2659AU

EGT increased running LOP

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Has anyone had a similar experience with an Acclaim? Our Acclaim has just started running a little rough in the cruise when running Lean of Peak. At the same time Cyl #2 has seen quite an increase in EGT. When reverting to Rich of Peak there engine runs smooth and EGTs are balanced.  Engine has 1200 hours, but about 200 hours since top overhaul. Ignition? Fuel? Valves? Compression?

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Sounds similar to a blocked fuel injector...

Got any engine monitor details to share?

saavy is our go to source for posting JPI data... not sure what your Acclaim has to share.

Best regards,

-a-

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How lean of peak were you? It’s not abnormal to see a second EGT rise as the engine nears roughness. It’s the result of a combustion event that is occurring so slowly that it is still burning when the exhaust valve opens and the piston pushes it into the exhaust stack.

Edited by Shadrach
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I’m having a very similar problem. 

Started at just rough lop, changed plugs, adjusted timing and swapped 3/6 to correct temp inversion injectors to see if that would help. Timing helped with starting, but still rough at lop. Brought it back changed diaphragm in the pump and cleaned the strainer, changed back injectors and same rough and now 2&4 are about 80deg higher egt than rest of cylinders. 

Mechanic said could be debris in injectors and cleaning today. 

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Have you done a careful, slow GAMI lean test, noting the FF where rack cylinder peaks? If they are close, then I would suspect an ignition problem: mags or harness.

Actual EGT number is not meaningful, and it is normal for the rear cylinders to be higher since they are exposed to the other two’s exhaust going by.

This is what mine looks like at peak while leaning: Er standby. Tapatalk won’t let me upload a picture...,

 

fixed it. I find that taking a picture of the display helps leaning to at least 50* LOP for each cylinder. Usually this requires 65* LOP TIT as #5 runs a little richer than the others

 


-dan

28FA6B34-3BC8-4472-9FE5-002253F510DB.jpeg

Edited by exM20K
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3 hours ago, Schllc said:

I’m having a very similar problem. 

Started at just rough lop, changed plugs, adjusted timing and swapped 3/6 to correct temp inversion injectors to see if that would help. Timing helped with starting, but still rough at lop. Brought it back changed diaphragm in the pump and cleaned the strainer, changed back injectors and same rough and now 2&4 are about 80deg higher egt than rest of cylinders. 

Mechanic said could be debris in injectors and cleaning today. 

It's hard to help without more information. What LOP setting were you using?  When did the change occur?  The rough running cylinder should be pretty apparent on the monitor. Which way was the timing adjusted? Retarding the timing will narrow the the spectrum of smooth LOP settings. It will also decrease max power on either side of the mixture spectrum.  There are mechanics that have a firm understanding of combustion science and there are mechanics that do not. AFAIK, certification does not focus on detailed analysis of combustion issues.  It's not unusual to find expensive parts being thrown at simple problems.

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My only other reference was my ovation with the same engine sans turbos...

that engine ran great @50deg lop, and the gain in speed didn’t justify the fuel burn.

when I try to lean the acclaim, at 8-10k (at all mp’s) it doesn’t even get to 30deg lop before it starts to get rough  cht’s are pretty fairly matched as were the egts with the biggest disparity being between 3&6.  If I leaned further it simply got rougher.

I can achieve some lop operations smoothly at low altitudes and low mp.

I have always read, and been told egt’s aren’t a factor in engine health. My mechanic who is well known and respected around here, when discussing this issue said that just isn’t true. He said elevated egt’s can damage your engine and plugs. 

I am not claiming to be a mechanic but I am far from helpless and he showed me the damage on my plugs. 

He cleaned all the injectors and still has the problem with 2&4.  

I ordered gami’s today.  At this point $500 is cheap compared to the commute back and forth to the mechanic, as well as his time, and can’t hurt anything.

i am interested to see how they use the engine data from the data card  I didn’t realize it was in a format I could import into a spreadsheet  

 

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The other possibility is the ignition system.  Leaner mixtures get harder and harder to ignite and will highlight any weakness in your ignition system.  Like @Shadrach mentioned, you can see a second EGT rise past peak, although I think this happens if one of the spark plug fails to ignite part of the time. Then you will see a gradual increase in EGT as the weaker spark fails to ignite the mixture more and more frequently.  Kind of like what happens if you do a mag check, but that fails one of the sparks 100% of the time.  This would only result in a little roughness and a little loss of power, certainly no worse than doing a mag check.

One suggestion might be to test your magnetos.  You can do a quick and dirty test by removing all the spark plugs, then checking how far each lead will spark to the airframe while someone cranks the starter (CAREFULLY!!).  IIRC, you should be able to get a 1/2" spark if your mags are good, less than 1/4" may be a sign of weak mags or bad e-gap timing from wear.  Don't quote me on those, and obviously don't try it without help from someone who's done it before.

Alternatively, if you know a mechanic who has a mag bench test setup, it should only take him an hour to remove each mag and check them.

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Typically an Aircraft engine will run further LOP at higher manifold pressure.   My normally aspirated four-cylinder will smoothly run 100° LOP down  on the deck.   It won’t come anywhere close to that at 10,000 feet.  Have you verified no intake leaks? 

