New owner: CHT LOP and gear questions.. Help

[201er]

Be carful about listening to Mike Busch. He's got some good ideas mixed with some crackpot ones. For instance he says (or at least used to say) to just lean LOP to the point where CHTs are below 380 and no problem. The thing he as neglecting was ICP. Exceedingly good cooling or low OATs might present low enough CHTs while you're pounding the crap out of the cylinders and possibly even detonating. The relative EGT method is universal. Mike's foolproof shortcut method is a convenient rule of thumb but in the hands of a fool or the wrong set of circumstances it can prove problematic.

[aaronk25]

Be carful about listening to Mike Busch. He's got some good ideas mixed with some crackpot ones. For instance he says (or at least used to say) to just lean LOP to the point where CHTs are below 380 and no problem. The thing he as neglecting was ICP. Exceedingly good cooling or low OATs might present low enough CHTs while you're pounding the crap out of the cylinders and possibly even detonating. The relative EGT method is universal. Mike's foolproof shortcut method is a convenient rule of thumb but in the hands of a fool or the wrong set of circumstances it can prove problematic.

There is no way possible to get any mooney turbo charged or not to detonate on 100ll. ZERO chance. Now you can get it hot and run it at the high factory chts limits or on turbos at the egt limits but your never going to get the engine to denonate running 100ll. Just not going to happen. 100ll is some really good stuff!

None of the mooney aircraft have really high strung motors. Now, there are some twins out there with geared higher rpm motors that this wouldn't apply to.

As far as a naturally aspirated M20 if you can keep the CHTs at 380 or below (and with turbos comply with egt and MP limitations) there is no power configuration the engine can be set as that won't yield a full TBO if run continuously.

Yes a O-360 or IO-360 will run wide open throttle at peak egt at sea level turning 2700rpm for 2000 hours.

It's not high power that kills these engines its heat and internal rust (sitting for long periods of time with infrequent operation).






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[carusoam]

Detonation would be bad.  Melting the Turbo blades down to nubs won't make you happy either... overheating cylinders can limit their life.

For interesting reading we have a few threads around here written by real Mooney pilots on how they operate their TC'd engines LOP. Some have the intercoolers and pressure controllers, some don't.

The things that stand out to me in this conversation is the the wrong power chart to go with the engine set-up, trying to fly LOP, and not following a checklist that always has the proper E gear stowage check right on it.

The problem with operating the gear when the emergency system is partially engaged is that the soft brass gear can easily get damaged. Damage the gear, then neither the mechanical or the electrical gear system can engage.

This seems like an expensive way to get trained in how to fly a Mooney. There is transition training that covers these details in a short number of flights.

Getting Mooney specific transition training would be a good match for a TC'd, intercooled, pressure controlled, engine.

Then you can avoid the old wives tails that go with that. Shock cooling, Turbo cool down period and others...

Welcom aboard khedrei.  You have covered a bunch of complex topics in one thread. As if they are some simple 'what's your favorite wax or soap.'  You have people in your plane and there are some important details that maybe are best to be trained on a little better.

A TC'd Mooney is a powerful traveling machine. Gain experience methodically... 

Best regards,

-a-

Edited April 21, 2017 by carusoam

[201er]

 OMG! Complete sentences! Punctuation. Capitalization. Not a numbered list! Did you have a breakthrough in your recovery or did you just sleep at a Holiday Inn?

[aaronk25]

Lol! I thought you were taking about me and then I realized it was Anthony you were taking about. Wow, I'm shocked too!


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[carusoam]

Every day, things get a little better. 

Read, write, jog, gym, tan, laundry...  (Jersey shore humor)

Best regards,

-a-

Edited April 21, 2017 by carusoam

[Pritch]

Look up posts by jlunseth, I have been reading a lot by him.  I now understand much more about how to operate my K. There are also several others on here that are very knowledgeable on flying the K LOP.

Pritch

 

[carusoam]

@jlunseth in case this helps. MS helps you find authors just by using the @ sign.

APS is also a place to go when discussing engine and Turbo operations. They have in person or online classes.

Best regards,

-a-

[jlunseth]

This whole question "how do I operate my 231" and "how do I make it LOP," seems to come up every couple of weeks.  There are lots of good threads on it by now.  

Here goes.

