LOP: A few questions.

[John Pleisse]

Quote: jetdriven

Actually, many Continental engines that have escaped the factory in the past decade have this shoddy machining. So much in fact, that some Bonanza owners were taking their factory reman engines to engine builders to remachine the valves before installing their engines.   

Some of the the quality of discussion on this thread would be laughable on beechtalk. Its like asking if air blowing off the bottom of the wing is the reason planes fly, or walking into the Vatican and asking if God exists.

[jetdriven]

Quote: N4352H

(picture of burned valve)

 

Perhas our dear friend John  (Hugs Byron.....)

can explain the fact that radial airliners operated LOP for about 40 years, and had TBOs of 3600 hours. In fact it won the War for us, as the ROP technique couldnt make a roundtrip to Germany.

WW2...large diplacement, low compression, radial engines...may super charged...using more oil than gas....we won the war.

Those superchrged engines had higher cylinder pressure than our small flat engines, and flew across oceans.  In fact, many of them ran water injection and 130 octane fuel to supress detonation. Since both are no longer used, they are restricted in HP for takeoff and METO. Stlll run LOP, though.

Or that the Continental TSIO-520BE engine in the Piper Malibu was designed to run LOP and did so.

Continental........... (and what was the HP rating on that engine? Service history)?

When flown according the the book, 50 LOP, the service history is the same as other engines. When flown 50 ROP, terrible.  IF ROP is so safe, then why does it ruin these engines? I wonder why? What changed?

Or the A-36 Bonanza with the IO-550-BB and LOP charts in the book.

Continental

How the Cirrus SR22 is authorized to cruise LOP and even has an LOP FF limit. NA or Turbo, and warrantied.

Continental

Or how 50 LOP is somehow hotter than 50 ROP.  Think about that one.

Well, it is...air will burn hotter than fuel.

How does air burn hotter than fuel?   ??

Also, this runs counter to your opinion  that says EGT is the primary driver of exhaust valve temp.  If so, then 50 LOP and 50 ROP should have the exact same exhaust valve temp. Hint: even at peak the exhaust valve temp is falling.

 

Or how an IO-360 like ours runs a 330 CHT LOP while 380 ROP.

Yes..and you have also made mesmorizing claims of 280 LOP. Less ferver?

Less fuel.  I can run a 250 CHT, or 380, depending on how fast I want to fly.  I have enough of it logged now to show you.

 

How the old "lean to rough, then enrich till smooth" technique is actually LOP on many engines.

Which ones?

R-985 on Beech 18s. E-185/E-225 Continentals. Continental IO-470/520/550.  Lycoming O-235, O/IO-320, O-IO-360, Lycoming TIO-540-J2BD (350 HP).  Norm, can you comment on the Lycoming IO-540-S1A5? How does it behave?

The total lack of any credible literature correlating burned up valves with LOP opearation.

And nothing is proven to the conbtrary with small Lyc's....other than test data on Continentals

Its the same metal, and the same physics, John. And NO evidence that LOP engines have worse service history than ROP ones. Lots of of FUD (Fear, uncertainty, and doubt) though. 

The fact Lycoming authorized operating AT PEAK at any power setting 75% or less. Go ahead. Its blessed.

Post it.... remember...we have 360 series engines.

The fact Lycoming actually says LOP is OK now (OSH 2011), but pilots arent adept enough at monitoring their engines to do it practically.

Yes...to you and a handful of others. I imagine you were quite assertive at OSH. You were quick to dissmentinate on the web. The margins are more narrow on the Lyc's, so as a manufacturer their position is reasonable.

From Mike Kraft, Lycoming Senior Vice President and General manager, Lycoming no longer objects to running their engines LOP.

 

But there is always "science by consensus" and "my mechanic told me in 1980 that too lean burns valves"

He was right...

Was he a pilot? Engineer?  Any data on that, other than opinion?  C'mon John. I can find someone to say anything. The data and service history to back it up is another.  Like I said, pre-renaissance style of thinking. Science by consensus.  Ignore hard data, and listen to the rumors.

 

At one time 100% of people thought the earth was flat.  Some still do.

I was hoping for something more profound...like............ the "metallurgy " of the cylinder..........

Its the same fuel, the same metal, and the same physics. Lycoming, Continental, Pratt, Wright, ect. Keep your ICP out of the limit area, temps below reasonable limits,  and your engine will run forever, ROP or LOP.  It will use less fuel LOP.

 

I buy it... I believe it...it's there. But $1.00 avgas would make this discussion irrelavent. Cylinders are worth more than avgas, because safety, reliablity, and liability never show up on the bottomline. The service history of the IO-360 series engine is exceptional and not by accident.

You are right, 1$ avgas makes this conversation less important.  When Avgas goes to 10$ a gallons, it will be the only thing discussed anymore. Then, the price of fuel per TBO cycle will exceed TWICE entire value of your aircrft (200K in fuel). Actually it will be four times the cost of the entire aircraft, as its value will be half what it is today.  Look at the L-29 market for a glimpse of the future.