Edited by Shadrach
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In fact I’d address any potential for induction leaks or a less than ideal ignition setup prior to ordering GAMIjectors.  Otherwise you’ll be asking for new restrictors if you discover anything else in the air / fuel / spark equation that will have an effect on GAMI spread. 

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It is my experience that whenever there is an issue with engine roughness running LOP in my 231, the first place to look is the ignition. The engine always runs more smoothly and deeper into LOP without a hiccup when I get it back from annual and the plugs and mags have been checked. More often than not it is one of the mags. That’s the first place I would look, the mags, then the wires and the plugs. Sometimes the connectors that plug into the mags get corroded, that will do it.

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A good inflight mag check with a full 60 seconds on each mag is good for gathering data. Upload the data to SavvyAnalysis and see what it shows.

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I am playing with this now, will get some pictures but when landing my No. 2 EGT Goes over 1700 on a normal basis.  On a 4.5 hr flight yesterday I was playing with it and runs great LOP but the 2 EGT worries me while leaning.  The TIT never gets to 1700, it tops out about 1670 or so it the EGTs go right through on the No. 2 ....

once I get it leaned and smoothed our it comes down to about 1670 or so, but is it ok running it there for extended periods?  I have read the same that you can’t get EGT hot enough to hurt anything but that seems pretty warm.

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On 8/30/2019 at 6:28 PM, Shadrach said:

How lean of peak were you? It’s not abnormal to see a second EGT rise as the engine nears roughness. It’s the result of a combustion event that is occurring so slowly that it is still burning when the exhaust valve opens and the piston pushes it into the exhaust stack.

Thanks for this. I've encountered this before and the reading I've done doesn't seem to mention this. Mike Busch mentions that he leans it to the extent needed for the range he wants, but when I tried this, I observed the second EGT rise and didn't understand why.

Edited by louisut

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EGTs have some interesting characteristics...

Often where we measure them has a distinct difference...

Thermodynamics makes it relatively easy to understand...

Most of us don’t remember much of the thermo stuff either... :)

How far down the exhaust pipe the thermocouple is, really counts... further from the exhaust valve, the colder... As exhaust gasses expand, they cool off... a lot!

Many thermocouples were installed after the plane left the factory... the exactness of the sensor location depended on the installer...

Next on the list of quirky sources of temp data... is the number of exhaust tubes feeding the thermocouple....

Exhaust gasses flow in waves of pressure... each time an exhaust valve opens... a wave of hot and burning gasses is released...

If you have a turbo charger (you do :)) where multiple tubes supply multiple waves of hot exhaust... the average reading over time (TIT) is actually higher than the average reading of only one exhaust tube (EGT) coming from a single cylinder...

The Long Body’s Ship’s EGT gauge is similar to the TIT... it has three tubes collected into one on the side of the Engine... rough leaning is done with the calibrated gauge using a blue box on the instrument... a white box if G1000 equipped...

Interestingly enough... some G1000 equipped Mooney Ovations actually callEd the EGT, a TIT... there is no turbo inlet temp on a NA Mooney... somebody didn’t finish the G1000 programming properly... For a few years...

When learning to lean a Mooney engine... some are so well balanced, like the M20K’s intake system... that you might lean until the fuel is no longer burning evenly enough... anything that interrupts the completion of the burn will have some raw fuel going into the exhaust... More opportunity for fuel burning down stream...

As Ross pointed out a case of slowing down the burn so much, it start to escape before completing the burn...
 

Any raw fuel getting to the exhaust system will cause elevated EGTs.... similar to a bad spark plug...
 

Compare your EGTs to you TIT and see if the TIT is reading higher... this is the case of six waves of exhaust feeding one thermocouple at the front of the turbo... 

The TIT sensor is pretty far downstream of the EGT sensors, but it is probably reading a higher number... This is all about the averaging of the Temp data...Over time... six pulses over the same amount of time...
 

How is that?

PP thoughts only, not a mechanic...

Fun stuff you can get involved discussing on MS...

Best regards,

-a-

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An additional leaning technique detail to consider...

Funny things happen when you lean too quickly...

Some of the newer TCs have thinner shielding... thinner shielding allows heat to transfer to the TC faster...

If you lean too quickly you go through peak and are LOP before the the TCs register a peak.... and start going down...

What happened?
If you begin enriching the mixture... to go back to where peak appeared to be the first time... it won’t be there... and it will be hotter....

There is some time required to allow the TCs to reach and equilibrate with the temperature of the exhaust gas...

The actual peak won’t move around... but finding it takes some practice...

When you get good at it... the OAT will change... or the altitude will be different... or something else will cause some difference....

Know that older TCs have thick sheaths or some mixture knobs that don’t have precise control... combine to make things more challenging...

Be patient and turn the knob slowly as you get near peak... you should be able to return if you went too far, slowly...

PP thoughts only...

Best regards,

-a-

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@exM20K looking at your picture, the only difference with my Acclaim is that the #1 EGT is consistently 50-75d lower than the rest of the EGTs.  I'm taking it this week for a 100hr and I'm going to have them look at it.  The CHT sensor has a problem too, it is all over the place.  

