Just started flying a k model… Is the juice worth the squeeze??

[Alan Fox]

Learning to fly this , just seems like constantly chasing temps…took off 34 inches full rich , pulled back for climb to 2500 and 30 inches fuel to 1550 tit rich … then about 29 inches over 6000 2400 , and 1550 tit , cht’s and oil temp , we’re not manageable unles I opened the cowl flaps , most of the trip was at 14500 , and started descent 75 out… I realize I am oversimplifying this , but all suggestions are welcome.. 

[Pinecone]

I fly a K, but 252.

I take off full throttle, max RPM, full rich, cowl flaps open.

I climb the same.

I level off, all the plane to accelerate.  Then pull the power back to 32 inches, 2300 RPM, pull the mixture back to 10.3 GPH (65%).  And enjoy the 174 KTAS ride.

Descent, I push the nose over and see over 200 KTAS.  

[smwash02]

I'm an encore, so grain of salt, but with mine if you're not using full power in the climb you're, in my experience, going to have temp issues. 

Full bore all the way up. 

In cruise fly LOP or you'll need to trail the cowl flaps a little above 8 or 10, been too long I always fly LOP and don't need to.

Above 18-20 even LOP I sometimes have to trail them a bit.

 

[Red Leader]

Yeah, you can't use full power all the way up in a "K". Being a turbo, our temperatures are especially sensitive. It's the cylinder temperatures that are the most watched, but I tend to run fairly rich, leaning only after passing 8k. I recently have had my baffling replaced and with the new material, I rarely see over 385 in the climb. You say it is an exercise in chasing temperatures, you are correct. Since the baffling replacement, I have to open the cowl flaps in cruise much less often - CHT's over 415 are a no-no in my book and they tend to creep up there in the flight levels (the air is thinner and cools poorly the higher you go). T.O. at 37", cruise climb about 32" and cruising at 29" @ 2400rpm. Got to watch the TIT as you don't want to exceed 1650. I have heard other 231 drivers running right at 1650, and from what I understand, that is acceptable - just don't go over for more than 30 seconds and never to 1750 as you will melt your turbo. Watch those CHT's, and yes, you may have to crack the cowl flaps from time to time to keeps those temps in check.

[ziggysanchez]

I only had temp problems in my K if I pulled back the power during climb out. Mine was a 231 LB with merlyn wastegate no intercooler. Take off was cowl flaps full open, full throttle (39-40 inches MP) max rpm. Left it the same for the climb. Climbing 700-1000 fpm usually kept CHT's in check. On hot days I did have to lower the nose and climb at 500 fpm to keep CHT's below 380. Between 380 and 390 were my max CHT's for all stages of flight. It did seem that I needed to constantly adjust the throttle in all phases of flight to keep the settings I wanted. That plane never was set it and forget it. In cruise it seemed like the higher the MP the cooler the engine ran so I would regularly cruise with 32-34 inches MP, 2500 rpm LOP (9.5 to 10.5 GPH). TIT in cruise was usually between 1580 and 1620. Cowl flaps were always closed during cruise below 16000 feet, in trail when above 16,000. The picture below were my settings at 15500 with cowl flaps closed.

[231LV]

2 hours ago, Alan Fox said:

Learning to fly this , just seems like constantly chasing temps…took off 34 inches full rich , pulled back for climb to 2500 and 30 inches fuel to 1550 tit rich … then about 29 inches over 6000 2400 , and 1550 tit , cht’s and oil temp , we’re not manageable unles I opened the cowl flaps , most of the trip was at 14500 , and started descent 75 out… I realize I am oversimplifying this , but all suggestions are welcome.. 

Why aren't you using full power during climb? If you have an intercooler, you are limited to 36-37 inches of MP but that is a lot better than pulling back to 30 inches. I climb at full power with full open cowl flaps, full rich and maximum RPM. The TIT sits  in the higher 1400's. Only after hitting the lower teens will you see your temps start to climb but with fully opened cowl flaps, you should not exceed 380 on CHT's unless you are climbing through 20,000 ft where the turbo has to work really hard and throw off lots of heat. Once level, I go LOP and  dial in 2500 RPM. I will stabilize at 9 GPH around 30 inches of MP with my hottest CHT at 320 . Cowl flaps can be reduced to trail although temps will climb a bit but usually not above 360. TIT usually sits around 1580. Temp management is what the K is all about which is why the 252 and Encore came along to simplify engine management. I don't fly with fully closed cowl flaps since temps go higher than I want but flying them in trial works albeit at slightly higher temps.

