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EGT whats good?


FlyboyKC

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In search of my oil consumption issue, my IA did a compression check and found that since January my compressions went from 72/80 to low 50s/80 one was at 45/50. The issue was the exhaust valves were leaking. The rings and cylinder bore were good shape. My IA state that I was running the engine too lean and that caused the valve guides to wear out and keeping the exhaust valve open.

I asked him what is a good value to keep the EGTs at and he stated no higher than 1250. He wasn't concerned with CHTs. From all the readings I have done, my IA logic seems reversed, and many sites indicate that EGT temps below 1600 are meaningless.

Before the engine repair, I was running the EGTs around 1279 - 1359 and the CHTs 279 - 330. 22mp/2400-2500 rpms.  My lean procedures were to pull the mixture until the engine started running rough and then push back in until it cleared.

The engine seemed like it was happy but I don't want to burn things up again. What values should I be targeting.
I have a M20G with the 180hp carburetored. 

Thanks
Neal

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What engine monitor do you have?  It sounds like you have a monitor that does each cylinder.  Most of those have a lean find procedure.  Whether you believe in LOP or ROP, if you have the equipment, you shouldn't be guessing by the engine running rough.  You could be way LOP or you could be right at peak when it smooths out - you just don't know.

If you want to run 15 LOP, or 60 ROP, you should be able to set it that way specifically and know the operating conditions.

Edited by hypertech
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19 minutes ago, FlyboyKC said:

In search of my oil consumption issue, my IA did a compression check and found that since January my compressions went from 72/80 to low 50s/80 one was at 45/50. The issue was the exhaust valves were leaking. The rings and cylinder bore were good shape. My IA state that I was running the engine too lean and that caused the valve guides to wear out and keeping the exhaust valve open.

I asked him what is a good value to keep the EGTs at and he stated no higher than 1250. He wasn't concerned with CHTs. From all the readings I have done, my IA logic seems reversed, and many sites indicate that EGT temps below 1600 are meaningless.

Before the engine repair, I was running the EGTs around 1279 - 1359 and the CHTs 279 - 330. 22mp/2400-2500 rpms.  My lean procedures were to pull the mixture until the engine started running rough and then push back in until it cleared.

The engine seemed like it was happy but I don't want to burn things up again. What values should I be targeting.
I have a M20G with the 180hp carburetored. 

Thanks
Neal

The misinformation fed to pilots by some A&Ps is astounding. There is nothing wrong with how you are managing your engine based on statements above. Your CHTs are enviable. Your EGTs are irrelevant. Your leaning procedure is perfectly acceptable and is being done at an appropriate power setting. You have done your homework, and you are right. Your A&P is dead wrong. Given the level of trust inspired by this individual, I would switch shops entirely and start over. Hopefully you are not in an annual inspection.

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19 minutes ago, hypertech said:

What engine monitor do you have?  It sounds like you have a monitor that does each cylinder.  Most of those have a lean find procedure.  Whether you believe in LOP or ROP, if you have the equipment, you shouldn't be guessing by the engine running rough.  You could be way LOP or you could be right at peak when it smooths out - you just don't know.

If you want to run 15 LOP, or 60 ROP, you should be able to set it that way specifically and know the operating conditions.

Disagree.  Lean find is of little use with carb'd engines because the cylinders are all quite different for peak EGT - you're just setting the leanest cylinder and the rest are all over the place.  Typically "lean to rough, enrich slightly to smooth" gives the same answer as trying to use lean find on the leanest cylinder.

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26 minutes ago, hypertech said:

What engine monitor do you have?  It sounds like you have a monitor that does each cylinder.  Most of those have a lean find procedure.  Whether you believe in LOP or ROP, if you have the equipment, you shouldn't be guessing by the engine running rough.  You could be way LOP or you could be right at peak when it smooths out - you just don't know.

If you want to run 15 LOP, or 60 ROP, you should be able to set it that way specifically and know the operating conditions.

I have the EI-UGB-16 Engine Monitor. As I explained to the IA, without knowing what values are correct, the only way for me to find any value is to lean to rough and pull back to get a baseline.

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I would also be interested in what everyone else is doing to properly lean their carb’d birds. I have an engine monitor that displays temps (egt and cht) and can scan for the highest. I scan for the highest egt while in cruise and try to go at least 60 ROP. My CHTs seem to have a rather wide gap between the highest and lowest so I try and keep the highest at 380 or lower (I never get close to this high in cruise).


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4 minutes ago, bradp said:

I’d be more interested to know how many engine hours, how many are yours and whether the valve wobble test or any reaming has ever been done.  The EGTs are from all objective perspective, meaningless 

The Engine has 660 hours SMOH. Not sure about the wobble test or reaming.

