M20J EGT Bouncing and Oil Sampling

[sgrooves]

Hey All, 

I've had my new-to-me 1981 M20J for about 9 months. I'm 2 months away from my first annual and I've noticed a problem that has become increasingly frequent over my past couple flights.... After more than an hour of flying, particularly after stabilizing in cruise and leaning out the engine, my EGT temps on cylinders 2 and 4 have become erratic. It usually starts as small bouncing and the temperature range becomes progressively wider as flight continues. There's no pattern or consistency to the bouncing. The CHT's on those cylinders remain perfectly stable and there is no noticeable vibration, mis-firing, or loss of speed. The engine appears to be purring along as usual. You wouldn't notice it unless you were staring at the JPI (oops). I've had the field mechanic take a look and they were unable to replicate this on the ground. I plan on having whoever does my annual really take a look at the probes and connections on the back of my JPI 700. However, what I find unusual is that this only happens after I've been enroute for over an hour. If I make a 40min flight to another local airport, it'll be good the entire way out and then start acting up on the way back. If I richen up, the bouncing seems to occur less. This has been going on intermittently since I've had the plane, but has only been truly consistent since a long flight from NC to FL over the holidays.

One more oddity that I'm hoping isn't related.... After that longer holiday flight my oil got black pretty quickly, I did run with the Ram Air open (4000ft+) for a period of that flight to try it out. I also came back with low oil and had to add 2 quarts. After a few more hours I had the oil changed in Feb (32 hours on the oil) and they sent a sample out for testing. There was no metal in the filter and the mechanic said that it just smelled like old oil, nothing special. The oil analysis showed higher Cr/Fe/Al/Si. Still in the caution range on everything but I'll be changing out the oil after <=25 hours this time, resending the analysis, and replacing the air filter at that time. My prior oil change in late September, coming off of mineral oil from a top overhaul, was all low/normal levels. I've put 10 hours on the oil since and it has stayed much cleaner, visually.

Some thoughts/opinions here would be appreciated. Are these events most likely unrelated? My initial thought is some cross-talk or bad probes on the EGT sensors. However, given the changes in the oil, I'm wondering if this something bigger that I should be concerned about? At this point I feel like I'm in wait and see mode- for the next oil change and/or my annual- but want to make sure I'm not doing more damage or being unsafe. Thanks in advance for the help.

[carusoam]

EGTs are in a nasty environment.  It is possible that the probes have eroded.  It is also possible that they are having loose connections...

1) They are pretty easy to inspect to see if there is anything wrong with them.

2) Often they get swapped with other ones to see if it is a probe issue, or a position issue.

3) Another engine monitor issue is caused by grounding.  Good grounding straps from the engine to the airframe to the instrument panel are really helpful.  Clean and reseat.

PP ideas, not a mechanic...

Best regards,

-a-

Edited March 22, 2017 by carusoam

[Marauder]

Hey All, 
I've had my new-to-me 1981 M20J for about 9 months. I'm 2 months away from my first annual and I've noticed a problem that has become increasingly frequent over my past couple flights.... After more than an hour of flying, particularly after stabilizing in cruise and leaning out the engine, my EGT temps on cylinders 2 and 4 have become erratic. It usually starts as small bouncing and the temperature range becomes progressively wider as flight continues. There's no pattern or consistency to the bouncing. The CHT's on those cylinders remain perfectly stable and there is no noticeable vibration, mis-firing, or loss of speed. The engine appears to be purring along as usual. You wouldn't notice it unless you were staring at the JPI (oops). I've had the field mechanic take a look and they were unable to replicate this on the ground. I plan on having whoever does my annual really take a look at the probes and connections on the back of my JPI 700. However, what I find unusual is that this only happens after I've been enroute for over an hour. If I make a 40min flight to another local airport, it'll be good the entire way out and then start acting up on the way back. If I richen up, the bouncing seems to occur less. This has been going on intermittently since I've had the plane, but has only been truly consistent since a long flight from NC to FL over the holidays.
One more oddity that I'm hoping isn't related.... After that longer holiday flight my oil got black pretty quickly, I did run with the Ram Air open (4000ft+) for a period of that flight to try it out. I also came back with low oil and had to add 2 quarts. After a few more hours I had the oil changed in Feb (32 hours on the oil) and they sent a sample out for testing. There was no metal in the filter and the mechanic said that it just smelled like old oil, nothing special. The oil analysis showed higher Cr/Fe/Al/Si. Still in the caution range on everything but I'll be changing out the oil after Some thoughts/opinions here would be appreciated. Are these events most likely unrelated? My initial thought is some cross-talk or bad probes on the EGT sensors. However, given the changes in the oil, I'm wondering if this something bigger that I should be concerned about? At this point I feel like I'm in wait and see mode- for the next oil change and/or my annual- but want to make sure I'm not doing more damage or being unsafe. Thanks in advance for the help.

