Mathew Sharp said:
The number one concern with LOP operation quite plainly is with detonation issues.
Click to expand...

This would not be the first time I've disagreed with a PhD. With all due respect, to you and the good Dr. detonation in a properly set up, properly tuned, properly leaned engine is easier ROP than LOP. The cylinder head temps are typically 75-100F cooler and the fuel mixture is less explosive LOP. Detonation is caused by hot spots on the cylinder head. Having the cylinder head cooler is a good thing, and having the mixture leaned out to a less explosive mixture is a good thing.

What you are stating is totally contrary to what I have been told by Lycoming engineers, expert engine builder, fuel injection system manufactures, and fuel experts. The biggest problem with LOP is operator error. Having the pilot forget to rich the engine on changes in altitude, and not finding peak properly before leaning.

Matt, what are you flying again?
 
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Geico266 said:
This would not be the first time I've disagreed with a PhD. With all due respect, to you and the good Dr. detonation in a properly set up, properly tuned, properly leaned engine is easier ROP than LOP. The cylinder head temps are typically 75-100F cooler and the fuel mixture is less explosive. Detonation is caused by hot spots on the cylinder head. Having the cylinder head cooler is a good thing, and having the mixture leaned out to a less explosive mixture is a good thing.

What you are stating is totally contrary to what I have been told by expert engine builder, Lycoming engineers, fuel injection system manufactures, and fuel experts. The biggest problem with LOP is operator error. Having the pilot forget to rich the engine on changes in altitude, and not finding peak properly before leaning.
Click to expand...

Larry,

It is not quite that cut and dried. I don't know if Lycoming Part Number SSP700 "Experts are Everywhere to Help You" has been referred to in this thread but it has much to say about LOP. This procedure has been used in the past extensively but usually with a qualified flight engineer to keep the lid on the situation. To quote the bulletin -

"There is nothing detrimental in operating an engine in
this manner. However, we can attest to the fact that things that
work well in the test laboratory have not always proven
successful in service. In the sales literature provided for this
“new” technique, (company not Lycoming) it is stated that Lycoming recommended this operational procedure in an owner’s manual that dates back to the late ‘60’s. No mention is made why it is no longer recommended
on our present engines. The fact is that the technique of operating
lean of peak and power recovery was discontinued due to the
resulting increase in service issues. Burned pistons, valves, ruined
rod and main bearings were traced to the inability of pilots to
utilize this technique with the instrumentation and distractions
found in the typical general aviation aircraft. If Lycoming felt that
this was indeed an efficient and reliable method of operation, you
can be sure that it would be in our recommended procedures."

I've known pilots who never lean an engine but that is a different issue from running LOP. To never lean an engine is poor operating technique.

A review of the three Cafe reports on electronic ignition and LOP tell the story as far as efficiency is concerned - running LOP with timing advanced as far as 40 degrees does burn less fuel per mile flown - but only up high. I believe the jury is out on how this will affect the long term life of the engine. I also believe operating from sea level up to 8500' with EI and aggressive leaning is a formula for trouble. The Cafe charts indicate there is no advantage to have EI and LOP ops up to 8500'. In fact timing at 30 BTC at 8500' may be too advanced. The mags at 25 degrees show better performance. Cafe also admonishes pilots of the inherent risk of operating LOP. They certainly do not put an unqualified stamp of approval on the procedure. They mostly just report what they recorded.

Interesting stuff to contemplate and for sure not without controversy. I have a good friend who flies up high LOP with Electroair all the time and swears by it....but I am not ready to bite that apple just yet and for now my new engine will have 2 Slicks and flown in accordance with current Lycoming recommendation.
 
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Geico266 said:
What you are stating is totally contrary to what I have been told by Lycoming engineers, expert engine builder, fuel injection system manufactures, and fuel experts. The biggest problem with LOP is operator error. Having the pilot forget to rich the engine on changes in altitude, and not finding peak properly before leaning.

Matt, what are you flying again?
Click to expand...

I am certainly not suggesting that leaning an engine is bad, it is a part of normal engine operation.

I don't think you said I had a Phd but to clarify, I certainly do not. Just a B.S. :D

Lycoming as well as many other engine manufactures will tell you that the number one cause of unscheduled required repairs is due to exhaust valve damage caused by improper leaning techniques. Trust me, we've spoken to most all of them.

What I was trying to share regarding the original post is what I believe to be the orginal aversion to LOP. Not all may agree but some certainly will.

I am just sharing the research that I subscribe to. My ultimate desire is to encourage a long, safe, and successful aviation experience for both my customers and my fellow enthusiasts. I hope I don't come off as opinionated as it certainly is not my goal. It is kind of hard to disagree with MIT and Cornell research. I am not qualified to, I know that!


