1978 M20J turbo normalized - Low(er) oil pressure above 12k

[N201MKTurbo]

Just now, Shadrach said:

It does recover it, but not at the same MP as a normally aspirated bird. 

That's my point, it isn't the same as as a NA airplane at the same power settings.

[Shadrach]

45 minutes ago, N201MKTurbo said:

That's my point, it isn't the same as as a NA airplane at the same power settings.

I know it was. I was just trying to articulate it as simply as possible.

Edited June 22, 2021 by Shadrach

[KSMooniac]

For the OP and anyone else that wants to learn more than old wives tales passed along by CFIs and mechanics, you can search up all of John Deakin's old Pelican's Perch columns on engine management and read them in bite-size chunks. Then go here: https://www.advancedpilot.com/onlinecourse.html and you'll learn even more! Sadly, I don't believe the live course is offered now... It was the best learning experience I've ever had in aviation, or engineering for that matter.

It will change the way you fly, and make you a much smarter/better-informed owner. (Even if you don't fly LOP!)

If I had the TN installed on my J, I'd be running around at 30", maybe 2350 RPM and 11 GPH. And my oil and cylinder temps would be noticeably lower too.

Sent from my LM-V405 using Tapatalk

[carusoam]

The STC for the turbo system is nicely written… (given above)

I read and understood everything in five minutes or so…

What stands out…

Very little data is included.

Saying just use the 201 data is nice… but the purpose of the turbo is to reach altitudes with power settings that are not available to the 201…

Not really a cop out… just very misleading to the people new to aviation…

 

What I found interesting…

Two modes of operation… one ROP. The other, less ROP…

Know the temp limits of your turbo’s vanes… and stay below them…

If using LOP, become familiar with the big pull… this allows the TIT to rise and fall quickly without staying in the hot zone for too long…

Staying in the hot zone should turn your vanes into nubs using the vane stretch method…

 

How this all applies to the OP’s question and thread title…

You have to know…. The oil cooler that came with the Mooney as an M20J….   wasn’t designed to handle the extra heat of the high power settings COMBINED with the thinner air of the higher altitudes that are now available to the turbo owner…

 

Do what other M20J owners do… check the oil cooler with an IR thermometer to see if it has any clogged tubes… check the fins from both sides to see if any have been crushed…

Get the oil cooler flushed out… or OH’d…

Check the thermostatic temperature control valve in the oil cooler aka the Vernatherm…. To prove that it is working correctly…

The STC for adding 30 more HP for the IO550 covers a dozen pages…

This turbo does a whole lot more… with documentation that seems to be a whole lot less… 

Looks like a great device…

The TAT device is similar for the IO550 in Scott’s plane above…

Adding turbo normalization comes with the cost of being an advanced engine operator… to keep from accidentally shortening their lifespans…

Typically it’s not a safety issue…. As much as it is an economics issue…

The economics kind of get covered loosely, or not at all…

Reminder to learn about engine oil temps, how hot they really get compared to what the single  instrument says…. And know what temperature oil degradation begins to occur…

This will help you decide  how often to change your oil… which may be twice what the NA IO360 recommends…

 

When you see the current OilT is only 20(?) degrees higher than the standard OilT… realize how much closer to the degradation temperature it is…

The onset of degradation of engine oil starts about 250°F…

Expect the bearings inside the turbo are seeing temps much closer to the EGT going through the vanes….  This is often the cause of destruction for turbos that have their oil lines get clogged…

There typically isn’t a flow meter or temp gauge on the turbo oil lines… there is a big assumption they are working correctly…

Also be familiar with proper turbo cooling knowledge… it isn’t the old style of letting the turbo cool anymore… the old procedures don’t work as well as the knew knowledge does…

PP thoughts only, not a mechanic…

Best regards,

-a-

 

[Shadrach]

16 hours ago, N201MKTurbo said:

First off Mr. Sandman advocated running at full power at peak TIT. That's about as bad as it gets. There are no power settings in the updated POH for the turbo installation. It just says to use the sea level power charts. I don't believe them for a second.

I also wonder why everybody thinks an A&P knows so much about running these engines? They aren't taught much about it in A&P school. There aren't many questions about it in the tests. Pilots on the other hand spend countless hours running these things and watching what happens under different conditions. All A&Ps are taught is how to take them apart and put them back together again.

