Engine leaning

[Jenna]

Hi. I just discovered this board and it looks like a good place to ask my stupid questions. I say they are stupid because everyone tells me how easy it is, but it never seems easy to me.

For example: ROP (Rich of Peak). Peak What? Do I lean to peak RPM or peak EGT? I was told to lean until it runs rough, then richen it up a little bit, but it never runs rough. At least I don't get there because the tach or the egt gauge reaches a peak then starts to drop. Should I richen it up when I notice they are dropping, or should I keep leaning until the engine runs rough. And how can you tell when it is making so much noise? What does a rough engine sound or feel like?

Ok, second question: I keep reading that you should never apply power when lean. Does never really mean never? Can you add just a little power? Or if you want to add a little power do you have to go full rich, then move the throttle and lean all over again? and how about when you are taxiing? On a hot day if I am idling, I will lean it out. When I start a long taxi do I need to go rich first, add throttle to gain some speed, then lean it again?

And I just read somewhere that said you should check your EGT right after takeoff and during a long climb keep leaning to keep the EGT at the takeoff value. I always heard to keep it full rich during climb.

Why does something that is supposed to be so easy seem so hard?

 

[Jeanie]

Jenna, welcome to POA! Well, you will get a lot of answers on this subject. First of all what plane are you flying? The engine in a Cessna 152 is very bad about fouling plugs during taxi so, no, leave it lean for ground ops. I assume you are close to sea level so leaning isn't as necessary below 3000AGL until you are in cruise actually level and going somewhere. In the 152 you lean it till rough then richer it back 2 1/4 turns or so.

Go up with your CFI and ask her to lean the mixture to show you what rough is like. You say it's noisy? What kind of headset are you using?

 

[BillTIZ]

What are you flying and what engine monitor instruments do you have?
No EGT or CHT? Lean to peak RPM, then enrichen slightly.
Fuel flow gauge? Lean to fuel flow according to performance manual.
EGT, manufacturer recommendation, I use 1380F on the highest temp cylinder, IO-360 at 210 HP.

 

[JasonCT]

Greetings and welcome to POA Jenna!

 

[dwalt]

Welcome Jenna...as Sac Arrow said, a lot depends on the engine in the particular plane, but in general ROP refers to the following technique:

Lean out the mixture and watch the EGT rise. At some point, the EGT will reach a "peak" temperature, and then as you continue to lean out the mixture, the EGT will start to fall again. Richen the mixture again to reach that "peak" EGT, and then richen to slightly rich of peak (usually 50-75 degrees).

 

[DaytonaLynn]

hey Jenna:\
Welcome. Its great to see someone so close to my hometown on the board!

You will recieve very good info here.
There are not any stupid/dumb questions here. How do you think I know that?

 

[Sac Arrow]

Honestly, if you're flying a 172 or similar airplane, which I'm going to guess is the case, the technique of leaning until it runs rough and richening it slightly works perfectly fine.

Peak EGT is approximately the exhaust gas temperature where the air fuel mixture is stoichiometrically correct. Richer (ROP) there is more gas than air. Full rich during climbout is used so that the excess fuel can keep the combustion chamber temperatures cools enough to prevent detonation. Lean of peak (LOP) is where there is more air than fuel.

Regarding your second question, you don't have to richen the mixture if you aren't adding more power than your POH specifies for operating at a full rich mixture, like climbout. If you were in cruise, pull your power, and add the power back you don't need to mess with the mixture.

 

[bbchien]

Welcome Jenna...as Sac Arrow said, a lot depends on the engine in the particular plane, but in general ROP refers to the following technique:

Lean out the mixture and watch the EGT rise. At some point, the EGT will reach a "peak" temperature, and then as you continue to lean out the mixture, the EGT will start to fall again. Richen the mixture again to reach that "peak" EGT, and then richen to slightly rich of peak (usually 50-75 degrees).

And Jenna, this is actually happening non-synchronously, as in not all four peak at the same time, one is usually still rich while the others are already going lean.

