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

[N201MKTurbo]

27.5 and 2450 is about 77% power.

[smccray]

On 6/20/2021 at 10:21 AM, Fasterthanmycherokee said:

Why do you recommend that? My POH specifically identifies running ROP. I know there is a lot of debate over the two, but my POH and A/P I/A both recommend ROP. I'm not as concerned with the fuel burn as I am engine health and life, so curious to hear about your take on it. 

There is a lot of info out there on ROP vs LOP operations.  Look here, look at Beechtalk, and you'll find more opinions than you care to read.  Beechtalk has a lot of LOP advocates; the community doesn't seem to be very tolerant of the ROP advocates, so tread lightly over there.  The data does seem to indicate that the engine health and life is better running the Continental IO-550 LOP.

I fly a TN engine.  The Tornado Alley setup wouldn't be possible to run the engine ROP.  The setup requires a lot of extra fuel while running ROP to keep CHTs in check.  Target is 1310 TIT when ROP; 36 GPH full throttle, still a lot of fuel at high MP.  LOP, the engine can be setup at ~1570 TIT wide open throttle burning 16.5-17 GPH.

I wouldn't be happy with the CHTs on your engine monitor.  You might try setting up your engine LOP.  I assume you pulled back the throttle a bit.  The Bonanza setup is wide open throttle, 2500 RPM, and adjust the mixture to 50-70 degrees LOP (based on TIT).  Based on the numbers from my old J, I bet you run less fuel, less heat, and comparable TAS.

 

[A64Pilot]

43 minutes ago, N201MKTurbo said:

27.5 and 2450 is about 77% power.

By what chart? The attached is for a NA motor, and if you assume standard adibatic lapse rate a NA motor can only hold 27.5” MP to 2500 ft. His is of course a TN motor, are there charts available?

‘Your going to lose some significant power from a turbo heating the intake air charge, but you have to use something.

Edited June 21, 2021 by A64Pilot

[N201MKTurbo]

[N201MKTurbo]

12 minutes ago, A64Pilot said:

By what chart? The attached is for a NA motor, and if you assume standard adibatic lapse rate a NA motor can only hold 27.5” MP to 2500 ft. His is of course a TN motor, are there charts available?

‘Your going to lose some significant power from a turbo heating the intake air charge, but you have to use something.

Set your pressure altitude to SL and adjust your temperature to 75F and see what you get.

[A64Pilot]

Just now, N201MKTurbo said:

Set your pressure altitude to SL and adjust your temperature to 75F and see what you get.

I don’t understand the huge disparity, can’t argue successfully with the factory charts though

[N201MKTurbo]

Just now, A64Pilot said:

I don’t understand the huge disparity, can’t argue successfully with the factory charts though

Probably because of the crappy stock airbox.

[Fasterthanmycherokee]

Still digesting all of the comments and concerns, thank you all. 
 

I just pulled the supplement from M-20 Turbos, Inc (in my POH) and found the below in Cruise. 
 

Both advocate ROP. 

[A64Pilot]

Just now, N201MKTurbo said:

Probably because of the crappy stock airbox.

J seems to have a good air box, or the air box and the ram air are both crap? Air box seems good enough to pretty much make the ram air not so useful, or at least on mine anyway it’s only about 1/2” difference.

Still there is a whole lot more going on, some that I can’t adequately explain.

‘For instance I can run 22 squared at 2500 or so at 7 GPH happily, but at altitude I can’t. it takes more fuel.

So a TN motor at 12,000 ft, is a seal level chart applicable? I don’t know

[N201MKTurbo]

Just now, A64Pilot said:

J seems to have a good air box, or the air box and the ram air are both crap? Air box seems good enough to pretty much make the ram air not so useful, or at least on mine anyway it’s only about 1/2” difference.

Still there is a whole lot more going on, some that I can’t adequately explain.

‘For instance I can run 22 squared at 2500 or so at 7 GPH happily, but at altitude I can’t. it takes more fuel.

So a TN motor at 12,000 ft, is a seal level chart applicable? I don’t know

I don't believe it for a minute, but that's what the STC says.

[A64Pilot]

6 minutes ago, Fasterthanmycherokee said:

Still digesting all of the comments and concerns, thank you all. 
 