[jlunseth]

5 hours ago, Alan Fox said:

Learning to fly this , just seems like constantly chasing temps…took off 34 inches full rich , pulled back for climb to 2500 and 30 inches fuel to 1550 tit rich … then about 29 inches over 6000 2400 , and 1550 tit , cht’s and oil temp , we’re not manageable unles I opened the cowl flaps , most of the trip was at 14500 , and started descent 75 out… I realize I am oversimplifying this , but all suggestions are welcome.. 

Before anyone can help you we need to know which K, which engine, and the configuration of the engine. There are three different K’s, the 231, 252, and the Encore, and two custom K’s by STC, the 261 and 262. The 231 can  have two different engines, the TSIO360 GB and the LB. EIther one can be fitted with common aftermarket modifications or not, a Merlyn wastegate controller and/or an intercooler. The 252 has a TSIO 360 MB and sometimes by modification an SB. The Encore has the SB. Tell us what you have and someone here can help. If you don’t know what you have then you need to find out what you have because each version has its own operating parameters and they are quite different from one to another. As a general rule you should climb any turbocharged engine at full power full rich. You should not ever lean a turbocharged engine back to some other setting than full rich while in a climb, you will cause high temps. A turbocharged engine is not the same as a normally aspirated engine and pretty much everything you know about operating a normally aspirated engine, such as leaning in climb, is not right for the turbo’d engine and can result in some remarkable CHTs and OT. 

Edited November 19, 2022 by jlunseth

[Alan Fox]

Lb with turbos plus intercooler and merlyn black magic

[Z W]

Full power, full rich, cowl flaps open in the climb to final cruising altitude will get you lowest temps, best speed, and best overall economy.  If you're going high and the air is warm outside, sometimes you do have to level off in the teens for a couple minutes to cool the engine down before continuing your climb.

Balancing RPM, MAP, CHT's, TIT, fuel flow, and cowl flaps is an art once you're in cruise.  Some days you can do better than others.  There is a wide range of settings available to optimize speed, efficiency, and temperatures, each of which is a tradeoff against the others.  Most here seem to agree that keeping the CHTs under 380 and the TIT under 1625 (some say 1600) will result in longer engine life.  The POH says as long as you're under redlines you're fine.

[LANCECASPER]

13 minutes ago, Z W said:

The POH says as long as you're under redlines you're fine.

Back in the 70's through the late 80's/early 90's it seems like the marketing department at Mooney had a big influence over how the POH was written. (Example: the red line on an M20M (TLS introduced in 1989) TIT was 1750 degrees. That yielded blistering speeds with the lowest fuel flows and best range, but cylinders were lasting about 200 hours.)

Being considerably more conservative that the POH red lines is good engine management. The people who wrote the POH aren't going to step in and buy new cylinders for you.

[hubcap]

7 hours ago, Alan Fox said:

Lb with turbos plus intercooler and merlyn black magic

I have the same setup and I typically fly in the mid-teens and lower flight levels. 99% of my flying is cross country. My plane is equipped with a JPI 900, so all temperatures are readily available. I have a little over 300 hours in my 231 and have settled on the following settings to give me the performance I like while managing my engine temperatures:

Take-off - cowl flaps open, 36" MP, 2700 RPM & full rich with ~22gph fuel flow. Get the gear and flaps up set for cruise climb at 33" MP, 2600 RPM & full rich, cowl flaps still open, and now I will see ~18gph fuel flow. Keep increasing the manifold pressure as you climb to keep it at 33". Temperatures will stay well below 370 degrees in climb even in the flight levels. Fly with mixture full rich and cowl flaps open until you level off and go to cruise configuration.

Cruise - I typically cruise at 26" MP and 2500 RPM with a TAS of ~170kts in the lower flight levels, running LOP with the TIT at ~1550 degrees at 10 gal/hr. Keep in mind that the TurboPlus has a manifold pressure conversion based on the air temperature and the amount of "cooling" that takes place. On average the MP is about 2" higher than the gauge reads, based on the conversion chart.

