Oil Consumption 2.5 qts in 1 hour! IO-360 A1A

[Cyril Gibb]

6 hours ago, PT20J said:

If I fly a M20J at 3000’ density altitude at 75% BHP and 50F ROP with CHT of 360F, exactly what damage would you expect that would shorten cylinder life and how do you know that?

A bit of a straw man, I think.  The OP says nothing of limiting power to 75%, nor does he mention 100 ROP only above 7500.

Taking only the information the OP provided at face value, he uses 100 ROP in all flight regimes without regard to MP or density altitude.

 

[bradp]

Let me rephrase- higher ICP creates higher internal temperatures for a given air fuel mass and is reflected in the heat delivered to that mass of cylinder.  This should be reflected in yes higher CHT.  If the cooling is adequate you are adequately extracting the flow of heat, but you are certainly making more pressure and making more heat to begin with.   Higher internal pressures also puts some unquantified additional stress on the internal components including valve train etc.  I'm leaving out the effect of low level detonation on all those fluid metal interfaces because I am not versed in it at all.  At the same settings ROP and LOP, you are running your engine harder than if at LOP and producing more power.  Does that mean you’re going to melt a cylinder or are significantly detonating.  No of course not.  Every time I run my engine at idle I’m causing some unquantifiable small bit of wear.  I’m just trying to amortize that wear based on pilot behavior over 10-20 years.  Maybe ROP >75%has a slightly 0.5% higher interest rate attached to it... 

Question back - why are some engine configurations notorious for running through cylinders?  Is it all cowling and heat removal problems or does some of it have to do with the heat produced minus the heat extracted, the compression ratio of the cylinder, valve train piling and cooling, etc etc .  I bet a lot of those configurations have to do with how the pilot chooses to run the engine.  

 

[N201MKTurbo]

This whole conversation is silly. It has nothing to do with ROP/LOP. The OP has a broken piston or ring. It happens some time.

Edited April 4, 2019 by N201MKTurbo

[Grandmas Flying Couch]

I appreciate all the feedback, I still haven't heard back from Mechanic.  I am going to install a g2 as soon as I get plane back.  Its 3.5 hours away by car.  I fly over nasty terrain, would like to have cht and egt on all 4 cyl.  I fly full throttle from takeoff to landing leaning above 5 or 6 k.  At about 2550 RPM (I adjust to smoothest RPM above harmonic no go region). 

[PT20J]

2 hours ago, N201MKTurbo said:

This whole conversation is silly. It has nothing to do with ROP/LOP. The OP has a broken piston or ring. It happens some time.

I agree. But some of the claims made around MS about operating LOP or ROP boggle my mind. I use both depending on what I'm trying to accomplish - I have no bias one way or the other. I've also instructed and flown at several operators of rental fleets comprising mainly Lycoming normally aspirated four-bangers, and they are very reliable. And, aircraft rented at wet hourly hobbs rates fly WOT and best power mixture a lot. Some of us are obsessing over cylinder pressures and red boxes too much, I think.  Of course these exist, but they are taken into account in the engine and airframe installation design. The primary parameter to watch when operating these engines is head temperature which is why I like Mike Busch's red box that starts at CHTs 400F and above - it fits with experience.

So, let's stop scaring the OP that his operating technique caused the damage. As you said, sometimes these things just happen.

[Marauder]

I think his oil consumption issue is related directly to his practice of doing touch n gos.


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[Grandmas Flying Couch]

1 minute ago, PT20J said:

I agree. But some of the claims made around MS about operating LOP or ROP boggle my mind. I use both depending on what I'm trying to accomplish - I have no bias one way or the other. I've also instructed and flown at several operators of rental fleets comprising mainly Lycoming normally aspirated four-bangers, and they are very reliable. And, aircraft rented at wet hourly hobbs rates fly WOT and best power mixture a lot. Some of us are obsessing over cylinder pressures and red boxes too much, I think.  Of course these exist, but they are taken into account in the engine and airframe installation design. The primary parameter to watch when operating these engines is head temperature which is why I like Mike Busch's red box that starts at CHTs 400F and above - it fits with experience.

So, let's stop scaring the OP that his operating technique caused the damage. As you said, sometimes these things just happen.

I agree, I believe these engines are designed to make TBO at best power settings.  I think avoiding the red box just puts LESS strain but I do not think best power kills engine as long as chts are in check.  Another words engine might go 2200 hours best power or 2800 hours lop, but I want to fly fast.  I will experiment once I have my g2 and use lop or rop depending on mission of the day as PT20J says

[N201MKTurbo]

All this being said, I once did a bone headed thing and forgot to richen the mixture before takeoff. 

