

The A, B, C, D, G, and M are a different story. They might be able to run LOP, but the O360 isnt fuel injected which makes it more difficult, and the TIO540 seems to be hit or miss. 

[Shadrach]

Engine make really isn’t the issue, although some Continental intake designs have an inherent fuel imbalance from cylinder to cylinder. As Scott mentioned above some specific models are more prone to challenges than others. The vast majority of normally aspirated, injected, angle valve, Lycomings will run beautifully at mixtures that are leaner than is practical for the power setting. My box stock IO360A1A will run smoothly to nearly 100° LOP down low. It will only run smoothly to about 50° LOP at 10,000 feet,  but that’s a pretty useless power setting at that altitude so it doesn’t  really matter.

Edited August 27, 2021 by Shadrach

[kortopates]

It really has nothing to do with the engine manufacturer and everything to do with the engine model.
But the Lyc IO-360 engine is really about the only 200 HP and up engine that runs consistently without tuned injectors.
Continental also supplies tuned injectors and those that say they run theirs without Gami’s may well be because their equipped with TCM’s tuned injectors.
Next to the Lyc IO-360’s for best LOP performer is the TCM family of IO-550’s both NA and TSIO’s. Once outfitted with tuned injectors they’ll typically support 100F LOP before misfire. They can do just as well as or better with tuned injectors as the Lyc IO-360’’s. The worst is really the Lyc 540 series, both the NA and the TIO in the Bravo. Getting mixture fixed/tuned is usually doable but the ignition system invariably shows some misfire starting around 25-40F LOP depending on state of ignition system health.

Of course there are always a few exceptions. But to say one manufacturer does it better than another is counter to the laws of physics. But every FI engine has the potential to some degree.
And believe it or not, even some carbureted engines are sometimes capable of light LOP with some carburetor heat - but that’s not common and requires pilot perseverance to figure out.


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[Ragsf15e]

2 hours ago, Mooney Dog said:

I dont think it matters either way so long as everything else is good with the engine. Though ive always been told if you want to fly fast, its ROP. LOP is for going far. 

I normally run ROP in planes that dont have proper CHT monitoring though. 

Cht monitoring is nice, however chts are lower when running lop.  It is important to have all 4 (or 6) EGTs so you can ensure you are really lop on each cylinder, but you’ll find that the chts are definitely less than rop.  If you are very close to peak on the rich side, you will get warm chts.

[A64Pilot]

1 hour ago, kortopates said:

It really has nothing to do with the engine manufacturer and everything to do with the engine model.

This is it, my IO54W1A5D with Gami injectors and fine wire plugs wouldn’t run LOP very well. by wouldn’t run very well I mean it lost excessive HP and would begin to miss.

Now it was a parallel not an angle valve motor and I did some testing with it, at 25 LOP of the richest cylinder I let it stabilize out, and then run it 50 ROP of the leanest cylinder and adjusted manifold pressure until the air speeds were identical, and guess what fuel flow was within .1 GPH. so no significant difference.

Now my IO-360 Lyc has stock injectors and massive plugs and will run deep, deep lop, it is the poster child for LOP.

The IO-520 in out C-210 also with Gami’s and fine wire plugs would run LOP fine, and you could get quite a boost in fuel economy by doing so, if your didn’t mind giving up a lot of cruise speed.

 

[philiplane]

One important point- Continentals need to be run LOP in order to get any reasonable life from the cylinders. They have more problems with exhaust valves when run ROP, resulting in 800 hour top overhauls. 

[ilovecornfields]

9 minutes ago, philiplane said:

One important point- Continentals need to be run LOP in order to get any reasonable life from the cylinders. They have more problems with exhaust valves when run ROP, resulting in 800 hour top overhauls. 

Is there really a source for this? I have an IO-550 and have a friend with a Bonanza that also has an IO-550. In similar timeframes he’s replaced 4 cylinders and I have replaced none. He runs LOP (or used to until that 4th cylinder) and I run ROP.  If there’s a definitive source that says that I “need to” run LOP I’d love to see it.