If you are truly truly lean, say 100 lean on one of the 4 cyls and lean on all the others, of peak, advancing the throttle kills the engine. In that case you need to advance mixture.

I'm LOP in climb and cruise, but below 5,000 AGL, I'm full rich.

 

[nosehair]

And I just read somewhere that said you should check your EGT right after takeoff and during a long climb keep leaning to keep the EGT at the takeoff value. I always heard to keep it full rich during climb.

Why does something that is supposed to be so easy seem so hard?

Think of it like this: When you lean, you are reducing the amount of fuel that mixes with the air to produce the most efficient power-producing burn and push for the engine.
When the mixture knob is set full rich, it is set excessively rich for a better starting/ start-up combustion, but, then it needs leaning for idle and higher power settings. At idle, the fuel is excessively rich, and will not burn completely. Unburnt fuel leaves deposits on the spark plugs which deplete power.

After start, pull the mix knob out about an inch, or to a position that you have learned will be good for ground taxi.

Generally, the only time the mixture should be full rich is for start-up, and full throttle take-off.

At full throttle in the beginning of the T.O. roll, the airflow insufficient to cool the engine at full throttle, so in this case, the over-rich mixture helps cool the engine. But it is still over-rich and costing some performance.

As soon as you reach cruise climb airspeed, you should begin the leaning process.

I taxi out with micture leaned and do a lean check during my pre-flight run-up. I push mixture rich, then after I check mags and such at run-up rpm and mixture at full rich, I lean the mixture to look for the rise in RPM, and listen/feel for engine roughness. Usually RPM rises slightly and that is also the smoothest running place. Take this time at the run-up spot to feel out your mixture.

It will be a little different each day, or place. Mixture is affected by temp and pressure altitude, so you need to check it before each flight.

So after T.O. and reaching cruise/climb speed, lean to that sweet spot you found during the run-up, and keep tweaking the leaning as you climb or cruise, or descend. It is a part of the throttle control.

However, you don't really need to change the mix for slight temporary power changes. The engine will run best at the best leaned mixture setting, Even on T.O. The best power will come from a leaned engine, leaned at the full throttle position, and if only for a moment, it won't overheat the engine.

General overall fear of improper leaning causes most of us to be cautious and not lean enough. Mostly, this just causes fouled plugs, and poor gas performance, but in the end, fouled plugs can cause a sputter in a critical moment on final approach and put you a few feet short.

However, if it is over-leaned, it can also cause a sputter at a critical moment.

To me, the solution is to practice the leaning drill before each flight and get practiced at leaning.

 

[Jenna]

Hey thanks for all the replies. Sorry I forgot to say what type of plane I fly. It is a 1978 Cessna 172 with a 180hp engine. I have a fuel flow gauge and an EGT gauge and of course a tach. One thing that confuses me is that they all vary so much it is hard to tell how much is due to leaning. EGT may go up when I lean then go down then go up then go down. It seems to vary even when I am not changing anything. I have seen it go over 1500 and I think it would go higher if I kept leaning but I am afraid to lean more. So I don't know if I am leaning enough or too much. The tachometer will vary from 2350 to 2450 while cruising too. Just as I think it has peaked and is starting to go down, then it goes up again. Then it goes down again but I never notice the engine running rough and I am afraid to keep leaning it.

I got my license over a year ago but my CFI has moved and I don't really have anybody else to ask right now. My ex-husband was a pilot and got me hooked on flying, but he developed "other interests" so to speak. So I got the plane and he got the boot.

 

[poadeleted20]

First, welcome to PoA.

Second, take a look at the Lycoming Key Reprints site, go to Operation, and search on "mixture." You'll find a wealth of information that will probably answer questoins you would never even think to ask.

 

[murphey]

1. What airplane & engine are you flying?
2. What does the POH say about runup?
3. If there's nothing in the POH, have you read the engine manufacturer's recommendations/instructions on runup?
4. You're at sea level. It really doesn't matter until you're taking off from an airport that's at least 5000 MSL.