A few minuets later I saw the CHT gauge pegged. My oil consumption went up to about two quarts an hour. I had to replace all the pistons.

It softened the pistons to where the piston pin holes elongated about 0.020" and the ring lands got malformed. I don't know how hot the CHTs were it was off the gauge and I didn't have a scanner. Probably >550.

I will never do that again.....

[Grandmas Flying Couch]

3 minutes ago, N201MKTurbo said:

All this being said, I once did a bone headed thing and forgot to richen the mixture before takeoff. 

A few minuets later I saw the CHT gauge pegged. My oil consumption went up to about two quarts an hour. I had to replace all the pistons.

It softened the pistons to where the piston pin holes elongated about 0.020" and the ring lands got malformed. I don't know how hot the CHTs were it was off the gauge and I didn't have a scanner. Probably >550.

I will never do that again.....

If I lean while waiting for takeoff, I try to leave hand on mixture, paranoid of doing this myself.  

[jaylw314]

14 minutes ago, Grandmas Flying Couch said:

I agree, I believe these engines are designed to make TBO at best power settings.  I think avoiding the red box just puts LESS strain but I do not think best power kills engine as long as chts are in check.  Another words engine might go 2200 hours best power or 2800 hours lop, but I want to fly fast.  I will experiment once I have my g2 and use lop or rop depending on mission of the day as PT20J says

Even if your engine operation contributed to a cylinder failure (and that's a big "if"), if you have a problem cylinder, you're just going to replace the problem cylinder, right?  As long as you don't cause a catastrophic failure, the worst you will do is replace cylinders early--engine operation technique shouldn't affect the bottom end of the motor or whether it meets TBO.  And the only way to cause catastrophic failure from engine operation is for you to cause pre-ignition, and if you're operating the way you describe, that shouldn't happen.

Granted, I think most of us continue to be paranoid about babying our cylinders to try to make them last because the cost is not trivial.  In the big picture, though, the cost of replacing a cylinder is small compared to the cost of an overhaul, and the two should not be conflated in our minds.

[jaylw314]

8 minutes ago, N201MKTurbo said:

All this being said, I once did a bone headed thing and forgot to richen the mixture before takeoff. 

A few minuets later I saw the CHT gauge pegged. My oil consumption went up to about two quarts an hour. I had to replace all the pistons.

It softened the pistons to where the piston pin holes elongated about 0.020" and the ring lands got malformed. I don't know how hot the CHTs were it was off the gauge and I didn't have a scanner. Probably >550.

I will never do that again.....

 

4 minutes ago, Grandmas Flying Couch said:

If I lean while waiting for takeoff, I try to leave hand on mixture, paranoid of doing this myself.  

Whenever I lean on the ground, I increase the throttle to 1200 RPM (what I typically use to start moving during taxi), and lean until it starts decreasing.  That way, I know that if I forget the mixture during takeoff, the engine won't go past 1200 RPM.  All that will happen is embarrassment  

[Grandmas Flying Couch]

5 minutes ago, jaylw314 said:

 

Whenever I lean on the ground, I increase the throttle to 1200 RPM (what I typically use to start moving during taxi), and lean until it starts decreasing.  That way, I know that if I forget the mixture during takeoff, the engine won't go past 1200 RPM.  All that will happen is embarrassment  

That's what I do, lean till stumble then turn in still smooth.  Cant add any power or she bogs

[jaylw314]

44 minutes ago, Grandmas Flying Couch said:

That's what I do, lean till stumble then turn in still smooth.  Cant add any power or she bogs

The main reason I increase the throttle to 1200 RPM first is that if I do it at idle RPM, it's easy to kill the engine, which is equally embarrassing

 

[carusoam]

9 hours ago, Grandmas Flying Couch said:

If I lean while waiting for takeoff, I try to leave hand on mixture, paranoid of doing this myself.  

Use a two three step approach....

0) lean for taxi... this will keep your plugs clean.

1) Leave your hand on the mixture... this can work, but at such a busy time your hand will come off the mixture knob without even telling you...

2) Lean so deeply, that when you go full throttle there is a bit of stumble that won’t seem right...

3) the run-up is done full rich, so this is another opportunity to remember to push the mixture in...

How many steps was that?

Best regards,

-a-

[jaylw314]

4 hours ago, carusoam said:

3) the run-up is done full rich, so this is another opportunity to remember to push the mixture in...

For the IFR folks out there, though, there may be a fairly long delay after the runup before takeoff, so I usually lean deep for taxi again afterwards.  Especially if you're trying to pick up an IFR clearance around LAX 

[cliffy]

On the flat 4s isn't there a Lycoming Bulletin  that allows flying at peak EGT below 75% power? 