I would check the probe connections closely. I was having problems with my #4 cylinder going up and down in temps and eventually showing an error on my JPI 900. The issue was due to a connection problem between the probe and the harness. It was the hidden connection under the fire sleeve.







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[Jeev]

Hello and welcome!!!  On the EGT's check the connections and probes as stated above, also download your engine monitor data and take a closer look at the spread to rule out an exhaust valve going bad (prob not since you just did a top).  You can use the free service here : https://www.savvyaviation.com/savvyaviation-home/savvy-services/savvyanalysis/ and learn about what a failing exhaust valve looks like.

On the dark oil, how many hours on the engine or more importantly the cylinders?  Sounds like excessive blow by. Were they broken in properly after the top overhaul?  Sounds like maybe they were not?  

When you say low oil how low was it?  Most LYC 360's like to be around 6-7qts, if you fill to 8 it will blow out 1-2qts and stabilize.  

Edited March 23, 2017 by Jeev

[sgrooves]

Sounds like I need to buy the attachment to download the JPI data (or see if my mechanic can help). I'm hesitant to spend the $180 because I was considering making the change to the JPI 830 or 900, but I'd rather spend the $$ for my safety. I believe the oil got down to about 4.5-5 qts. The plane does not like anything more than 7.

I have 105 hours on the cylinders. 200 since a lower overhaul and 1600 SMOH. Unfortunately, I can't speak to the break-in and the previous owner passed away. 

[sgrooves]

Here's a video taken a while back when it first started. The bouncing is on 2 and 4 now, mostly later in flight, and the fluctuations are much more erratic and in greater magnitude (sometimes nearly to the top). I'll try and get another video of it this weekend.... last time up was way too bumpy.

IMG_0463.m4v

[jaylw314]

You can get the Keyspan USB adapter on Amazon for $30

https://www.amazon.com/Tripp-Lite-Keyspan-High-Speed-USA-19HS/dp/B0000VYJRY/ref=sr_1_1?ie=UTF8&qid=1490328015&sr=8-1&keywords=keyspan+usb+to+serial+adapter

I used that for my EDM-700 and it works fine.

The IO-360 is has a low oil limit of 2 qts (!) on its TCDS.  I try to keep it below 6 qts

The speed at which your EGT changes seems too fast even for a clogged fuel injector.  I'm guessing it's a bad connection.

You should not have Silicon increase in your oil analysis unless you have a bad air filter system (or unless a piece of silicone rubber ended up in you oil system).  Check your air filter and the alternate air intake behind the air filter.  Cr, and Fe could all be related to your new cylinders.  Al could be anything, but frequently happens with an overhauled oil cooler.

[carusoam]

The JPI700 series came with a 1/8" plug that looks like a headphone jack and may not have gotten anything to label it.

There is a plug that goes in that with an Rs232 plug on the other end.

The RS232 plug was great for old dinosaur computers...

A Keyspan converter plugs into the RS232 and then plugs into a USB port.  Now you can use an ultra modern PC...

The JPI software can be downloaded of the internet.

All for less than $100 I bet.... including the 1/8" plug if you need to buy that from JPI...

See if that helps.

I got my keyspan device through Walmart.  I bet Amazon has it too...  JPI lists it on their site, but they are not the manufacturer of it.

Best regards,

-a-

 

Edited March 24, 2017 by carusoam

[cnoe]

I would check the probe connections closely. I was having problems with my #4 cylinder going up and down in temps and eventually showing an error on my JPI 900. The issue was due to a connection problem between the probe and the harness. It was the hidden connection under the fire sleeve.

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What he said.

Also note that the JPI probe leads are connected to the harness leads with a small machine screw, nut, and star washer which fasten two ring terminals together. Unconventionally the washer goes between the two ring terminals instead of under the nut (this is commonly done wrong during installation). Also the ring terminals are crimped onto the wire after it's folded over to double its thickness. Either a poor crimp or improper connections (washer in wrong orientation) can cause jumpy readings.

This is just stuff you learn when you install the JPI yourself.


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[Jeev]

18 hours ago, sgrooves said:

Here's a video taken a while back when it first started. The bouncing is on 2 and 4 now, mostly later in flight, and the fluctuations are much more erratic and in greater magnitude (sometimes nearly to the top). I'll try and get another video of it this weekend.... last time up was way too bumpy.

