What are the highest Lean of Peak power settings you guys are comfortable using in the big 6 engines, specifically the Lycoming guys?

I have started out never above 23" and 2300 RPM, LOP for a few hundred hours now.
That buys me about 120 KTAS at higher altitudes for about 37 L/hr (9.8 US Gal/hr) and beautifully balanced CHTs, as well as very clean plugs and cylinders.

Now I am trying 25" and 2300 RPM, burning 39.5 L/hr (10.5 US Gal/hr). That has me about 20 degrees Celsius on the lean side of peak EGT.
The extra 2.5 L/hr more buys me 10 knots more airspeed at most altitudes below about 6000 or wherever the WOT MAP drops below 25", which is a no-brainer from a fuel efficiency perspective. 130 KTAS for 10 gal/hr is a good cruise setting!

Just looking for comfort that I'm not the only guy pushing my engine that hard, lean of peak. The engine definitely runs cooler and cooler, the more I open the throttle (more air to cool it with less fuel to burn). So CHTs are of no concern.
In fact, I don't know exactly what I am concerned about.... Just looking to see what everyone else is doing.

Cont..io550 c206 flying jumpers .Sea level climb out..25-29 gph . (She loves fuel) 4k back to around 20gph....8k back to 18gph .rpm at 2700 till it drops to 25 inches manifold .Then I roll it back to 2500 or 2450 rpm.. Pretty much running it hard as possible /lean as possible for happy temps and hard climb. If not getting paid it's nowhere near run that hard when I'm just going somewhere . My take is that they want to run hard if flown all the time .

That is with wide open throttle the whole way from sea level to 11-13 thousand .Has not exploded yet and it seems to really like it .

Assuming there is an engine monitor that measures all cylinders I would be trying LOP at wide open throttle and 2500 or even 2550 RPM.

If your engine "conforms" that is all cylinders reach peak egt within a very small fuel flow range you are doing the engine a favour. CHT is the determining factor and it looks like you have that sussed.

A couple points:

Lycoming says DO NOT lean their engines below 5000 ft DA. Of course, they also say don't run their engines LOP.

Continental says don't lean their big engines above 75% power......which, coincidentally is roughly equal to the power of a normally aspirated engine operating at 5000 DA.

Think there might be a clue there?

I ran an IO 550 in a 206 LOP regularly for over 1100 hours, always leaning only when power was below 75 %. Then one of our other pilots used the plane for 25 hours. Right after, a 100 hour inspection was done.....with two bad cylinders. I asked the other pilot what kind of power settings he'd Ben running during that 25 hours. He was running about 80% and LOP.

In the early operating service of the IO550, there were a lot of cylinder problems....part of which were caused by pilots not understanding the differences between these engines and the 520s they were used to, and partially due to pilots running LOP without fully understanding the process.

And, of course, Continental gave bad information on fuel flows.

You can run your engine however you like, but I think there are some valid reasons not to lean these engines aggressively at high power settings.

And I am a firm believer in running many engines LOP, as long as it's done intelligently.

MTV

Looking forward to following this thread.

Doesn't Mike Busch say you should not run LOP unless you are below 75% power? That also lines up with what MTV is saying. According to the power chart I found for the IO540 25"/2300 is right about 75%.

Just over 500 hundred hours on current engine, Continental 0-470-U/TS running LOP mostly at 23-25"/2300 (10gph) or 24"/2450 (11gph). Checked compression n bore scoped cylinders yesterday during annual, all 6 are 78/80 and valves look great. Mechanics said whatever I'm doing keep it up. Best results have been keeping CHT's between 330-360, it will run leaner (i.e. cooler), but lead build up has been an issue for running CHT's between 300-330. Avblend or something comparable in the oil is a good idea, fuel additives too.

Not a big motor but our Lyc 0-320-B2B runs great LOP at 2450 RPM (6.2 gph)

whee wrote:Looking forward to following this thread.

Doesn't Mike Busch say you should not run LOP unless you are below 75% power? That also lines up with what MTV is saying. According to the power chart I found for the IO540 25"/2300 is right about 75%.

I agree with and I am following the advice about running below 75% before leaning. Mike V and I have discussed this before on previous threads
One question that raises, is how much can you lean at 74%.... all the way back to the lean stumble? ...and what's so special about 75% - I would love to know why they put that in there. But that's another question.