I don’t think peak (or richest cyl) is as bad as it gets. Indeed, I find it to be a  reasonably cool place to run. My CHTs are on the way back down by the time I hit peak. My recollection is that at peak EGT, CHTs are typically a bit cooler than 100ROP. 

Edited June 22, 2021 by Shadrach

[Shadrach]

5 hours ago, carusoam said:

The STC for the turbo bullet is nicely written… (given above)

I read and understood everything in five minutes or so…

What stands out…

Very little data is included.

Saying just use the 201 data is nice… but the purpose of the turbo is to reach altitudes with power settings that are not available to the 201…

Not really a cop out… just very misleading to the people new to aviation…

 

What I found interesting…

Two modes of operation… one ROP. The other, less ROP…

Know the temp limits of your turbo’s vanes… and stay below them…

If using LOP, become familiar with the big pull… this allows the TIT to rise and fall quickly without staying in the hot zone for too long…

Staying in the hot zone should turn your vanes into nubs using the vane stretch method…

 

How this all applies to the OP’s question and thread title…

You have to know…. The oil cooler that came with the Mooney as an M20J….   wasn’t designed to handle the extra heat of the high power settings COMBINED with the thinner air of the higher altitudes that are now available to the turbo owner…

 

Do what other M20J owners do… check the oil cooler with an IR thermometer to see if it has any clogged tubes… check the fins from both sides to see if any have been crushed…

Get the oil cooler flushed out… or OH’d…

Check the thermostatic temperature control valve in the oil cooler aka the Vernatherm…. To prove that it is working correctly…

The STC for adding 30 more HP for the IO550 covers a dozen pages…

This turbo does a whole lot more… with documentation that seems to be a whole lot less… 

Looks like a great device…

The TAT device is similar for the IO550 in Scott’s plane above…

Adding turbo normalization comes with the cost of being an advanced engine operator… to keep from accidentally shortening their lifespans…

Typically it’s not a safety issue…. As much as it is an economics issue…

The economics kind of get covered loosely, or not at all…

Reminder to learn about engine oil temps, how hot they really get compared to what the single  instrument says…. And know what temperature oil degradation begins to occur…

This will help you decide  how often to change your oil… which may be twice what the NA IO360 recommends…

 

When you see the current OilT is only 20(?) degrees higher than the standard OilT… realize how much closer to the degradation temperature it is…

The onset of degradation of engine oil starts about 250°F…

Expect the bearings inside the turbo are seeing temps much closer to the EGT going through the vanes….  This is often the cause of destruction for turbos that have their oil lines get clogged…

There typically isn’t a flow meter or temp gauge on the turbo oil lines… there is a big assumption they are working correctly…

Also be familiar with proper turbo cooling knowledge… it isn’t the old style of letting the turbo cool anymore… the old procedures don’t work as well as the knew knowledge does…

PP thoughts only, not a mechanic…

Best regards,

-a-

 

Don’t mistake the turbo bullet STC for the M20 turbos STC. The bullet conversion involves a piston swap to lower compression ratio. The M20 turbos STC is turbo normalized so utilizes stock pistons.

[A64Pilot]

There is a huge misunderstanding about peak and how it’s terrible to operate at peak etc.

‘If your some arbitrary number, let’s use 65% power or less, then peak is a perfectly logical place to operate, you just don’t do it at high power. Real high power you operate full rich, yes you can go LOP, but your losing quite a bit of power, it does take some attention to ensure you don’t do damage too, leaving it full rich doesn’t and the assumption is if your operating at high power, you need it to take off or climb etc.

‘Lycoming has a problem with what mix ratios etc they can recommend, first and foremost they have to warranty the engine, if you break the thing operating it as they recommend, they have to pay for it. Secondly and likely just as important the sales dept would go nuts if they recommended a procedure that resulted in a significant loss of power

The only time you can operate a engine at full power or high power continuously and it not significantly shorten its life, is if it’s been de-rated. the TBM’s for example, their engine cores are 1700ish HP cores, derated to 800 or whatever so that at high altitude they still give good performance. So running one at 800 HP continuously down low isn’t going to hurt it, at least not the core, gearbox possibly.

Its not common to derate smaller piston engines.

People all the time complain about how their airplane engines are junk compared to cars, automobile engines do have several advantages, but the primarily reason they live so long is that only very rarely if ever are they operated at a aircraft power levels, and when they are, it’s usually only for a few seconds

 

[KSMooniac]

Actually the TAT installations on the Bonanza and SR22 have power settings to run 87% power LOP for cruise at 17.5 GPH, and that's where most folks run them from everything I've read in the last 14 years I've been paying attention. And those engines are 300 HP 550's (or 285? HP 520's on some Bo's), not de-rated engines like the 244 HP M20S installation. They run cool, make TBO, etc.

