High CHT, 470 degrees +.

[ragedracer1977]

Yes.  That's accurate.  

I've been chasing a hot #4 for a couple months now.  I had an EI UBG16.  It was showing #4 getting up to 450+ on climb out.  I made sure the baffles were tight.  They're probably the tightest baffles on the planet right now.  I changed spark plugs.  I basically did everything I can think of.

Now, I've installed a JPI EDM900.  Things have not improved.  It's the hottest cylinder by far. I could cook it pretty quick if I wanted to. On the flight linked below, I had to reduce MP, pull back the prop, and reduce climb to 2-300 fpm at 120 mph.  That kept it under 470.  Barely.

Notice that the EGT on 4 is fairly low compared to the other cylinders.  What would cause high CHT but lower EGT?  This is a carbureted O-360.  We borescoped the cylinder, exhaust valve looks fine (see photo), if maybe a little lean? Compression was 78/80.

I'm guessing it's time to call in a big gun.  I'm just trying to lead whoever it is in the right direction.

I tried to do the tests savvy lists (in flight mag check, gami spread, and intake leak test per this link https://www.savvyanalysis.com/articles/in-flight-diagnostics) but I'm not sure if I did it correctly.  If you see the big MAP drops, each test was just after each one, in order.

 

https://apps.savvyaviation.com/flights/3848176/e49136de-09b7-42e2-8cba-889fd5808680

[carusoam]

First thing that comes to mind...

CHTs are a function of heating-cooling.... as in H minus C...

Sounds like you put a fair amount of effort into evening out the cooling...

So... let’s spend a moment on the heating part...

Have you done a gami spread?

Is this cylinder running leaner than all the others, when ROP?

similar question...

Is this cylinder running richer than all the other ones, when LOP?
 

If something is causing an actual elevated EGT in that cylinder... it will be producing more heat than the others...

Best regards,

-a-

[orionflt]

I am assuming you changed the probe when you upgraded the engine monitor. 
 

are your cowl flaps open? 
what was your oil temp?  

how did the EGT compare to the other cylinders?

where is your oil cooler located? Lower cowling, or relocated behind #4 cylinder?

Brian

 

[ragedracer1977]

3 minutes ago, orionflt said:

I am assuming you changed the probe when you upgraded the engine monitor. 
 

are your cowl flaps open? 
what was your oil temp?  

how did the EGT compare to the other cylinders?

where is your oil cooler located? Lower cowling, or relocated behind #4 cylinder?

Brian

 

Yes, new probe.  I tried swapping from #2-4 also.  No change.  

Oil temp maxed out at 191, but was under that most of the time.

Cowl flaps opened.  

EGT was mostly the 2nd lowest.

Oil cooler is in the cowl 

[ragedracer1977]

13 minutes ago, carusoam said:

First thing that comes to mind...

CHTs are a function of heating-cooling.... as in H minus C...

Sounds like you put a fair amount of effort into evening out the cooling...

So... let’s spend a moment on the heating part...

Have you done a gami spread?

Is this cylinder running leaner than all the others, when ROP?

similar question...

Is this cylinder running richer than all the other ones, when LOP?
 

If something is causing an actual elevated EGT in that cylinder... it will be producing more heat than the others...

Best regards,

-a-

I tried the gami spread per the savvy article, but I don't really know how to interpret it from the JPI data.  It's also a carbureted engine.

EGT is actually depressed compared to the other cylinders, it's just the CHT that's high

[carusoam]

Brice,

can you describe the difference between your flight at 10:00 and again at 30:00... (generally)

There is an interesting change between the two...

The hottest EGT turns into the coldest EGT between the two times... the red line swaps (sort of) with the purple line...

The EGTs are still valid like in an IO360, just not as well controlled...

Anything more than just the 100rpm difference? 2540 vs 2400...

I see many changes of the FF, but no MP data to match...

Best regards,

-a-

[N201MKTurbo]

That cylinder must be running lean. Possibly an intake leak. Have you done a GAMI test? I know you have a carb, but it will show your mixture distribution.

[ragedracer1977]

4 minutes ago, carusoam said:

Brice,

can you describe the difference between your flight at 10:00 and again at 30:00... (generally)

There is an interesting change between the two...

The hottest EGT turns into the coldest EGT between the two times... the red line swaps (sort of) with the purple line...

The EGTs are still valid like in an IO360, just not as well controlled...