But to answer your question, you set the throttle to whatever the POH states. On most trainers (C172, cherokees) the engine is a Lycoming and the RPMs are usually 1800 for runup. Then you only touch the mixture, decreasing it until you see the RPM go up, probably 50 - 100 RPM - that's your Peak RPM, then increase the mixture a bit. You'll see the RPMs drop a bit. In a C172 with the vernier (knob that rotates), probably half turn, maybe more, but that depends entirely on the engine.

As for seeing the RPMs change in flight, that's to be expected. These engines and the instruments are not what you might call "finely tuned or calibrated".

Prop spinning? Engine running? Still in the air? Don't worry everything is fine.

 

[docmirror]

I'm a bit troubled about your engine changing 100 RPM with no control inputs or changes(if I read that right). This would tend to indicate that you have an issue with your engine, perhaps a vacuum leak in the intake area. Not to frighten you or anything but it's worth looking at. During level unaccelerated flight, your tach should remain pretty constant.

Now, on to leaning. I presume you want the application side of it and not the theory. So, you have an EGT gauge. When you are below about 2100 RPM, you can do basically anything with the mixture and not do any damage. Although this is not exactly 65% power, it's going to be close. So, when flying set your plane up in level flight at 2100 RPM, full rich and note the EGT setting. Now, pull the mixture and you will see the EGT go up as you lean the mixture until near perfect ratio of 14.7:1 of air to fuel. Your engine RPM may climb slightly, maybe 20-50 RPM as you are making more power. Make sure you don't accidentally climb as you lean.

Keep leaning and watch the EGT. It will reach a peak and begin to fall. You have just reached 'peak EGT', I won't go into the theory involved. Go back slightly rich so that you are at peak, check you are still level fight. Now continue to lean carefully and watch the EGT begin to fall. This is because you are now starving the engine of fuel for the amount of air entering. The air to fuel ratio will be 15:1, or 15.5:1, or even 16:1. You will also note you are losing power! Yup, this makes sense, because fuel is power. Since you have a fixed pitch prop, the engine tach will begin to fall as you pull back to maintain level flight(lift+thrust = drag+weight), as thrust goes down, lift has to be increased.

At some point in your leaning after you have passed peak EGT, the engine will start to run rough. I don't know when, but it will start to run rough because there's just not enough fuel to support combustion in one or more of the cylinders and they will sputter. Once you find this point, richen the mixture knob very slowly until the engine runs smooth, but before you reach the peak EGT observed before. You are now running lean of peak(LOP) and are saving fuel and your engine from unneeded wear.

Sadly, this position of the mixture knob is not fixed because lean operations are affected by altitude, temp, RPM, load, etc. But it's good to know how to find it so that you can use the same process to find LOP anytime. Just set up your cruise power, lean the mixture, note peak, keep leaning until rough, then just nudge the mixture back in until it runs smooth. Since it's carburated, and you don't have a 4 cylinder EGT, each cylinder will be at different places on the EGT curve. If you are operating at 75% power it might be best not to run LOP as one cylinder may be running at peak EGT and that could cause damage. However, at lower power settings you can safely run LOP because there isn't enough pressure in the cylinders to do damage.

Maybe have your intake boots and gaskets checked for air leaks. It's a common fault and isn't really cause for concern, but might be looked at.

 

[Tom-D]

I'm a bit troubled about your engine changing 100 RPM with no control inputs or changes(if I read that right). This would tend to indicate that you have an issue with your engine, perhaps a vacuum leak in the intake area. Not to frighten you or anything but it's worth looking at. During level unaccelerated flight, your tach should remain pretty constant.

Why would a constant vac leak cause a fluctuating RPM?

 

[docmirror]

Why would a constant vac leak cause a fluctuating RPM?

You added the word 'constant' to my description, you can then explain your own question.