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27 minutes ago, bradp said:

I’d be more interested to know how many engine hours, how many are yours and whether the valve wobble test or any reaming has ever been done.  The EGTs are from all objective perspective, meaningless 

Actual EGT numbers mean nothing, especially when comoaring against another airplane. The reason why is that moving the thermocouple a quarter inch will have a signjficant effect on the value it shows. 

What is important is how far you are running below peak. My C has the same engine as your G, and I often cruise at 1450°F. For me, with my factory single EGT probe (mounted on #3), I lean to peak then push for 50° cooler. It generally gets rough at peak. 

As long as you are at 65% power or less, you can put the mixture just about anywhere. One often-recommended procedure that saves flipping through your Performance Charts is to use the numbers on MP and tach like this:  MP + RPM = 46, a conservative, safe place to run.

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1 hour ago, FlyboyKC said:

I asked him what is a good value to keep the EGTs at and he stated no higher than 1250. He wasn't concerned with CHTs.

 

Look into how many GPH is being burned at 1250... provided you have accurate EGT probes.

EGT values aren't carved in stone. That said, saying they are meaningless might be going a bit far.

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21 minutes ago, Hank said:

The reason why is that moving the thermocouple a quarter inch will have a signjficant effect on the value it shows

 

Just how much of a "significant effect" will a 1/4" placement make when the EGT Thermocouple it's properly positioned in the exhaust stack?

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2 hours ago, FlyboyKC said:

In search of my oil consumption issue, my IA did a compression check and found that since January my compressions went from 72/80 to low 50s/80 one was at 45/50. The issue was the exhaust valves were leaking. The rings and cylinder bore were good shape. My IA state that I was running the engine too lean and that caused the valve guides to wear out and keeping the exhaust valve open.

I asked him what is a good value to keep the EGTs at and he stated no higher than 1250. He wasn't concerned with CHTs. From all the readings I have done, my IA logic seems reversed, and many sites indicate that EGT temps below 1600 are meaningless.

Before the engine repair, I was running the EGTs around 1279 - 1359 and the CHTs 279 - 330. 22mp/2400-2500 rpms.  My lean procedures were to pull the mixture until the engine started running rough and then push back in until it cleared.

The engine seemed like it was happy but I don't want to burn things up again. What values should I be targeting.
I have a M20G with the 180hp carburetored. 

Thanks
Neal

That is a BIG change in compression.  Are you CERTAIN the compression test was done correctly?   Given the questionable statements he is making, I would probably find someone to do a compression test to verify his numbers.  He could have done it wrong or even had a misbehaving gauge.

Your temps are really cool!

Edited by Austintatious
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One problem I’ve had with the key numbers and poh cruise settings is they don’t always give the same guidelines. There can also be large discrepancies between factory gauges. However, the OP mentions power settings of 74-76 percent power based on the POH. His leaning implies running the engine at peak egt’s.  The mechanic might have a point. I normally run peak on my C at setting lower than 20/24 with a lot of time spent at 19.5 and 2350 burning 6gph.  If I’m running 22/24 I’m well rich of rough, 75-130 rop because of the wide carb cyl spread. 

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With enough work fixing induction leaks, especially the carb heat box, it is possible to run our O-360s LOP; mine is often good to about 25°LOP now. But I still run 50 ROP. the trip to the Summit was right at 50°ROP; initially 7500 msl, 21"/2500 before clibing to 9500 and running (WOT - a tad) / 2500. Both peaked right at 1500, so I pushed the red lever for 1450. ASI was hovering between 140-145 mph, a little higher at 9500 than at 7500. 

I've been doing this the last 700 hours; the plane had ~180 on the engine when I bought it, it's now about 860, and compressions have never fallen below 75 on any cylinder and are often 76-78 on all four. The MAPA PPP saved me lots of page flipping, as I just make sure MP + RPM <= 46 instead of worrying about % power. But I verified things for a year or so before figuring out some basic settings that cover most of my flying (whuch also simplifies IFR flying with step changes up and down).

The important part of EGT is not the absolute number, but the distance from peak.

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2 hours ago, Huitt3106 said:

I would also be interested in what everyone else is doing to properly lean their carb’d birds. I have an engine monitor that displays temps (egt and cht) and can scan for the highest. I scan for the highest egt while in cruise and try to go at least 60 ROP. My CHTs seem to have a rather wide gap between the highest and lowest so I try and keep the highest at 380 or lower (I never get close to this high in cruise).


