Lean of Peak

[Martorious]

Do I sense a new "alternative" engine?

The engine was bulletproof. 200 hp/ liter specific output (that would be 720hp on an O-360)

If you don't mind my asking, what did it cost? Will it fit in an RV-8?

(Just trying to keep up with the Joneses and their rockets/super-8s !)

PS, For those who may be concerned about my mental health, I'm just kidding, I'll be going with a mid time Lyco, I don't have the background or nerve to 'experiment' with the powerplant. More power to those that do, though!

PPS, thanks guys for all the info in this thread, it's been a real education for me!

 

[rv6ejguy]

The whole engine was under $5K, Yes it would fit in an -8. No, I would not recommend it. TBO about 40 hours! Need some mighty redrive as this one spins at 8000 rpm!

 

[Stephen Lindberg]

LOP operation - a question

Years ago it was frequently and commonly noted that LOP operation produced an oxidizing environment which resulted in exhaust valve stem erosion. None of the posts in this thread have mentioned this topic. Is this no longer an issue? Was it ever a real issue? Steve

 

[pbesing]

rv6ejguy,

You're referring to "PEAK spread," and I agree that this is the critical factor. For example, my IO-360-A1B6 is balanced to the point where all cylinders reach peak EGT at identical fuel flow, meaning there is no cylinder that reaches peak first. They all peak simultaneously as the mixture is leaned. When one cylinder is 40 LOP, *all* cylinders are 40 LOP. All cylinders are at the same point in the curve at any given mixture setting. That is the condition we strive to achieve to make LOP a safe ordeal.

How'd you accomplish this, Dan?

 

[dan]

How'd you accomplish this, Dan?

It's a matter of fine-tuning your injectors until you get the EGT peaks occurring at the same fuel flow, or as close to it as possible.

I got extremely lucky. My Airflow Performance injectors and stock restrictors were balanced out of the box. Why I got lucky, I have no idea, because several others that I know (Scott Bilinski, Mike Stewart, etc.) have had to do a little tuning to achieve this synchronicity of EGT curves.

Mike Stewart's site has a good write-up with some before & after data tables if I recall, and that's where I'd look if you want to see how it's done.

 

[mlw450802]

...
Detonation is caused by pre-ignition (not the other way around). ..., "it can be compounded by pre-ignition". No, No, No, No , No, Pre-ignition comes first, not detonation. Detonation is a by-product of pre-ignition. Detonation describes the affect of combustion happing abruptly, that is all, that is it, nothing more. Detonation is not a cause or mechanism, it is just a definition of the type of combustion you have. YOU MUST HAVE PRE-IGNITION TO HAVE DETONATION. To say detonation causes pre-ignition is like the putting the cart-before-the-horse, or pre-flight you airplane while it is cruise flight.

George,
I know how you love to have references, so here you go.

"Pre-ignition may lead to detonation and detonation may lead to pre-ignition or either may exist separately."

References

• Charles Fayette Taylor, Internal Combustion Engine in Theory and Practice: Vol. 2, Revised Edition, MIT Press, 1985, Chapter 2 on "Detonation and Preignition", pp 34-85. ISBN 0-262-20052-X

-mike

 

[Yukon]

Longevity

Hey guys, excellent thread, but what is clearly missing from this discussion
is longevity and reliability.

So let's stipulate that with matched flow fuel injection, electronic ignition, and an engine analyzer, we can make our big engine sip gas like a small
one.
Can it be done for 2000 hours? What happens when one of the above components malfunctions, and causes an upset in the delicate balance?
What happens when the pilot forgets to enrichen for the descent? What happens when a tank runs dry inadvertently? A cracked spark plug
electrode?What happens when the car gas you have chosen to run has
too much ethanol blended?

These issues are the driving force behind much of Lycoming's conservatism , and come from years of costly experience with the Sunday pilot. When Lycoming talks, I listen. The same for goes for Van.

You boys have fun!

John

 

[dan]

What happens when the pilot forgets to enrichen for the descent?

If left alone from high altitude LOP, as the pilot descends, theoretically the mixture gets "leaner" and eventually the engine will sputter. Big deal.

What happens when a tank runs dry inadvertently? A cracked spark plug electrode?

Huh? What's the difference in this scenario LOP vs. ROP? I've run tanks dry when LOP a few times. I've pulled my purge valve to ICO when LOP several times for glide testing & stopped-prop testing. Haven't seen any spark plug issues. I must be missing something...why would LOP present any more of a problem in this scenario than ROP?