Perhaps Scott M will share a pic of his POH supplement on his TN A36 and some CHT and oil T data.

The Lycoming IO 360 will run LOP very well, and that's why I run mine that way and am anxious to TN it so I can run 80% or more power LOP and go much faster on just a little more fuel. LOP procedures were not widely known or shared when Sandman got the STC, and I bet his instructions would be quite different if he were to do it today with all of the evidence of the benefits and modern engine monitors to help.

A knowledgeable pilot/owner is free to learn all of the ways to operate their engine and choose what they feel is best. And it's not always what is in a POH! (the advanced pilot course has examples of bad POH procedures and contradictory info... and they give you the background and real data to really demonstrate the physics) Learn all you can, and decide for yourself.

Sent from my LM-V405 using Tapatalk

[smccray]

15 minutes ago, KSMooniac said:

Perhaps Scott M will share a pic of his POH supplement on his TN A36 and some CHT and oil T data.

I don't have it in an electronic form, but I found a link:  http://www.malusflyers.com/Malus_Flyers/Malus_Flyers_files/AFMS-550 Rev H.pdf

Even Tornado Alley played the game of saying "equal or better" to original POH.  In my mind that's a regulatory hurdle.  There is extensive info in the attached document about lean of peak operations.  I haven't read the detail, but the recommended setup changes based on the TAT setup, meaning WhirlWind II is a little different than the WhirlWind III.  The specifics probably don't really matter if you're looking for an operating methodology for a Mooney install, but the background is likely helpful- google is your friend.  All engine systems really have to be operating in good condition to get the performance out of the engine.

Garmin records all of the engine parameters every flight.  My CHTs rarely exceed 380, and then I make adjustments (e.g. fuel pump, mixture setting, airspeed) to reduce CHTs.  In cruise, CHTs are general low to mid 300s.  Oil temps are in the green.  Generally the oil only gets hot sitting on the ground at a busy airport waiting to depart.

I'm unable to to push 17.5 GPH thorough my engine generally and to stay cool.  In the winter I'm able to get to the low 17 GPH, but in the spring/summer I generally see ~16.5.  It may be because my engine is high time, or it may be something else- but I'm pretty close to book numbers on speed.  An interesting side note- when I installed new spark plugs, I installed cooler plugs.  I was able to push a little extra fuel through the engine and stay cool.  The engine is really fine tuned- small changes to the setup have an impact on the final results.

[Shadrach]

6 hours ago, A64Pilot said:

There is a huge misunderstanding about peak and how it’s terrible to operate at peak etc.

‘If your some arbitrary number, let’s use 65% power or less, then peak is a perfectly logical place to operate, you just don’t do it at high power. Real high power you operate full rich, yes you can go LOP, but your losing quite a bit of power, it does take some attention to ensure you don’t do damage too, leaving it full rich doesn’t and the assumption is if your operating at high power, you need it to take off or climb etc.

‘Lycoming has a problem with what mix ratios etc they can recommend, first and foremost they have to warranty the engine, if you break the thing operating it as they recommend, they have to pay for it. Secondly and likely just as important the sales dept would go nuts if they recommended a procedure that resulted in a significant loss of power

The only time you can operate a engine at full power or high power continuously and it not significantly shorten its life, is if it’s been de-rated. the TBM’s for example, their engine cores are 1700ish HP cores, derated to 800 or whatever so that at high altitude they still give good performance. So running one at 800 HP continuously down low isn’t going to hurt it, at least not the core, gearbox possibly.

Its not common to derate smaller piston engines.

People all the time complain about how their airplane engines are junk compared to cars, automobile engines do have several advantages, but the primarily reason they live so long is that only very rarely if ever are they operated at a aircraft power levels, and when they are, it’s usually only for a few seconds

 

To add to what Scott posted, I would say that I am 95% sure that both Continental and Lycoming TBO recommendations are based on 100% power. There are no recommendations with regards to power percentage and TBO.  There are indeed recommendations with regard to leaning and power percentage.

let’s talk about high power operations for a moment?

In what way does it increase wear on an engine?
 