My question, however, is with respect to your EGTs in your Acclaim.  Are those figures in the picture about what you run after leaning or are you in the process there?  During cruise, I'm dialing it back to about 75% power and getting 185kts...my CHTs stay just north of 300 for the most part, which is actually on the chilly side, and my EGTs are in the 1640-1650 range, is that where yours stay during cruise?  What about CHTs?  Is low 300s about right in cruise?  I'm usually about 16000-18000'.  I usually file for 21k or 22k but so far they have never given it to me.

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@Bentonck I don’t care much about absolute EGT readings, only how far below peak each cyl is.  I do care about TIT for exhaust system life.  The pictures are snapshots I take at peak so I can be sure all are at least 50 LOP.  IUSUALLY WIND UP 65 ish LOP in  TIT, which has all cylinders where I want them.

on today’s trip to Florida, I tried running 2400 to lower the TIT.  The attached picture shows the power setting, and I found a few knots vs 2500 with a cooler exhaust.  That was 17,000 and about 200 KTAS.  Not too shabby on 16.2GPH. not book speed, but that’s the toll of TKS. 

CHTs are great in the acclaim.  Max 330 at those settings and ISA +5

 

 

DA16B76C-6E3D-4510-B7E7-D3E9869B1D60.jpeg

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Thanks for the feedback @exM20K .. that looks like my bird too.  I have not found a setting in the POH that yields what it says.  Mostly the fuel flows are too high for Best Economy.  If I run there I'm at or very close to peak EGT.  I have to pull the red knob back to get it leaned and all the BE settings are 2-3 gallons lower at TIT -50 than what the POH shows, which obviously is giving up the ponies so it's not going to make the speed they have on there but she runs like a top.

How many hours do you have on yours now?  Mine got two new cylinders at 650hrs buthe compressions are all good accross the board now and the guy I bought it from was running it ROP 30.5" - 2500rpm all the time. I think leaning it and bringing the RPM back a bit will help cylinder life, too.

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@Bentonck I pretty much disregard the factory power settings, and I agree that they run at temps that could put a real hurt on an exhaust system long term.  Finding peak takes a little time - it's not just the big pull, enrichen,  and lean.  that quick look shows a peak TIT that is often 15-20* lower than what it will settle at if you fiddle around the peak for a while.  so true 50*LOP can be 1690-1700 - at 2500rpm, it's not too hard to show a 1740+ peak tit.

Compression readings tell only part of the story.  borescope and oil consumption will tell you a lot more about a sick cylinder, and CMI is pretty liberal with what's allowable on compressions.

250 STOH and 1150TT.  My top was for corroded jugs and resultant high oil consumption.  The received wisdom is that 30.5x2500 ROP increases wear.  I choose not to run there because it is horrendously inefficient (25% more gas for 5-10% more speed), and I'm a CB.  Plus range.... and useful load.

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On 8/30/2019 at 7:08 PM, 2659AU said:

Has anyone had a similar experience with an Acclaim? Our Acclaim has just started running a little rough in the cruise when running Lean of Peak. At the same time Cyl #2 has seen quite an increase in EGT. When reverting to Rich of Peak there engine runs smooth and EGTs are balanced.  Engine has 1200 hours, but about 200 hours since top overhaul. Ignition? Fuel? Valves? Compression?

You have a monster fast (fuel guzzling) aircraft.   You could afford to buy it, now feed it and enjoy.

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My dad has a C-414A and he looked at the EGT gauge when I pulled up the engine screen and nearly fainted.  I told him that was normal... 

I am pulling back the RPM in flight due to the Mike Busch school of thought, I did get the TSIO-550G Engine Installation and Operation Manual and it shows the cruise range from 2500 down to 2100 RPM allowing up to 30.5" at any of those settings.  I am currently running most of the time at 30.5" - 2200 RPM - LOP and getting arnd 190kts +/- with 14.4gph...the cylinders are real, real cool there though.  In the POH they say to keep cylinders above 300 and at that setting they'll be right at or slightly below at cruise altitude.  This is when I'm going far and don't want to stop.  (In Brazil my average mission is several 200nm legs after one initial 860nm leg that I need to pull back the power to make without stopping)  ... the short legs I just leave the power in and pull the mixture back and run around 200kts on the shorter legs when I don't need to conserve fuel.

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On 9/14/2019 at 8:15 AM, Schllc said:

I have always read, and been told egt’s aren’t a factor in engine health. My mechanic who is well known and respected around here, when discussing this issue said that just isn’t true. He said elevated egt’s can damage your engine and plugs. 

I am not claiming to be a mechanic but I am far from helpless and he showed me the damage on my plugs.

How odd that your spark plugs are located in your exhaust port.

Edited by EarthboundMisfit
Typo
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17 hours ago, EarthboundMisfit said:

How odd that your spark plugs are located in your exhaust port.

Lol, to quote the Great Mark Twain, who also was not a mechanic, 

“Never argue with an idiot, They will drag you down to their level and beat you with experience”

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