Lean of Peak

[Floyd R. Turbo]

I do know that there is a group of Mechanics and Piston Engine Experts that run a class in Ada, Oklahoma. The Cirrus pilots highly reccommend it. Evidently these guys will change the whole way you think about and operate high perfomance piston engines.

I forgot the name of the class but I do know that they have a website. If you go to www.cirruspilots.org and ask on the public side of the site I am sure they can direct you in the right direction.

Advanced Pilot Seminars www.advancedpilot.com

 

[Dangerkitty]

Advanced Pilot Seminars www.advancedpilot.com

Thats the one! Have you been to it? Is so is it is great as all the Cirrus pilots say it is?

 

[PeteCO]

Thats the one! Have you been to it? Is so is it is great as all the Cirrus pilots say it is?

I'd imagine it's great. Read John Deakin's articles on the subject on Avweb. He is a principal of Advanced Pilot Seminars.

 

[Moonfly201]

That's the myth these folks have been busting for the last 5-10 years... lean of peak (LOP) in SOME circumstances, if done correctly, IS safe for your engine and will NOT result in burned valves if you follow all the caveats.
In fact they say it is a better way to run some engines.

I used to violently resist this philosophy too until I did some learning about it! It seems it is less of an opinion now.... they have developed some pretty good science to back it up.

Absolutely correct. Deakin is right. You need GAMI's and a four probe EGT/CHT gauge to do it properly.

I have been running my GAMI and Insight GEM equipped Mooney Lycoming IO-360 lean of peak for about 650 hours. Saving fuel, babying my cylinders, valves, valve guides and piston rings. And burning a lot less fuel and oil.

LOP allows me to manage the engine like a turbine. Since I'm already cooled down in a normal LOP cruise, I can enrichen slightly (so temps don't get too cold) for a high-speed descent into the airport environment and pull off all the cruise power at once to level off and slow down to gear speed and land.

 

[Bryan D]

Absolutely correct. Deakin is right. You need GAMI's and a four probe EGT/CHT gauge to do it properly.

I have been running my GAMI and Insight GEM equipped Mooney Lycoming IO-360 lean of peak for about 650 hours. Saving fuel, babying my cylinders, valves, valve guides and piston rings. And burning a lot less fuel and oil.

LOP allows me to manage the engine like a turbine. Since I'm already cooled down in a normal LOP cruise, I can enrichen slightly (so temps don't get too cold) for a high-speed descent into the airport environment and pull off all the cruise power at once to level off and slow down to gear speed and land.

This is contrary to the the principals on which every internal combustion engine operates. Leaning the fuel increases combustion chamber/cylinder head/exhaust gas temperature, a rich mixture cools the same. So how do you enrichen the mixture "so the temps don't get to cold". At any altitude I lean the mixture until I see a slight increase in RPM's or slight roughness, then I richen the mixture about 1/4 turn. If I have an EGT guage, it will be at peak everytime with this procedure. Now if I did not turn the mixture 1/4 back in, it would be lean of peak. It would be very likely that I would have detonation but would not hear it because I'm wearing a headset.

 

[casper1nine]

moonfly is right and it does work. cht decreases when lop, so if operating lop, enrichening the mixture towards peak heats it up. this is not contrary to anything. for what it's worth, sometimes this is useful, and sometimes not. moonfly's example is one where he was on the winning end of the equation, financially, and performance wise. when i was flying a TC piston plane w/ similar engine monitoring equipment, i found that in my situation i couldn't make lop with the ballsy power settings allowed by a host of mods i had installed, without exceeding the max TIT. so.... in order to operate LOP, i had to run some pretty weak power settings. the moral of the story is that is DOES work with out harming anything, and that the #'s all stay where they should be. in my example though, the reduced power settings were not worth the speed loss, so it was strictly academic. note: don't try it in aircraft where you can't monitor the cylinders individually. i am just supersticious like that

regards,
casper1nine

 

[casper1nine]

1: egt an cht don't usually peak at the same time
2: peak is PEAK. the engine does not continue to get HOTTER than PEAK, so guess what that means..... LOP is COOLER than peak.

regards.

casperthe1timecfi1niner

 

[GravityHater]

This is contrary to the the principals on which every internal combustion engine operates. Leaning the fuel increases combustion chamber/cylinder head/exhaust gas temperature, a rich mixture cools the same. So how do you enrichen the mixture "so the temps don't get to cold". At any altitude I lean the mixture until I see a slight increase in RPM's or slight roughness, then I richen the mixture about 1/4 turn. If I have an EGT guage, it will be at peak everytime with this procedure. Now if I did not turn the mixture 1/4 back in, it would be lean of peak. It would be very likely that I would have detonation but would not hear it because I'm wearing a headset.

Read Deaken's and ask around on the GA plane usenets. A lot has happened in the last 5 years. I was adamant at first too, but have since learned. Keep an open mind! Things really have changed.

 

[ackattacker]

L.O.P. works great at low power settings where it's safe. I wouldn't try it at >65% power or on turbocharged engines... the risks are not worth the extra fuel economy. Many people have been sold on lean of peak operations only to start replacing valves and cylinders at 500 hours. I don't know of any large commercial operators out there who run lean of peak... that speaks volumes. One cylinder can offset all your fuel savings and then some.

But the economy is impressive. I once flew a Cirrus SR-22 at 55% power lean of peak MMU-DAB nonstop. Fuel burn 10gph and TAS 150kts. Landed with 20 gallons remaining.

 

[GravityHater]

LI wouldn't try it at >65% power or on turbocharged engines... the risks are not worth the extra fuel economy.

Many people read just the "risks are not worth it..." and that's all they hear. To a discriminating listener, if you follow the restrictions (<65%hp, never exceed manuf. cht limits, don't forget when descending) then there are no risks. Detonation, or valve/exhaust port damage is impossible in the conditions specified.

Many people have been sold on lean of peak operations only to start replacing valves and cylinders at 500 hours.

and then it turned out what really happened is they didn't understand the restrictions or just weren't careful. To be honest it's not rocket science.

I don't know of any large commercial operators out there who run lean of peak... that speaks volumes. One cylinder can offset all your fuel savings and then some.

If I had an air taxi op or something I wouldn't do it either - the pilots have enough on their plate as it is in these circumstances.