Does it increase metal to metal friction and therefore wear the engine components out? Of course not. If you have metal on metal friction, power setting is the least of your worries. Under such a situation the engine’s useful life will likely be measured in minutes not hours. 

Does high power operation create more heat? Absolutely. There’s no getting around that burning higher volumes of fuel generates more heat. 
Is the aforementioned heat detrimental to engine life? Well that depends on how and how well that heat is removed from the engine.

Quick digression on Brake Specific Fuel Consumption (BSFC) here. Operating at mixture ranges with the lowest BSFC extracts the most work for the amount of fuel used/heat produced. Or simply stated this is the mixture range in which the highest proportion of the combustion event is converted to work and the lowest proportion of the combustion event is wasted as excess heat. This means that If you’re operating at a mixture setting outside of the min BSFC spectrum less of the fuel is doing the good work of moving the plane through the air and more of it is being pushed through the cooling fins as heat.

Does running at max RPM shorten engine life? Likely not. All things being equal (only possible with a CS prop) internal cylinder pressures go UP when RPM is reduced. So while the engine will complete less rotations over a given period of time the power strokes are completed under higher pressure. Engines are designed to easily accommodate whatever approved rpm setting we desire. There may be an argument that increasing the number of power strokes reduces engine life but I’ve never read or heard anyone articulate a good case for why.

it may seem like common sense that running at lower power levels conserves engine life. That is likely true when lower power levels correspond to lower heat levels. but it’s not always the case. It is indeed possible to run an engine at high power in a gentle way. The converse is also true. One can run engine at low power in the least gentle way.

I don’t recall if it was an email or web board exchange with Walt Atkinson where he said “it’s not how hard you run but how you run hard”.  It’s a simple but true statement.
 

Edited June 22, 2021 by Shadrach

[A64Pilot]

Any one with any actual engine experience knows that any engine operated continuously at high power won’t last nearly as long, from Sportfisherman Diesels to motorcycles, amy internal combustion engine that’s not seriously derated, a derated motor at 100% really isn’t at 100% of coiurse.

So far as Lycoming high power cruise, I don’t remember seeing any cruise power charts for higher than 75%.

‘High power loads everything in the engine to higher levels. bearings, rings, most everything, it’s not just temps, but temps are a large part of it. RPM does increase wear as there is more kinetic energy in the rotating components, and they stop and change direction often, and higher kinetic energy equates to higher bearing loads.

‘You’ll argue of course, but you can’t develop rated power in a NA engine LOP, and if you use ROP charts to determine power setting LOP, your not developing near chart power.

‘So how do you determine LOP percent power? Other than comparing air speeds achieved with chart settings I haven’t idea.

Most aircraft are NA, and most aircraft cruise at a altitude where actual high power isn’t possible 

[Shadrach]

4 hours ago, A64Pilot said:

Any one with any actual engine experience knows that any engine operated continuously at high power won’t last nearly as long, from Sportfisherman Diesels to motorcycles, amy internal combustion engine that’s not seriously derated, a derated motor at 100% really isn’t at 100% of coiurse.

So far as Lycoming high power cruise, I don’t remember seeing any cruise power charts for higher than 75%.

‘High power loads everything in the engine to higher levels. bearings, rings, most everything, it’s not just temps, but temps are a large part of it. RPM does increase wear as there is more kinetic energy in the rotating components, and they stop and change direction often, and higher kinetic energy equates to higher bearing loads.

‘You’ll argue of course, but you can’t develop rated power in a NA engine LOP, and if you use ROP charts to determine power setting LOP, your not developing near chart power.

‘So how do you determine LOP percent power? Other than comparing air speeds achieved with chart settings I haven’t idea.

Most aircraft are NA, and most aircraft cruise at a altitude where actual high power isn’t possible 

Actual engine experience would dictate that one understands the fundamental difference between various internal combustion engines. I’ve rebuilt number a number of engines on a number of different machines. I’ve seen air cooled twins hole pistons at moderate power settings.

We are talking about aeroengines specifically aeroengines with constant speed props. Here’s a simple question  using a normaly aspirated IO360 as an example - On climb out of a pilot reduces RPM from 2700 to 2500 how does that affect internal cylinder pressure?