I think you're reading the power chart correctly, for full rich mixture. The power drops back sharply as you lean past peak. My engine monitoring computer is constantly calculating the %power output. At leaned mixture, 20*C LOP, 25" and 2300 is about 60% power. So there is lots of room to open the throttle further.

Pierre R - I liked your post in Whee's thread so much, I stole it and put it here!

Follow that advice (the three simple rules) when leaning and you can't go wrong, I say.

Pierre_R wrote:http://www.avweb.com/news/pelican/pelicans_perch_84_mixture_cht_194816-1.html

Long article but well worth reading, digesting, then reading again.

Below are my "Cliff notes" regarding mixture that guided me through 2900 hours on my NA IO550 with individual EGT and CHT indication. (Still should read the article and also look up some of Mike Busch's blogs or webinars. Better yet, take the Advanced Pilot Seminar: http://www.advancedpilot.com/

1. Avoid the "red fin".
2. You can't hurt it below 65% power. i.e. peak or either side of it is OK, so sometimes when want or have to fly high (say 11,500 or higher), it's OK to go on the rich side a bit to get max output.
3. Don't target anybody's specific CHT or EGT recommendations. Go by how many degrees LOP you are.

aussie bob wrote:Assuming there is an engine monitor that measures all cylinders I would be trying LOP at wide open throttle and 2500 or even 2550 RPM.

If your engine "conforms" that is all cylinders reach peak egt within a very small fuel flow range you are doing the engine a favour. CHT is the determining factor and it looks like you have that sussed.

Bob - what engine do you run, and are you pushing yours as hard as you suggest in the above post?

At higher RPM and WOT running LOP at low level, the engine could develop a whole lot of power. Looking at the leaning diagram, definitely >80% to keep it running without a stumble, perhaps as much as 85% or 90% depending how perfectly balanced your injectors are.

mtv wrote:A couple points:


And, of course, Continental gave bad information on fuel flows.

You can run your engine however you like, but I think there are some valid reasons not to lean these engines aggressively at high power settings.

And I am a firm believer in running many engines LOP, as long as it's done intelligently.

MTV

Well put. Traditional ROP recommendations put cylinders right smack in the middle of the "red fin". If you're going to run rich, the new consensus of the really smart guys (not me), is to run very rich, like 120d ROP.

The Red Fin.



My "other plane" is a Cirrus SR22 with a normally aspirated IO550 with GAMI injectors. On the Cirrus Owners and Pilots Association Forum (COPA) over the eight years I've been active, there has been a lot of discussion and now with a large fleet (around 6,000 Cirrus out there) and millions of hours and a lot of data, it was found that a lot of the turbonormalized SR22's were needing cylinder work at 800-1100 hours. When they first came out (2007) the sales and marketing hype was a 200 knot plane. Too many were operated at 85% power, basically WOTLOP (wide open throttle, lean of peak).

At the same time, the majority of the fleet of normally aspirated SR22's, like mine, quietly were making it to TBO and beyond (2960 hours in my case). The takeaway was that the NA birds were being run mostly from <65% to 70% power. (For example, 90% of my SR22 flying is cruising point A to point B WOTLOP at 10,500 to 12,500, where it can't make over 65%.) Probably 90+% of the Cirrus operators run lean of peak the majority of the time. The difference was the TN ships were just being run at too high a power.

With the low altitude type of flying many on this forum enjoy, the conclusion would seem to be that it would be a good idea to pull the power back for LOP ops. One of the reasons I bought my modified 1964 182-G seaplane (now a backcountry plane) is that it has an IO550 with GAMI injectors and a JPI with individual EGTs and CHTs so I can run it like my CIrrus engine. The difference is that down low I pull it back, to say, 21" MP and then lean to about 20d LOP.

Oh, BTW, with this setup I lean "brutally" for taxiing and ground ops.

Pierre

Very interesting reply you posted there Pierre.

So that SR22 data does strongly support the theory that you can overdo the power settings for LOP ops, and do damage to the cylinders.

As you can see on the red fin, (the power settings version, not the altitude version) the harder you run the engine lean of peak, the more you need to lean - and thus the less power it makes... so it's a Catch-22 situation, you are approaching a limit. You can't get above a certain power output LOP, without causing damage in the longer term, because you'll be unable to run the engine smoothly at a lean enough mixture setting.