 

[Yukon]

Longevity

Yes Dan, what you are missing is the major premise of my post.

John

 

[N395V]

of fine-tuning your injectors until you get the EGT peaks occurring at the same fuel flow

I thought the purpose of customizing the injector orifice for slightly different flow to each cylinder so that they would peak at the same time. Except by freak of nature I cannot see how to achieve simultaneous peaks unless the fuel flow in each cylinder is different than it's neighbors.

 

[dan]

I thought the purpose of customizing the injector orifice for slightly different flow to each cylinder so that they would peak at the same time. Except by freak of nature I cannot see how to achieve simultaneous peaks unless the fuel flow in each cylinder is different than it's neighbors.

We're saying the same thing in two different ways. When I say "at the same fuel flow" I don't mean flow at each injector. I mean the flow of the system. How much fuel is being consumed in gallons per hour. Measured at a transducer somewhere inline with the fuel system. But this is not to imply the actual flow at each cylinder, which would be difficult to measure with what we're working with.

So yes, I agree with what you're saying about peaking "at the same time." Same time, same overall fuel flow, we're saying the same thing.

Sure, you could theoretically use "time" as one axis of the curve instead of fuel flow, but the time it takes to reach peak would vary, well, based on how quickly you pulled the mixture knob/lever. Fuel flow won't vary in that way. The fuel flow vs. EGT curve will look the same regardless of the speed (time) at which you pull the mixture (within reason of course, yanking the lever back doesn't count).

So "fuel flow" is the way we correlate the data when doing balancing tests.

 

[N395V]

These issues are the driving force behind much of Lycoming's conservatism , and come from years of costly experience with the Sunday pilot. When Lycoming talks, I listen

I think the key comment in your post is the one about the Sunday pilot.

I take that to mean one with relative lack of experience and knowledge about LOP operations and I fully concur that if you wish to run LOP you need to be equipped for it and know how and when to make the appropriate adjustments.

There are no well done controlled studies that I know of that answer the question of ROP vs LOP relative to engine health or longevity.

There is scientific data that supports LOP with facts of decreased internal cylinder pressures and temps when LOP.

There are many operators of big bore turboed Continentals that have taken the same engines LOP through TBO and reman and then to TBO again as there are ROP operators who have done the same.

My personal opinion is that the reason to run LOP is to extend engine life and reduce maintenance not so much to save fuel.

The fuel savings for the average pilot would take several years of flying to pay for the balanced injectors and engine monitor.

My own experience with LOP is with GTSIO 520s on a Twin Commander and Twin Cessna.

Changing to LOP significantly reduced cylinder and valve problems and decreased maintenance costs.

Did not run them to TBO so do not know their condition at teardown and I will concede that the decreased maint cost may have been a result of finally getting the planes in a state of repair they had not seen in years. I tend however, to attribute it to LOP.

 

[N395V]

When I say "at the same fuel flow" I don't mean flow at each injector. I mean the flow of the system.

OK I understand your meaning now. Just misinterpreted it in my 1st read.

 

[Joey]

When Lycoming talks, I listen.

Here's what they say about operating on the lean side of peak EGT:

Lycoming is in complete agreement that it is possible to
operate an engine on the lean side of peak TIT. It is done on
engines in our well-instrumented Experimental Test laboratory
every day. There is nothing detrimental in operating an engine in
this manner.

I linked to the rest of the article. Their concerns focus mainly on the human factors when operating lean of peak, not technical reasons. Multi-cylinder electronic engine monitors with configurable alarms are commonplace these days, relieving the need for constant monitoring on the part of the pilot.

What happens when the car gas you have chosen to run has
too much ethanol blended?

Testing for ethanol is quick, cheap, and easy. If ethanol is detected, the fuel doesn't go in the airplane.

 

[Yukon]

Si-1094d

Joey,
First of all, TIT refers to turbocharged engines. Don't think most RV's fit in this catagory. Second of all, Lycoming Service Instruction 1094D specifically recommends against lean of peak operation.

http://www.lycoming.textron.com/sup...ePublications/serviceInstructions/SI1094D.pdf

Checking for water is "cheap and easy" too, but there are plenty of fuel contamination accidents.

The point of the post was that a richer mixture provides detonation margin under difficult and unforseen circumstances. I believe this is what Lycoming is trying to say, if you will take the time to read 1094.