 

[Henning]

Hey thanks for all the replies. Sorry I forgot to say what type of plane I fly. It is a 1978 Cessna 172 with a 180hp engine. I have a fuel flow gauge and an EGT gauge and of course a tach. One thing that confuses me is that they all vary so much it is hard to tell how much is due to leaning. EGT may go up when I lean then go down then go up then go down. It seems to vary even when I am not changing anything. I have seen it go over 1500 and I think it would go higher if I kept leaning but I am afraid to lean more. So I don't know if I am leaning enough or too much. The tachometer will vary from 2350 to 2450 while cruising too. Just as I think it has peaked and is starting to go down, then it goes up again. Then it goes down again but I never notice the engine running rough and I am afraid to keep leaning it.

I got my license over a year ago but my CFI has moved and I don't really have anybody else to ask right now. My ex-husband was a pilot and got me hooked on flying, but he developed "other interests" so to speak. So I got the plane and he got the boot.

LOL, it's easier to fly with someone and teach them in 3 minutes than it is to explain it. Basically watch your EGT as you lean when you see the needle reach its peak, that is 'Peak', before then you are rich of peak or ROP after that you are LOP or lean of peak.

 

[MAKG1]

LOL, it's easier to fly with someone and teach them in 3 minutes than it is to explain it. Basically watch your EGT as you lean when you see the needle reach its peak, that is 'Peak', before then you are rich of peak or ROP after that you are LOP or lean of peak.

And the mistake that everyone makes early on is to expect instant feedback from the EGT. It takes a bit. You make a mixture adjustment, wait for EGT to settle, make another adjustment, etc. If you just crank it out continuously, you'll hunt around for the peak.

With a fuel flow gauge, you can approximate the mixture well by setting it to the book flow rate for conditions.

 

[gismo]

And the mistake that everyone makes early on is to expect instant feedback from the EGT. It takes a bit. You make a mixture adjustment, wait for EGT to settle, make another adjustment, etc. If you just crank it out continuously, you'll hunt around for the peak.

As you lean past peak, the EGT is likely to rise somewhat after falling if the cylinder to cylinder mixtures are consistent. If the mixtures aren't balances well the engine will get rather rough before the EGT starts to rise again. At the point where the EGT begins to rise on the lean side of peak the mixture is excessively lean (won't hurt anything but this is wasting fuel).

A few other things to remember:

1) Don't lean to anywhere near peak EGT at full or near full power (full throttle is not full power except at low DA so leaning to peak is OK with ful throttle above about 6000MSL on a 172).

2) A single EGT gauge may be sensing the EGT of one cylinder or the "average" across multiple cylinders. If only one cylinder is sensed it's supposed to be the one that reaches peak EGT first (from the rich side) but that's rarely the case under all operating conditions. If multiple cylinders are sensed (e.g. two on one side) the "peak" is likely to be much wider (i.e. small change in EGT for a relatively large change in mixture) and may show multiple peaks of nearly the same temperature.

3) Many engines simply will not run smoothly LOP. For carbureted engines it may help to add carb heat and closing the throttle slightly (from wide open) helps on many carbureted and injected engines.

4) GAMI has built a business on selling "balanced" injectors that improve engine's abilities to run LOP smoothly.

5) To really understand what's going on as you lean it really helps to have the ability to see the EGT of each cylinder simultaneously, something that's provided by an "engine monitor".

6) Operating LOP improves fuel economy and is considered to be generally better for the engine.

7) For years pilots were taught that leaning "excessively" will "burn up the valves". This has pretty well been proven to be total BS when leaning is performed properly. OTOH, it is true that leaning insufficiently (i.e running ROP but not rich enough) at high power (more than 60-65%) is bad for engines.

8) Mixtures leaner than best power (around 80°F ROP) will result in a reduction in power and airspeed.

9) Some pilots may recommend running full rich below an arbitrary altitude like 5000 MSL. This is NOT a good practice for most engines if taken literally but it's not a bad idea for takeoff and climb power. In cruise there are benefits to leaning at any altitude.

 

[bobmrg]

I note the use of the word "afraid" quite often in your post. Are you afraid of the engine quitting? My suggestion would be to go up (with an instructor if you feel the need), get a bunch of altitude, and slowly pull the mixture knob out until the engine runs rough and then keep pulling. The engine will quit and you will be flying a glider. Your engine needs three things in order to develop power: fuel, compression, and spark, and you still have compression and spark. Push the mixture back in to return fuel to the equation and the engine will start. Honest! I went through this exercise with all of my students because a significant number were wary of the red knob.