I just pulled the supplement from M-20 Turbos, Inc (in my POH) and found the below in Cruise. 
 

Both advocate ROP. 

That is very close to Lycoming gospel and I maintain that a engine can be safely operated that way and make TBO.

Follow those directions and things are easier, your burning more fuel,but it’s harder to mess up.

Guy I bought my airplane from when I asked him what egt he ran and he said between 725 and 750, Well that threw me, EGT’s will change from one day to the next. So when I asked him where those numbers came from, he said his CFI.

I know the CFI well, he’s also an IA, so I asked him WTH? His answer was he didn’t want to overwhelm a novice pilot, this guy apparently shouldn’t really be in a Mooney yet, so he gave him some numbers that were on the rich side of safe, so he wouldn’t hurt anything.

Edited June 21, 2021 by A64Pilot

[A64Pilot]

Just now, N201MKTurbo said:

I don't believe it for a minute, but that's what the STC says.

You lost me, don’t believe what?

[N201MKTurbo]

Just now, A64Pilot said:

You lost me, don’t believe what?

That the sea level power chart is valid at all altitudes with the turbo system.

[Fasterthanmycherokee]

9 minutes ago, N201MKTurbo said:

That the sea level power chart is valid at all altitudes with the turbo system.

 

[N201MKTurbo]

16 minutes ago, Fasterthanmycherokee said:

 

But the performance is enhanced at higher altitudes, he left out the part about it being degraded at lower altitudes.

I never could never understand how he got away with this cop out.

Edited June 21, 2021 by N201MKTurbo

[Shadrach]

3 hours ago, A64Pilot said:

LOP is another tool in the box, but it’s not the best for fangs out, hair on fire speed

 There’s a good argument to be made that indeed is the best for fangs out here on fire speed if you have a turbo. 
 

It’s also my preferred method of high power operation at any DA below 4000 feet.

[A64Pilot]

In theory 22 inches of manifold pressure is 22 inches, at seal level or at altitude.

But in practice in my NA motor it’s not, I can’t run the same fuel flows even though the pressure and RPM are identical, and I’m not sure why.

In theory a TN motor can hold sea level power all the way up to critical altitude, and I’m not sure they can. My reasoning is that pressure is irrelevant,it’s actually the mass of air that’s important.

‘So air at 59f at 30” has a lot more mass than air at 300F or so at 30”. Don’t know the temp of a non aftercooled turbo and am sure it will vary depending on how hard the turbo is working to maintain 30”, but 5th stage bleed air from a turbine and APU bleed air is about 400F on average, but it’s at a much higher pressure too, but there is some heat from the turbo and heat of course causes expansion, and expansion decreases density.

[A64Pilot]

43 minutes ago, N201MKTurbo said:

But the performance is enhanced at higher altitudes, he left out the part about it being degraded at lower altitudes.

I never could never understand how he got away with this cop out.

Why would performance be degraded? Charge air heating?

[Shadrach]

4 hours ago, A64Pilot said:

Who is Mr sandman? Who recommended peak at full power?

Quick question for those that abdicate high power LOP. How lean are you on takeoff?

If your going to run the thing at or above 75% power, turbo or not, your safer if you run it rich, it’s why I hope all of us take off with everything full forward.

I am not against LOP, I can run deep LOP 22 squared and 130 kts on 7 GPH, To go 160 kts down low on my J doubles the fuel consumption and I can assure you reduces its life too, so I don’t, but some choose to. I’m just not in as big a hurry as I used to be, and I haven’t a schedule anymore. 130 kts to me isn’t bad, others couldn’t stand it, but speed is relative. I lived and cruised on a sailboat for three years, 7 kts was fast then.

‘LOP is another tool in the box, but it’s not the best for fangs out, hair on fire speed

On full rich take off I’m about 315to 330 ROP depending on cylinder.

I takeoff and climb with everything full forward because I want max performance with good detonation margins. I have done LOP takeoffs just for my own edification. It’s not a big deal but given that the fuel system isn’t set to do it automatically it requires more work. It also requires leaving  ~20% of your horsepower on the table if in a normally aspirated aircraft.
 