What do I fly? I have time in a M20, an Navion A model with an O-470 running a pressure carb as well as a Diamond DA20 with an O-200, and some others. :cool:


Matt
 
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Mathew Sharp said:
I don't think you said I had a Phd but to clarify, I certainly do not. Just a B.S. :D
Click to expand...

I was referring to Dr. John B. Hayward. MIT Professors are usually required to have a PhD hanging on the wall.


Mathew Sharp said:
What I was trying to share regarding the original post is what I believe to be the original aversion to LOP. Not all may agree but some certainly will.
Click to expand...

The theme behind this thread is the aversion to leaning an aircraft engine period. Which technique the pilot / operator employs is up to the individual.

If you or Electronics International MVP-50P does not advocate running LOP then why does it have a "Leaning Mode" built into the system specifically for running LOP? Matt, I've been flying LOP on fuel injected engines using your Electronics International monitoring equipment for hundreds of hours and loved it up to now. Now you are telling me your engine monitors are not up to the task? Why would your engineers have gone to all of the trouble of designing a LOP mode that give you temperature differential in each cylinder, when each cylinder peaks, and what the temperature each cylinder is from peak, if you are not advocating running LOP? According to what you are saying your engine monitoring system should warn the pilot of impending doom if you reach LOP? Can I set up the monitor to flash a red warning if I ever hit LOP again? Are there plans for a software update to remove the leaning function?

Can you explain why on page # 10 & 11 of the Electronics International MVP-50P Operating Manual your engineers talk about how to run LOP on your engine analyzer and that (quoting from the manual); "This is exactly the information needed to properly operate LOP." is written in your manual?

Can you explain why on page # 19 & 20 of Electronics International's "The Pilot's Manual For Leaning And Diagnosing Engine Problems" (the same manual you posted a link to on post #40 of this thread) your manual tells how to set up and run an engine LOP, and the benefits of running LOP?

Electronics International advocates LOP operations in it's sales literature, but what you are saying is in actual practice it is a bad idea. Can you recommend a engine monitoring system that does work well monitoring an aircraft engine LOP? Dynon has the same feature and seems to work just fine. I thought I was using the best engine analyzer on the market today that supported running a fuel injected engine LOP.
 
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Geico266 said:
If you or Electronics International MVP-50P does not advocate running LOP then why does it have a "Leaning Mode" built into the system specifically for running LOP? .
Click to expand...

To be clear, I am not speaking on behalf of EI. I do not visit this forum to tout company philosophies. I come here due to personal interest in RV aircraft. I am still trying to get a project off the ground and RV's are the direction in which I will probably head. (I keep going back and forth with RV's and Cubs)

You may not know it but EI is purely a data reporting business. They are NOT engine operation instructors. They are not flight instructors. They are data collectors and indication specialists. They make the best instruments they can to monitor the entire operational envelope. I am sorry but no EI staff member will tell you where to operate you engine literally. The world is WAY to lawsuit happy these days for us to make these sorts of recommendations. But are they going to make all the cool toys with amazing tool for precision operation? Are they going to record it for you to aid further analysis? You betcha!

Geico266 said:
Matt, I've been flying LOP on fuel injected engines using your Electronics International monitoring equipment for hundreds of hours and loved it up to now. Now you are telling me your engine monitors are not up to the task? Why would your engineers have gone to all of the trouble of designing a LOP mode that give you temperature differential in each cylinder, when each cylinder peaks, and what the temperature each cylinder is from peak, if you are not advocating running LOP? According to what you are saying your engine monitoring system should warn the pilot of impending doom if you reach LOP? Can I set up the monitor to flash a red warning if I ever hit LOP again? Are there plans for a software update to remove the leaning function?

Can you explain why on page # 10 & 11 of the Electronics International MVP-50P Operating Manual your engineers talk about how to run LOP on your engine analyzer and that (quoting from the manual); "This is exactly the information needed to properly operate LOP." is written in your manual?.
Click to expand...

Impending doom notification? I am not sure of that voice annunciation but we can set limits for any parameter you wish. Color coded and auditory!

Why do we state that in the MVP manuals? We are very clearly state that because that is precisely the information you require to run LOP.



Geico266 said:
Electronics International advocates LOP operations in it's sales literature, but what you are saying is in actual practice it is a bad idea.
Click to expand...

I did not say that it was a bad idea I am simply theorizing on the original causes for the aversion to leaning engines and the hazards of incorrect operations.






Geico266 said:
Can you recommend a engine monitoring system that does work well monitoring an aircraft engine LOP? Dynon has the same feature and seems to work just fine. I thought I was using the best engine analyzer on the market today that supported running a fuel injected engine LOP
Click to expand...

That's a easy one. I have not seen a multi-function system that out performs the MVP-50P in regards to leaning tools or engine/airframe monitoring in general.

I gotta ask though, can you save me any money on my car insurance?
..I am serious...I am getting hosed by another outfit.

