Battson that also was my understanding - on the NA Aztec typical CHT was 360-380 F, EGT varied quite a lot depending on power setting, ambient conditions.

The bar display helped identify a cylinder which might be acting up.

ya know, after thinking about it, and my mech agrees...when u fly a 540 by the book, turbo or not, it gets high temps. my book says 23sq. if u do that, it burns a bunch of fuel fast, and only results in 5 or so kt. better, so im thinking like mine Rob, just run 2100 and about the same mp...cowl flaps open 1 notch...cht's @ 360-380...fuel burn @12-13...seems much happier there and oil temp stays down, and i see 130-140 kt. with stol kit, and v.g.'s...oh yeah and i lean it to 390 ish on the egt...cuts out at 1425...so a little rich of peak...just an idea...the day i flew it home from tahoe, i flew it by the book, and i remember it being a pain to manage the heat...good luck Rob...!

First, in case nobody has read Lycoming's guidance on how they want you to run their engines, it is worthy of note that Lycoming specifically says DO NOT run their engines lean of peak. Do a Google search for Lycomings Key Reprints document. Then try reading it....lots of good information there.

Now, assuming that you're still willing to run your engine contrary to the manufacturers recommendations, read up on the GAMI web site. And try following THEIR instructions on how to run LOP.

Finally, assuming you're just dead set against reading engine manufacturers and maintainers recommendations, consider this: Lycoming and most engine manufacturers prohibit ANY leaning of most of their engines when they are running at greater than 75 % power. And, 24 square in a Lyc IO 540 is going to be pretty close to 75 % power. Please consult that handy little booklet that Maule provided with your plane and study the power charts therein. And, if you didn't receive a Lycoming engine operating manual with that plane, call Lycoming and order one. Then, READ it.

Just a few thoughts. Detonation will KILL that very expensive engine, and detonation, while difficult to achieve with these engines, can be accomplished with focus and determination.

FWIW

MTV

MTV, not arguing with you at all as I have no IO-540 time, but I thought I read somewhere that Lycoming had updated their guidance to include LOP operations. I think it was connected to their FADEC release since that runs LOP, but opened to all engines regardless of FADEC install or not.

Not positive or anything, but I think I remember seeing that.

mtv wrote:First, in case nobody has read Lycoming's guidance on how they want you to run their engines, it is worthy of note that Lycoming specifically says DO NOT run their engines lean of peak.
...
Lycoming and most engine manufacturers prohibit ANY leaning of most of their engines when they are running at greater than 75 % power.

And yet, Lycoming has long authorized leaning all the way to peak EGT at any cruise setting up to 75% power. Now there's a risky idea.
So far as I can see, the latest version of the -540 OM provides absolutely no guidance about running beyond peak EGT, in the affirmative or otherwise. They simply pass the buck to the airframe manufacturer. I am not sure why you're so keen people read it with regards to LOP operations, it's totally unhelpful.

To quote a different document by Lycoming...

With a normally aspirated engine, if leaning is initiated at 75% power and leaning past peak EGT is accomplished, it is unlikely (but not impossible) to induce detonation by opening the throttle to regain power.

Now there's another dreadful idea... I am not going to argue, there is a very real risk of doing damage if you [have no idea what you're doing] get it wrong. FWIW, going LOP above 60% power is asking for trouble IMHO, I like a big safety margin.

BUT, there are literally hundreds of pages written by various reputable authors on how and why it is a good idea to run LOP (safely).

And there's one from Lycoming (SSP700A) realised to try and counter the above authors [which Lycoming have since removed from their website!!!]. It opened by subversively ridiculing GAMI for encouraging LOP operations. The document then seems to suggest people are going trying to LOP at 75% power in an effort to avoid losing airspeed... no wonder they were worried about it...

The hearsay persists that 50*F ROP is the "best/recommended place to lean your engine". AKA "How to run hard and hot while wasting fuel". These days, largely thanks to GAMI & others like them, it's widely known that 50 ROP creates the harshest conditions inside the cylinder, and that well-executed LOP operations are cooler and gentler on the cylinders...