When you are convinced that having the engine stop is not the end of the world, go back to the lean-until-rough-then-richen-a-tad method. As others have noted, it takes a while for the EGT to react to change. Ever notice that when you push the bread down in the toaster the heating elements don't get hot instantaneously? Same thing with an EGT.

Bob Gardner

 

[Sac Arrow]

So basically, what you are saying, is you won't toast your engine by leaning it out.

 

[Tom-D]

You added the word 'constant' to my description, you can then explain your own question.

Vac leaks don't change with out changing the throttle. (MAP) so why would the engine fluctuate?

 

[Tom-D]

So basically, what you are saying, is you won't toast your engine by leaning it out.

You can not harm any engine by removing fuel.

It will simply quit. as it does when you pull the mixture to shut down, you can harm an engine by not removing enough fuel as in 50-100 Rich of Peak. This is usually the best power range and will cause some engines to over heat and run too high of CHTs and cook cylinders. not all engines have this problem, but big bore continentals are know for short cylinder life because of this.

 

[N801BH]

..... My ex-husband was a pilot and got me hooked on flying, but he developed "other interests" so to speak. So I got the plane and he got the boot.

Welcome to POA......

You must have had a good attorney.... You got the plane..

 

[MAKG1]

You can not harm any engine by removing fuel.

no no no NO NO NO NO NO !

Run a turbocharged engine with more than a smidge of boost lean and full throttle, and you can do a tremendous amount of damage in a very short time.

Naturally aspirated engines can detonate lean under high power conditions. While this isn't likely to cause a lot of damage unless it's severe, it does remove small amounts of aluminum from piston heads. If severe, it can break piston rings and cause serious blow-by and oil consumption problems. That usually won't cause an engine failure unless you burn all the oil first, but it's very expensive to fix. It might cause a low-power condition, which would have bad consequences if operating near performance limits.

Now, at cruise power in a 172, you won't harm anything by removing fuel. Even at climb power, you won't harm much in a 172 (but you will weaken the cylinder castings if the CHT isn't under control). But it's severely wrong to say you won't do any damage to any engine.

If you meant to say you won't damage an engine by removing all the fuel, that's true. But only removing some of it (incorrectly) is a bad thing, and can be a really bad thing.

 

[Tom-D]

no no no NO NO NO NO NO !

Run a turbocharged engine with more than a smidge of boost lean and full throttle, and you can do a tremendous amount of damage in a very short time.

Naturally aspirated engines can detonate lean under high power conditions. While this isn't likely to cause a lot of damage unless it's severe, it does remove small amounts of aluminum from piston heads. If severe, it can break piston rings and cause serious blow-by and oil consumption problems. That usually won't cause an engine failure unless you burn all the oil first, but it's very expensive to fix. It might cause a low-power condition, which would have bad consequences if operating near performance limits.

Now, at cruise power in a 172, you won't harm anything by removing fuel. Even at climb power, you won't harm much in a 172 (but you will weaken the cylinder castings if the CHT isn't under control). But it's severely wrong to say you won't do any damage to any engine.

If you meant to say you won't damage an engine by removing all the fuel, that's true. But only removing some of it (incorrectly) is a bad thing, and can be a really bad thing.

Your post assumes that you are running in the "Decon's" Red box, rich of peak, Knowing that re-read my post.

running any where lean of peak will never harm your engine. but remember the induction system in flat engines is not a balanced system, you may leave 1 or 2 cylinder rich of peak if you do not lean enough, This is why some engines can not be run lean of peak. simply because you will have some cylinders at lean misfire before the others are lean of peak.

 

[gismo]

no no no NO NO NO NO NO !

Run a turbocharged engine with more than a smidge of boost lean and full throttle, and you can do a tremendous amount of damage in a very short time.

Depends on what you mean by lean and where you are WRT power output.

