LOP in IO-360 Continental

[dell30rb]

Globe Swift with a Continental IO-360 210hp.

Have the continental engine manual, but the installation is not factory and there is no POH or anything like that.

The manual references 75% power as 25 squared (not to go over square for cruise). It also states that you should be leaned to 50deg ROP for cruise power, and operations AT PEAK are permitted at 65% power or less.

What about lean of peak? If I want to run at 25 squared and am leaned 20F LOP then I am probably okay correct.

Also curious about fuel pump settings for hot/cold starts and during flight. This one has a high/low fuel pump setting. I have been priming it with the low setting and takeoff/landing with the pump off. I believe the advice from the previous owner was something like "you can put it on low for takeoff/landing if you want to. Most folks just use it for priming and leave it off" The continental manual is no help here, says to refer to POH...


I have been using 25 squared and leaned well ROP for climb, then 2450 and 24.5" MP or lower depending on altitude for cruise, LOP. Been seeing about 9GPH and almost 150ktas. CHT's in the 320-340 range

 

[Clark1961]

Got an engine monitor? Run the GAMI test and see where you are.

Prolly need to balance out the fuel flows to run the IO-360 very far LOP. GAMI's are one way to go. A full fuel & flow balance is another. Neither option is really cheap but it sure does make for a smoooooth engine which is a very good thing from a maintenance perspective.

I went with GAMI's on the 'kota which is the same base engine with a turbo added and lower compression pistons.

 

[Henning]

Go LOP, save yourself a lot of money and headaches. 20°LOP will have you safe at whatever numbers you want to run, I would have the throttle wide open and set RPM for what speed you want. Don't get hung up on MP when LOP, it's meaningless in the expression of % power, what you need to go by is your IAS for the altitude. What speed does 62% power get you? At 20°LOP I bet you need WOT and 2500rpm.

Continentals I prime by going full throttle, mixture rich, pump on HIGH, see the fuel pressure gauge hit full count 1,2,3,4 pump off. This is for any start above 50°, below I will increase the count. I crack the throttle 1/2-1" and bring the mixture back to idle then crank and throttle as necessary.

 

[Checkout_my_Six]

@ 75% HP you'll want to make sure you are at least 20 deg lean (of the last cylinder to peak)....if you operate more than 75%HP....30-50 lean is recomended. If you are going to lean you'll also want to monitor your CHTs....and verify the cylinders are cool and not having issues with detonation....or any other things that may cause additional heating.

Regarding the two speed fuel pump....I have the same setup in my Bonanza. High boost till the fuel pressure rises to prime for about a second or two....then off. I'll use low boost for a hot start after it's primed. But, I never use the pump for take off or landing....like a Piper recomends. High boost on landing or takeoff could kill the engine with too much fuel.....so, careful there.

Everyone seems to recommend full power for climbing....so that you achieve max fuel flow for cylinder cooling. Pulling power back to 25 squared will reduce your fuel flow and cause excessive cylinder heating....as seen with CHTs. I just climb full power till at altitude then make all my adjustments....after I've leveled off at the speed I'll be cruising. Power back....then mixture back quickly to the fuel flow that will get me 30-60 deg lean.

http://www.csobeech.com/files/LOP-Suggestions.pdf

Globe Swift with a Continental IO-360 210hp.

Have the continental engine manual, but the installation is not factory and there is no POH or anything like that.

The manual references 75% power as 25 squared (not to go over square for cruise). It also states that you should be leaned to 50deg ROP for cruise power, and operations AT PEAK are permitted at 65% power or less.

What about lean of peak? If I want to run at 25 squared and am leaned 20F LOP then I am probably okay correct.

Also curious about fuel pump settings for hot/cold starts and during flight. This one has a high/low fuel pump setting. I have been priming it with the low setting and takeoff/landing with the pump off. I believe the advice from the previous owner was something like "you can put it on low for takeoff/landing if you want to. Most folks just use it for priming and leave it off" The continental manual is no help here, says to refer to POH...


I have been using 25 squared and leaned well ROP for climb, then 2450 and 24.5" MP or lower depending on altitude for cruise, LOP. Been seeing about 9GPH and almost 150ktas. CHT's in the 320-340 range

 

[dell30rb]

It has GAMI injectors. Runs very smooth LOP.

Reducing power causes high CHT's... I don't buy it. This airplane has plenty of HP and I have no reason to climb out several thousand feet at 2700+ rpm. Makes a lot of racket for you and people on the ground.

I leave the mixture rich and pull the MP and then prop back to 25 squared once I hit about 700-800 AGL. At that power setting and maybe 110kts i'm climbing about 1000FPM. Once I hit 3000' i'll start leaning, making sure to stay well rich of peak.

Thanks for the tips on starting. I'll try the high setting for priming. It did seem to take awhile to prime for a cold start with the low setting.

