LOP Operation. Can someone explain for FI Lycon?

[N62XS]

Can someone, in plain english, explain LOP, settings for running LOP, EGT, CHT and Oil Temps while running LOP, the proper equipment for determining LOP and the difference between LOP and ROP?

[penguin]

For the full explaination go to Avweb, click on columns, then on Pelican's Perch (John Deakin) and read all he has written on the subject. It will take you a while, so its difficult to do the subject justice in a few words here. Then taken one of the Advanced Pilot Seminars, and learn even more.

LOP = Lean of peak (EGT)
ROP = Rich of peak (EGT)

To simplify it in the extreme (and so not tell the whole story), leaning off the mixture will cause your engine to make more power, and so run hotter. When running with a rich(er than optimum for best power) mixture the excess fuel helps to keep the engine cool. At high power settings, say greater than 75%, there is a possibility of something called detonation happening - its to do with how the fuel & air burns in the cylinder - which is very bad news for the continued health of your engine. So the general recommendation is to run at least 50F below peak EGT on the rich side.

As you change the mixture from too much fuel to too little the EGT will increase to a maximum value, then decrease until the engine stops running. The absolute value of EGT is relatively unimportant as it is dependant on many things , including how far down the exhaust pipe the sensor is placed. CHT will follow EGT in general, but is much slower to react (as a large lump of meatl must heat up or cool down. However the absolute value of CHT is very important, the maximum CHT recommended by those who know is in the range 380 - 400 F. It is vital that CHTs do not exceed these values very much very often if your engine is to stand a good chance of reaching TBO.

To run LOP with any kind of success requires an engine monitor that displays each CHT and each EGT - in fact many would argue that to run your engine at all with any kind of success requires such a monitor.

The real reason running LOP is attractive is that it saves gas (1 or 2 gph in the cruise in RVs) and is better for the engine. A well balanced fuel injection system is required for really successful LOP operation - balanced means that each cylinder gets a equal dose of fuel and air. However, it is possible to run LOP with a carb - just not as easy.

During climb out leaning should be confined to keeping the EGTs around the take-off value, once in the cruise aggressive leaning can take place to reduce the fuel flow past the peak EGT (in every cylinder) and, say 50F, beyond it. Hence the term running lean of peak. It is also desireable to run with the throttle wide open (Wide Open Throttle) and regulate the power output with rpm using a constant speed prop - so called WOT LOP operation. John Deakin explains it much better than I can.

If you run LOP incorrectly it is possible to wreck your engine, if you do it properly it is possible to save fuel and extend the life of your engine. Engine manufacturers typically don't encourage running LOP as some skill is required to do it successfully (to avoid law suits). But read Deakin's views on the manufacturers' position.

I haven't found much difference in oil temp when running LOP, but it should be cooler as the engine is generating less heat.

Please read Deakin's articles for a much better account of this whole subject. I found them very enlightening.

Yours, Pete

[fodrv7]

Good to see the Penguin revere the Pelican.
Pete.

[f1rocket]

Here's a good article on the subject.

http://www.taturbo.com/future.html

[gmcjetpilot]

Some engines and installations are physically incapable of operating LOP operations, especially with small cubic inch engines.

If the discussion is saving fuel, the best way to do that is SLOW DOWN and throttle back. If you are burning 8.5 gal/hr at 190 mph, go 150 mph get way better air MPG's, saving way more fuel than you could with LOP operations.

Most of the LOP topic is towards thirsty 260HP, 310HP and 350HP crowd. LOP can mean a lot more to them. Also with a bigger 6 cylinder it is easier to get smooth LOP ops. LOP is not new, 1950's big radials had LOP operations.

Also some talking about LOP are selling expensive "custom" fuel injectors. I am not debating if it can work and be safe, hey 50 LOP is cooler than 50 ROP, but I suggest is not alway practical for use little guys (but some are able to do it).

If there is ANY uneven fuel flow than LOP is hard to achieve, at least smoothly. The EGT spread must be small. Besides uneven fuel flow and EGT between cylinders, many (most) airplanes have exhaust systems that have uneven length pipe lengths between cylinders. This produces differnt power characteristics and does not promote smooth operations, again especially in 4 cylinder engines. Uneven fuel injectors and carburated engines are just unable to run LOP operations, typically.


In general you need a balanced fuel injectors engine and the bigger the better the engine. Lycoming's opinion is LOP is really only applicable or worth while on larger 6 cyl engines; although many individuals have claimed routine LOP ops with there little 360's in RV's. Clearly it can be done, but it takes knowledge, effort and skill.

I understand Lyc's comment and where it comes from. They know the average (General Aviation) individual is not willing to go thru the effort to groom their engine for LOP. Also you MUST HAVE an ENGINE MONITOR, with each cylinder instrumented with EGT/CHT. It was only in the last 10 years or so that these monitors have become common. I was thrilled when I was renting planes, if it came with a single EGT gage; WOW, that was hot stuff. Now 4 and 6 channel monitors are common. Also you have to have the knowledge and skill to read and set the engine. Many will find their EGT spread is too wide to allow smooth LOP operations.