 

LOP power can be approximated by fuel flow with reasonable accuracy  since all of the fuel is being consumed is used to make power. There is no surplus fuel being used to slow the combustion event.  I have verified this against ROP settings. You’re right, I cannot run 100% LOP.  Max power I can run lean of peak is right around 80% and that’s down low on a cold high pressure day. Maybe a little more with ram air open. I can easily run 70% power LOP I can also run 70% power ROP. The only difference is I save a little over a gallon an hour on the lean side and that the engine runs cooler. The downside being that I can never make as much power at a given altitude LOP as I can ROP. This problem is much diminished for turbo operators.  As an NA operator I takeoff and climb on the rich side. I’ve then lean for the best combination of power and BSFC. I’m on the East Coast and operate my aircraft between sea level and 12,500. As I climb from sea level up to cruise alt I transition from LOP to Peak to ROP depending on where I stop the climb.  Air is in short supply as you get higher so I use all of it for combustion and only need a small amount of surplus fuel to control the combustion event. Air is not in short supply down low so I use all of the gas for combustion and control the combustion event with surplus air.  This works out well considering it requires a great deal more fuel to manage the combustion event at the high power levels required to go fast at low altitude.

Edited June 22, 2021 by Shadrach

[A64Pilot]

By reducing RPM but keeping manifold pressure high, is known as lugging, yes peak cylinder pressures do increase, that’s why within reason don’t oversquare too much, the old teaching method of running square isn’t necessary, but it will keep a novice out of trouble.

Every fixed prop airplane that I have ever flown is way oversquare in takeoff and climb, most don’t have a manifold pressure gauge so it’s not apparent, but my little C-85 turns about 2300 Static if memory serves and of course at full throttle is about 30” manifold pressure, so it’s way oversquare every takeoff and climb, because you don’t reduce power even a little bit in climb with a mighty 85 HP, or you don’t climb.

Many or most of the old rules of thumb are exactly for that reason, if a novice follows them, they can’t hurt anything, it’s not that other operating methods aren’t just as feasible, but often they require some knowledge and attention, and a new pilot is often task saturated, they need simple operating rules like full rich above 75% power, don’t lean below 5,000 etc.

Of course we know altitude doesn’t mean squat for leaning, it’s manifold pressure that does, but that means the newby has to pay attention and make decisions, attention that may be better spent elsewhere.

RPM in and of itself usually doesn’t add all that much wear, but usually higher RPM comes with higher power, or why run higher RPM? High power output does decrease engine life, a low revving stationary diesel generator turning 1800 RPM (1500 in Europe) and at partial power can easily go 10,000 hours or more, identical engine in a Sportfisherman run 100 off of the top and close to max power is doing good to get 1,500.

Our engines combustion chambers and cylinders to some extent are air cooled, but the rest of the engine is oil cooled, the main and rod bearings, cam etc are oil cooled, and of course the oil is air cooled, oil is a transfer medium just like water is in a car.

‘The reason you get high oil temps when you run an engine hard is from higher than normal friction which creates higher than normal temps that the oil carries away. This higher friction of course causes wear.

‘Just remember this with engines, TANSTAAFL, There Ain’t No Such Thing As A Free Lunch

We operate engines pretty similar, except at high altitude I’ll run peak,I don’t usually like continuous ROP, I’m probably more conservative than most as an engine overhaul is more work and money than I want to put into it, I have a C-85 that while it runs fine and is only about half through TBO hour wise, needs overhauling. I’ll eventually get to it, but I don’t want if I can help it any un-scheduled events 

Edited June 22, 2021 by A64Pilot

[smccray]

29 minutes ago, A64Pilot said:

By reducing RPM but keeping manifold pressure high, is known as lugging, yes peak cylinder pressures do increase, that’s why within reason don’t oversquare too much, the old teaching method of running square isn’t necessary, but it will keep a novice out of trouble.

Every fixed prop airplane that I have ever flown is way oversquare in takeoff and climb, most don’t have a manifold pressure gauge so it’s not apparent, but my little C-85 turns about 2300 Static if memory serves and of course at full throttle is about 30” manifold pressure, so it’s way oversquare every takeoff and climb, because you don’t reduce power even a little bit in climb with a mighty 85 HP, or you don’t climb.

Many or most of the old rules of thumb are exactly for that reason, if a novice follows them, they can’t hurt anything, it’s not that other operating methods aren’t just as feasible, but often they require some knowledge and attention, and a new pilot is often task saturated, they need simple operating rules like full rich above 75% power, don’t lean below 5,000 etc.