Thanks
 
Well, I have to admit I found myself getting a little cranky reading Mathew's posts regarding LOP and detonation - just doesnt match what I considered to be the bible - the various Deakin articles. However, all was forgiven and forgotten after his "Can you save me money on my car insurance" post in reply to Geico. Man, that was hilarious Mathew.

So, I just dont have it in me anymore to argue over LOP and detonation here. For those interested, Deakin's "Detonation Myths" article can be found here:

http://www.avweb.com/news/pelican/182132-1.html

Lots and lots of stuff on LOP in multiple Deakin articles as mentioned previously. The complete index to his articles is here:

http://www.avweb.com/news/pelican/182146-1.html

regards
erich
 
Mathew Sharp said:
I gotta ask though, can you save me any money on my car insurance?
..I am serious...I am getting hosed by another outfit.

Thanks
Click to expand...

Now that was funny! I needed to grab the Windex and clean the coffee off the puter screen. :D

Sorry, no affiliation with the lizard dude. I was here first, registering Geico as a family company name in 1972.

The only advice I can give you on car insurance is what I had to do; Slow down? ;)

Your comments are always welcome and encourage as EI is on the cutting edge of engine monitoring. I really like your stuff!
 
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erich weaver said:
Well, I have to admit I found myself getting a little cranky reading Mathew's posts regarding LOP and detonation - just doesnt match what I considered to be the bible - the various Deakin articles. However, all was forgiven and forgotten after his "Can you save me money on my car insurance" post in reply to Geico. Man, that was hilarious Mathew.

So, I just dont have it in me anymore to argue over LOP and detonation here. For those interested, Deakin's "Detonation Myths" article can be found here:

http://www.avweb.com/news/pelican/182132-1.html

Lots and lots of stuff on LOP in multiple Deakin articles as mentioned previously. The complete index to his articles is here:

http://www.avweb.com/news/pelican/182146-1.html

regards
erich
Click to expand...

With all do respect to Mr. Deakin, he is an example of an expert claiming to know more about a product than the people who designed it. (Such experts are not confined to general aviation. In years past airline management officials claimed to know more about a 707 and how it should be operated than Boeing. We went through at least 10 different climb profiles always claiming to be more efficient than what the manufacturer recommended. None ever were as each new manager did it again.)

Truth is, if one pays for an airplane and all that goes with it, he can operate it anyway he wishes so long as no FAR's are violated. But I can not buy into an idea that straying too far from a manufacturers recommendations is in the best interest of safety and longevity in this business. Lycoming has an enormous amount of data based on years of service issues to back up their recommended operating policy. It just isn't real smart to reinvent the wheel in this area.

 
I'm with David on this one. Until Lycoming approves it, you do it at your own risk. The manufacturer usually knows best. When 100 pilots fly a hundred engines to TBO running LOP with no interim repairs, maybe it's valid.

Continental approves LOP operation for many of their engines but they seem to get soft cylinders no matter which way they are operated. Might as well save the fuel!:rolleyes: The old Wright 3350s were exclusively run LOP successfully but these are not Lycomings.

People ask me if we can run the Subarus LOP. I reply that the OEM does not at high power settings so until we accumulate substantial flight hours to prove no reduction in longevity, you do it at your own risk. I lean to 1400F which is about 125 ROP.

In summary, it might be safe but I'm not sure there is enough running time LOP to confirm on Lycomings.
 
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rv6ejguy said:
I'm with David on this one. Until Lycoming approves it, you do it at your own risk. The manufacturer usually knows best. When 100 pilots fly a hundred engines to TBO running LOP with no interim repairs, maybe it's valid.

Continental approves LOP operation for many of their engines but they seem to get soft cylinders no matter which way they are operated. Might as well save the fuel!:rolleyes: The old Wright 3350s were exclusively run LOP successfully but these are not Lycomings.

People ask me if we can run the Subarus LOP. I reply that the OEM does not at high power settings so until we accumulate substantial flight hours to prove no reduction in longevity, you do it at your own risk. I lean to 1400F which is about 125 ROP.

In summary, it might be safe but I'm not sure there is enough running time LOP to confirm on Lycomings.
Click to expand...

Ross, I really wondered about reducing fuel pressure to control the air/fuel ratio with Subaru. There were no EGT readings so we really did not know what was going on except there was an A/F ratio reading if one had the device installed.

Many years ago I flew about 800 hours in the right seat of the KC-97G with P&W 4360's. Those engines probably were operated LOP in cruise but no one on the crew knew what was going on except the flight engineer. He was in his own world surrounded by gages and scopes. The training criteria for pilots did not include much about his duties. I do know he could look at the spark pattern of every one of the 56 plugs on each engine. The 4360 probably had more moving parts than any engine ever built except the Lycoming 7755. :) Now that was a radial engine to end all radials.
 