[John Pleisse]

Quote: jetdriven

 

Now you are babbling... I will PM you.

[danb35]

Quote: N4352H

Now you are babbling... I will PM you.

[John Pleisse]

Quote: danb35

Now you are babbling... I will PM you.

[jlunseth]

Hmmm.  So I went and looked at the Mike Busch article #26.  It is an article on engine monitors, not so much on LOP ops, and in fact he discusses his go fast method of leaning for cruise, which is ROP, and his fuel efficient method which is LOP, so it appears he uses both methods.  Then the picture of the burned valve is not from his plane, it is from a Turbo Centurion not owned by Busch.  The picture was sent to Busch.  Aaaaand, last but not least, the picture appears in the article as an explanation of why it is important to watch for a jittery EGT in normalize mode on an engine monitor during cruise, namely, it is diagnostic of a leaking valve (example in the picture that cause the jittery EGT), it is not in the article as an example of anything to do with LOP ops, or ROP ops. 

I am not taking sides on this LOP/ROP thing, just wondering what the heck the valve picture has to say about the whole discussion, and the answer appears to be absolutely nothing. 

It is true from my own airplane that leaning to LOP drops the CHT's and boosts the EGT's about a hundred degrees.  I guess I don't see how they higher EGT burns out valves, they are made for quite a bit higher temps, and they disperse heat primarily through contact with the valve seat - which obviously is cooler if the CHT is down.  Does not seem to me that it is going to make much difference, but then, I am not an engineer.

[KSMooniac]

Quote: jlunseth

Hmmm.  So I went and looked at the Mike Busch article #26.  It is an article on engine monitors, not so much on LOP ops, and in fact he discusses his go fast method of leaning for cruise, which is ROP, and his fuel efficient method which is LOP, so it appears he uses both methods.  Then the picture of the burned valve is not from his plane, it is from a Turbo Centurion not owned by Busch.  The picture was sent to Busch.  Aaaaand, last but not least, the picture appears in the article as an explanation of why it is important to watch for a jittery EGT in normalize mode on an engine monitor during cruise, namely, it is diagnostic of a leaking valve (example in the picture that cause the jittery EGT), it is not in the article as an example of anything to do with LOP ops, or ROP ops. 

I am not taking sides on this LOP/ROP thing, just wondering what the heck the valve picture has to say about the whole discussion, and the answer appears to be absolutely nothing. 

It is true from my own airplane that leaning to LOP drops the CHT's and boosts the EGT's about a hundred degrees.  I guess I don't see how they higher EGT burns out valves, they are made for quite a bit higher temps, and they disperse heat primarily through contact with the valve seat - which obviously is cooler if the CHT is down.  Does not seem to me that it is going to make much difference, but then, I am not an engineer.

[jetdriven]

Actually, all Lycoming valve stems are sodium-filled (melts into a liquid at operating temp) and transfer a much greater quantity of heat through the valve stem than Continentals.  May be correlated to the fact Lycomings burn much less valves than Continentals, yet Lycomings can have more guide problems (Mooney TLS).   Neither I believe are related to LOP.

[John Pleisse]

Quote: KSMooniac

[Cruiser]

Quote: N4352H

[jetdriven]

[John Pleisse]

My favorite passage....Estimates..inconclusive temeprature guessing.

review of published literature disclosed lit~e information
on the measurement of temperatures in a sodium-cooled
exhaust vrdve during normal engine operation. Colwell
(reference 7) tested a sodium+moled valve of a special steel
for which the relation between the hardn= and the drawing
temperature was accurately known. -The valve was hardened
and then used in rm engine. Upon removal from the
engine, the valve was sectioned and the temperatures @-
tai.ned at various locations on the valve were determined by
hardness measurements. By this method it was intimated
that the center of the valve crown reached a temperature
between 1140° and 1300° l?. The operating conditions,
however, were not reported.
The temperate of an exhaust valve has been estimated
by visurd observation of its color (reference 3) and found to
be 1300° to 1400° F at a fuel-air ratio of 0.06S and at an
indicated mean effective pr-ure of 190 pounds par square
inch. This method of temperature determination is, liowever,
open to criticism because the scale on the surface of the
exhaust valve may reach a higher temperature than the valve
materinls.

[jetdriven]

Correct.  Except the passage you quoted is the reference and citation by the author of other works.  The underlined text explains that looking through a window at a glowing exhaust valve gives an unreliable estimate of exhaust temp because the scale coating the valve is hotter.  The very next paragraph describes how this paper is where they equipped an exhaust valve witha thermocouple and DIRECTLY measured the exhaust valve temperature.  Presumably to clear up any ambiguity in exhaust valve temperatures.  DATA.  FACTS, not some mechanic without a pilot's license in 1980.

Now, if you scroll to page 7, you will find that the maximum valve temperature MEASURED, occurs at ~30 ROP.  Note that 15 LOP is 45 degres to one side of this data point. According to the graph,  you must be 80 degrees ROP to have the same valve temperature as 15 LOP.