John

 

[Joey]

Joey,
First of all, TIT refers to turbocharged engines. Don't think most RV's fit in this catagory.

The point is that a turbocharged engine in this case is the worst scenario, yet even Lycoming is forced to admit that there is nothing detrimental in operating it lean of peak EGT. If there is nothing detrimental in operating a turbocharged engine in this manner then the same would apply for a normally-aspirated engine as well, obviously.

Second of all, Lycoming Service Instruction 1094D specifically recommends against lean of peak operation.

Yes, but not because it's harmful to the engine. They made their anti-lop case very well with the SSP700 document I linked to earlier. Their concern is that pilots can't handle the extra workload of managing the mixture. Sorry to put it so bluntly, but that's a steaming load of crap.

I'm not sure what point you're trying to make with the whole fuel contamination issue. I don't see what it has to do with LOP operation.

The point of the post was that a richer mixture provides detonation margin under difficult and unforseen circumstances. I believe this is what Lycoming is trying to say, if you will take the time to read 1094.

I agree that a rich of peak EGT mixture increases the detonation margin. You need to realize that a leaner than peak EGT mixture increases detonation margin as well. Your detonation margin is at its least right at peak EGT, or maybe a hair richer. Moving the mixture either way, rich or lean, improves it. So it's your choice: You can have the same detonation margin at a high fuel flow or a low one. Avgas at my airport is $4.96 a gallon.

Now, about this document you linked to. In the section labeled "Leaning the normally aspirated engines" it says, "Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM."
Where do you think this will put you? Check out the chart on page 6 for your answer. Note the entire "best economy" range is lean of peak EGT.

Look, I can appreciate the fact that Lycoming doesn't want hamfisted stick actuators sullying their good name by toasting engines left and right from leaning without the required knowlege and/or equipment. They are telling you not to run lean of peak because they think that the average pilot can't chew gum and fly at the same time. If you are happy with their assessment of your abilities, more power to you.

 

[Yukon]

LOP and engine displacement

Joey,

So to summarize your many posts, you are advocating the new builder install the largest engine he can find, and then lean it to a fraction of it's rated horsepower to obtain the fuel economy of a smaller engine???? Why not just install an appropriately sized engine from the start?

John

 

[dan]

So to summarize your many posts, you are advocating the new builder install the largest engine he can find, and then lean it to a fraction of it's rated horsepower to obtain the fuel economy of a smaller engine???? Why not just install an appropriately sized engine from the start?

It's your plane, install what you want. I like having mucho horsepower available even if I don't use it. I use it on takeoff, in the climb, when in formation, when out goofing around.

My philosophy is that I would run LOP on any engine/setup capable of doing it. When done properly it has potential to extend engine life. And running WOT LOP on an IO-360 will get you there faster than running WOT LOP on an IO-320.

Yes, the engine costs a fair amount more, but I'm willing to pay more for it in order to have that wonderful horsepower reserve when I want it! That's my mission profile. If it's not yours, don't waste your money on a big engine.

 

[Joey]

Joey, So to summarize your many posts, you are advocating the new builder install the largest engine he can find, and then lean it to a fraction of it's rated horsepower to obtain the fuel economy of a smaller engine????

You misunderstand, I'm not advocating anything.

If someone tells me they are installing an O-235 in their -9 or they like to run full rich all the time, I say good for them! It's your airplane, do what you want.

But, if someone online tells me the O-320 is a gas hog at O-235 speeds and LOP is harmful... well, I might have a thing or two to say about that. If I post something that is inaccurate, by all means bring your proof and correct me. We're here to learn, after all.

 

[f1rocket]

Yes, the engine costs a fair amount more, but I'm willing to pay more for it in order to have that wonderful horsepower reserve when I want it!

I know what your next airplane project ought to be!

 

[Kahuna]

I know what your next airplane project ought to be!

Thinking the same thing Randy
But yours or mine?
HA!
Nothing beats cubes. Except cubes, and LOP.
Sharpie is right on all points. I flew 1400 LOP (well not all of it of course) hours on my rv6 4 banger and when the local engine guy stuck a bore scope in my plug hole he could not believe the hours the engine had. He had never seen one so clean. More like a 100hour engine. I swear by running LOP. I ran that engine at 2450rpm and usually 2"less than WOT.

Now that I have a 6 banger, and run 21squared and LOP, I think my engine will last forever., IMHO of course. FLying around in formation with other 4 bangers and running this engine at 1950 and 17" is one of lifes great pleasures. Quiet, calm, smooth, LOP, CHT's under 280F. Life is good. I do spend about 1/3 of my flying under these conditions since I rarely go anywhere alone. My guess is the engine would last forever under these low power settings.