Well, not really expecting to change your minds here, but jeez, the lycoming stuff is written for the lowest common denominator - the plane with little if any engine monitoring information. LOP operations cant really be conducted under those conditions, as clearly stated in the various Deakin articles. But many (most?) of the RV builders these days have full instrumentation, meaning EGT and CHT for every cylinder, as well as flashing lights to hit us in the head when we get anywhere near our operating limitations. If your CHTs are approaching limits or increasing rapidly, duh, change your mixture and lower the nose - we are all capable of that. The plane isnt going to instantaneously drop out of the sky. LOP has benefits that go beyond saving gas - and its not just Deakin that says so. Mike Busch is another well respected writer with good credentials who touts the benefits of LOP, and many of us are familiar with Dan Checkoway, to name just two.

Ok, not as funny as Mathew, but I feel better now

erich
 
David-aviator said:
Ross, I really wondered about reducing fuel pressure to control the air/fuel ratio with Subaru. There were no EGT readings so we really did not know what was going on except there was an A/F ratio reading if one had the device installed.

Many years ago I flew about 800 hours in the right seat of the KC-97G with P&W 4360's. Those engines probably were operated LOP in cruise but no one on the crew knew what was going on except the flight engineer. He was in his own world surrounded by gages and scopes. The training criteria for pilots did not include much about his duties. I do know he could look at the spark pattern of every one of the 56 plugs on each engine. The 4360 probably had more moving parts than any engine ever built except the Lycoming 7755. :) Now that was a radial engine to end all radials.
Click to expand...

What Jan was trying to do without re-flashing the ECU was to reduce the fuel delivered at high rpm and high throttle where the ECU was not running in closed loop (off the O2 sensor at stoich and peak EGT). Unfortunately this put mixture control in the hands of the regulator rather than the ECU directly. So the theory was reasonably sound but hopefully the pressure setting was arrived at only after plenty of testing.

I remember 2 trips in a DC3 where the flight engineer showed us his oscilloscopes and the spark plug firing on each cylinder too. I thought that was pretty cool. My Dad flew the Argus ASW aircraft with four Wright 3350 TC engines with WM injection and in that aircraft, the FE controlled everything to do with the engines too- a full time job for sure. The pilot simply asked for a certain manifold pressure- give me 58 inches wet.:cool:

I think the 3500hp Rolls Royce Eagle H24 engine may have been the most complex engine ever devised by man- two flat 12s in one case with the cranks geared together, sleeve valves (the Brits loved these???) , supercharged , 2 stage, 2 speed, intercooled, aftercooled and a reduction drive!
 
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Funny how for years Lycoming said stay away from autogas, and now they're approving it. They use the same sort of rhetoric with LOP operations. The truth is those who are knowledgeable about their engines are running LOP with good longevity and fuel economy.

I have a R-3350 manual from a Connie and it specifically describes LOP operations.

LOP operations have been around for 60+ years, in fact Lindberg came up with the idea to extend the range of P38's in the Pacific theatre.

There's no incentive for Lycoming to approve LOP operations, and that's why they won't every approve it in an official sense.
 
rocketbob said:
Funny how for years Lycoming said stay away from autogas, and now they're approving it. They use the same sort of rhetoric with LOP operations. The truth is those who are knowledgeable about their engines are running LOP with good longevity and fuel economy.

I have a R-3350 manual from a Connie and it specifically describes LOP operations.

LOP operations have been around for 60+ years, in fact Lindberg came up with the idea to extend the range of P38's in the Pacific theatre.

There's no incentive for Lycoming to approve LOP operations, and that's why they won't every approve it in an official sense.
Click to expand...

You are probably right on this and people have to understand Lycoming's position. It goes something like this: idiot pilot doesn't lean correctly or doesn't have the right instrumentation, heads crack or exhaust valves fry- customer is PO'd and wants warranty. Why should they bother?

I know a couple people running Lycs LOP with EFI and so far so good but only with a few hundred hours each so far.
 
nuanced

rv6ejguy said:
You are probably right on this and people have to understand Lycoming's position. It goes something like this: idiot pilot doesn't lean correctly or doesn't have the right instrumentation, heads crack or exhaust valves fry- customer is PO'd and wants warranty. Why should they bother?

I know a couple people running Lycs LOP with EFI and so far so good but only with a few hundred hours each so far.
Click to expand...
I know Ross is being funny, but Lycomings position is nuanced. Lycoming is not dumb or condescending, I've talked to their engineering many times. There are people (no one here) saying how dumb Lycoming is and how they invented LOP. That is fine, but "they" make the broad brush comment it can be done on any engine any time. That is too sporty in my opinion.

