M20K - Leaning and Engine Temp Practices

[N5756v]

Now my head hurts . i think i will have to read this a few times to wrap my head around LOP . Any other threads that I should read ?

[jlunseth]

For the 231 owners, I have done a fair amount of experimenting with LOP and have come up with a pretty good setting I think.  I use 34" MP, 2450 RPM's and keep the fuel flow at 11.0 GPH.  11.5 is 75% HP but I did a little experiment with the JPI and found that one or two of my cylinders were within a few degrees of peak.  I ran a couple of lean tests in LOP mode on the JPI and that is what it was telling me.  11.0 is about 70% HP and not a significant loss in speed.  The cylinders are in a range of -34 to -20 degrees LOP and all of the other temps are good.  TIT stays under 1600.  THis works in my plane up to about 12k, over that it depends on the OAT, the cylinder temps start to get too hot.

TAS at 12k is around 165 kts.

With a tank capacity of 75.6 gallons, that is very nearly 7 hours of endurance.

I saw earlier that someone noticed their #6 cylinder is the coolest.  The reason for that in the 231 is pretty simple and has nothing to do with fuel flow to the respective cylinders.  The number 6 cylinder is directly in the cowling intake hole.  So is the number 5, but the intake hole on that side is partially blocked by the induction air intake.  The #6 is not blocked, so it runs cooler than the #5 and all the rest, which are further back on the engine. 

[N231BN]

On 6/11/2016 at 11:29 PM, jlunseth said:

For the 231 owners, I have done a fair amount of experimenting with LOP and have come up with a pretty good setting I think.  I use 34" MP, 2450 RPM's and keep the fuel flow at 11.0 GPH.  11.5 is 75% HP but I did a little experiment with the JPI and found that one or two of my cylinders were within a few degrees of peak.  I ran a couple of lean tests in LOP mode on the JPI and that is what it was telling me.  11.0 is about 70% HP and not a significant loss in speed.  The cylinders are in a range of -34 to -20 degrees LOP and all of the other temps are good.  TIT stays under 1600.  THis works in my plane up to about 12k, over that it depends on the OAT, the cylinder temps start to get too hot.

TAS at 12k is around 165 kts.

With a tank capacity of 75.6 gallons, that is very nearly 7 hours of endurance.

I saw earlier that someone noticed their #6 cylinder is the coolest.  The reason for that in the 231 is pretty simple and has nothing to do with fuel flow to the respective cylinders.  The number 6 cylinder is directly in the cowling intake hole.  So is the number 5, but the intake hole on that side is partially blocked by the induction air intake.  The #6 is not blocked, so it runs cooler than the #5 and all the rest, which are further back on the engine. 

Can you always close your cowl flaps without having Oil Temp issues?

I run similar settings in my 231: 32" MP, 2400 RPM, and 10-10.5 GPH. My mixture control has been touchy ever since I replaced the fuel pump so if it's stable somewhere between 10-10.5 I leave it. My TIT is usually just above 1500 which is 40-50 LOP. I have the slow probes for my UBG-16 so I don't know exactly how far LOP the EGT's are but the engine is happy(CHT's below 360). This setting gets me 160 KTAS at 10k if I can close my cowl flaps. My last trip it was ISA +20 at 10k and my oil temp was shooting up so I had to leave them in trail.

[FBCK]

231BN, I run exactly what you described above (even have the UBG-16). I have the same issue with the fuel slow creeping up and down, maybe within .2-.5 per hour as you describe as well, but never had the oil get hot, it stay pretty  much at a constant.

[N5756v]

I think I am going to take the advanced pilot Siminar online course to really wrap my head around how to lean . My transition training was a little lacking and the

engine managment training was less then stellar also . I knew I was in trouble when he had no idea about how the Intercooler worked . He said he had over 500 hrs in a mooney turns out it was a short body and I don't know how long ago . All I know really is to keep my cylinder temps down under 380 and  my tit under 1600 , I usually keep the tit around 1430 . I am terrified I am going to do the engine harm . So with all that said the online course seems like the way to go . 

[jlunseth]

I haven't been around for a bit.  I see I was asked a question about cowl flaps in my 231. The answer is that I can fully close the cowl flaps the vast majority of the time, with either a LOP or ROP setting as long as the setting is reasonable.  Hard to think of an exception in cruise flight.  There have been a very few times when the OATs were high and I was climbing to the flight levels, when the CHT's got higher than I would like.  But I climb full fuel, cowl flaps full open, so there is not much further that can be done.  Slack off on the climb rate and gain airspeed is about it.  I do, though, have a problem running LOP and what I consider a decent cruise setting, usually above 12k.  The CHTs and TIT start to get too hot, just not enough air for cooling.  When that happens I go 125 degrees ROP and the problem goes away. 

I just don't have a heat issue with my engine as long as the settings are reasonable. 

[N5756v]

So I am looking for some Input . I have a 231k with an Intercooler. The Intercooler was cooling 60 degrees witch let's me drop my mp an additional 3 inches  so on my last trip I was running 26 mp and leaned it out 50 LOP on the TIT . This is how your supposed to run it? My fuel flow was almost all the way down to 8.2 gallons an hour . That seems a little low but what do I know . But all my temps were good . Does this sound like it's right? Can somebody even tell me what info I need to be keeping track of? I have been reading some articals on this stuff and just making sure I am on the right track. Let me know if I need to move this to anouther thread please .