Absolute v. Relative EGT.  Absolute EGT is a meaningless number.  Absolute EGT will vary from cylinder to cylinder simply because of the location of the sensor in the exhaust manifold.  Also, the sensor does not measure the temperature of the exhaust gas, believe it or not.  The sensor sits outside the exhaust port, which opens and closes as the engine operates.  So the probe is actually measuring the average temperature of the probe itself, heated by the periodic blasts coming out of the cylinder.  Also, the probes need to be the exact same distance from the port or they will be heated by the temperature in a different part of the exhaust flame.  Typically there are obstructions or simply turns in the manifold that require installing some probes a different distance from the port than others.  EGT is not a redline number, it does not matter what absolute EGT the engine produces, there is no limit to worry about.  

Relative EGT, on the other hand, is very important.  When you run LOP in particular, you want each of the six cylinders to be running sufficiently lean of its peak EGT.  As 201er points out, you need to treat each of the cylinders as a separate little engine.  If you have five of the cylinders safely lean of peak but one at peak or even over on the rich side of peak, that cylinder will  be hotter and experience much different ICP than the five LOP cylinders.  The GAMI's are an effort to balance fuel flow among the cylinders so that all six peak relatively close together.  You can determine that with a lean test, as has been mentioned, and it is not necessary to measure the fuel flow at each cylinder.  The lean test measures the total fuel flow when each cylinder peaks, not individual cylinder flow, what you want is all six cylinders peaking within .5 GPH (total fuel flow) of each other.

Power on the lean side is not determined by manifold pressure as it is on the rich side, it is determined by fuel flow.  There is a simple formula for it, which is a multiplier times the fuel flow.  The multiplier depends on the compression ratio of the engine, the compression ratio of the turbocharged engine being lower than an NA.  The multiplier for our engine (I have the TSIO360LB), is 13.7.  So if fuel flow is, say, 11 GPH, times 13.7 equals 151 HP, divided by total rated HP of 210 is 72% power.

While MP does not increase or decrease power on the lean side (this according to APS), it does affect degrees lean of peak.  Degrees lean of peak is determined by how lean the fuel air mixture is.  Duh!  You can make the fuel air mixture leaner two ways.  One, you can keep the MP at a set value, but reduce the fuel.  Two, you can keep the fuel flow at a set value and increase the MP.

This brings me to something I think you may be doing wrong.  In the 231, you can't make a power setting, let's say 28" MP and 13 GPH, and then just dial the fuel flow back to, say, 9, believing you are running LOP because you cut the fuel flow.  The reason is that the MP and fuel flow controls are interlinked, so if you make that 28 and 13 setting and then dial the fuel flow back, the MP is also going to drop, and you will wind up at a lower power setting but basically the same ROP mixture.  To get LOP from that 28 and 13 setting, you need to adjust the MP up as you dial the fuel flow back, so you wind up at the same 28" and 9 GPH (or wherever you want to set it).  

There is, however, something we turbo guys can do to affect the LOP setting that the NA guys can't for the most part.  Since more air makes the mixture more LOP, and since power is not affected by MP on the lean side, we can dial the MP up.  And that is what I do.  I like to operate at that 72% setting, but to make sure I am sufficiently lean of peak to protect the cylinders I usually use 34" of MP!  That's right, 34.  RPMs are 2450.  This puts me somewhere around 20-30 degrees LOP on all the cylinders and they stay cool while producing good cruise power.  I can't do this over about 15 or 16k except on cold days, because the thinner air does not cool well and the temps get out of line.  I have to go over to a ROP setting.  Probably if I tinkered with the baffling and the engine I could improve this, but my engine is near TBO so I don't bother.

At your 9 GPH I would probably use 30".  However one of the "rules" the APS guys have given us is that at 65% power you can run the engine anywhere you want, LOP, ROP or right at peak, without hurting it.  At 9 GPH you are probably under 60%.  Given that, the temp you are seeing on the one cylinder is a little puzzling.  I would run an airborne mag check to make sure both plugs are working on that cylinder.  It is also possible that the fuel flow on that cylinder is way out of line despite the fact that you have GAMI's, I would also do a lean test, you can find instructions on the APS website.

There is a temp. you do have to watch in addition to CHT and that is TIT.  The APS guys tell us that a turbo is fine running at any temp up to its constant operating temp redline.  For our engine that is 1650.  However, I keep the TIT at or under 1600.  If it goes higher I dial the fuel flow back, and if that is not working I will go over to the ROP side, which is not often.  The Bravo and Acclaim owners run their turbos hotter, I just don't like to.