"Rocketbob" is right, LOP has been around a long time. Lycoming has tested, for countless hours, in test cells and flight test ALL kinds of mixtures. They know what the detonation margins in real world conditions. They do have a deep understanding. Still you are free to do as you like. I am not anti-LOP, just pro knowing what you are doing.

Lyc knows LOP can be done (and recommends it for one of their larger turbo engines), but the advantage and extra effort (and instrumentation) in their professional opinion is not practical or value added for their smaller engines. Of course this opinion was written when gas was a buck and digital computer chip engine monitors where not invented yet. We crazy :D home-builders know every inch of our plane, have the desire to learn every aspect of the engine operation in LOP conditions. We also put in the most fancy engine monitors you can get and are willing to balance injectors to a nats backside. However Lycs go in trainers and maintained by folks that don't have time to hyper tune the induction.

As a CFI, I'd have to add hours to the private pilot syllabus to teach LOP ops, if that's even possible in a little carborated 4-banger. LOP works best in larger FI engines, and works rarely or inconsistently in smaller and carborated engines.

LOP as I understand it can be done safely. If you can get smooth LOP operation LOP, keep the temps out of the "RED ZONE" than go for it, but if burn something its on you.

Lyc does recommend LOP for max econ but only if you down well below 75% percent power. If you are down in the 50's (percent power) you have more lattitude to do as you like, Peak or LOP.

Lyc is very simple lean; lean to rough and enrichen for smooth ops. The relative degrees from peak are an unknown with out a EGT gauge, which is the case with most GA planes. If you have one EGT (in theory on hot cylinder) the recommend lean than rich +150F.

In the 80's I never saw a multi channel egt/cht engine monitor on kit plane or factory job. If you had one EGT or one CHT gauge you where, WOW! My first RV had a single cyl EGT/CHT combo gauge on the #3. The latest has more probes and sensors than (insert funny analogy here). Will it change my leaning habits? A little may be.

I find the best way to save fuel is pull BOTH the black knob and red knob back. I find flying closer to best range speed (way below our normal 190 mph cruise) saves fuel. And if the trip is long enough fly as high as you can PRACTICALLY with all factors considered (weight, density alt, winds, weather). Leaning can bring in a few percent in econ in cruise but there is a big picture out there. LOP is not the panacea for free fuel.
 
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Extra O2?

I run LOP every time I fly X-country but will always wonder if that extra O2 is looking for Aluminum and/or Iron to turn into their respective oxides, a scary proposition cost-wise to be sure... Maybe the temps aren't hot enough to cause a reaction? Inquiring minds want an answer...Haven't checked Deakins on the matter.

Jerry

rv6ejguy said:
You are probably right on this and people have to understand Lycoming's position. It goes something like this: idiot pilot doesn't lean correctly or doesn't have the right instrumentation, heads crack or exhaust valves fry- customer is PO'd and wants warranty. Why should they bother?

I know a couple people running Lycs LOP with EFI and so far so good but only with a few hundred hours each so far.
Click to expand...
 
I actually wasn't trying to be funny, my point is why should Lycoming bother to endorse this practice? It will only be a waste of time and resources for them and a source of customer induced headaches. I doubt if they will lose a sale because of it to Continental. Conti has their customers and Lyco has their own.

Haven't seen anyone put a Conti 550 in an RV10 yet just because it can run LOP and maybe burn a bit less fuel. Cost and weight might be factors here.

Jerry,

Theoretically running LOP will reduce all temps in the engine so operation there should extend engine life.
 
How I toasted an IO360

Well, it was actually an O360A1A with Bendix fuel injection added to it - a nice motor that Monty Barrett did, so I had a great motor to start with. Everything was wired up to an EPI 800 enigne monitor system.

I'd added a LSE Plasma II ignition system which advanced the spark to approx 37 deg at around 12000 MSL, and I ran LOP routinely. Fuel flows up there were about 7.1 to 7.2 gph at 165 KTAS. Everything was cool and way in the green.

BUT - I also did a fair amount of hard time on the powerplant and this is where the damage probably happened, although I had no idea at the time. Three of us here in OKC like to dogfight, and its hard on everything. To gain every advantage, I had the engine leaned close to peak EGT. We fought from 8000MSL to a floor of 4500MSL. I saw over 1400F alot of the time, but my EGT probes were located only 4.5" down from the flanges. More than once, the oil smelled like it had been burned in the dipstick tube, so I changed it often - 10 hours between changes wasn't uncommon.

After about 300 hours of this, the #1 cylinder showed a loss of compression. It was leaking out the exhaust valve, and I could see coking on the valve stem. The valve wasn't closing all the way by a couple thousandths. The engine started and ran just fine. Then I sold the plane to build an 8. I even warranted the questionable cylinder for the new owner. After 4 more years, the new owner (who also flew the sh*t out of it) had to replace all cylinders.