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Frankly the carb'd birds are so imprecise in leaning that there's not that much to say here.  Even talking about "ROP" and "LOP" as general statements about the overall combustion state of an O-360 makes little sense to me -  each cylinder is doing something different.  I also see no reason to consistently cruise at 60 ROP on your leanest cylinder - waste of fuel for little added benefit, though probably nothing really wrong with doing it.  If you're going for best power, it's hard to predict exactly where you will get it based on that one cylinder anyway but it will be somewhere with the majority of cylinders ROP.  Don't lean at all above 75% power. I start leaning gently in the climb as tolerated by CHTs once at 75% based on MP at WOT - just to get a little more power for climb and cut fuel flow slightly.  At or below 65% power, you really can do no wrong- might as well take the maximal fuel savings possible by leaning to roughness and then enriching slightly (assuming CHTs stay under 400). Trying for best power is guesswork since the cylinders are all different. It also won't be much faster but may cost a couple more gph.  

There is some concern with stressing your cylinders by leaning aggressively between 65% and 75% power based on the "red box/red fin" charts, but I have stopped worrying about this so much. I simply let my CHTs tell me how far I can go under those power settings as well and try not to cruise at settings above 65% all the time. Inevitably some cylinders will be stressed more than others under these conditions, but the "bulletproof" O-360 is not going to make you fall out of the sky because of this. 

Edited by DXB
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55 minutes ago, MIm20c said:

. However, the OP mentions power settings of 74-76 percent power based on the POH. His leaning implies running the engine at peak egt’s.  The mechanic might have a point. 

The OP describes using 2400-2500rpm and 22mp. It's hard to predict where the individual cylinders each fall relative to peak EGT if you lean to roughness and enrich slightly until smooth again, but they will all be different.  For me, one is 10 LOP and the other are various degrees ROP.  2400 and 22mp does adhere to the MAPA "magic number" of 46, and I doubt he is really ever leaning above 75% power against the POH and lycoming guidelines. I am utterly incredulous that all of his cylinders simultaneously developed exhaust leaks and resulting compressions in the 50s because of operating the way he describes.  

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If you have not read what Mike Busch (Savvy Aviation) has written on leaning you should Google "Mike Busch leaning". Mike's been studying engine management for a very long time. He has debunked quite a few OWTs. Below is a video seminar but there are many other articles as well as 2 books. 

(FWIW, I cruise my IO360 LOP and 65% power. Exhaust valves are sealing just fine... compressions are always 78/80 or better. Running LOP lowers CHTs, saves fuel, reduces lead buildup, and extends range.)

 

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1) Raw EGT data is indeed hard to compare when the sensors are placed without using a fixture designed for the purpose....  the exhaust gasses are expanding rapidly as they go down the pipe... the random expansion drops exhaust temps a lot as they go down the pipe...  check your EI installation procedures for where they should be... and compare to where they actually are...

2) 60’s Mooneys didn’t get that fixture like the more recent birds did... some installations by shops around the world were done differently for a variety of reasons...

3) There is an answer to what EGTs are good...  use the ones that don’t allow the exhaust tubes to glow bright red... if possible...

4) Glowing red is a hint of the metal getting to a softer status than when cold...

5) For the O360 heat damage appears in a couple of places... the exhaust tubes right outside the exhaust valve... and the flame tubes inside the muffler... melted and missing flame tubes occur just before the Muffler leaks internally... a strong source of CO in the heat system...

6) the exhaust system is  sensitive to time and temperature...   PIC gets to decide how hot to run the exhaust...

7) Soooo... Actual EGTs do have a meaning.   :)

8) Just Peak EGT has more meaning...

9) Now we covered what probably isn’t today’s challenge... Neal, its time to check how the compression test was run... hot or cold? Sounds like it was done cold... air leaking into the exhaust can be heard at the exhaust pipe...

10) re-run the compression tests the proper way... if it still leaks, dental camera in the cylinder looking at the valves... Pizza or no pizza?

11) this is what happens when valves stop rotating...

12) Got any EI data to share?   Download, send to savvy, drop the link here... :)

13) EGT/CHT data combine with FF data, MP and RPM, often makes a picture of what isn’t working properly... a picture is worth...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

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5 hours ago, Bob_Belville said:

If you have not read what Mike Busch (Savvy Aviation) has written on leaning you should Google "Mike Busch leaning". Mike's been studying engine management for a very long time. He has debunked quite a few OWTs. Below is a video seminar but there are many other articles as well as 2 books. 

(FWIW, I cruise my IO360 LOP and 65% power. Exhaust valves are sealing just fine... compressions are always 78/80 or better. Running LOP lowers CHTs, saves fuel, reduces lead buildup, and extends range.

Mike Busch certainly knows much more than I do, but either way, it's difficult to run an O-360 like the OP and I both have, using typical fuel-injected LOP procedures, and the speed reduction is significant when it does work. I haven't given up on leaning to the extent that @DXB has yet, though, and think that I actually get meaningful, beneficial information. She sure does speed up when I pull the prop back, slightly reduce throttle and pull the red lever back . . . .