Oh dont you worry, she gets the occasional hard workout to get that cardio going.
Best

 

[rv8ch]

Frequent Fliers

Sharpie is right on all points. I flew 1400 LOP (well not all of it of course) hours on my rv6 4 banger and when the local engine guy stuck a bore scope in my plug hole he could not believe the hours the engine had. He had never seen one so clean. More like a 100hour engine. I swear by running LOP. I ran that engine at 2450rpm and usually 2" less than WOT. ...

Not in any way to minimize the advantages of LOP operation, but I'm sure the fact that you guys fly a lot helps keep your engines in top form. Nothing worse than letting your engine sit around oxidizing.

I think if you take this to its logical conclusion, flying more saves you money!

 

[Yukon]

Need for Speed

Yes Dan, we are all well-aquainted with your need for speed. As you know,
this discussion started over in the RV-9 forum where I was relating my reasons for selecting the O-235 for my airplane. Joey tried to make the point that your IO-360 will burn 4.8 gph at 170 mph, in an attempt to show the folly of an O-235.

Time will tell if that kind of incredible efficiency is sustainable over time from a large block Lycoming. We will all be watching closely. In the interest of full disclosure to the lurking newbie, let's itemize the costs of LOP:

ECI O-360 $21,000
C/S Prop & gov 6,500
fuel injection 3,000
GAMI Injectors 5,000
Engine Analyzer 2,000

So for $37,500 in propulsion costs you can match the efficiency (or maybe beat) an O-235 with a fixed-pitched prop. That doesn't pencil out for me,
Dan, but then again, my hair isn't on fire!

I'll have about $12,000 in engine and prop (23k if you buy new). True, I'll land about 10 minutes behind you, but that's whole point, isn't it, to be in the air???

You are right, every man needs to do what makes him happy. I just want the newbies to be armed with all the figures before they write that big check!

John

RV-9 / O-235

 

[dan]

GAMI Injectors 5,000

Collossal waste of money imho. Call Airflow Performance if you want to save, well, thousands on getting your injectors/restrictors balanced. There's no need to blow big bucks on GAMIjectors imho.

(To clarify, I'm talking about experimentals...TC'd airplanes are kinda stuck blowing $$$$ on the GAMIs.)

 

[dan]

Collossal waste of money imho. Call Airflow Performance if you want to save, well, thousands on getting your injectors/restrictors balanced. There's no need to blow big bucks on GAMIjectors imho.

I should clarify that I'm kinda stuck in the Lycoming mindset. I forget sometimes that there are other engine types out there...

Somebody pointed out that he has a Continental and is kinda stuck paying for GAMIjectors. I thought AFP might do Continental injectors, but perhaps not?

 

[donahuedc]

I put Gami's in a debonair. Think it was about $800.

 

[Yukon]

Need for Speed continued.....

Dan,

I forgot to include the electronic ignition and Superior composite sump (you know, the one that tends to rupture when the engine backfires during start).
That brings the approximate cost for the LOP powerplant to around $43,000.
That's more than twice the cost of the airframe kit, and some pocket change!

John

 

[Jekyll]

In the interest of full disclosure to the lurking newbie, let's itemize the costs of LOP:

ECI O-360 $21,000
C/S Prop & gov 6,500
fuel injection 3,000
GAMI Injectors 5,000
Engine Analyzer 2,000

So for $37,500 in propulsion costs you can match the efficiency (or maybe beat) an O-235 with a fixed-pitched prop. That doesn't pencil out for me,
Dan, but then again, my hair isn't on fire!

No wonder you appear to balk at LOP if you think those are the equipage and costs required.

You don't need C/S.
Yes, injection does help considerably.
You don't need GAMI Jectors, balance the injectors yourself (if injected).
Basic analysers are available such as EI's smart analyser for $1400. With all the EFIS systems being installed, you can likely get a good deal on a used analyser for much less.

The way I see it, you can safely, efficiently and inexpensively run LOP with little additional costs by using analog EGT and CHT guages with probes on each cylinder running through a 4-way switch! IO with a C/S will give you most of the benefit.

So, let's see, $21,000, an extra 3 sets of sensors and a 4-way switch, plus a F/P prop can get me into cheap efficient and NEW LOP equipment for around $23,200. This is a NEW system that is fully capable of efficiently running LOP.