So, in retrospect, I believe the LOP operation probably didn't help anything, but I think the extended WOT operation at peak EGT was the main problem. Much of this time was at fairly low airspeeds and I had a fixed pitch cruise prop which lugged the motor down too much when dogfighting.
 
gmcjetpilot said:
Lyc does recommend LOP for max econ but only if you down well below 75% percent power. If you are down in the 50's (percent power) you have more lattitude to do as you like, Peak or LOP.
Click to expand...
Forgive me my ignorance, but won't non charged engine always be below 75% at any altitude above 8500? Or am I missing something?
 
LOP

600 hours now LOP. Climb once above 1000 feet agl included. As a matter of fact, when it starts to get hot, I go leaner. CHT alarm set to 360 and always keep it below 370. It is still smooth to 100 degrees or more LOP. 9.2:1 compression.

Cleaner oil (visually and documented with lab tests).

Not a single fouled plug.

Less vibration.

I scope the cyls every other oil change - fewer deposits but no sign of erosion.

With balanced AFP injectors, EI EGT/CHT and Electroair ignition.

It will be up to RVrs to prove LOP up in small Lycomings. Keep the information flowing!
 
So what is Lycoming worried about? I think the biggest single thing is how equal the mixture distribution is between cylinders. I've seen 180F EGT difference on an O-360 at some throttle angles, almost as bad on a carbed Rotax 912. The injected models are much better and better candidates for LOP operation.

Why is this potentially dangerous? Let's assume that we have a 125F spread between coldest and hottest cylinders. We lean until the first one peaks and continue to lean to say 100F LOP. Our coldest cylinder is now maybe 25F ROP but operating very close to highest EGT See the problem?

LOP is probably just fine if the EGT spread is not very much but not so good for at least one cylinder if you have a high spread. This why the matched GAMI injectors were really a good idea on the Contis- all the cylinders were peaking at close to the same time.

It can't be conducive to long exhaust valve and seat life running near max EGT in cruise, even at somewhat lower power settings.

Done right, with close spreads and proper instrumentation and technique, I don't see a problem with LOP operation on a Lycoming. Lycoming is worried about the people who don't have all three happening at once.
 
rv6ejguy said:
Why is this potentially dangerous? Let's assume that we have a 125F spread between coldest and hottest cylinders. We lean until the first one peaks and continue to lean to say 100F LOP. Our coldest cylinder is now maybe 25F ROP but operating very close to highest EGT See the problem?
Click to expand...

Ross,
I have no expert knowledge on this subject and accept that logic would support your statement about the dangers of peak EGT. The logic behind your statement would be one of the reasons why pilots (especially those with carbs) do in fact have an aversion to leaning. I would just like to remind pilots that Lycoming sees no problems with peak EGT in the cruise. Lycoming recommends; "Best Economy Cruise (approximately 75% power and below). Operate at peak EGT, or if desired, drop 50 degrees F on the rich side of peak EGT."

Fin
9A
 
If Lycoming says peak EGT is ok for cruise at less than 75%. I don't see any problem doing anything you want with the red knob above say 8500 feet...

Why their reluctance to embrace LOP cruise procedures then?

Me thinks peak EGT operation actually isn't going to have zero impact on exhaust valve and seat life. In the real world, (where some certified engines actually need work before TBO) seems to me more of my friends with Lycos have valve problems rather than piston or ring problems.
 
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rv6ejguy said:
If Lycoming says peak EGT is ok for cruise at less than 75%. I don't see any problem doing anything you want with the red knob above say 8500 feet...
Click to expand...

I've been told by the injector guys that anything below 21" of MP around 6,000' MSL and peak EGT's are just an efficent way to fly. Just watch your EGT's and see. If peak is 1350F low and 1300 up high you are good to run peak all day long, and even better to run LOP -40F.

My problem is remembering all of the parameters I have learned. I really need to write them down for inflight reference. I guess my rule of thumb is #1 cylinder 1275F LOP, 10.2 GPH and sit back and enjoy the view. This works for my engine, and everything runs cooler.
 
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Geico266 said:
I've been told by the injector guys that anything below 21" of MP around 6,000' MSL and peak EGT's are just an efficent way to fly. Just watch your EGT's and see. If peak is 1350F low and 1300 up high you are good to run peak all day long, and even better to run LOP -40F.

My problem is remembering all of the parameters I have learned. I really need to write them down for inflight reference. I guess my rule of thumb is #1 cylinder 1275F LOP, 10.2 GPH and sit back and enjoy the view. This works for my engine, and everything runs cooler.
Click to expand...

I really think you and I are in agreement in how to run the engines Larry, but one comment I'd make is that I am suspicious of using any absolute EGT numbers, since they are totally dependent on where the probes are placed relative to the exhaust flange. The difference between 3" and 4" placement can be a hundred degrees or more, and everyone puts them in different spots, so I pretty much ignore absolute EGT numbers, and simply talk about where it is relative to peak. For a specific installation, you can develop a good rule of thumb for what you are comfortable with, but that really doesn't translate to a diffferent setup.