• 
  
• You never explained how EGT of 50 LOP is hotter than 50 ROP.  Can you develop that further?  Becaue I think  1450 degrees is........1450 degrees.
  
• Please quantify your statement "EGT's are the only indication of a thermal runaway". Runaway of what?
  
• What makes you think that LOP "#'s" are not as stable as ROP "#'s"
  
• In your opinion, what is "aggressive or improper leaning"?
  
• So how is it again that lean burns valves? 
  

C'mon man. We arent frogs at the bottom of individual wells anymore. We collaborate, and disprove science by consensus and old wives tales.       So here is some hard data regarding exhaust valve temperature behavior.  Where is yours?

[jetdriven]

Quote: N4352H

Quote: jetdriven

 

Now you are babbling... I will PM you.

[PTK]

Thank you Cruiser for finding that article. Excellent, excellent science! What I get out of it is:

1.  Low CHTs, although good for the metallurgy of the cylinders, do not translate to low exhaust valve temps

2. Sufficiently ROP yields low CHT and lower valve temps.

ROP all the way! Why risk burning valves! In our engines a few extra gallons of fuel on a typical trip will not break the bank!

Could it be that the Lycoming engineers know something more than the "self proclaimed lop gurus"?

[John Pleisse]

Quote: jetdriven

Correct.  Except the passage you quoted is the reference and citation by the author of other works.  The underlined text explains that looking through a window at a glowing exhaust valve gives an unreliable estimate of exhaust temp because the scale coating the valve is hotter.

[jetdriven]

Are we talking about the same article?  Did eaither of you read it?   1 cylinder or 36, it doesnt matter  Each cylinder will behave the same whether it is bolted to an IO-360 or an IO-540.  The cowling?   There was no rudder on it either.  Neither matters.  They did do cooling and valve temps based on inches of water column pressure drop across the cylinder.  Which is effectively what we do see in cowlings.  It changes little after 10" of water.

 

Please read the article.  I feel like I am explaining heaven to bears.

[Cruiser]

Quote: allsmiles

Thank you Cruiser for finding that article. Excellent, excellent science! What I get out of it is:

1.  Low CHTs, although good for the metallurgy of the cylinders, do not translate to low exhaust valve temps

2. Sufficiently ROP yields low CHT and lower valve temps.

ROP all the way! Why risk burning valves! In our engines a few extra gallons of fuel on a typical trip will not break the bank!

Well, let's do the math. A typical ROP cruise setting is about 12 gph. I run LOP at 9.2 gph. A difference of 2.8 gph. In a normal 100 hr/yr that is 280 gallons less fuel at a conservative $5/gal. = $1400. About the cost of a new cylinder. I have been running my engine LOP for 5 yrs now so I have already paid for four new cylinders plus the labor to install HOWEVER, the engine is showing no signs of needing cylinders replaced. The oil analysis is good and my mechanic continues to ask why I am changing the oil when it looks so good.

Could it be that the Lycoming engineers know something more than the "self proclaimed lop gurus"?

I really, really, really don't thinks so..............

[jetdriven]

Cruiser, thats 56,000$ saved in fuel over 2,000 hours.  Or, put another way, free engine, prop, and insurance when operated LOP. 

But wait, didnt my mechanic  say "Fuel is cheaper than engines" and "LOP burns valves" ???

[Cruiser]

Quote: jetdriven

Cruiser, thats 56,000$ saved in fuel over 2,000 hours. 

[PTK]

Yup! And in 50 years you can even buy a new Mooney! But not green, it just wouldn't look good on a Mooney!

[carusoam]

Doing the math, you can upgrade from a J to an R by operating LOP in accordance with the POH.

Saving fuel bucks, paying the bank, go faster with greater comfort...

The point being, Mooney / Continental does print IO-550 LOP data.

You can follow ROP or LOP procedures without peril, as suggested in the POH for an Ovation.

Wouldn't that be nice to have for the J?

Just stirring the pot, no need to reply.

Best regards,

-a-

[KSMooniac]

Quote: carusoam

Doing the math, you can upgrade from a J to an R by operating LOP in accordance with the POH.

Saving fuel bucks, paying the bank, go faster with greater comfort...

<snip>

Just stirring the pot, no need to reply.

Best regards,

-a-

[jlunseth]

I was unable to access Cruiser's article but have read the posts about it.  They seem to be about the same advice that APS puts out.  For a turbo, they advise operation at 125 ROP or more, or 60 LOP or more.  I do not recall their generic "red box" for NA engines, probably have it at home in my notes.  But the point is, valve temps appear to be about somewhat higher on the ROP side, and it is important to go further ROP than one would go LOP.

[KSMooniac]

My recollection is that valve temps track/correlate pretty closely with CHTs, and they peak in the 40-50 ROP range, so 100 ROP or peak should yield approximately the same CHTs.