[carusoam]

Just because you can doesn't mean you should..?

It's fun to go deep LOP.  But when you fly slower than a C152, you may not like it very much.

what was the TIT reading while you were this deep LOP?

Best regards,

-a-

[N5756v]

1525 degrees and 140ish knots

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[N5756v]

From your comments I need to do some more reading I guess . I will keep better track of the numbers next time for sure .

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[carusoam]

You may want to post your JPI graphs in the event you are missing something important.

What speed do you see if you were to run 125°F ROP like JL indicated above?

Best regards,

-a-

[N5756v]

I will keep track of that on Saturdays flight

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[SkyBound]

N5756V - Flying LOP is controlled by fuel flow.  When you are at 11.5 GPH you at 75% power.  If you can sustain that by keeping all CHTs below 380 and TIT below 1650 great, if not lean more or open cowl flaps.  I have a Merlyn wastegate and an intercooler and typically cruise at 2400 RPM. My TAS speeds flying LOP between 65% and 75% - around 10-11 GPH are 140 kts near sea-level, 150 kts 6,000+, 160/165 KTS in the teens, and 170-175 kts in the flight levels.  If the winds are favorable and the distance is 300+ nm I will climb to FL210 or FL230.

How do the speeds above compare to what the others on the thread experience?

Feel free to share more data and we'll be happy to give you more feedback.

--Alex

[carusoam]

Just be extra, super, very familiar with your O2 system prior to flying in the FLs... And the back-up system when you go really high up.

Useful time of consciousness can be disastrous.

Public service message,

-a-

[N5756v]

So this is how I was running on Saturday . Seems like I could have leaned a little more . Seems like I can't get the speeds I have seen some of you guys posted . Looking forward to your input. I am running an Intercooler . No Merlyn waste gate .

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[SkyBound]

I think your MP is too low. At 11,500 you should be 31"-32" and 10.5 GPH which would give you about 65% power and 155-160 kts TAS / 125-130 kts IAS.

[N5756v]

The Intercooler was cooling 60 degrees so that lets me drop an additional 3 inches of mp

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[SkyBound]

The intercooler is irrelevant in the equation.  Your limiting factors are CHT and TIT.  

[N5756v]

My understanding is that you get the mp and fuel flow off the visor then you have to subtract .5 inch for every 10 degrees it's cooling . Am I reading my supplement wrong in my POH? From there is how I got to the above mp by leaning to peak. That's how I was running was peak.

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[carusoam]

1) It is good to know your inter cooler is working...  A 60° C delta is a hint that it is working. From an engineering point of view, it doesn't tell an important number.  What is the temp of the air leaving the inter cooler /going to the engine...

2) The reason you watch this is to keep from running at too high of a power setting with a chance of pre-ignition.

3) pre-ignition is often caused by too high of air temp entering the throttle.  (Leaving the inter cooler))

4) there must be another temperature indicator of importance.

5) TIT is monitored for turbine health on the hot side or exhaust side of the turbo.

6) Turbine outlet temperature is the temperature of the heated, compressed air leaving the turbo.

7) inter cooler exit temperature would be most helpful to know what is being sent to engine's intake.

8) throttle and or power settings are best handled knowing the temperature and pressure (MP) of the air entering the engine's intake.

9) MP is what we use to set power when running ROP.

10) FF is what we use to set power when running LoP.

11) maintaining TIT is for turbine health.

12) maintaining Temperature of the air exiting the inter cooler (heat exchanger) is for engine health.

13) Check to make sure you are using the proper documents for setting power.  If the turbo controller and inter cooler are STC'd modifications, the original power setting charts have probably been superseded.  The STC will have the new procedures.

 

Let me know if this is making any sense?  I only have a big NA engine because the TC power setting is too complex for me...

Best regards,

-a-

[N5756v]

The Inter cooler is stc'd but it does not give me a new chart it just says to decrease MP by .5 inch for every 10 degrees of Cooling . So I took that to mean use the chart on the visor and then subtract .5 inch of mp for every 10 degrees of cooling . Just for clarification the STC is what they put in the POH ? And sorry about this next question but can you define turbo controller ?

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[carusoam]

A number of TC systems have been upgraded in various ways.  Some have MP controllers of differing skills others got inter coolers. Some got both...

The POH is the baseline document.  The STC is an add on for the plane that will have documents related to the upgrade and how to use it.  Often the STC documents go right into the POH.  Depending on the documentation skills of the owner and his mechanic.

Some owners and mechanics will differ from others.

Your maintenance logs will indicate if the hardware was original to the plane or if any of it was added afterwards...

page by page, reading your POH, will probably divulge some other unknowns (regarding operations) hiding in there.

STCs often give contact information if they are still live.  This would allow you to contact them to ask if you have the proper procedure and chart to follow.  There shouldn't be any guessing regarding setting power.  Getting it wrong could lead to some expensive maintenance.  It may be as simple as sending an email.

Another thing, Sometimes controlling CHTs is used to partially avoid pre-ignition.

note: I am only a PP, not a mechanic or CFI.

Best regards,

-a-

[N5756v]

This goes with the pictures I posted also I misplaced it until now

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[N5756v]

Those temps look acceptable ?

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[jerryg324]

Looks like our speeds and fuel burns are pretty close lean of peak...