Most of the time I am able to fly with the cowl flaps closed while in cruise. I was unable to fly with them closed until I learned from one of the Mooney engineers that on the 231 the cowl flaps are supposed to be 1" open when set to the closed position. This allows the plane to fly cooler and faster.

My engine has 800 hours on it and is just finished with the annual. The compressions, valves, lifters are in great shape, and the Blackstone analysis says keep it up. The oil burn is a quart every 10 - 12 hours.

I think the 231 requires attention to engine temperatures, but with the JPI it's not difficult.

In my opinion "The juice is worth the squeeze."

[jlunseth]

Yeah the POH gives you a max cht of 460 for the LB. Those cylinders are then good for at least a couple of flights, maybe three or four. 

[jlunseth]

A lot has been learned about good engine operation since the POH was written. Generally, the healthiest way to run a turbo is to climb full power full rich to whatever altitude you are going to cruise at. I use 36” for that. Full power at ground level is actually around 37” for the intercooled LB but 36 works fine. For climb operations you need a rich mixture. The POH says you need to see a fuel flow of 22.5-24 GPH. You won’t get that if you climb at reduced power. There appears to be a sharp bump up in the fuel flow at 36-37. You should also have the prop full forward in the climb and the RPMs should be 2700 or pretty close. If they are less then you are operating at reduced power and won’t get the fuel flow you need. If you try to climb at say 34 you will only see maybe 19 GPH. If you don’t see 22.5-24 at 37 you need to take the aircraft back to your mechanic to get the fuel flow set higher. Leaning during the climb is for normally aspirated aircraft and the reason it is done in NAs is because their MP is capped at ambient and it falls as they climb so the mixture becomes too rich. That is not at all true in the turbo which can make full power all the way up to the critical altitude, which is around 22,000 in the LB with a Merlin.

We have had lots of threads about operating that engine Lean of Peak at cruise. It seems that question comes up about every week. You might do a search and find a couple of recent ones. As a general rule 2500 is about right for rpms at cruise, I use 2450. If you are going to operate rich of peak then you need to be well rich of peak. I use 31”, 2450 rpms and at least 13.3 GPH. If there are cylinders that are too hot, as on a hot day out west, then increase the fuel flow to as much as 14.5 GPH. 

I typically operate lean of peak at 34” MP, 2450 rpms and 11.1 GPH. I watch the TIT and if it goes over 1600 I will reduce power a little by reducing fuel flow to say 10.8. I can only operate this way up to around 12-16k depending on day temps, higher than that and temps are just too hot. I must operate rich of peak.

In general stay away from any power setting where the fuel flow is in the 12’s. That is right around peak and gives you the worst and highest CHT’s. A setting in the 12s is ok if you are flying at a reduced power setting, maybe 27 to 28” but is not ok for any cruise setting above that and definitely not ok for full power ops. Generally you should strive to keep CHT’s around 380, if they are going over 400 then you need to do something different.

Edited November 19, 2022 by jlunseth

[Fly Boomer]

17 hours ago, Alan Fox said:

Learning to fly this , just seems like constantly chasing temps…took off 34 inches full rich , pulled back for climb to 2500 and 30 inches fuel to 1550 tit rich … then about 29 inches over 6000 2400 , and 1550 tit , cht’s and oil temp , we’re not manageable unles I opened the cowl flaps , most of the trip was at 14500 , and started descent 75 out… I realize I am oversimplifying this , but all suggestions are welcome.. 

Lots of good stuff above, but also search MooneySpace for topics discussing 231 cowl flaps.  The meaning of "closed" varies from airplane to airplane.

EDIT:  Because the Continental fuel system is difficult to set up correctly, some airplanes are too lean even when the red knob is all the way in.  In fact, some people who know these engines well, set them slightly richer than book numbers.

[jlunseth]

PS I generally climb at 500 fpm and full power. You can probably climb at 1,000 fpm or even more at full power but it comes at the cost of slower airspeed which translates to less airflow over the engine and less cooling. I use 500 fpm because it is easy on passenger ears and I fly a lot of medically compromised (Angel Flight) passengers. 700 fpm works pretty well. Over that, and especially during the summer, and you will see a long persistent climb in all temps.