Here is some reading:
http://www.lycoming.textron.com/main...ngEngines.html

100F ROP is best power, Peak EGT best economy. (personaly 75F ROP for me)
http://www.lycoming.textron.com/main...erLeaning.html

Good info on EGT interpretation
http://www.lycoming.textron.com/main...mperature.html

Applies to TIO-540 but good general tips
http://www.lycoming.textron.com/main...TradeOffs.html

If you can operate LOP (more than 50F lean and get even smooth operations with out large EGT spread between cylinders) than good for you. If you can't or have a carb, than by all means lean properly (as discribed above) or even better fly at 65% or even 55% power. You can always run 50F ROP, but clearly from the data 50 LOP is better (cooler). Again throttle back and get better gas mileage. If you are willing to go 130 mph than you can save huge fuel.

On large engines LOP pays back more, so it is worth the effort. On little engines 1% or 4% is not a big deal and chasing it may be more difficult. Just slow down. Van flew a RV-9A down to 3.2 gal per hour.

Cheers George

[osxuser]

I don't know George, the Cardinal RG guys do it all the time, running the IO-360A1B6 (and A1B6D). Doesn't seem to be a big deal to balence injectors anymore either, GAMI will do it for you (they even provide a Lean Test on their website to see if you need Gaminjectors at all). Airflow Performance will also do it for you. Also, Powerflow claims that using their exhaust allows Carb'd engines to run LOP, and appartently proved it on GAMI's dyno, but I obviously haven't seen it personally. I don't think it's as big a deal as your making out.

[gmcjetpilot]

Originally Posted by osxuser

I don't know George, the Cardinal RG guys do it all the time, running the IO-360A1B6 (and A1B6D). Doesn't seem to be a big deal to balance injectors anymore either, GAMI will do it for you (they even provide a Lean Test on their website to see if you need Gaminjectors at all). Airflow Performance will also do it for you. Also, Power flow claims that using their exhaust allows Carb'd engines to run LOP, and apparently proved it on GAMI's dyno, but I obviously haven't seen it personally. I don't think it's as big a deal as your making out.

Many good points, lets see.....

I agree. I think the (200HP) fuel injected angle valve, counter weighted engine is a better candidate than say the (180HP) parallel non-counter weight engine. I am sure the 180HP could be tuned to do LOP ops as well, however the 200HP seems to be more suited. I am sure I did not say it can't be done, Dan C. does it all the time on his 200HP Lyc. We know how picky he is, which is good. He can get 40F LOP. He also says just a HAIR leaner the power drops radically. Like he said that is good. I am guessing but if his engine is that close to the "stochimetric" edge any little change, even turbulence would affect that delicate balance. Possible yes but its got to be right. The engine needs to be well tuned, adjusted, balanced and healthy, that is all.

I agree balancing injectors with Performance Airflow is pretty cheap verse the GAMI for Contenentals. I think he will do a data eval of you engine monitors output.

GAMI injectors are way too much. I understand the who, how and why of fuel balancing, and it is not big deal. However it is something that needs to be done on many engines to get LOP ops. It may need "re-tuning" from time to time to keep that tight tolerance in fuel balance. I agree it's not a big deal to you and I, but most GA pilots just want it good enough. However with fuel prices going up the interest will go up on saving fuel.

I did say the typical Cessna pilot is not willing or able to take the effort to run LOP, I stand corrected. Cardinal RG guys are hard core. I am sure there are many more Cessna drivers out there that take the time, but I bet most don't care or are clueless.

Powerflow is nice and I grant their right to Hype and advertise their product all they want. I have 4 into 1's and my pipes are all within an inch on my low tech carbed 360. I am going to experiment with LOP, but will not be heartbroken if I can't achieve perfect fuel Nirvana.

If I can get LOP ops I will be lucky. I have heard a Carb guy say he got LOP ops? Again it's a matter of practical. If mine will not, do I want to spend the time to trace the reason and solve it? I find most say they can't get it to run smooth LOP. If I can get tight EGT's spread (less than 100F) I will be happy LOP or not.

What is practical for the masses on all engines of various "average" tune and condition? What Lycoming suggest.


If you try hard I think you can get any engine to do it, but some are easier than others, like BIG Fuel Injected 6 bangers. Also, bigger 6 cylinders will benifit more for LOP ops. They are burning more fuel, so 4% on 15 gal is way more than 4% on 9 gal. At $3.50 a gal 0.30 gal/hr is a buck five. Five hours you got lunch!

Again to save way more than the 0.30-0.50 gal and hour LOP gives by cranking the RPM back and enjoying the ride. I will try for stochimetric perfection but will be happy with mediocre fuel distribution.

Cheers George

[rv8ch]

Originally Posted by gmcjetpilot

...Again to save way more than the 0.30-0.50 gal and hour LOP gives by cranking the RPM back and enjoying the ride...

Can't you do both? BTW, LOP has other advantages besides saving fuel, from what I've read. Things like carbon buildup, for example.

[dan]

Originally Posted by gmcjetpilot

Again to save way more than the 0.30-0.50 gal and hour LOP gives...

FYI, running LOP on my engine saves waaaay more than that. On my setup, the difference between 100 ROP and 40 LOP at any given average cruise power setting is more like 2 gph (~10.0 gph ROP, ~7.7 gph LOP).

[gmcjetpilot]

Originally Posted by dan

FYI, running LOP on my engine saves waaaay more than that. On my setup, the difference between 100 ROP and 40 LOP at any given average cruise power setting is more like 2 gph (~10.0 gph ROP, ~7.7 gph LOP).

Thanks I thought it was like 0.50 gal/hr, I had no idea, good info. Quite amazing. I assume your 10 g/h was 100F or best power.

As far as way throttled back and LOP, I guess you could? I don't know why not. G