That would have been in descent I think. I'm on my phone and it's really hard to look at the graph to make sense of it

[ragedracer1977]

Just now, N201MKTurbo said:

That cylinder must be running lean. Possibly an intake leak. Have you done a GAMI test? I know you have a carb, but it will show your mixture distribution.

I did, it's in the graph from the analysis. I just need to interpret it

[carusoam]

So far...

we (MS) is possibly seeing a fuel distribution challenge... the fuel ratio for that cylinder may be getting interrupted...

Possibly an air leak form the outside, or excess fuel getting there from the inside...

The savvy page you included mentions how to test for air leaks... hi and low MP tests...

 

The third thing that is sticking out a little... the run-up should have two similar peaks... when one is taller than the other that is an indication of different timing between the mags... (probably not the issue with one hot cylinder...)

Slowing down the tests to include more data is always going to be helpful...

Best regards,

-a-

 

[carusoam]

Let’s look at the first half of the graph...

See the first two peaks... they should be near identical... their not really identical...

and the red EGT is worth looking at closer...

As much as EGT4 is sky rocketing unlike the others...

EGT1 has fallen out the bottom and doesn’t even show a peak....

Cht4 hot

Cht1 cold

Back to running a Gami test as smoothly as possible...

And an intake leak test to see if the intake is the cause of the bad Gami results...

Full power is showing the hottest EGT... looks like a leak may be occurring more under WOT...

PP thoughts only, not a mechanic...

Best regards,

-a-

[cbarry]

A couple of items yet mentioned:  1) could there be an exhaust flange leak throwing heat over the probe? 2) have you confirmed adequate oiling of that cylinder (oil return line restricted causing poor oil flow thus causing reduced heat dissipation...)?

[carusoam]

Using the FF as a substitute for MP...

you can see when WOT occurs (near 7:00), and how the MP is dialed out after 9:00... FF isn’t stable, as the MP is falling with altitude...

I included RPM for reference this time...

Probably good to invite @Hank to this conversation...

Any idea how many hours on the carburetor?  
 

Which reminds me to invite @DXB Dev... as he has chased a few O360 challenges over his ownership... Dev may be Corona-busy...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

 

[ragedracer1977]

22 minutes ago, carusoam said:

Let’s look at the first half of the graph...

See the first two peaks... they should be near identical... their not really identical...

and the red EGT is worth looking at closer...

As much as EGT4 is sky rocketing unlike the others...

EGT1 has fallen out the bottom and doesn’t even show a peak....

Cht4 hot

Cht1 cold

Back to running a Gami test as smoothly as possible...

And an intake leak test to see if the intake is the cause of the bad Gami results...

Full power is showing the hottest EGT... looks like a leak may be occurring more under WOT...

PP thoughts only, not a mechanic...

Best regards,

-a-

I'm not sure they should be identical. The first peak is the standard magneto.  The second peak is the surefly electronic ignition.  I think I would expect slightly different results.  But I don't know.

[ragedracer1977]

24 minutes ago, cbarry said:

A couple of items yet mentioned:  1) could there be an exhaust flange leak throwing heat over the probe? 2) have you confirmed adequate oiling of that cylinder (oil return line restricted causing poor oil flow thus causing extra friction...)?

#1 I don't believe so. There aren't any signs of an exhaust leak.

#2.  No. This is where a mechanic would come into play as I have no idea how to do that 

[carusoam]

Makes you want to check the timing on the old mag...

The peak behavior of the mag test is a mag timing related test...

If advanced... more fuel is burned before leaving the exhaust valve... (lower peak EGT)
If retarded... More fuel gets burned in the exhaust pipe as it is passing the EGT sensor... (higher peak EGT)

 

The usual JPI graphs around here have near identical peaks...

It will be interesting to see if other Surefly users are seeing the same thing...

Best regards,

-a-

[ragedracer1977]

5 minutes ago, carusoam said:

Makes you want to check the timing on the old mag...

The peak behavior of the mag test is a mag timing related test...

If advanced... more fuel is burned before leaving the exhaust valve... (lower peak EGT)
If retarded... More fuel gets burned in the exhaust pipe as it is passing the EGT sensor... (higher peak EGT)

 

The usual JPI graphs around here have near identical peaks...

It will be interesting to see if other Surefly users are seeing the same thing...