Oh yeah... here is the plane

 

[Checkout_my_Six]

what are your CHTs?...do you know what they are when you are 25/25?


If you are getting them below 380 deg F....then yes, there is no need to change anything. If however they are hotter....well then you will eventually burn up your cylinders...probably well before the next 1,000 hrs.

 

[Henning]

You need turbos and a lot of boost to make 75% power 30-50° LOP.

 

[Checkout_my_Six]

You need turbos and a lot of boost to make 75% power 30-50° LOP.

Oh...M K.

 

[Henning]

I can't read the second chart, not sure what you're trying to show, I see nothing on % power being made. Once LOP the only accurate gauge of %power is airspeed. At 50° LOP WOT you'd have trouble making 60% power even down low.

 

[Checkout_my_Six]

It's 100% HP at sea level.....and full throttle from there.

So, You don't need a turbo to make power above 75% power.

Now, if you're at or above 8,000 feet MSL....I'd agree wit ya.

 

[Jaybird180]

It has GAMI injectors. Runs very smooth LOP.


Oh yeah... here is the plane

Ooohhh....centersticks!

 

[Henning]

The main thing to watch running LOP is your CHT, that's the relevant number. If you are staying below 380° you are not showing evidence that you are 'operating in the red box' when you are running in conditions that favor detonation, you are making a lot of heat.

If you lean by sound, you won't go wrong, especially if you run smooth and can lean all the way back until the engines drop off. I just pull back until the engines quit pulling (you'll notice airspeed drop off) and they start sounding breathy, then I come back in until I feel it pull and the throat fills into its voice. At that bottom point where she comes onto the pipe, that's where she has just come up the ramp onto the plateau of the torque curve, this is where I get the greatest work/fuel ratio. This by nature also means this is the easiest on my engine getting me the most work/heat/time and also deposits the least amount of crud on my exhaust valves. Once you find this point, you can make a power/altitude chart using fuel flow LOP as a variable criteria so you know which number to pull back to to speed the process.

 

[dell30rb]

what are your CHTs?...do you know what they are when you are 25/25?


If you are getting them below 380 deg F....then yes, there is no need to change anything. If however they are hotter....well then you will eventually burn up your cylinders...probably well before the next 1,000 hrs.

None are over 350F on climbout. I'm leaving the mixture rich when reducing power. They would be hotter if I was WOT and prop full forward.

 

[dell30rb]

According to the chart, Henning is not far off. If the red line on the lean side is depicting the limitation as "no LOP above 75%" then according to the chart, at WOT @ sea level, 50F LOP the engine IS making less than 75% power

 

[KSMooniac]

It sounds like you are trying to fly efficiently... I agree about climbing out at max MP and max RPM, and leaning in the climb to maintain a Target EGT as originally published by the Advanced Pilot Seminar folks. A test pilot working on a master's thesis took this concept and expanded it further to find the most efficient climb/leaning protocol and here it is:

ttp://www.openclip.net/Benchmark/IntroducingVz.pdf

If you're *going* somewhere, this method will get you to altitude AND downrange in the climb as efficiently as possible, while treating your engine well.

 

[Checkout_my_Six]

It sounds like you are trying to fly efficiently... I agree about climbing out at max MP and max RPM, and leaning in the climb to maintain a Target EGT as originally published by the Advanced Pilot Seminar folks. A test pilot working on a master's thesis took this concept and expanded it further to find the most efficient climb/leaning protocol and here it is:

ttp://www.openclip.net/Benchmark/IntroducingVz.pdf

If you're *going* somewhere, this method will get you to altitude AND downrange in the climb as efficiently as possible, while treating your engine well.

I read that.....and that's 20 minutes of my life that I will not be getting back.

Ummmm....so, just climb at the most efficient forward speed (Carson or whatever speed)....and at the most efficient engine power producing schema, LOP whatever....since by definition, climb rate is due to excess power not needed for forward motion.

But....it's a Riddle paper. I hope he got his "A".

 

[GeorgeC]

Another LOP noob question: Does the red box still apply if you are not WOT? Various guidance indicates that it's ok to lean at any altitude at <= 75% power, or that detonation is not a concern at <= 65% power. If I'm putting along at 65% economy cruise, can I lean anywhere I want without fear of cooking anything?

 

[Henning]

Another LOP noob question: Does the red box still apply if you are not WOT? Various guidance indicates that it's ok to lean at any altitude at <= 75% power, or that detonation is not a concern at <= 65% power. If I'm putting along at 65% economy cruise, can I lean anywhere I want without fear of cooking anything?

The "Red Box" represents a pressure/temp/time regime that is conducive to supporting detonation.

 

[jesse]

Oh...M K.

That chart is a terrible way to display information. I stared at for 30 seconds which is basically my maximum attention span and couldn't really make sense of what it was plotting.