Naturally aspirated engines can detonate lean under high power conditions. While this isn't likely to cause a lot of damage unless it's severe, it does remove small amounts of aluminum from piston heads. If severe, it can break piston rings and cause serious blow-by and oil consumption problems. That usually won't cause an engine failure unless you burn all the oil first, but it's very expensive to fix. It might cause a low-power condition, which would have bad consequences if operating near performance limits.

Now, at cruise power in a 172, you won't harm anything by removing fuel. Even at climb power, you won't harm much in a 172 (but you will weaken the cylinder castings if the CHT isn't under control). But it's severely wrong to say you won't do any damage to any engine.

With any gasoline powered piston aircraft engine (NA or supercharged) there are mixture ranges which are detrimental to the engine above certain output power, but any such engine that will run smoothly sufficiently on the lean side of peak EGT can be operated there without harm, and in general this is better for the engine's longevity than ROP operation.

And based on what I've assimilated, the typical cause of piston and ring damage isn't detonation but rather pre-ignition (often accompanied and/or preceded by detonation).

 

[DavidWhite]

Just lean it until you get scared, then richen it back up until you aren't scared anymore.

 

[N801BH]

Just lean it until you get scared, then richen it back up until you aren't scared anymore.

ya got to love kids...

 

[Henning]

And the mistake that everyone makes early on is to expect instant feedback from the EGT. It takes a bit. You make a mixture adjustment, wait for EGT to settle, make another adjustment, etc. If you just crank it out continuously, you'll hunt around for the peak.

With a fuel flow gauge, you can approximate the mixture well by setting it to the book flow rate for conditions.

Actually, the best way to do it is to just yank back until the engine almost dies, push it in until it runs then keep richening slowly until you peak then lean back to the setting you desire.

 

[Jenna]

Ok, I have read over this thread a couple of times. I cut and pasted most of the comments into a word document. I am beginning to understand it but I am going to read over it a few times before I go up again and then practice leaning until it quits. (If I die, I'm coming after you Bob Gardner!).

But I have one more question for now: If it is ok to run LOP, and it is ok to run ROP, then why is it so bad to lean it until some cylinders are lean, but others are still rich? At least that is what I think I read.

 

[N801BH]

Ok, I have read over this thread a couple of times. I cut and pasted most of the comments into a word document. I am beginning to understand it but I am going to read over it a few times before I go up again and then practice leaning until it quits. (If I die, I'm coming after you Bob Gardner!).

But I have one more question for now: If it is ok to run LOP, and it is ok to run ROP, then why is it so bad to lean it until some cylinders are lean, but others are still rich? At least that is what I think I read.

a motor lives a hellish life..... Temps are ALOT higher then you can imagine.... The distribution of fuel to each cylinder are critical to smooth operation... carbs will generally not give even distribution and the "split" in temps because one cylinder is rich and the other one is lean can be catastrophic..... Fuel injected motors usually have a more even spread and are easier to go to LOP......

Look at this pic closely.... When you see 1400 f on your EGT gauge the exhaust pipes that are 3 feet infront of you are glowing this HOT...

 

[Henning]

Ok, I have read over this thread a couple of times. I cut and pasted most of the comments into a word document. I am beginning to understand it but I am going to read over it a few times before I go up again and then practice leaning until it quits. (If I die, I'm coming after you Bob Gardner!).

But I have one more question for now: If it is ok to run LOP, and it is ok to run ROP, then why is it so bad to lean it until some cylinders are lean, but others are still rich? At least that is what I think I read.

There is a small range of ROP at high power outputs where the cylinder can see detonation which will eat a hole in the piston. This is almost impossible to achieve in a 172 or other O-320 powered plane.

 

[N801BH]

There is a small range of ROP at high power outputs where the cylinder can see detonation which will eat a hole in the piston. This is almost impossible to achieve in a 172 or other O-320 powered plane.

Henning is correct...............

Higher powered planes can do this to a perfectly good pistons....


Of course I had 7 more good pistons to "limp" back to the airport with...