Let's be honest for the newbie lurker: One person wants an engine with 235 CI and another wants one with 200 HP. You can both buy what you want and you can both run LOP without spending obscene gobs of money. Yup, Dan bought a tiger but, that shouldn't be confused with buying for LOP operation. He spent money to buy top-end performance but he only tweaked it and his operating modus to run LOP.

Cubes are great for a number of reasons. Sure you can drive a 1979 Chevy Chevette at highway speeds but don't count on passing anyone (except a 1985 Yugo)! (I'm not comparing the O-235 to a Chevette, only highlighting power reserves).

Jekyll

 

[Joey]

Joey tried to make the point that your IO-360 will burn 4.8 gph at 170 mph, in an attempt to show the folly of an O-235.

Actually, I made my point with Van's RV-9A prototype which has an O-320 equipped with magnetos and a carburetor. No fancy hardware there.

Okay, had to come back and edit this post. Yukon, we seem to be miscommunicating on some fundamental level.

When I say:

An O-320 powered RV-9 burns virtually the same amount of fuel at 170mph as an O-235 powered RV-9.

You seem to be reading it as:

Not originally Posted by Joey
The O-235 sucks, don't use it.

--
Likewise, with this LOP thread. I'm saying:

If you have an engine that can pull it off, there's nothing wrong with operating it lean of peak EGT.

You're reading it as:

Not originally Posted by Joey
Don't buy an O-235 to get that low fuel burn, buy a GTSIO-520-OMGWTFBBQB6 and lean that puppy until the EGTs are in the double digits!

Can you see where I'm coming from here?

 

[AK180Driver]

LOP OPs

One factor not discussed so far in this thread when attempting LOP ops on carbureted engines is this: Not only can you obtain a more even fuel distribution by a slight displacement of the throttle butterfly, you can do even better by running partial or full carb heat while doing so. The warmer induction air atomizes the fuel more thoroughly and homogenously. Only do so in clean air at moderate to high altitude regimes.

I've been doing this with the factory new O-470R Continental in my Cessna 180 (same engine as in most C-182's) for years and achieved significant fuel savings with no apparent ill effects after 700 + hours since my factory new O-470R installation in March of 2001. All cylinders in the mid 70's & more money in my wallet--to finish my RV-7! The key safety factor is to never push your luck at over-leaning at high power settings! I never shoot for LOP unless at 65% or less power setting.

 

[BOBM]

If you fly an RV built simple, light, & CHEAP, as God & Van intended, try this. All you need is a carb O320 with a F/P prop, dual mags, tach, & mixture control.

Climb to desired cruising altitude, accelerate to cruise speed, & set RPM for 75% power. After everything stabilizies, lean the mixture to obtain a reduction of 100-125 RPM. If your experience is similar to mine, you will see the following:

A power setting of about 65% with a smooth running engine.

A loss of 5-8 kts in speed (3-5%).

Up to 20% drop in fuel consumption & increase in range from the best power mixture setting.

A drop of 30-50 degrees F in cht

A noticable drop in oil temp

A drop of about 50 degrees from peak EGT (if you had an EGT guage)

It would appear that this procedure is EXACTLY in conformance with Lycoming recommendations for leaning a normally aspirated engine & for obtaining maximum engine life.

BOB

 

[Yukon]

I have tried to approximate Dan's costs, as he is the most vocal proponent of LOP.

John

 

[dan]

I have tried to approximate Dan's costs, as he is the most vocal proponent of LOP.

Your estimate is much higher than what I invested, but that's neither here nor there. How exactly are you helping the readers of this thread?

 

[fodrv7]

Noise from Down Under

Mind if I throw some Avgas on the fire.

My RV7 (in round figures. Let's not get picky here) burns 40 litres/ hr ROP and around 30lph LOP. Don't worry about the units, they could be kilocarrots; it doesn't change the argument.

At AUS$1.50 / litre the difference during 2000hr to TBO is:
30 x 1.5 x 2000 = AU$90,000
40 x 1.5 x 2000 = AU$120,000

That's a difference of $30,000 even if it is 'baby' $ (The Australian ones.)

I think you need to subtract US$20,000 in your 'theoretical' approximation of Dan's costs. Plus a lot for inflation the way fuel prices are going.

Frankly, after climbing a 1000' up the face of a big cu yesterday, half rolling and pulling down the other side, I personally, am glad I 'blew' so much money FWF.
Pete.