[PeteMc]

2 hours ago, Fly Boomer said:

The meaning of "closed" varies from airplane to airplane.

If you're referring to adjusting the cowl flaps so with the handle in the Closed position the CFs stay open a bit... YES!  Very important thing for a 231 driver to know.

Mine are set so the right side is open a bit so that my #5 cylinder doesn't go over 380 in normal cruise and normal power settings.  If they are in the fully *Closed* position it's almost impossible to keep the #5 cyl cool.

 

[jlunseth]

I have my mechanic set the cowl flaps to fully close in the winter, and to stay slightly open the rest of the year. I also get an oil cooler block installed in the winter and taken out in the spring. Need all the heat I can get in the winters we have here.

[geoffb]

I climb at full power, 23.5-24 gph and 120 knots indicated.  I get 700+ fpm out of that in the summer and can start shutting the cowl flaps some.  In summer, I can't run cowl flaps full shut at 65% ROP, but need to keep them 20-25% open to keep my hottest under 380.

yes, you spend more time flying the temperature guage(s) and it can be distracting.

Alan, you're in Jersey, keep the S35.  On your side of the country, the juice is not worth the squeeze.

[aviatoreb]

8 minutes ago, geoffb said:

I climb at full power, 23.5-24 gph and 120 knots indicated.  I get 700+ fpm out of that in the summer and can start shutting the cowl flaps some.  In summer, I can't run cowl flaps full shut at 65% ROP, but need to keep them 20-25% open to keep my hottest under 380.

yes, you spend more time flying the temperature guage(s) and it can be distracting.

Alan, you're in Jersey, keep the S35.  On your side of the country, the juice is not worth the squeeze.

There are other factors besides rocks that make a turbo nice.  1) In the east coast corridor I often fly mid teens since it keeps me out of what is otherwise lots and lots of traffic and I get much more direct routing, and pretty quiet skies. 2) Ice - if you do screw up the solution might be to climb.  This is a less strong argument since - well you shouldn't screw up.  But I carry tks and a turbo since yeah - I have screwed up a handful of times in the past.  I am a true inadvertent guy though - planning on no ice.

[Pinecone]

Yes, amazing how few aircraft in the mid to upper teens

I have a 252, but as others do, climb at full throttle, full rich, full RPM.  Cowl flaps typically full open, but may close of CHTs indicate.

Cruise is 32 inches, 2300, 10.3 GPH LOP for 65% power.  In summer, I may have to open the cowl flaps a bit to keep all CHTgs under 380

 

[Parker_Woodruff]

Climb should be max MP and RPM at or near max or you will have temp issues.  For a 210hp M20K, you'll want 24-25 GPH and for an Encore (220hp), you'll want about 26 gph.

With the K, get the induction (leaks) & spark (Tempest Fine Wires) handled first.  Then fine tune with GAMIjectors.

[M20F]

Hard to say which was a worse airplane the Statesman or the 231.  Certainly takes a new engine, intercooler, and a host of other things to allow it to fly more hours in a year than sit in the shop.  If you want to jump into the world of turbo Mooney’s start with the 252.

 

[Q The Engineer]

It is if you're into engines and managing their complexities.  If you don't like engines, likely not.  A J would be a better machine IMO.

[carusoam]

Keep in mind what Alan typically flys…

He is most often found shuffling NA IO360s around the country…

His personal machine has an IO520 on the front and a V on the back…

All NA….

 

To make a turbo Mooney worth the squeeze….

Long distance flying…

High altitude flying…

Where high speed makes it worth it…

 

For simplicity… go 310hp IO550!

For ease of operation of a turbo Mooney… go MP controller, and intercooler…. All worth the squeeze…

Best regards,

-a-

[geoffb]

19 hours ago, M20F said:

Hard to say which was a worse airplane the Statesman or the 231.  Certainly takes a new engine, intercooler, and a host of other things to allow it to fly more hours in a year than sit in the shop.  If you want to jump into the world of turbo Mooney’s start with the 252.

 

there are plenty of examples to the contrary.

And what's wrong with a G model?