I take off and climb at around 36", full rich.  At cruising altitude I level off, close the cowl flaps, adjust the temp and speed on the ASI, letting the plane get up to cruising speed.  Then I dial the MP back slightly to about 35", dial the RPMs down to 2450, and do the big pull to bring the fuel flow down to about 11.  Then I have to do some adjusting to get the MP to 34 because it drops when I adjust the fuel flow, and I adjust the fuel flow to get it right at 11 or just under.  So there I am, 34", 2450 RPMs, 11 GPH, 72% power, about 20 LOP on all cylinders.

Edited April 21, 2017 by jlunseth

[pinerunner]

I agree with what Mooniac said. If you can afford that much airplane and with turbocharging to boot then taking the course would be best route to getting on top of how to run it best. Everyone that I've talked to says the Advanced Pilot Seminars was money well spent.

Low power setting are where you can stay out of trouble easily and the best place to start is leaning for taxi. It sounds like you got into the middle of the red box with 28" of manifold pressure at a high power setting. I bet you did have some detonation going on. 

The big pull means pulling mixture smoothly and fairly quickly until you actually feel the plane slow due to the sharp drop in power on the lean side of peak EGT. By doing that you spend very little time in the dreaded red box at a high power setting.

I suspect that people who approach LOP cautiously set themselves up for the worst possible outcome by stopping at peak instead on continuing on into actual LOP. 

I'd start with aggressive leaning for taxi and very low power settings where you can't hurt anything and stay ROP for everything else especially the higher power settings doing things just as you were taught the old-fashioned way. Then take the course and you'll be way ahead and confident in what you're doing as you advance your engine manegment savy into the higher power settings . 

[khedrei]

So it's been a couple weeks and I've had time to digest, and research all the great info I got from all the replies.

I have watched the video for the JPI and doing the lean find.  I have yet to experiment with it.  I understand exactly what everyone has been saying regarding getting all the cylinders over the hump to the lean side and measuring the fuel flow between the leanest and richest cylinder.  I plan to do that.  I also plan to try and get to that course.  Hopefully I can find some locals that want to fly there together.

I did notice what seems to be an ongoing issue with my #4 cylinder and wondered if anyone would have any insight before I take it in to either my mechanic in Burlington or to Clarence.  This is the same cylinder that gave me an issue last time.  I took off with the mixture leaned slightly and noticed right away and selected full rich.  Everything was still in normal ranges though with the TIT higher around 1450 until I pushed the mixture in then of course it cooled down.  On the climb, with the cowl flaps open I got a CHT warning on Cylinder #4.  The gauge seemed to be going up and down erratically, but climbing none the less.  It hit around 520.  I already had the mixture full rich so I pulled the power back to 20" and leveled off.  It calmed down reasonably quickly and then settled back to stable with the rest of them.  After a few minutes at low power setting I increased the power to 25" then back to normal cruise at 28" and it was fine at first, then it happened again.  My fuel flow at 28" was around 12GPH or more.  Even when the power was at 20" and 10GPH it would read erratically high (giving me a warning in the 400's) and then settle down. But only on #4.

I am now wondering if it is more likely that the sensor is faulty and there is nothing wrong with the temperature.  Or, maybe the reading is right and there is an issue with a fuel injector or spark plug?  Looking for some insight from people more knowledgeable than I am to tell me what the likelihood of any of these situations causing what I am seeing, even at low power settings.  The first leg of the flight at 28" normal cruise the whole 45 minutes I did not notice anything out of the ordinary.

Any ideas or suggestions would be greatly appreciated.  Or anything I am able to do myself before taking it in to the mechanic to have it narrowed down first.  It seems that if this is a problem, it is intermittent.  So I am worried they may not be able to duplicate it easily.

Edited May 4, 2017 by khedrei

[DonMuncy]

The first thing would be to swap the sensor with another cylinder and see if the high reading follows the sensor. I suspect it will.

[Shadrach]

On April 20, 2017 at 10:58 PM, aaronk25 said:

 

There is no way possible to get any mooney turbo charged or not to detonate on 100ll. ZERO chance. Now you can get it hot and run it at the high factory chts limits or on turbos at the egt limits but your never going to get the engine to denonate running 100ll. Just not going to happen. 100ll is some really good stuff!

None of the mooney aircraft have really high strung motors. Now, there are some twins out there with geared higher rpm motors that this wouldn't apply to.

As far as a naturally aspirated M20 if you can keep the CHTs at 380 or below (and with turbos comply with egt and MP limitations) there is no power configuration the engine can be set as that won't yield a full TBO if run continuously.