 

[Yukon]

Peak vs LOP

Peter,

The issue we are discussing is Peak vs LOP , not ROP vs LOP. Rich of Peak is best power. Peak is the Lycoming recommended power setting for cruise for normally aspirated engines.

John

 

[Yukon]

You engine costs

Your estimate is much higher than what I invested, but that's neither here nor there. How exactly are you helping the readers of this thread?

Post your engine costs, Dan, if my estimates are inaccurate.

John

 

[jcoloccia]

re: engine costs. Who cares? It's his money, not ours, and while we're all entitled to our opinions, this is getting a little tedious.

re: ROP vs LOP. The Lycoming bulletin is irrelavant. They could have printed "Jimmy Carter is the emperor of Hawaii" but it wouldn't make it so. Dan, and others, claim that LOP operations are safe and effecient. You claim that it's not safe and will (or may..whatever) lead to premature engine wear. Lycoming doesn't claim anything either way...they just say "Don't do it." Okay, fine. Please indicate WHY LOP operations, when done properly, will lead to premature engine wear. It does no good to quote the bulletin. If the CHT's are reasonable, and there is no detonation, what possible harm could come of it? If it comes back to your argument that you "need" a fancy engine monitor to do it, then what of it? Will you next get upset at the folks with glass panels? I don't get it. I want a fancy engine monitor too! It's my plane, and I'll spend my money how I see fit, just as you're free to do the same.

re: the bulletin. If you read the bulletin, you will see that it contradicts itself somewhat. It indicates that it's acceptable to lean as long as the engine is still running smoothly, but later on it admonishes us to avoid LOP operations. I suppose it assumes that the engine can't be made to run smoothly LOP. Frankly, I think it's CYA on Lycoming part because you KNOW that someone out there is gonna lean the bejeezus out of their engine without paying attention to anything, and something's gonna go boom. Then they'll sue Lycoming because they said it was OK. His argument will be that "engine roughness" is a subjective thing and it's not his fault he couldn't follow such a vague metric (and he would be right). Lycoming fixes the whole thing by saying "Don't run LOP". It makes sense and is the right thing to do from their standpoint.

Sorry for the rambling but for the sake of newbies reading, I think they need to understand that there's nothing wrong with LOP operations anymore than there's something wrong with flying through clouds. All it requires is the proper techniques and the proper instrumentation.

 

[osxuser]

The thing that blows me away about people who say running LOP will damage then engine is this:

The top end of the engine cares how the mixture is burned, it's important to note that running LOP keeps the CHT's low. If running LOP let the CHT's get high, there would be a problem. The lean mixture should burn faster than the rich mixture, all this means is that combustion will be complete before the gases go past the exhaust port, another common failure point (burned exhaust valves) is elminated. Someone on the Socal RV list mentioned that he was waiting for Dan to 'drop a valve' any day now. But since there is no extra stress on the valvetrain at all, so that makes absolutely zero sense. Another function of running LOP is that their is no extra Lead deposits in the cylinders to stay on the valves, plugs and cylinder face, therefore a much cleaner running engine after time. Lead deposits on the valve faces can cause leaking valves over time.

So we have lower CHT's on the cylinders and cooler, already burned cleaner by-product flowing past the valves to prevent valve leakage and burning. So basically the top end is happy.

On the bottom end, it has no clue what your doing on the top, as long as the piston is putting the same amount of power out as all the others, it will happily reciprocate for 2000+ hours with very little or no problems. So any failures there are not going to be a factor of LOP vs. ROP. One thing that GAMI did in their LOP research was to investigate where the highest stresses on the bottom end were for a given power setting. It turns out they are between 50?ROP and peak, right where Lycoming tells you to run. It's obvious from this that the bottom end failing is not going to be an issue.

Now for the other gotcha's with ROP vs LOP. When you are at altitude running leaned to 50? ROP and start a decent, if you forget to richen as you decend you will end up running at peak or LOP anyway, but not intentionally. If your running LOP at the same altitude and decend, you will be getting LEANER, therefore you engine will start loosing power, and you'll realise what you did (hopefully) or it'll just hit a spot where it dies. The catch is LOP is safe when you are monitoring the engine, so running LOP accidentally is a bit more risky then letting your engine die on a let down, and you should have plenty of warning signs before that happens anyway.