IMG_0463.m4v

My vote is a loose connection somewhere on #2 EGT.  

[Jeev]

19 hours ago, sgrooves said:

Sounds like I need to buy the attachment to download the JPI data (or see if my mechanic can help). I'm hesitant to spend the $180 because I was considering making the change to the JPI 830 or 900, but I'd rather spend the $$ for my safety. I believe the oil got down to about 4.5-5 qts. The plane does not like anything more than 7.

I have 105 hours on the cylinders. 200 since a lower overhaul and 1600 SMOH. Unfortunately, I can't speak to the break-in and the previous owner passed away. 

By 105hrs they should be broken in with stable oil consumption.  If I were you I would start logging my oil consumption over the next 25hrs.  Oh and by the way nice panel and your engine sounds real smooth in the vid!  Enjoy the J its a wonderful aircraft!

[AlexLev]

I experience the same issue in my 1968G and my #3 cylinder. EGT bounces anywhere from 1000-1500 in cruise. Sometimes I think there's a weird vibration, but I've only owned my plane for three months so I'm not sure yet. It could just be normal and the way the plane cruises. I've taken 4+ hour cross countries multiple times and CHTs are stable and plane performs fine. I've put over 50 hours on the engine since the problem started happening and it flies well, but hoping to get it worked out in the next month or two.

Wanted to buy some extra probes to bring into the shop, but having trouble locating the Westech 713-2dwk probes that the Aerospace Logic EGT-4 unit recommends using. Let me know if you figure this out and I will as well! Hopefully it's just some bad probes and not any issue creeping up on the engine...

Edited March 25, 2017 by AlexLev

[madjano]

JPI also recommends keeping their leads away from the plug wires. I just installed mine this annual and mentioned it to my mechanic. He said he has never had problems running them along with the plug wires. But if JPI recommends it.....

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[kortopates]

JPI also recommends keeping their leads away from the plug wires. I just installed mine this annual and mentioned it to my mechanic. He said he has never had problems running them along with the plug wires. But if JPI recommends it.....

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Mechanics continue to do this incorrectly, but they don't see the erratic indications - you do.
It's frustrating because it's a few hours of work to re-do it right. And since most owners don't read the install manual many just live with it.


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[carusoam]

1) The voltage signals sent along the TC wires are in microvolts.  Very, very,  tiny.

2) The voltage sent along the spark plug wires is in 10s of thousands of volts.  Very, very, large.

3) when current is sent down a wire, it generates magnetic fields.

4) when magnetic fields are generated, they can interrupt the flow of electrons in wires that are subjected to the accidental magnetic fields.  

4a) when the signal wire is carrying microvolts, it doesn't take much interference to ruin the signal.

5) putting instrument wires next to current delivering wires has become a general no no Over the past few decades.  Even for industrial machines. Conduits are split for supply vs. Instrument wires.

6) For a belt and suspenders approach, people use shielded wires to block the RF interference.

7) relying on the shielded wires while putting them close to high power wires can one day lead to dissapointment and money spent investigating...

PP thoughts only...

Best regards,

-a-

 

 

 

Edited March 26, 2017 by carusoam

[cnoe]

I can testify that re-routing the EGT/CHT probe wiring away from my spark-plug leads definitely helped remedy some jumpy/erratic readings. The graph-traces still aren't silky smooth like I'd prefer but they're good enough (even with a 2-second sampling rate).


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[sgrooves]

By 105hrs they should be broken in with stable oil consumption.  If I were you I would start logging my oil consumption over the next 25hrs.  Oh and by the way nice panel and your engine sounds real smooth in the vid!  Enjoy the J its a wonderful aircraft!

 

Thanks! Enjoying it. Here's a pic of the full panel. Debating swapping the 530W/430W for the IFD's but kind of want to see how the first annual goes. It does purr.

 

And thanks to all the others for the suggestions, the more I read, the more it sounds like a bad connection or some interference. I'll have it looked at during the annual.

 

 

 

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[sgrooves]

I realized I never followed up on this post. A few of you were definitely on the right path. The EGT probe that was bouncing most frequently, #4, died completely just before my annual. Once that EGT probe went out, the bouncing stopped on #2. I guess the probe beginning to fail was sending shocks that was cross-talking to #2. They replaced the probe at the annual and all has been good since then.

As far as the oil analysis goes. Maybe it was from the RAM air or a bad sample. If I recall, it could have been my first change since mineral oil. I've had the oil changed twice since, with analysis, and everything has been perfect. Had the plane at AGL for the annual and everything checked out great there too. Oil consumption has been about 1qt / 10 hours too. 

[carusoam]

Great follow up, SG!

Best regards,

-a-