You'd be forgiven for thinking engine manufacturer's didn't know much about operating their own engines, when you read some of the one-eyed publications they have released. Maybe the Maule book you refer to offers better guidance (buck-passed??), but the Lycoming Operating Instructions offer no help at all.

mtv wrote:First, in case nobody has read Lycoming's guidance on how they want you to run their engines, it is worthy of note that Lycoming specifically says DO NOT run their engines lean of peak. Do a Google search for Lycomings Key Reprints document. Then try reading it....lots of good information there.

Now, assuming that you're still willing to run your engine contrary to the manufacturers recommendations, read up on the GAMI web site. And try following THEIR instructions on how to run LOP.

Finally, assuming you're just dead set against reading engine manufacturers and maintainers recommendations, consider this: Lycoming and most engine manufacturers prohibit ANY leaning of most of their engines when they are running at greater than 75 % power. And, 24 square in a Lyc IO 540 is going to be pretty close to 75 % power. Please consult that handy little booklet that Maule provided with your plane and study the power charts therein. And, if you didn't receive a Lycoming engine operating manual with that plane, call Lycoming and order one. Then, READ it.

Just a few thoughts. Detonation will KILL that very expensive engine, and detonation, while difficult to achieve with these engines, can be accomplished with focus and determination.

FWIW

MTV

LIKE!

Battson,

I am not necessarily supporting Lycomings assertions regarding LOP ops on their engines. I'd probably try LOP on a fuel injected Lyc if it was fully instrumented.

My primary point, however, was he's talking about leaning at what I believe is a pretty high power setting. Not only does Lycoming say don't do that, most POHs I've seen say that, and the GAMI guys also say that.

That may in fact be why he's not been successful to date, and the consequence of leaning at too high a power setting CAN be detonation.

Finally, while Braly and company may have some valid reasons to disagree with some of Lycomings recommendations, I wouldn't be quick to preach doom and gloom for SOME of those practices.

Case in point: GAMI says peak EGT to 50 rich of peak is the worst place to run your engine, and that running there can (will?) cause damage.

So, here's an exercise for you: Get in a plane with good multi probe instrumentation and a Lyc engine. Now, follow the leaning procedure most of us were taught before the advent of engine analyzers.....pull the mixture out till the engine roughens a bit, then push the mixture in 1/4 inch or so. Sound familiar?

Now, look at your CHT and EGTs. I think you'll find that the EGTs are running real close to peak EGT. This doesn't really prove anything EXCEPT that thousands of engines have been run with this type of leaning for decades, and I'd bet that the vast majority of those engines went to TBO without cylinder changes.

Point is, it may or may not be the most efficient way to run your engine, but it's been done fore decades, with success.

But again, my point was and is that Lycoming says don't lean AT ALL when the engine is running more than 75% power. 24 square is more than likely more than 75% depending on altitude, of course. And GAMI pretty much agrees with that notion, last I heard.

MTV

mtv wrote:But again, my point was and is that Lycoming says don't lean AT ALL when the engine is running more than 75% power. 24 square is more than likely more than 75% depending on altitude, of course. And GAMI pretty much agrees with that notion, last I heard.

MTV

Almost exactly 75% at 24 square, according to the power curves and my EMS computer. As you say, depending on altitude.

Myself, I add a big fat margin of safety to that recommendation. 60% is enough for me.

Here is something you guys need to consider for efficiency,

Run "over square"!

Below 65% in Continental's or 75% in Lycoming's.

Example Io-520 in a 185 I used to run 2100 rpm and 23 inches. Excellent results!

In my Husky I run 1900 RPM and 23 inches. Once again, excellent results!

These results were confirmed with GPS and fuel computers for hundreds of hours, not just one flight. Running over square will yield the best miles per gallon.

