mschmuff

High EGT on one cylinder

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Need a little help here.....'67 M20F IO-360A1A

I searched this topic and found the cause to usually be a fouled/bad spark plug or clogged injector.  One said bad cylinder but mine only have about 400hrs on them....I know that's no guarantee but not where I want to start.

Here's what's strange (I think)!!

#1 cyl on take off and descent is high full rich - 1440-1450 where the other EGTs are all below 1330 (DIF is 170-200)

At cruise leaned out it is totally normal.....1415 on #3 which has always the hottest and #1 drops to 1375.

And its just EGT - CHT's are all normal.  This has happened on the last three flight.

Any ideas??

I'm going to clean the plugs, injector and swap probes to start off with but wanted to see if anyone else out there has seen this issue before I get started.

Thanks!!!!

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I was going to say start with switching probes.   Is this something new and it was fine before?  Also, check how the probes are installed.  Is there something different about the placement of the one probe?  Check depth, angle, distance from the head, etc.

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Definitely sounds more like a probe issue than something to do with the cylinder itself.


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New issue.  Both probes are mounted the same.  Runs smooth all of the time.  Would have no idea there was a problem unless I saw it on the monitor.

Pulled both plugs today - both clean and dry.

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Do an inflight mag check. Follow the instructions on the Savvy website regarding the inflight mag check. Report back.

A number on the EGT gauge is meaningless. What is important is how that number moves. If it moves up and down, peaks, etc. with the other cylinders it's nothing. If it's movement is out of proportion to all the others, then we can diagnose a problem.

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10 hours ago, neilpilot said:

Fouled injector on #1

+1. A fouled injector on #1 would explain near peak EGT when full rich, and lower EGT when leaned for cruise. I assume you are cruising ROP? If so, I suspect that your #1 is looking normal again because it is LOP while the other three cylinders are still ROP.

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neilpilot nailed it!! - pulled the fuel line off of the injector on the #1 cyl - cleared it with just air......issue is gone!!

Another Mooneyspace win!!!

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On 11/29/2017 at 5:43 PM, gsxrpilot said:

Do an inflight mag check. Follow the instructions on the Savvy website regarding the inflight mag check. Report back.

A number on the EGT gauge is meaningless. What is important is how that number moves. If it moves up and down, peaks, etc. with the other cylinders it's nothing. If it's movement is out of proportion to all the others, then we can diagnose a problem.

I have to say that I am tiring of people saying EGT numbers are meaningless.  I understand that it's useful to say that to people who think having closely matched EGT numbers means something (which I am sure we agree is a useless pursuit). That being said, 1440 on take off is a number to be genuinely concerned about. Sure 170 is a large spread, but more importantly for 1440 to be 250 ROP at full rich the cylinders peak EGT would have to be 1690. NFW that the actual peak EGT. 

Raw EGT numbers do indeed mean something when they are outside the realm of what's healthy. 1440 is not a healthy take off EGT reading.

 

Edited by Shadrach
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2 hours ago, Shadrach said:

Raw EGT numbers do indeed mean something when they are outside the realm of what's healthy.

Well said. It sounds oxymoronic, but as long as they are in concert and CHT's are good, who cares about EGT.

Like one of your kids, when one strays from the pack it is time to reel it in.

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Hmm, I seem to have a similar issue. My #1 EGT is high on take off and at low altitude, close to same #'s as OP, but evens out when at a higher altitude 6-8k.

I have a carbureted engine, so it can't be a clogged injection line. I just rotated/cleaned the spark plugs, but I've done it before and I don't remember it fixing anything. I'll check when I get the plane back online though. If it's not fixed - any ideas?

Edited by AlexLev

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1 minute ago, AlexLev said:

Hmm, I seem to have a similar issue. My #1 EGT is high on take off and at low altitude, close to same #'s as OP, but evens out when at a higher altitude 6-8k.

I have a carbureted engine, so it can't be a clogged injection line. I just rotated/cleaned the spark plugs, but I've done it before and I don't remember it fixing anything. I'll check when I get the plane back online though. If it's not fixed - any ideas?

I would do a lean test at altitude. Focus on that Cylinder. Lean to peak EGT if possible. If you can't, note how far you can lean to roughness. 

An intake leak is a possibility, but unlikely

EGT in the 1400s is too low to be an ignition issue and too high to be a healthy full rich number. If I were a betting man, I'd wager that all of your EGTs are on the high side, this is just the worst.

 

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The reason raw EGTs get ignored...

1) Back in the day we only got one... Often it didn’t get numbers on it... (OWTs were perfectly supported by this)

2) Then somebody added the additional EGTs, But were unable to mount them in similar locations...

3) Modern Mooneys got their EGTs mounted with pretty good accuracy, but some have struggled with the ship's EGT gauge vs. all the other EGTs...

4) Raw EGT data is very useful.  Just very sensitive to so many variables.

@mschmuff Got any JPI graphs you can post?

Best regards,

-a-

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7 hours ago, HRM said:

Well said. It sounds oxymoronic, but as long as they are in concert and CHT's are good, who cares about EGT.

Like one of your kids, when one strays from the pack it is time to reel it in.

Just because airplane engines are simple and reliable and will tolerate things like poor fuel distribution, induction leaks, clogged injectors etc without overtemping a CHT does not mean that an unhealthy EGT indication should be ignored. The whole purpose of having an engine monitor is to verify proper operation of the engine. My #1 cyl struggles to break 300 degrees in moderate weather. It is entirely possible that it would operate reliably for some time with acceptable CHTs even at abusive mixture settings.  I've never found the "head in the sand"  approach to engine analysis to be very effective when it comes to maintaining a solid dispatch rate.

I've two kids under two. I try to anticipate and rectify issues before they "overtemp" as well. 

Edited by Shadrach
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6 hours ago, Shadrach said:

➀ an unhealthy EGT indication should (not) be ignored...

➁ I've two kids under two. I try to anticipate and rectify issues before they "overtemp" as well. 

➀ Exactly! But overall high EGTs can be ignored if CHTs are in line (unless, of course, they are all off the chart).

➁ Good luck with that.

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