Obviously everyone has an opinion on this subject, but I think that LOP ops is backed by enough data, where it shouldn't be an issue for anyone who wants to run that way. I'm planning on having FI anyway (carbs are soooo 1950's) so that wasn't an added cost for my FWF plan, and EI is growing on me... as is EFIS.

 

[gmcjetpilot]

It's all good

If you read the bulletin, you will see that it contradicts itself somewhat. It indicates that it's acceptable to lean as long as the engine is still running smoothly, but later on it admonishes us to avoid LOP operations.

Sorry for the rambling but for the sake of newbies reading, I think they need to understand that there's nothing wrong with LOP operations anymore than there's something wrong with flying through clouds. All it requires is the proper techniques and the proper instrumentation.

100%. Lycoming basically says it's not practical, especially for smaller 4 cylinder engines. Their criteria is smooth operations not necessarily engine damage.

If you already have a FI engine, with full engine monitoring and are up on the principle of LOP operations, go for it. You may need to do injector balance and that is fairly cheap on "experimental" Lyc's.

I have a O-360A1A and I just can't get consistent smooth operations that I am comfortable with. This is my reality or fact, in my experience, it does not work for me (at this time with this setup). We can talk about adjusting the throttle plate a short HAIR closed, holding your breath, feet off the floor boards and mouth a certain way, but it just does not work consistently from my experience on several different carb'ed Lyc engines I've flown. I am OK with that and very happy with my simple carb'ed engines.

LOP is fuel savings. My fuel savings plan (without LOP operations) is leaning when EVER below 75% power. I shoot for the leanest cylinder to be at 75-100F ROP. More important I try to fly well below 75% as much as possible. If you really want to save money, fly at 140 mph, not 195 mph.

If you can't do LOP and want to save money, pull the throttle back more and lean as much as possible on the RICH side. Don't worry about it and go fly.

Cheers George

 

[Yukon]

Change the Channel

John,
IF you are bored with this discussion, may I politely suggest that you not read it? There are many subjects here, pick one that holds your attention.
Now if you are interested, and you seem to be, I'll answer your questions.

Lycoming Bulletins: How do you make the decision about which manufacturer
guideance to ignore? Will you replace your crankshaft if directed to do so? Will you comply with an oil pump service bulletin? Do you consider .005" crankshaft runout to be a service maximum, or do you have your own value?
Do you set your timing at 30 degrees BTC instead of 25 for better performance? The problem with thinking you are smarter than the manufacturer is it is hard to know where to draw the line once you start.

As far as costs go, Dan was trying to justify LOP on a financial basis, and I was pointing out that it was not economic, from the standpoint of initial investment. And that's if nothing goes wrong like a dropped valve or seat. I can't tell you for sure that it will damage your engine, anymore than you can be sure that it won't.

Yes, I agree that every man has the right to buy as big an engine for his RV
as he can afford, and then trick it out with the all the latest "tuner mods"
he can find. Then he can load the panel up with glass, yank out the vacuum pump, fill'er up with mo gas and launch for Oshkosh! After all, this is America,
and you're flying experimental!

I have chosen a different route, and with your permission, will share that information with anyone who is interested. If you find the discussion tedious, change the channel.

John

RV-9 / O-235

 

[jcoloccia]

Then he can load the panel up with glass, yank out the vacuum pump, fill'er up with mo gas and launch for Oshkosh!

LOL...I'd never do that. The mogas around here is getting more expensive than avgas...to bad I can't run avgas in my Durango.

 

[Joey]

Lycoming Bulletins: How do you make the decision about which manufacturer
guideance to ignore?

They advise me to not run LOP because they are of the opinion that I can't handle the extra workload. I know my skills better than they do, so I choose to ignore that particular bit of advice. How do they know what I personally am capable of?

Dan was trying to justify justify LOP on a financial basis, and I was pointing out that it was not economic, from the standpoint of initial investment.

You're looking at it the wrong way. The point of installing big engine is to go fast, not save money. LOP is to save fuel when they choose to not go fast. LOP gives you the option.

The issue we are discussing is Peak vs LOP , not ROP vs LOP. Rich of Peak is best power. Peak is the Lycoming recommended power setting for cruise for normally aspirated engines.

Is this statement true or false: There is more detonation margin when running lean of peak as opposed to peak.

If you answered true (and I seriously hope you did) then consider your earlier post:

The point of the post was that a richer mixture provides detonation margin under difficult and unforseen circumstances. I believe this is what Lycoming is trying to say, if you will take the time to read 1094.