Why are you safer with everything full forward above 75%. What happens if there’s an obstruction in one of the injectors (it’s rare but it happens)? Where does that do to the mixture for that cylinder if set ROP? What does it do to that cylinder if set LOP?

there is no safe setting, there is only situational awareness coupled with an understanding of what to do when the situation calls for it.

We often talk about being head of the airplane in aviation. I submit that it’s just as useful to be ahead of the engine. To be watching for clues and have an understanding what it’s telling you. For years, engine operations were checklist items before takeoff and after landing.  We have so many more tools now for engine management and analysis yet there are still plenty of folks who don’t really take advantage of this paradigm shift in comprehensive real time info.

Edited June 21, 2021 by Shadrach

[Shadrach]

19 minutes ago, A64Pilot said:

Why would performance be degraded? Charge air heating?

That and the additional exhaust back pressure.

[A64Pilot]

8 minutes ago, Shadrach said:

On full rich take off I’m about 315to 330 ROP depending on cylinder.

I takeoff and climb with everything full forward because I want max performance with good detonation margins. I have done LOP takeoffs just for my own edification. It’s not a big deal but given that the fuel system isn’t set to do it automatically it requires more work. It also requires leaving  ~20% of your horsepower on the table if in a normally aspirated aircraft.
 

Why are you safer with everything full forward above 75%. What happens if there’s an obstruction in one of the injectors (it’s rare but it happens)? Where does that do to the mixture for that cylinder if set ROP? What does it do to that cylinder if set LOP?

there is no safe setting, there is only situational awareness coupled with an understanding of what to do when the situation calls for it.

We often talk about being head of the airplane in aviation. I submit that it’s just as useful to be ahead of the engine. To be watching for clues and have an understanding what it’s telling you. For years, engine operations were checklist items before takeoff and after landing.  We have so many more tools now for engine management and analysis yet there are still plenty of folks who don’t really take advantage of this paradigm shift in comprehensive real time info.

I’ve had an injector clog several times in the 210, it never happened on takeoff, but if it did, I’d abort the TO or reduce power to min and land. It happened in flight, first time I fought to keep it rich enough, full rich and high boost, made the other 5 slobbering rich, after that I’d reduce power and let the lean one go wherever it wanted, power was low enough it didn’t hurt anything, it woud just lean out and pretty much die.

‘I got so I carried a 7/16” deep well socket and shorty wrench and a can of carburetor cleaner. Then one day it stopped clogging injectors and never did again, only did it three or so times.

[N201MKTurbo]

1 hour ago, A64Pilot said:

Why would performance be degraded? Charge air heating?

Well, there is a giant restriction in the exhaust. I realize they say that the heat recovery makes up for it, but that turbo produces many shaft horse power. It doesn't come from nowhere.

This turbo system is working just as hard at sea level as it does at FL200. 

Edited June 22, 2021 by N201MKTurbo

[A64Pilot]

10 minutes ago, N201MKTurbo said:

 

This turbo system is working just as hard at sea level as it does at FL200. 

I think I understand what your saying, it wastes compressor air as opposed to exhaust? Still an inch or two of boost ought to easily recover any HP lost, so just run 32” on takeoff ?

 

[N201MKTurbo]

5 minutes ago, A64Pilot said:

I think I understand what your saying, it wastes compressor air as opposed to exhaust? Still an inch or two of boost ought to easily recover any HP lost, so just run 32” on takeoff ?

 

I takes off just fine. It seems to cruise a bit slower at low altitudes than I think it should, You are correct, it has a fixed waste gate and a special popoff valve that maintains a constant upper deck pressure (~32 in). It dumps extra compressed air overboard. The MP is limited to 30 in. per the STC.

The plus side is it is rock solid. You can set the MP and mixture at FL180 and not touch it until the wheels hit the ground. (well there is that landing pattern thing)

[Shadrach]

14 minutes ago, A64Pilot said:

I think I understand what your saying, it wastes compressor air as opposed to exhaust? Still an inch or two of boost ought to easily recover any HP lost, so just run 32” on takeoff ?

 

It does recover it, but not at the same MP as a normally aspirated bird. This is why Rich was taking issue with the STC using SL power settings from the J’s POH.

Edited June 22, 2021 by Shadrach