 

[docmirror]

But I have one more question for now: If it is ok to run LOP, and it is ok to run ROP, then why is it so bad to lean it until some cylinders are lean, but others are still rich? At least that is what I think I read.

My answer, and my answer only(will not speak for others) is that you can safely do anything you want with the mixture control as long as you are below 65% power. This is because you cannot achieve a dangerous internal cylinder pressure that will damage any parts of your (specific) engine. We don't know if you have some lean, and some rich of peak unless you have a 4 point EGT.

What is best, is to not linger at peak EGT, in case some are too hot, and cause trouble when above 65% power. It's unlikely, but possible for one cylinder to be ROP while the others are beginning to sputter due to lean misfire.

That's why I, and I alone recommended you investigate a potential vacuum leak. A vacuum leak could cause your RPM to fluctuate, and it could also cause a large delta in lean readings between cylinders due to excess air getting into some cylinders. I stand by that recommendation, but of course you can continue to operate as you are rich of peak. Since you have a single point EGT that might be safer.

 

[Tom-D]

But I have one more question for now: If it is ok to run LOP, and it is ok to run ROP, then why is it so bad to lean it until some cylinders are lean, but others are still rich? At least that is what I think I read.

in most cases it is not harmful, but it really depends upon which engine you have, most 0-300 and 0-320 engines will have the cylinders go over peak close enough together to get all cylinders out of the rich of peak area that has enough fuel to do harm.

 

[Tom-D]

That's why I, and I alone recommended you investigate a potential vacuum leak. A vacuum leak could cause your RPM to fluctuate, and it could also cause a large delta in lean readings between cylinders due to excess air getting into some cylinders. I stand by that recommendation, but of course you can continue to operate as you are rich of peak. Since you have a single point EGT that might be safer.

there are lots of ways to tell which cylinder is running hot or rich. simply looking at the plugs is the easiest.

 

[Tom-D]

Henning is correct...............

Higher powered planes can do this to a perfectly good pistons....


Of course I had 7 more good pistons to "limp" back to the airport with...

liquid cooled auto engines, is way out of the realm of aircraft aircooled engines.

 

[Henning]

My answer, and my answer only(will not speak for others) is that you can safely do anything you want with the mixture control as long as you are below 65% power. This is because you cannot achieve a dangerous internal cylinder pressure that will damage any parts of your (specific) engine. We don't know if you have some lean, and some rich of peak unless you have a 4 point EGT.

What is best, is to not linger at peak EGT, in case some are too hot, and cause trouble when above 65% power. It's unlikely, but possible for one cylinder to be ROP while the others are beginning to sputter due to lean misfire.

That's why I, and I alone recommended you investigate a potential vacuum leak. A vacuum leak could cause your RPM to fluctuate, and it could also cause a large delta in lean readings between cylinders due to excess air getting into some cylinders. I stand by that recommendation, but of course you can continue to operate as you are rich of peak. Since you have a single point EGT that might be safer.

Peak EGT is the recommended mixture for several Lycoming engines, it's actually the 60°-85° ROP setting at high power (.5:1 HP to Cubic Inch ratio hardly qualifies for 'high power' even when making max rated power), you won't get into it right away either, CHT has a factor to play in detonation as well.

 

[docmirror]

Peak EGT is the recommended mixture for several Lycoming engines, it's actually the 60°-85° ROP setting at high power (.5:1 HP to Cubic Inch ratio hardly qualifies for 'high power' even when making max rated power), you won't get into it right away either, CHT has a factor to play in detonation as well.

Whatever you want to argue minutia about, please argue with yourself. If the engine is rated at 180HP and it's a 360Cu In, then 180HP is high power. Now, just to tweak your nose some more, I can detonate an IC engine at room temp - so, na-ne-na-ne-boo-boo on your CHT argument.

You aren't helping the OP, and you're annoying me - but I suspect that was your original goal. Go ahead, get the last word in, the whole board expects it.

Sigh,,,,,

 

[JOhnH]

And the degeneration of another perfectly good thread continues.