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Placement of a temperature probe and the temperature it measures, in this case an EGT probe, is sensitive to its location.  Move it up or down the temp will change with the exact same engine settings.  Move the probe around from say a 1o'clock position to a 3 o'clock position in the tube the temperature measured will change.  How much change that is unknown to me. 

 

One day I would like to temporarily place 12 EGT probes in the same tube at different heights and locations to record the temperature differences in temperature on a single cylinder just to see how much the temperatures can vary due to probe location.

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For those who may not be aware, and I am sure most are, most of what Mike Busch and others talk about in engine management and leaning comes from the engine management seminars with Advanced pilot Seminars in Ada, Oklahoma (www.advancedpilot.com).  I have done their online course and it was great.  I know that the in person course is even better but I have not been.  I don't really have the need to go since I have an O-360-A1D and it won't even get close to LOP.  I have had intakes checked for leaks, I try to add carb heat and crack the throttle, etc... all the tricks they talk about it and no soap.  When I do get everything running LOP according to my engine monitor, the engine is so rough that it feels like it could quit at any moment. :) 

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13 hours ago, FlyboyKC said:

In search of my oil consumption issue, my IA did a compression check and found that since January my compressions went from 72/80 to low 50s/80 one was at 45/50. The issue was the exhaust valves were leaking. The rings and cylinder bore were good shape. My IA state that I was running the engine too lean and that caused the valve guides to wear out and keeping the exhaust valve open.

I asked him what is a good value to keep the EGTs at and he stated no higher than 1250. He wasn't concerned with CHTs. From all the readings I have done, my IA logic seems reversed, and many sites indicate that EGT temps below 1600 are meaningless.

Before the engine repair, I was running the EGTs around 1279 - 1359 and the CHTs 279 - 330. 22mp/2400-2500 rpms.  My lean procedures were to pull the mixture until the engine started running rough and then push back in until it cleared.

The engine seemed like it was happy but I don't want to burn things up again. What values should I be targeting.
I have a M20G with the 180hp carburetored. 

Thanks
Neal

Did your A&P show you borescope pics of the leaking valves?

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2 hours ago, Hank said:

Mike Busch certainly knows much more than I do, but either way, it's difficult to run an O-360 like the OP and I both have, using typical fuel-injected LOP procedures, and the speed reduction is significant when it does work. I haven't given up on leaning to the extent that @DXB has yet, though, and think that I actually get meaningful, beneficial information. She sure does speed up when I pull the prop back, slightly reduce throttle and pull the red lever back . . . .

Hank, do you have FF? Can you use flow to get close to an acceptable mixture?

And I would suppose that even if the gami spread for the O360 is too great to run LOP it still would be useful to do a ROP lean find and know how far ROP you're running on the leanest cyl. 

My experience with carburetor'd engines is limited. I know I ran out of gas early in my flying career in a rented G. At least the way I ran it, the G used a lot more fuel that the E I had flown.   

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3 hours ago, bluehighwayflyer said:

Agreed.  It’s fuel injected engine and ability to run LOP and set power via fuel flow is what I miss most about my former J.   This carbureted engine management stuff is a pain. I find the “lean to rough then enrichen until smooth” technique combined with the key number of 46, although crude, works best for me.  I need a vernier mixture control, though.  The OEM ‘65 push button and pull or push mixture control is suboptimal at best.  

Jim

I know a lot of people haven't watch a lot of Savvy aviation videos, but I do remember him talking about trying to get better efficiency out of carburated engines... One thing he mentions that I thought would be worth mentioning is to NOT fly at WOT.  Instead you should pull back just below WOT.  This does 2 things.   The first is that at WOT a little extra fuel is being sent into the engine to protect it on takeoff.  By reducing below WOT this "circuit" is eliminated.  The second thing this does is add turbulence to the intake which better mixes the air and fuel.

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44 minutes ago, Austintatious said:

I know a lot of people haven't watch a lot of Savvy aviation videos, but I do remember him talking about trying to get better efficiency out of carburated engines... One thing he mentions that I thought would be worth mentioning is to NOT fly at WOT.  Instead you should pull back just below WOT.  This does 2 things.   The first is that at WOT a little extra fuel is being sent into the engine to protect it on takeoff.  By reducing below WOT this "circuit" is eliminated.  The second thing this does is add turbulence to the intake which better mixes the air and fuel.

Yep, that's what I call "WOT-". Pull the throttle back just enough to make the MP needle move, remember the number; set RPM; pull throttle back to restore previous number. Then lean.

Works great for me. Ever since fixing my carb heat box, I can run smoothly down to 25°LOP like this, without experimenting with partial carb heat. But it's so S - L - O - O - O - W - W . . .  

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