You are concerned about having a detonation margin, yet you want to follow Lycoming's recommendation to run at peak EGT, right where that margin is thinnest?

 

[Yukon]

Enough

Joey,

Your arguments are circular and non-responsive. Please move on.

John

 

[Joey]

I would like to kindly suggest that you follow your own advice:

I have chosen a different route, and with your permission, will share that information with anyone who is interested. If you find the discussion tedious, change the channel.

Like I said, if I have posted inaccurate information, please bring the proof and correct me. The bottom line is I haven't, and you can't.

 

[Jekyll]

Yawn, zzzzzzz

 

[fodrv7]

CX4 to Contol

Quite a reasonable expectation. And you are to be admired for seeking to KNOW.
It is all fairly simple, once you get your head around it.

LOP is not new, nor is the validity of LOP disputable. Super Connies and DC-7 ran with it.

The combustion process is the same in the cylinder of a Lycoming as a Chev, Porsche or John Deere tractor. And lets not hear this **** about four and six cylinders. When #1 cylinder fires and does not know how many more will fire before it becomes it's turn again.

The only difficulty with running at Peak EGT (Which is where the fuel:air ratio is chemically perfect {Stoichiometric Combustion} or lean of peak is that unless each cylinder is receiving exactly the same fuel mix they will not all be at peak EGT at the same time, as the mixture is leaned. Some will be a bit rich. Some will be a bit lean.

The problem then becomes that at power settings above 65% if you run AT PEAK, you risk "detonation' where the combustion pressures can exceed the design of the engine, so you must lean the mixture to ensure you ARE LOP- where the combustion pressures are lower.

This is fine if all the cylinders are receiving similar fuel mixes, as with Fuel Injection and accurately matched injectors.

If not, and one of the cylinders is receiving a particularly LEAN mix, as you lean away from PEAK EGT, that cylinder will miss fire and produce rough running.

Normally it is accepted that you cannot run LOP with carbys, but John Siebold started this thread to point out that under some circumstances and provided you know what you are doing, it may be possible.

He is quite right.

But you ought to make sure you understand the subject thoroughly before you embark on it. It takes a while to get your head around it, after being told as I was for 40 years of aviation, that lean is HOTTER. This, of course, is only half the truth. If you are open minded and you read the available literature, you will, eventually see the sense in it. But it is a difficult concept to master. Do not be put off by the doubter.

If you do wish to pursue this matter then please email me at [email protected] and I shall be delighted to provide you with literature on the subject.

Pete.

 

[N395V]

When running LOP as CHTs drop does anybody have a target CHT they consider too low?

 

[Yukon]

Australia LOP Accident

Peter,

Here's some LOP data that's pretty close to home. It's not easy to wade though Deakins endless self-important commentary, but there is lots of good information on what happens when LOP goes wrong.


http://www.avweb.com/news/columns/182152-1.html

John

RV-9 QB

 

[osxuser]

When running LOP as CHTs drop does anybody have a target CHT they consider too low?

It's very difficult to say a CHT is too low. The thing that kills the top end of an engine is heat, too much heat will cause premature failures. The problem with low temperatures is that lycoming designs their cylinder bores with a taper to allow for the top of the cylinder to expand more than the base. This means that running 'too' cold could increase wear and stress on the top of bore. Personally I'd shoot for CHT between 320 and 380, topping out at 400 in the climb. I do not have any data to base this on, it just feels right to me.

Running LOP is find, but unless you have excellent cooling, I doubt the engine will continue to run if you go far enough LOP to allow CHT's lower than 300.

 

[dan]

Running LOP is find, but unless you have excellent cooling, I doubt the engine will continue to run if you go far enough LOP to allow CHT's lower than 300.

Could be the angle valve vs. parallel valve thing, but mine (angle valve) runs below 300F CHT on a normal basis when LOP. Even in the summertime, once I'm at altitude and things have cooled down in cruise, CHTs hover around 280-290F (oil temp around 176F). That's at WOT at altitude, typically around 20 to 22" MAP, 2300 RPM or so at about 40-50 LOP.

But if I start bringing the throttle back and run at reduced (less than WOT) power settings, the CHTs will drop a bit more:

Note that if I bring the throttle back even more, the CHTs and oil temp start rising again...slower airspeed, less cooling air flow. But the CHTs rarely go higher than 300F once stabilized at any LOP cruise power setting.

Your mileage may vary...angle vs. parallel valve, your baffles vs. mine, plenum vs. baffles, whatever.