Yes a O-360 or IO-360 will run wide open throttle at peak egt at sea level turning 2700rpm for 2000 hours.

It's not high power that kills these engines its heat and internal rust (sitting for long periods of time with infrequent operation).






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Aaron,

i agree that it would be difficult, but "zero chance" is the kind of statement that get's folks into trouble. I am pretty sure that I could purposely induce detonation in both an NA or turbo'd Mooney. It would take some positively abusive power settings, steep climbs at ruduced rpm and high OATs, but I think I could do it. With a turbo it would be easier. 

[jlunseth]

1 hour ago, DonMuncy said:

The first thing would be to swap the sensor with another cylinder and see if the high reading follows the sensor. I suspect it will.

i agree with Don, it sounds like a sensor issue, but do get it checked out because if the temp really is that high it is a safety of flight issue.

 

 

[Bob - S50]

11 hours ago, khedrei said:

So it's been a couple weeks and I've had time to digest, and research all the great info I got from all the replies.

I have watched the video for the JPI and doing the lean find.  I have yet to experiment with it.  I understand exactly what everyone has been saying regarding getting all the cylinders over the hump to the lean side and measuring the fuel flow between the leanest and richest cylinder.  I plan to do that.  I also plan to try and get to that course.  Hopefully I can find some locals that want to fly there together.

I did notice what seems to be an ongoing issue with my #4 cylinder and wondered if anyone would have any insight before I take it in to either my mechanic in Burlington or to Clarence.  This is the same cylinder that gave me an issue last time.  I took off with the mixture leaned slightly and noticed right away and selected full rich.  Everything was still in normal ranges though with the TIT higher around 1450 until I pushed the mixture in then of course it cooled down.  On the climb, with the cowl flaps open I got a CHT warning on Cylinder #4.  The gauge seemed to be going up and down erratically, but climbing none the less.  It hit around 520.  I already had the mixture full rich so I pulled the power back to 20" and leveled off.  It calmed down reasonably quickly and then settled back to stable with the rest of them.  After a few minutes at low power setting I increased the power to 25" then back to normal cruise at 28" and it was fine at first, then it happened again.  My fuel flow at 28" was around 12GPH or more.  Even when the power was at 20" and 10GPH it would read erratically high (giving me a warning in the 400's) and then settle down. But only on #4.

I am now wondering if it is more likely that the sensor is faulty and there is nothing wrong with the temperature.  Or, maybe the reading is right and there is an issue with a fuel injector or spark plug?  Looking for some insight from people more knowledgeable than I am to tell me what the likelihood of any of these situations causing what I am seeing, even at low power settings.  The first leg of the flight at 28" normal cruise the whole 45 minutes I did not notice anything out of the ordinary.

Any ideas or suggestions would be greatly appreciated.  Or anything I am able to do myself before taking it in to the mechanic to have it narrowed down first.  It seems that if this is a problem, it is intermittent.  So I am worried they may not be able to duplicate it easily.

If the CHT got that high I would probably have my mechanic borescope it just to make sure there was no damage.  I would probably have him check the injector nozzle for an obstruction.  And I would download the data from the 730 and view it.  I would pay particular attention to the EGT as I changed the mixture.  Does the EGT track along with the others or is it much higher than the others?  That is, does the EGT on that cylinder approach peak EGT while the others are still well ROP?

If the injector on that cylinder was partially blocked, it would cause that cylinder to run much leaner than the others.  At high power settings you could be getting detonation, but hopefully not pre-ignition.  Although if the CHT really did get to 520, you may have gotten into pre-ignition.  Seems like the engine would have been complaining though.

Hopefully it is just the sensor though.

[khedrei]

I honestly can't accurately remember how the EGT behaved.  #4 and #5 seem to always be hottest even when everything is stable.  That is, just one or two ticks higher on the graph for CHT and EGT.  I will have to look into downloading the JPI.  Not even sure how to do that.  I will have to talk to my CFI, he is very helpful when it comes to this stuff.  And I will call the mechanic and book an appointment.  The engine never ran rough, and never seemed to behave poorly.  Everything was smooth the entire flight.

 

Thanks for the input.  I will post further developments if I need more suggestions.  I appreciate all the responses.

 

Kevin

Edited May 5, 2017 by khedrei

[kortopates]

If it was me, I would download the data to see if it's a bad probe and if there was any uncertainty in that I would borescsope the cylinder in an abundance of caution before further flight. 520F is way over redline.



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