[Shadrach]

On 4/4/2019 at 2:24 AM, PT20J said:

Help me understand some things, because I’m confused. 

I know what heat is, and I know what mass is, but what is heat mass and how does ICP affect it?

If I fly a M20J at 3000’ density altitude at 75% BHP and 50F ROP with CHT of 360F, exactly what damage would you expect that would shorten cylinder life and how do you know that?

 

I think Brad is suggesting that high heat and high pressure are a bad combination. His numbers are pretty conservative. Your numbers are not very conservative (75%@50ROP). In fact, that power setting is outside the factory recommendations for my airplane. I think your point is that the engine is under no eminent threat at that power setting. Inducing detonation in an NA injected Lycoming is nearly impossible at any setting. Nevertheless, some of them still need cylinder work at mid time. I don’t have any data to suggest that power settings have any bearing on mid time cylinder work, but I’d not begrudge someone setting conservative parameters. The thing is, those parameters keep shifting. 400 used to be the get your attention CHT then it was 380. if 380 is good, why not set the alarm for 370 if 370 is good why not...rinse and repeat enough times and people keep revising there parameters down to the point that they’re ultra conservative and proclaim anything outside their comfort zone as abusive. I am thrilled with the engine monitor tech we have today but it can get extreme. Folks managed to run engines to TBO long before we had decent monitors but you wouldn’t think that possible the way we talk today.

[EricJ]

4 hours ago, cliffy said:

On the flat 4s isn't there a Lycoming Bulletin  that allows flying at peak EGT below 75% power? 

Lycoming SI-1094D says peak EGT is best economy cruise for naturally aspirated carbureted engines equipped with EGT on the leanest cylinder.    Otherwise, lean to roughness or loss of power then enrichen to smooth operation for best economy.

https://www.lycoming.com/content/service-instruction-no-1094d 

 

Edited April 6, 2019 by EricJ

[Shadrach]

46 minutes ago, EricJ said:

Lycoming SI-1094D says peak EGT is best economy cruise for naturally aspirated carbureted engines equipped with EGT on the leanest cylinder.    Otherwise, lean to roughness or loss of power then enrichen to smooth operation for best economy.

https://www.lycoming.com/content/service-instruction-no-1094d 

 

That’s an interesting read. If I lean to rough and enrich until smooth, that puts me way leaner than I would ever want or need to be. At 4-5,000” I don’t start to feel any noticeable roughness until the vicinity of 100 LOP. By the time the engine gets rough I am way down on air speed. I actually see a second EGT rise just before it starts to sputter. This is without GAMIs. If I were to try to lean my engine without a monitor, the best instrument I have for the job is the ASI.

[cliffy]

Just as a point of reference- way before we had monitors i ran a Navajo for almost 1900 hrs with just a TIT gage, 

Changed only 3 cylinders in that time but I did pay attention to CHT and stage cooling. 

On a Navajo one can look out at the cowl at night and see through the cooling louvers and look at the bright orange exhaust system. Its a warm, fuzzy feeling :-)

[Shadrach]

9 minutes ago, cliffy said:

Just as a point of reference- way before we had monitors i ran a Navajo for almost 1900 hrs with just a TIT gage, 

Changed only 3 cylinders in that time but I did pay attention to CHT and stage cooling. 

On a Navajo one can look out at the cowl at night and see through the cooling louvers and look at the bright orange exhaust system. Its a warm, fuzzy feeling :-)

Same with a C421. It’s a nice warm glow...slightly dimmer than what you’d see being poured from a foundry crucible.

[cliffy]

Yes I know I've got several hundred hours a in a 421C

[Grandmas Flying Couch]

Results are back, stuck oil ring.  Compression rings gunked up shortly after.  Mech wants to send in cyclinder and piston for at least IRAN.  I don't know if I could have caused this, plane sat for two years before I bought it.  Oil was 7 hours per quart when I for it.  Stuck oil ring may have been from heat, fluke, or was partially stuck and getting worse since I had the plane.  

[Shadrach]

That cylinder looks amazing for having sat two years. Nothing that you did with the mixture knob caused this.  How do the cam and the lifters look?

[Hank]

4 hours ago, Shadrach said:

That’s an interesting read. If I lean to rough and enrich until smooth, that puts me way leaner than I would ever want or need to be. At 4-5,000” I don’t start to feel any noticeable roughness until the vicinity of 100 LOP. By the time the engine gets rough I am way down on air speed. I actually see a second EGT rise just before it starts to sputter. This is without GAMIs. If I were to try to lean my engine without a monitor, the best instrument I have for the job is the ASI.

Note that this Service Bulletin in for naturally aspirated, carbureted engines, which is not what you have in your F.

But it should be fine in my C, although I try to keep it to 70% or less myself.