Could you explain to me how that chart is indicating you'll make greater than 75% power LOP at oh say 6,000 ft? Could you point out how that chart displays at ALL what percent power you can make? I'm not seeing that...

 

[dell30rb]

It took me a minute to figure out the chart as well. Actually I like that it suggests running rich of peak above 9500'. Makes sense to run about 50 ROP and get the extra HP to take advantage of the thinner air.

You're probably making 65% power at 6000 feet WOT and ROP. The chart is saying to avoid the area between peak and 50 ROP at that altitude.

Below 65% you can operate wherever you want. At 75% you want to be either LOP or more than 100 ROP.

 

[Henning]

Just watch your CHT, it will tell you all you need to know. If in doubt, raise RPM, the faster it turns the further from detonation the burn is since you have fixed ignition timing.

 

[GeorgeC]

Alas, I do most of my flying these days at 3000' in aircraft with neither CHT nor EGT gauges. Set 65%, lean to rough, enrich to smooth, fuggedaboutit?

 

[AESpecialists]

Here's our take on LOP. ( I was going to say 'excessive', but that's too subjective) All numbers rounded to make the math easier.

First, let me point out that TCM 360 cylinders have surprisingly narrow service margins. There is not a lot between 'new' and 'toast' on bore, clearances etc.

Our shop sees a lot of bad cylinders come in with 500hrs or less, where the owner/operator has 'admitted' running lean of peak.

A set of six new IO360 cylinders is +- $7500, overhaul for a set is +-$4500 on average.

Using 500hrs that is $15hr and $9hr respectively. With 100LL here at $6/gal, that means you would need to save an additional 2.5 to 1.5 gph over conservative leaning to break even, not including R&R costs, and down-time.

A lot of the early work on lean of peak operations comes from the Pacific theater of WWII, extending the range of P-38's for photorecon etc. If you are not a twentysomething kid in a government supplied and maintained high performance aircraft, with the immediate prospect of being shot at, or having to swim the last hundred miles home then it behooves you to take a rational look at all the potential pluses and minuses of the LOP bandwagon.

 

[KSMooniac]

Our shop sees a lot of cylinders come in with 500hrs or less, where the owner/operator has 'admitted' running lean of peak.

A set of six new IO360 cylinders is +- $7500, overhaul for a set is +-$4500 on average.

Using 500hrs that is $15hr and $9hr respectively. With 100LL here at $6/gal, that means you would need to save an additional 2.5 to 1.5 gph over conservative leaning to break even, not including R&R costs, and down-time.

Your (faulty) assumption is that LOP ops are killing cylinders. It can also be attributed to poor assembly of the cylinders at the factory, which is the more common reason for modern cylinders.

 

[AESpecialists]

Your (faulty) assumption is that LOP ops are killing cylinders. It can also be attributed to poor assembly of the cylinders at the factory, which is the more common reason for modern cylinders.

A poorly assembled cylinder is more likely to suffer 'infant mortality'. We see those too, but they aren't part of this discussion.

To the experienced eye, and our cylinder shop does over a thousand cylinders a year, the effects of over-lean operation are readily apparent in the size shape and color of deposits, in the softening of the edges of the piston crown and the state of the valves - particularly the exhuast.

 

[Checkout_my_Six]

A poorly assembled cylinder is more likely to suffer 'infant mortality'. We see those too, but they aren't part of this discussion.

To the experienced eye, and our cylinder shop does over a thousand cylinders a year, the effects of over-lean operation are readily apparent in the size shape and color of deposits, in the softening of the edges of the piston crown and the state of the valves - particularly the exhuast.

how far lean does one need to go for this to occur?

 

[KSMooniac]

and what does an exhaust valve look like that fails due to LOP ops?

 

[Henning]

A poorly assembled cylinder is more likely to suffer 'infant mortality'. We see those too, but they aren't part of this discussion.

To the experienced eye, and our cylinder shop does over a thousand cylinders a year, the effects of over-lean operation are readily apparent in the size shape and color of deposits, in the softening of the edges of the piston crown and the state of the valves - particularly the exhuast.

Hmmm... Tell me about the 'size and shape' and color of these deposits from running LOP?

 

[James331]

Every piston operator I've flown for forbids LOP ops.

I sure ain't going to fly my newly acquired 185F LOP.


To each their own.

 

[AESpecialists]

Hmmm... Tell me about the 'size and shape' and color of these deposits from running LOP?

A normal piston crown will develop a layer of hard combustion deposits that range from medium to very dark grey. Excessively rich running, or high oil consumption trends more to black, softer, and well, oiler.

LOP operation yields deposits that are pale grey to white, with some evidence of colours The edges of the piston will be sparsely covered, or bare, with sometimes a softening of the edges of the piston crown.

 

[Henning]

So which deposits are more likely to cause valve and cylinder issues?