I never used charts, diagrams, or had any engine instrumentation other than oil temp, RPM, and oil guage. Flew fixed pitch 0-540s for years at lean to peak using RPM before takeoff. Also flew almost always at full throttle and below 200' AGL. Pawnees and Callairs. 15 gph on 235 hp 0-540s. More gph on 250 and 260 hp 0-540s. Short hops depending on gallons per acre put out and engine cooling at idle during loading.

contactflying wrote:I never used charts, diagrams, or had any engine instrumentation other than oil temp, RPM, and oil guage. Flew fixed pitch 0-540s for years at lean to peak using RPM before takeoff. Also flew almost always at full throttle and below 200' AGL. Pawnees and Callairs. 15 gph on 235 hp 0-540s. More gph on 250 and 260 hp 0-540s. Short hops depending on gallons per acre put out and engine cooling at idle during loading.

Yeah but how many engine failure did you say you've had

All high time except one with 50 hrs SMOH. Most dangerous after poorly maintained is recently maintained. Human error type thing.

Correction: five on engine with 50 hrs. I finally crashed and got to send it back to re overhaul.

Just giving you a hard time.

I live for a hard time. Retirement, injury, and old age are boring.

Whee,

To give you a hard time since you have sold the Luscombe and are building, I have to tell you a homebuilder story. The mechanic from whom I leased Pawnees and Callairs, including the 50 hr rebuild, was deep in an engine on a Pawnee when a man came through the hanger door. He asked Dave if he had a cable clamp tool. Without turning around Dave said, "On the bench." The man picked up the cable clamp tool, looked at it with a scrunched up look on his face, and asked, "Do you have a (I forget the make) tool? Dave's tool clamped cables fine but left a little cable after the cut that frayed. Dave came out of the engine, turned around, and said, "Mister! You go down to the National Guard, walk into the hanger, and yell, Homebuild. They will either bend over backwards to help you or do what I'm going to do: They will beat you to death with a prop before you can get out the door." The man left without the cable clamp tool.

Good luck with your project.

Contact

Why does this "red fin" chart reference the red area to be >200 ROP when your altitude is only 1,000'? Why not reference power or fuel flow?

Would the recommendation from TCM change if the MP was 25" and 2500rpm versus "full throttle?"

I run an IO-520 D at 25 squared below 1,000' and normally run 100-150 ROP. Is this considered in the "red zone?" CHT's run 335-360.

Sorry to sidetrack from LOP, this IO-520 engine does run very well LOP at altitude or below 75% power. If only the O-470R I fly could run LOP.

Pierre_R wrote:

mtv wrote:A couple points:


And, of course, Continental gave bad information on fuel flows.

You can run your engine however you like, but I think there are some valid reasons not to lean these engines aggressively at high power settings.

And I am a firm believer in running many engines LOP, as long as it's done intelligently.

MTV

Well put. Traditional ROP recommendations put cylinders right smack in the middle of the "red fin". If you're going to run rich, the new consensus of the really smart guys (not me), is to run very rich, like 120d ROP.

The Red Fin.



My "other plane" is a Cirrus SR22 with a normally aspirated IO550 with GAMI injectors. On the Cirrus Owners and Pilots Association Forum (COPA) over the eight years I've been active, there has been a lot of discussion and now with a large fleet (around 6,000 Cirrus out there) and millions of hours and a lot of data, it was found that a lot of the turbonormalized SR22's were needing cylinder work at 800-1100 hours. When they first came out (2007) the sales and marketing hype was a 200 knot plane. Too many were operated at 85% power, basically WOTLOP (wide open throttle, lean of peak).

At the same time, the majority of the fleet of normally aspirated SR22's, like mine, quietly were making it to TBO and beyond (2960 hours in my case). The takeaway was that the NA birds were being run mostly from <65% to 70% power. (For example, 90% of my SR22 flying is cruising point A to point B WOTLOP at 10,500 to 12,500, where it can't make over 65%.) Probably 90+% of the Cirrus operators run lean of peak the majority of the time. The difference was the TN ships were just being run at too high a power.

With the low altitude type of flying many on this forum enjoy, the conclusion would seem to be that it would be a good idea to pull the power back for LOP ops. One of the reasons I bought my modified 1964 182-G seaplane (now a backcountry plane) is that it has an IO550 with GAMI injectors and a JPI with individual EGTs and CHTs so I can run it like my CIrrus engine. The difference is that down low I pull it back, to say, 21" MP and then lean to about 20d LOP.

Oh, BTW, with this setup I lean "brutally" for taxiing and ground ops.

Pierre