I have nothing against LOP. I actually used it on my last flight to stretch the fuel reserve a little but that just seemed like a pretty strong statement to make and contrary to my experience.

[carusoam]

8 hours ago, wdeninger said:

Shopping for a plane and considering engine variants.

I've heard some aviation enthusiasts state….

-W

 

 

Find new aviation enthusiasts….  

 

Running LOP is all about….

1) gasoline distribution being as close to equal for all cylinders….

2) air distribution being as close to equal for all cylinders…

 

Fuel distribution is….

3) Much easier with four cylinders…

4) More challenging with six cylinders…

 

When you have a six cylinder engine…

5) It is better to have the curvy intake pipes for air flow balancing… see pics of Continental IO550s…

6) The log style intake pipes are good… at a more narrow range of operations…  see pics of the Bravo’s engine…

 

How you know LOP is acceptable…

7) Some POHs clearly state power charts for both LOP and ROP…

8) Some POHS ignored what the customer wanted, as if LOP didn’t exist…

 

How to get up to speed yourself….

There are resources that cover the technical things to look for… 

9) Power settings where LOP can’t possibly harm the engine…

10) Something called the red box or red fin…

 

It helps to have…

11) a good engine monitor…

12) interest in what this is all about…

13) a drive for speed and efficiency…

 

Or get an NA Mooney and fly it above 8k’ and experiment until you like what you get…  

Go Mooney!

Best regards,

-a-

[A64Pilot]

The IO-520 I had was a factory overhaul, and I ran it 100 to 150 ROP always and ran it hard, right after takeoff I’d run the RPM back to 2500 and woud leave it there for the entire flight and left the throttle wide open until I began a descent.

I had well over 1,000 hour on it and it ran perfect.

There are a great many Cessna Crop Dusters down South that run Continentals and run them hard and get good lives out of them, but they run them very rich, it’s my opinion that for a Continental to live a good long life, run it real rich if you must have the power, or run it real lean if you can live with lower power output, just don’t run it a little rich or a little lean.

The Conti’s are hot rods, listen to one idle and you can hear it has an aggressive cam profile, so if your want high HP be prepared to feed it. But you can get great economy too.  Just don’t expect high power and good economy. Pick one

Edited August 28, 2021 by A64Pilot

[KSMooniac]

The Continental valve issues are due to their inability to get valves installed concentrically, resulting in uneven heat transfer out of the valve, and faster wear/failure. Running LOP might kick the can down the road a little further, but this is 99% a manufacturing issue that they just won't fix.

I read a lot of Beechtalk (heavy Continental user base!) and the savvy owners there send brand new Continental jugs (or new engines) to a good shop to get all of the valves reworked before flying. That greatly increases the chances of making TBO without a TOH, regardless of LOP/ROP ops.

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[MikeOH]

3 minutes ago, KSMooniac said:

savvy owners there send brand new Continental jugs (or new engines) to a good shop to get all of the valves reworked before flying. That greatly increases the chances of making TBO without a TOH, ...


 

Hmm, so they 'voluntarily' remove cylinders and rework valves (kinda of a 1/2 TOH IMHO) on a brand new engine so that they don't have to do it later.  Okey dokey.

I agree it makes sense if you are REPLACING a jug...but on a new engine???

[KSMooniac]

Yes, that's what many do that have seen the movie before. I bet if you go ask the question over there you'll get lots of confirmation, or "i should have done that" responses.

Cost savings in the factory dropped that important step... At least that is the theory. So the savvy owners pays am experienced shop to do it after the factory ships. Yes, it's terrible.

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[Niko182]

That right there is the main reason when the io550 needs an overhaul, it will be send to gann or powermasters instead of getting a reman or a new engine from continental. 

an overhauled engine from gann or powermasters is better than a new engine from TCM in my opinion.

[ArtVandelay]

The Continental valve issues are due to their inability to get valves installed concentrically, resulting in uneven heat transfer out of the valve, and faster wear/failure. Running LOP might kick the can down the road a little further, but this is 99% a manufacturing issue that they just won't fix.