Paul
 
Just got back from LOP vacation

where I ran my (oh gosh) 7th hour on 10% ethanol....:)

Ok so I'm a data jocky but I have not had a chance to pour ethanol free fuel in one tank and etoh blend in the other and switch between them to see the effect on performance.

Speed seems to have dropped off a few knots on 10% etoh but I need to run the test at various altitudes to be sure.

What I did find however was that the engine is LESS tolerant of LOP than with etoh free fuel.

Ok I need to explain..I can run LOP with both fuels quite happily, but the ETOH fuel will not allow me to lean as far into LOP as with non etoh fuel before it runs a little rough.

Not normally a problem but I have not balanced my injector nozzles yet and the leanest will tend to flame out at a slightly higher fuel flow than before.

The richest cylinders are still running about 50F LOP on this fuel however.

I have now flown IFR for 2 hours right at the freezing level, which happened to be about 9000ft.

No ill effects noted so far.

Frank
 
Any percentage of alcohol will tend to increase the fuel flow required at a given hp as the stoichiometric ratio for ethanol is about 9 to 1 (14.7 for gasoline). Your observations would appear to confirm theory.
 
Ironflight said:
, but one comment I'd make is that I am suspicious of using any absolute EGT numbers, since they are totally dependent on where the probes are placed relative to the exhaust flange.
Paul
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Absolutely! I have flown IO-540's that can hit 1550F EGT's and some that can't hit 1400F. I meant to say 1275F LOP on #1 cylinder in MY plane only guys & gals. Find your own numbers, please! Make sure you have "Nozzle Tuned" your fuel injection system.

http://www.vansairforce.com/community/showthread.php?p=251160#post251160
 
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Keep it Within Limits

While EGTs may vary according to where the probes are, the values are important to the engine. Where the EGT peaks is essentially meaningless from an engine standpoint, it simply indicates when stoichiometry has been reached and gives the pilot a point to judge the relative air/fuel ratios with some accuracy.

Manufacturers redlines for all temperatures should be heeded to obtain the best life from any engine. You can't simply say it is ok to run at an indicated 1600F when peak was at 1500F for example if this is higher than recommended limits.

Timing and compression ratio will affect the EGT on a given engine type quite dramatically. Adjustment of the fuel injection system or carb jetting will have an effect on the EGT obtained as well at full rich mixture.
 
rv6ejguy said:
Manufacturers redlines for all temperatures should be heeded to obtain the best life from any engine. You can't simply say it is ok to run at an indicated 1600F when peak was at 1500F for example if this is higher than recommended limits..
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Of course you want to obey redline limits on any machine Ross....do you happen to know what the EGT limits are for a Lycoming? And where the measurement is taken? I don't recall having seen that written down anywhere, but I haven't seen every Lycoming document either.....

And I should have been specific about my post relating to Lycs and their clones.

Paul
 
rv6ejguy said:
Where the EGT peaks is essentially meaningless from an engine standpoint, it simply indicates when stoichiometry has been reached and gives the pilot a point to judge the relative air/fuel ratios with some accuracy.
Click to expand...

While I agree at what value (or what number) the EGT reaches peak is not important, having all cylinders reach peak EGT's at the same time (same fuel flow) is critical. Obviously, the cyinders cannot peak all exactly at the same time, but all within .2 GPH is ideal.
 
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I haven't read all the posts so bear with me if I'm repeating. Some time ago,a tech from Lycoming told me that the flame front propagation changes lean of peak and is very dangerous to do this. I was worried as I always run LOP.
When I told him I had a XP360 he gave me his condolences and wished me luck at reaching any amount of hours before my engine blew up. He seemed to think my XP is an inferior product. I was kinda shocked at his mannerism.
I don't always believe what I'm told or what I read .
Can anyone here explain what this flame front propagation is all about, and if there is any truth to the dangers he emphasized?
 
Peak and mean cylinder pressures are lower LOP than at peak or ROP.

Flame speed in the chamber is highest at about 11 to 1 AFR (very rich) and falls off at both richer and leaner AFRs (air/fuel ratios). As an example, flame speed was about 77 fps at 11 to 1, 75 at 10 to 1 which is about the rich misfire range on most engines when warmed up and about 59 fps at 17 to 1 which is probably on the order of 75-125F LOP on most engines. Best power is obtained at around 12.5-13.0 to 1 on most engines- roughly 100-150F ROP. Best economy is obtained at about 18 to 1 AFR- assuming good mixture distribution between all cylinders.

Leaner mixtures also delay the point where PCP (peak cylinder pressure) occurs (assuming fixed ignition timing). This, along with lower energy available from reduced fuel mass, contributes to the lower power delivered as a result of the less advantageous crank pin position during the combustion cycle.