If you think it will hurt the engine, what do you think the various power settings are in radial engines are? Most of the time over square. Point being, it won't hurt a thing if done properly.

As far as LOP, I am a believer if fuel flows are matched and the engine is below a prescribed percent power setting, timing is correct and engine is properly instrumented (all cylinders EGT and CHT).

LOP can help with efficiency , over square can help with efficiency, and now combined, over square and LOP can yield some amazing results.

G44
(Kurt)

Best idea yet...pull the power back.....these old skool aircooled motors really dont like to be run hard...yup, they will do it for a long time, but there are only so many hours at WFO that they will go. these are aircooled, they aint no watercooled hotrod like my new KTM...and that i think is good. these are torque motors at low revs, and really pretty efficient when run in certain parameters...dont let people tell u to run 'em hard All the time cause thats best...bullshit! most of those guys dont even own a bird with a bigger powerplant, let alone a rotax or whatever...and again, run your motor hard getting off something short, but at cruise, save yourself some major $ and pull it back...as said 60% or less does work just fine...aircooled motors like these are way different than anything else a guy can operate...take good care of it, and it will return the favor...!

G44 wrote:excellent results!

These results were confirmed with GPS and fuel computers for hundreds of hours, not just one flight. Running over square will yield the best miles per gallon.

Kurt - thanks for posting. This is another interesting area. How significant was the result?

I have been playing with different settings, including over-square, but have yet to find any conclusive results (lots of wind messing with my x-country flights).

I like running lower RPM, if for no other reason than it's more relaxing for me and the passengers. I hadn't been able to convince myself whether 23" 2100 or 2300 and 21" made any difference to the overall result.
How much fuel per distance were you saving by running over-square?

About 1 to 2 GPH at the same speed. Airplanes with the MT prop do better, the MT does better than other props at the lower RPM's, it does well at higher rpm's also.

That is just the over square part of it. In a 185 with fuel injection and GAMI injectors doing over square and LOP around 2 GPH at the same speed.

Give it a try. Be careful, some engine props have a restricted RPM range, don't operate in the restricted range. Example, 0-360 Lyc and Hartzell 76" 2000-2250 is restricted RPM range.

Cabin noise is reduced too as well as flyover noise.

Kurt

I too have run a lot of engines over square. At one point, because of all the wives tales regarding oversquare ops, I asked a Lycoming rep about this on their engines. He equivocated some, so I asked for something in writing. He sent me a note that said "don't run our engines more than 9 inches oversquare.......!

It's virtually impossible to get that far oversquare in any case.

Oversquare works, but some engine/prop combinations don't seem to like it much.

MTV

mtv wrote:I too have run a lot of engines over square. At one point, because of all the wives tales regarding oversquare ops, I asked a Lycoming rep about this on their engines. He equivocated some, so I asked for something in writing. He sent me a note that said "don't run our engines more than 9 inches oversquare.......!

It's virtually impossible to get that far oversquare in any case.

Oversquare works, but some engine/prop combinations don't seem to like it much.

MTV

MTV, I have always figured if you are in the green on both gauges and it sounds ok then that is why they have the green arc's!!
I know when you put a turbo on them you are always over square?
All the old-old radials run over square, the 985 in the Broussard will run 36 over 23 if you want to!!
The io540 in my M6 ran over square all the time, it was rated @ 235 , When running in cruise at about 65% there was a sweet spot where the engine ran really well just above the rough spot when leaning, was LOP, would drop the power back as you could feel it make more if you went to the rich side, Plane flew well, about 6-7 mph slower than ROP, but could go fore ever!, Ketchican - Blaine fully loaded with wheel ski's on it as they would not fit inside, had my reserve when I got there.
JMHO

Good information. I have not posted lately because I don't have anything to add but I have been reading all replies and storing the data. I was previously running 24 square because that is what the instructor who had more hours than me in the IO-540 recommended. Wanting more than 1 person's opinion is why I posted this question. Thanks for the help.