I read a lot of Beechtalk (heavy Continental user base!) and the savvy owners there send brand new Continental jugs (or new engines) to a good shop to get all of the valves reworked before flying. That greatly increases the chances of making TBO without a TOH, regardless of LOP/ROP ops.

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That doesn’t say much for Continental’s quality.

[aviatoreb]

42 minutes ago, KSMooniac said:

The Continental valve issues are due to their inability to get valves installed concentrically, resulting in uneven heat transfer out of the valve, and faster wear/failure. Running LOP might kick the can down the road a little further, but this is 99% a manufacturing issue that they just won't fix.

I read a lot of Beechtalk (heavy Continental user base!) and the savvy owners there send brand new Continental jugs (or new engines) to a good shop to get all of the valves reworked before flying. That greatly increases the chances of making TBO without a TOH, regardless of LOP/ROP ops.

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That’s what I did.

[Niko182]

38 minutes ago, ArtVandelay said:

That doesn’t say much for Continental’s quality.

I think at this point its a matter of luck getting a good engine from TCM. Some get lucky and their engines make it to overhaul. Im at 1956 hours on the engine right now with 1 cylinder changed at 1400 hours and the other about 20 hours ago.

[philiplane]

18 hours ago, ilovecornfields said:

Is there really a source for this? I have an IO-550 and have a friend with a Bonanza that also has an IO-550. In similar timeframes he’s replaced 4 cylinders and I have replaced none. He runs LOP (or used to until that 4th cylinder) and I run ROP.  If there’s a definitive source that says that I “need to” run LOP I’d love to see it.

I have nothing against LOP. I actually used it on my last flight to stretch the fuel reserve a little but that just seemed like a pretty strong statement to make and contrary to my experience.

15,000+ hours of fleet experience with IO-550N's shows that LOP results in cleaner valves & piston ring grooves. The LOP engines go to TBO with their original cylinders. The mixed use and ROP engines get topped at least once in 2000 hours. 

LOP results in cooler valves and less deposits on the valve seats. Hot valves with contaminated seats burn easily. Lycomings don't have this problem since their top mounted pushrod design cools better. Continentals are always going to be problematic because the pushrods, and the oil they bring, are below the valve. They get less oil on the valve stem, and on the exhaust valve spring rotocoil. Once the rotocoil stops working, the valve is doomed. ROP just kills it faster with all the lead build up on the seats. If you could run unleaded fuel, the valves would last much longer.

Ask George Braly if you want engine test stand observations of LOP versus ROP engine health.

 

[Schllc]

On 8/27/2021 at 2:47 PM, wdeninger said:

Shopping for a plane and considering engine variants.

I've heard some aviation enthusiasts state.....

That’s your first mistake. 90%, if not more of what you read from “aviation enthusiasts”, is... well, to be kind.... inaccurate at best.

Pick up a book by mike bush, or some simplified thermodynamics explanation.  
Heat exchange, and temperature management is not rocket science, nor reserved for one engine make or model.

I have observed people fly their planes without ever touching the mixture or even noting temperatures. I even flew with someone who started the engine cold and idled all the way to take off at 1700rpm. When I asked him why he said “this engine loves fuel”.

My point is good engine management is incredibly important and buying a plane from someone who flys it regularly and treats it right will almost always have less issues. 
I would bet money that many of the problems that both lycoming and continental have are from mismanagement or misunderstanding of parameters. 

 

[A64Pilot]

A whole lot of, I’d say most of Continentals exh valve problems are because they are not Sodium filled.

Lycoming’s stick valves largely because they are sodium filled and cool so well.

I hear a lot of how valves operated LOP run cooler, I’d like that explained, LOP is almost always higher EGT, so how do they run cooler? The heat comes from exhaust gasses.

[Andy95W]

100° Lean of Peak EGT = cooler exhaust gases than 50° Rich of Peak EGT.

With fewer exhaust byproducts being the bonus. 

Edited August 28, 2021 by Andy95W