Best regards,

-a-

Timing was checked 3 days ago. It's dead nuts on 25 degrees. Brand new magneto 30 or so hours ago.  If I had a monitor before the new magneto, I imagine it would show similar behavior.  I've been dealing with this heating issue for quite some time

[ragedracer1977]

I did the intake leak test at 26-28 minutes.  The behavior is unexpected.  At 23" mp, the egt on 1,2,4 were lower than at 13" mp.  #3 was higher at 23" than 13"

[ragedracer1977]

FF WOT full rich 13.9 #1-1190 #2-1123 #3-1290 #4-1157

#3 FF 10.3gph 1446 EGT rise 156f

#1 FF 8.7gph 1419 EGT rise 229f

#2 FF 8.5gph 1438 EGT rise 315f

#4 FF 8.5gph 1427 EGT rise 270f

 

theres the GAMI spread.  #2 and #4 peaked at the same time. #4 being the hottest CHT at the time at 428f, #2 at 378.

 

Edited April 7, 2020 by ragedracer1977

[ragedracer1977]

If anything that even deepens the mystery. #4 seems not to have an induction leak nor does it seem to be too lean, judging by the EGT rise.

[carusoam]

Double check your FF at WOT...

Or... what altitude MSL is your airport at?  240’

I was expecting a number closer to 18gph at sea level...

At 310hp... my WOT is close to 30gph...

Just a detail we should look up...
 

I looked this one up... it said 14.9 gph at 2700 rpm, WOT... O360(E) but yours is not the E version.

https://www.lycoming.com/sites/default/files/O-360- (76 Series) Oper Manual 60297-25.pdf

 

Realistically.... the O360A1D May be found in here... just more complex to find your actual engine... and it may take being a mechanic to determine what the FF should be for your engine...

https://www.lycoming.com/sites/default/files/O-HO-IO-HIO-AIO %26 TIO-360 Oper Manual 60297-12.pdf

 

It looks like you may be running a touch lean... and that may explain why such a hot cylinder without any air leaks or any leaning involved...

If nothing else...

There is a document used to set up the max FF for every Mooney... FAA TC for M20s... (type certificate) find the section for M20C... it is full of great details like this...

Best regards,

-a-

[ragedracer1977]

I believe it's 18 gph at sea level.  Density altitude today was 3600'.  

Nope, it's 16.  So my fuel flow shouldn't be an issue 

Edited April 7, 2020 by ragedracer1977

[carusoam]

Density altitude definitely affects the HP... MP, and the ability of the prop to pull through the air...

And the wing’s ability to generate lift...

Surprised that the book doesn’t mention DA when handing us the FF chart...

Hmmm...

When it comes to tough engine monitor challenges...  we can see if @kortopates Paul is around...

He can probably see what we missed... or give us better insight to what needs to be done next...

Best regards,

-a-

[MikeOH]

1 hour ago, ragedracer1977 said:

Timing was checked 3 days ago. It's dead nuts on 25 degrees. Brand new magneto 30 or so hours ago.  If I had a monitor before the new magneto, I imagine it would show similar behavior.  I've been dealing with this heating issue for quite some time

Do you know you had the issue BEFORE the new mag? How about BEFORE the Surefly?

When you say the timing was checked at 25 degrees, that was only for the mechanical mag, correct?

I'm just suspicious of the electronic mag.  Take a flight, get the #4 CHT temp up and then kill the Surefly mag...see if the CHT drops.  That would at least eliminate the Surefly as a contributor.  Do the same with the mechanical mag.

[carusoam]

Brice do you have other flights you can share?

The one we are looking at has a few extra variable tossed into the mix...

The FF/MP is getting bumped around a bit... so the EGTs will change each time with that... mixture changes will also affect the data...

It looks as if the flight we are looking at really changed the air/fuel going to each cylinder...

As in EGT1 goes from hottest to coldest after your inflight mag check... red line...

At 6:30... the throttle is opened up... and all four cylinders do something different... one goes straight up, one doesn’t show a change of EGT at all, the other two take an average approach... and one of them shows a delay before rising...

4&3 rise with the power being added... 

EGT1 looks like nothing changed...

EGT2 looks like it waited a minute to fully react...

When talking to your mechanic... focusing a minute on that first full power run may show something interesting... there may be something blocking airflow in front of the carb, of the carb heat misbehaving, or something unexpected...

Comparing to other flight data would be helpful to see if this is a one time event or if every take-off has a bit of wacky power related to it...

PP thoughts only, so... don’t get nervous... yet.  

Best regards,

-a-