From this standpoint, LOP is not harder on the engine in any way. Power will drop off measurably LOP which is why on turbocharged engines, the throttle is advanced a bit once leaned to restore the power lost when leaning through the addition of some more manifold pressure.

I can't say I agree with this Lycoming tech on his comment and maybe it was just sour grapes.
 
rv6ejguy said:
Peak and mean cylinder pressures are lower LOP than at peak or ROP.

Flame speed in the chamber is highest at about 11 to 1 AFR (very rich) and falls off at both richer and leaner AFRs (air/fuel ratios). As an example, flame speed was about 77 fps at 11 to 1, 75 at 10 to 1 which is about the rich misfire range on most engines when warmed up and about 59 fps at 17 to 1 which is probably on the order of 75-125F LOP on most engines. Best power is obtained at around 12.5-13.0 to 1 on most engines- roughly 100-150F ROP. Best economy is obtained at about 18 to 1 AFR- assuming good mixture distribution between all cylinders.

Leaner mixtures also delay the point where PCP (peak cylinder pressure) occurs (assuming fixed ignition timing). This, along with lower energy available from reduced fuel mass, contributes to the lower power delivered as a result of the less advantageous crank pin position during the combustion cycle.

From this standpoint, LOP is not harder on the engine in any way. Power will drop off measurably LOP which is why on turbocharged engines, the throttle is advanced a bit once leaned to restore the power lost when leaning through the addition of some more manifold pressure.

I can't say I agree with this Lycoming tech on his comment and maybe it was just sour grapes.
Click to expand...

My Xp 360 has about a .8gal spread between peaks. I run #4 at 50 degrees LOP and #1 at 10 degrees LOP. Is this a issue? Should I go gammi injectors to decrease the spread ?
BTW thanks for the enlightening lesson above. I learned something new.
 
I'd agree with Larry on this one, closer is better but a 40F spread is not bad. If you wanted to fool around flowing and changing injectors, you could probably close that gap. Would be a lot of work though.

It should be mentioned that unequal air distribution between cylinders is just as much of a factor as unequal fuel. Manifold design and mismatched port flow can affect how much air actually flows though the intake valve.

Certain engines also have a large variation in EGTs at certain throttle angles and less so maybe at WOT. If you change injectors, you may fix the problem at one throttle angle and make it worse somewhere else.:(

What does Superior recommend for a max EGT vs. power setting?
 
rv6ejguy said:
If you wanted to fool around flowing and changing injectors, you could probably close that gap. Would be a lot of work though.

Certain engines also have a large variation in EGTs at certain throttle angles and less so maybe at WOT. If you change injectors, you may fix the problem at one throttle angle and make it worse somewhere else.:(
Click to expand...

Assuming the engine is fuel injected it is not hard at all to "Nozzle Tune" the injectors, and only take about 15 mins of flight time, and 15 mins to change the injector nozzles (including removing the coweling!).

The nozzles are tuned at one specific throttle setting, say 23" squared. Once "tuned" they are pretty consistant through the whole throttle range.
 
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O I really

Ought to do this...but never got around to it.I have a pretty big spread.

So tell me....Why can't you drill the nozzles to get the right size rather than change the nozzles??

Like you can with the carb??

Frank
 
frankh said:
Ought to do this...but never got around to it.I have a pretty big spread.

So tell me....Why can't you drill the nozzles to get the right size rather than change the nozzles??

Like you can with the carb??

Frank
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I'm sure you could, but it is a heck of a lot simplier (to me anyway) easier just to e-mail the results of your Nozzle Tuning EGT Test to Air Flow Precision and have Don Riveria examine the results and recommend the correct nozzles for which cyinder.

When I looked at the holes in the nozzles I got from Don they looked they had been honed, or at least reamed smooth. I'm not so sure you could do that with a drill. You want them to flow smoothly. But hey, go for it Frank!

You really need to balance your injector nozzles. Get-r-done.
 
yakdriver said:
Just did my data test today and will talk to Don on Tuesday. Thanks again for sending the forms Larry. Don
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Fax them in, or e-mail them to Don and he will let you know right away. Ask Don about running LOP. He is an expert on aircraft engines and fuel systems.

Pretty easy test huh? I'm not sure what all the fuss is about.
 
frankh said:
Why can't you drill the nozzles to get the right size rather than change the nozzles??
Frank
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Uh, yeah, I tried that. No bueno. I opened up one nozzle by .001" and that cylinder went from leanest to richest BY FAR. So, I called Don the next day asked how I managed to screw that up so badly. He replied that even if I had simply run a reamer through the nozzle the same size as the nozzle was stock, I'd still have ruined it. He calibrates each nozzle on a flowbench. You need to do the lean spread and give Don the results.

Heinrich Gerhardt
 
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