I've heard the oversquare rule of thumb.  I haven't ever heard an explanation of why it's better for the engine.  I have tried an after takeoff RPM reduction to 2500 rpm and reduce the MP by 2", full rich.  The engine runs hotter compared to everything full forward.  In other words, more HP, cooler engine.  I don't know if it's just a Bonanza peculiarity, a Continental engine setup, or common to all plane/engine combinations, but it's easy to try in your own airplane.

In my J, I flew basically WOT, 2500 RPM, lean for constant EGTs in the climb, lean to peak in cruise (over 8K MSL).  Descend in the green WOT without changing the mixture, then power back/mixture to ROP to land.  It's pretty simple...

Edited June 22, 2021 by smccray

[A64Pilot]

25 minutes ago, smccray said:

I've heard the oversquare rule of thumb.  I haven't ever heard an explanation of why it's better for the engine.  I have tried an after takeoff RPM reduction to 2500 rpm and reduce the MP by 2", full rich.  The engine runs hotter compared to everything full forward.  In other words, more HP, cooler engine.  I don't know if it's just a Bonanza peculiarity, a Continental engine setup, or common to all plane/engine combinations, but it's easy to try in your own airplane.

In my J, I flew basically WOT, 2500 RPM, lean for constant EGTs in the climb, lean to peak in cruise (over 8K MSL).  Descend in the green WOT without changing the mixture, then power back/mixture to ROP to land.  It's pretty simple...

It’s very common for any engine to go into “power enrichment” at high throttle settings, so reducing power often leans the mixture and the engine gets hot. Even with the mixture at full it’s a little leaner with reduced throttle.

‘Not saying your Bo did this, just thst it’s common as extra rich at full throttle protects the engine.

https://www.aopa.org/news-and-media/all-news/1998/april/flight-training-magazine/the-economizer

It sometimes takes a lot of convincing a new turbine Ag pilot that it’s best to not run the turbine at max power unless necessary, because they got so used to running the R-1340 at max power until they were at a point to where they could reduce to 30/20 or so, wide open was cooler than backed off some, and it was due to power enrichment

Also often a power reduction in climb came with a airspeed reduction, and that is a reduction in cooling.

‘But operating an NA engine at full throttle until descent is pretty common, the reason it’s not so bad is at altitude, especially if you reduce RPM to a comfortable level the altitude has you at a much reduced power output,often well below 75%

‘It’s how I would operate the IO-520 in the 210. I would take off full throttle, reduce power to 23” after takeoff after gear and flaps up, reduce prop to 2500 which brings power back to 25”, lean to maintain EGT constant and in less than 5min I’m climbing through an altitude where I can’t maintain 25”, from then on maintain 2500 RPM and whatever manifold pressure full throttle would give me. Best speed was usually about 7500.

I reduced to 25 squared on the IO-520 because in the Cessna it was a 300 HP engine, with a 5 min limit, at 5 min you needed to reduce power to 285, the IO-520 in a Bonanza is I believe reduced by RPM to be a 285 HP engine.

Edited June 22, 2021 by A64Pilot

[A64Pilot]

Oversquare isn’t recommended because if you get extreme with it, due to higher peak cylinder pressures and the temps that come with this pressure, you can hurt the engine.

‘So instead of laying out a chart for a newby pilot to try to make sense of, he’s told don’t oversquare the engine, if he follows that simple rule that requires no learning, no interpretation etc, he can’t hurt the engine. Later on assumption is he learns better and within reason can operate the engine oversquare, within limitations, sticking to published cruise charts is safe.

As I said, every single fixed pitch airplane I can think of is operated oversquare at most every takeoff, and they don’t explode or burn up.

‘The whole purpose of all these “rules of thumb” is to give new pilots simple instruction thst if followed won’t have the hurting themselves.

Take the don’t lean below 5,000 ft for example hopefully we all know that if we are out sightseeing at low power less than 5,000 that leaning is entirely proper

[smccray]

9 minutes ago, A64Pilot said:

‘Not saying your Bo did this, just thst it’s common as extra rich at full throttle protects the engine.

  That's exactly what the Bo install does.  Full throttle is actually better for the engine vs a post takeoff power reduction. 

[smccray]

3 minutes ago, A64Pilot said:

Oversquare isn’t recommended because if you get extreme with it, due to higher peak cylinder pressures and the temps that come with this pressure, you can hurt the engine.

‘So instead of laying out a chart for a newby pilot to try to make sense of, he’s told don’t oversquare the engine, if he follows that simple rule that requires no learning, no interpretation etc, he can’t hurt the engine. Later on assumption is he learns better and within reason can operate the engine oversquare, within limitations, sticking to published cruise charts is safe.

Yes- that's the explanation I've heard, but I've also heard that it's more applicable to the old radials than it is to a "modern" piston engine.  Hard to call the old technology we fly "modern" but it seems relevant distinction, particularly with a well balanced fuel distribution.  As with the extra fuel at full throttle on the bonanza, the rule of thumb is actually harder on the engine.

[Guest]

1 hour ago, A64Pilot said:

Oversquare isn’t recommended because if you get extreme with it, due to higher peak cylinder pressures and the temps that come with this pressure, you can hurt the engine.

‘So instead of laying out a chart for a newby pilot to try to make sense of, he’s told don’t oversquare the engine, if he follows that simple rule that requires no learning, no interpretation etc, he can’t hurt the engine. Later on assumption is he learns better and within reason can operate the engine oversquare, within limitations, sticking to published cruise charts is safe.

As I said, every single fixed pitch airplane I can think of is operated oversquare at most every takeoff, and they don’t explode or burn up.

‘The whole purpose of all these “rules of thumb” is to give new pilots simple instruction thst if followed won’t have the hurting themselves.

Take the don’t lean below 5,000 ft for example hopefully we all know that if we are out sightseeing at low power less than 5,000 that leaning is entirely proper

It's not just fixed pitch propellers, I'd guess that your J will be oversquare on every take off at lower field elevations. Or do you limit MaP to 27"?

In my case it would be 26.5"

 

Clarence

[A64Pilot]

2 hours ago, smccray said:

Yes- that's the explanation I've heard, but I've also heard that it's more applicable to the old radials than it is to a "modern" piston engine.  Hard to call the old technology we fly "modern" but it seems relevant distinction, particularly with a well balanced fuel distribution.  As with the extra fuel at full throttle on the bonanza, the rule of thumb is actually harder on the engine.

No, the old Radials very often had Superchargers. I test flew two dozen with R-1340’s so I should remember but don’t, I think you got 40” on takeoff, I know they seemed to like to cruise at 30” and 2,000 RPM, which is real oversquare. I think max RPM was 2250? Besides with a max RPM that low, even without forced induction, you have to be oversquare a lot.

No engine really “likes” to be lugged, ever driven a stick shift car and pulled a hill at slower speeds and didn’t downshift? Cylinder pressure gets high enough so that they may rattle from light detonation, your way oversquare is why

‘Following the rules of thumb will simply keep you out of trouble, guaranteed and they are real simple and easy to remember.

‘Later on your can get into what I call Graduate level engine management, but you need to understand what’s going on, because your possibly operating near a condition that if you don’t pay attention you could end up damaging the engine.

To give a for instance, I don’t know why, but when i open the ram air I get a small increase in manifold pressure, it’s not much but I also get a significant increase in fuel flow, enough fuel flow to take me out of the safe zone of lean and put me into a position that could hurt the engine if I was at a high enough power.

Similarly, if I didn’t know about power enrichment I could be cruising along just fine, but add just a bit of power, enough to enable power enrichment and again put me in a position to hurt the engine. if again I was at a high enough power to hurt the engine

So you have to understand what your doing and pay attention, and understand above what power you can hurt an engine and have a decent understanding of how to determine what your power level is.

‘If you follow the old rules of thumb, you don’t have to understand and don’t have to pay nearly as much attention.

I am not sayin that you need to or should follow the rules of thumb, but I am saying that to not do so requires more thought, attention and understanding is all.

Edited June 22, 2021 by A64Pilot

[A64Pilot]

53 minutes ago, M20Doc said:

It's not just fixed pitch propellers, I'd guess that your J will be oversquare on every take off at lower field elevations. Or do you limit MaP to 27"?

In my case it would be 26.5"

 

Clarence

No of course I don’t limit manifold pressure, to be truthful I don’t even look at it on takeoff, I do look at fuel flow though.

‘But in truth it’s not manifold pressure that really matters, it’s mass airflow, There is a whole lot more air density in real cold dry weather than say in hot and humid Florida, and engine manufacturers have to have enough leniency in the design so that someone in North Dakota in the dead of winter doesn’t detonate an engine to death at full throttle with the super dense cold dry air.

On a 90 degree day with 80% RH us Fl guys don’t even come close

Edited June 22, 2021 by A64Pilot

[smccray]

 

3 hours ago, A64Pilot said:

No, the old Radials very often had Superchargers. I test flew two dozen with R-1340’s so I should remember but don’t, I think you got 40” on takeoff, I know they seemed to like to cruise at 30” and 2,000 RPM, which is real oversquare. I think max RPM was 2250? Besides with a max RPM that low, even without forced induction, you have to be oversquare a lot.

I don’t know  !  I don’t have any personal experience with old radials, but I bet you have some stories!!!  Wish i could buy you a beer at Oshkosh!

3 hours ago, A64Pilot said:

 

No engine really “likes” to be lugged, ever driven a stick shift car and pulled a hill at slower speeds and didn’t downshift? Cylinder pressure gets high enough so that they may rattle from light detonation, your way oversquare is why

No doubt!  However, we’re operating on the assumption that operating “over square” is lugging the engine.  I’m quickly out of my depth here, but I haven’t seen a full explanation of that statement either.

If we take the scenario of reducing the RPM while keeping a high throttle (lugging), I believe you’re increasing internal cylinder pressure (ICP) assuming fixed engine timing and fixed mixture setting.  Higher ICP leads to higher heat which leads to detonation.  By that definition, lugging is certainly bad- and I think you’re analogy to a car is exactly right.

However, this “over square” condition isn’t itself a problem.  We can manipulate the mixture, rich or lean of peak, controlling the combustion event, and the engine is no longer experiencing  the high ICPs expected with lugging an engine. The problem isn’t the over square operating condition, it’s the fuel air mixture (as measured in each individual cylinder).  As you mentioned, turbo aircraft generally operate “over square” in cruise.

I hear you that there’s a rule of thumb/ short hand that is used.  It makes sense to make new concepts simple as much as possible for people learning. However, these old rules of thumb seem to drive a lot of misunderstanding.  As you noted, pilots think they can pay less attention by following rules of thumb- they think they’re making choices to be easier on the engine when in fact they’re doing the opposite.  

[carusoam]

you guys are good…

We used to have somebody that would summarize all of this great information into a single post…. 
 

Some things do stand out…

The IO550 has a very high output for max power… depending on the plane it is installed in…. Over 500hp.   Check in with the guy who wrote the 310hp STC for tech details…

I had a brief discussion with him when purchasing the STC… I wanted to operate at less than 65%bhp… was that 65% of the original 280hp, or the new 310hp…. With the 500hp rating… it was clear I could use the 65% of 310hp without much concern… 

In the Ovation… Max HP comes with WOT… where the fuel pump is turned on automatically… I haven’t seen a step in FF when the pump turns off… the O doesn’t merit getting a fuelP sensor…

I considered for a while flying LOP from climb to landing…

There are two challenges with the LOP in the climb…

ROP climbs begin at 2k’pm… as you go higher… the EGT gets cooler as the mixture automatically gets richer with altitude… a safe way for an errant pilot to not break something… climb mixture using the blue box… is 2-300°F ROP…

LOP, it would be hard to maintain such a cool EGT… and there is no guidance in the POH for climbing while LOP… 

The real challenge left… as you climb LOP… the mixture is trending more rich automatically moving back towards peak…

The IO550 climbs very quickly, changing the mixture as she climbs… without specific guidance on how to climb LOP… I gave up on that part of the LOP mission…

Its only a few minutes to my usual cruise altitude of 12.5k’…

PP thoughts only, hope that adds to the conversation…

Makes me really want to fly an IO550 past TBO…   

PP thoughts only…

Best regards,

-a-

[Fasterthanmycherokee]

Still digesting all of this that pertains to my TN setup.

I did go up for about an hour yesterday to play with cowl flap settings, ran it ROP per the EI program, then downloaded the last 20 flights and will look them in savvy. Temps were all very much inline with all your points.

Bottom line is yes, I want to go fast, it’s why I bought a Mooney. 
I don’t want to do any damage to it in pursuit of speed which is why I came to this forum, and it’s with an open mind I hope to be a better operator.

How many in here that commented are running this same setup with the TN?

[Fasterthanmycherokee]

On 6/19/2021 at 8:36 AM, Shadrach said:

In my bird there is a notable difference in oil pressure as the temps cross 200F.  It appears the power is well north of 80% and leaned on the rich side of peak.  CHTs are warmer than I'd like to see, but certainly within reason given that you're running it hard at 12,500 on a hot day.  I'm curious what kind of TAS you're seeing at that altitude.

I was showing 191 TAS at 12,500