Hot EGT/TIT with low CHT

[Davidv]

I'm starting this topic mostly because I'm curious why this would occur and also because I'm seeing this scenario after picking my plane up from annual.

When I first bought my plane about a year ago it had only around 100 hours on the engine.  It was running pretty hot and often tough to keep all cylinders under 390-400 at fuel flows around 18 GPH at 29/24.  I put new baffle seals (Geebee) and my CHT's greatly improved at the same power settings (360-380).  Leading up to annual I noticed that my #5 EGT was getting slightly over 1600 at these temps and (I didn't have a working TIT gauge at the time) but was running the engine the same as before.  My strategy for flying without a reliable TIT guage was to monitor fuel flow and try to keep the EGTs around 1550.

I picked up the plane last week (From Phil J. here in Florida), and everything seemed to be running well except I'm now seeing even lower CHT's (340-360) but I can't go below 19 gph and get a TIT of less than 1650 (he installed a new probe).  He also said that my timing was off by 2 degrees and it was adjusted accordingly.  Anyone know why the low CHT with hot EGTs?  Or does everything seem perfectly normal?

Thanks,

David

[N201MKTurbo]

I assume he retarded your timing. That gives less time for the combustion charge to burn. This puts less energy into the cylinder and leaves more energy in the exhaust. Therefore lower CHTs and higher EGTs.

[irishpilot]

If you are running between 18-19 gph at 29/2400, you should be nowhere near 1650 TIT. Something is off. What is your peak TIT when leaning? Confirm you are leaning to peak and then enrichening to 50-100 ROP? If not, you probably should.

 

My Bravo usually peaks between 1625-1650 and I run 75-100 ROP at 18.3-19.0 GPH. My cylinders run 370-380 at that temp.

 

It sounds like timing is the place to double check and ensure it is set right.

 

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[carusoam]

+1 on rechecking the timing... 

PJ comes with really high respect after so many years in the Mooney business...

Start with a phone call, it shouldn’t take long to get the timing checked...
 

FF, MP, and rpm haven’t changed right?

Best regards,

-a-

[alextstone]

If you are running between 18-19 gph at 29/2400, you should be nowhere near 1650 TIT. Something is off. What is your peak TIT when leaning? Confirm you are leaning to peak and then enrichening to 50-100 ROP? If not, you probably should.
 
My Bravo usually peaks between 1625-1650 and I run 75-100 ROP at 18.3-19.0 GPH. My cylinders run 370-380 at that temp.
 
It sounds like timing is the place to double check and ensure it is set right.
 
Sent from my Pixel 3a using Tapatalk
 
 
 
 

My numbers are the same as@irishpilot



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[Davidv]

3 hours ago, irishpilot said:

If you are running between 18-19 gph at 29/2400, you should be nowhere near 1650 TIT. Something is off. What is your peak TIT when leaning? Confirm you are leaning to peak and then enrichening to 50-100 ROP? If not, you probably should.

 

My Bravo usually peaks between 1625-1650 and I run 75-100 ROP at 18.3-19.0 GPH. My cylinders run 370-380 at that temp.

 

It sounds like timing is the place to double check and ensure it is set right.

 

Sent from my Pixel 3a using Tapatalk

 

 

 

 

Thanks, what kind of EGT’s are you seeing when running 100 LOP? 

[Davidv]

3 hours ago, carusoam said:

+1 on rechecking the timing... 

PJ comes with really high respect after so many years in the Mooney business...

Start with a phone call, it shouldn’t take long to get the timing checked...
 

FF, MP, and rpm haven’t changed right?

Best regards,

-a-

No, I’m running at the same power settings as I was previously, but I never really had a good TIT indicator and this is the first time that it seems to be working correctly after he changed the probe.  However, I’m seeing EGTs in the high 1500s so it appears that a TIT 75-100 degrees hotter wouldn’t be out of the question.

[philiplane]

If the magneto to engine timing has been changed 2 degrees, look in the logs to see if it was adjusted previously. When external timing drifts more than 4 degrees, the mag should be opened up to re-set the E-gap, because the points are wearing and retarding the timing. This makes the mag less efficient and will cause EGT variations. The problem with the Bravo installation is that you can only have Slick mags, which are basically high maintenance low performance junk. They need to be opened every 500 hours, or less, to insure optimal performance. I do the 500 hour inspections on everything I service, and Slicks rarely get past 500 hours without needing some repairs.

[Davidv]

Thanks, I’ll look into that and mine have about 250 hrs on them.

1 minute ago, philiplane said:

If the magneto to engine timing has been changed 2 degrees, look in the logs to see if it was adjusted previously. When external timing drifts more than 4 degrees, the mag should be opened up to re-set the E-gap, because the points are wearing and retarding the timing. This makes the mag less efficient and will cause EGT variations. The problem with the Bravo installation is that you can only have Slick mags, which are basically high maintenance low performance junk. They need to be opened every 500 hours, or less, to insure optimal performance. I do the 500 hour inspections on everything I service, and Slicks rarely get past 500 hours without needing some repairs.

 

[carusoam]

Mag timing often slips... after installation...

It is sort of normal to schedule a recheck/set of the timing after a short time...

Unfortunately, I’m just a PP, and don’t recall why this happens...

Or why this would happen for a mag that is not so new...

But, enough evidence points towards getting the slick’s timing checked...

Start looking forward to an electronic mag to go with that... as turbos are slowly getting added to the lists...

Best regards,

-a-

[LANCECASPER]

Something's not right. I had a similar situation and tried tracking it down for months, with good advice from a lot of people, but it turned to be something so obvious that we overlooked it - a leaking line to the fuel injector on one cylinder. That could have turned out really bad. Don't give up until you find it.

The Bravo engine needs all of the instrumentation working at all times or you can cook the engine in not too many hours. If my TIT was INOP I wouldn't fly the airplane until it was working. There is no way to know for sure what your TIT is by monitoring your EGT. Your TIT must be working to fly the airplane legally.

 

Usually the first thing to go, if the engine has been run too hot, are the exhaust valve guides.

(Since there is so much heat produced with turbo-charged engines, and especially this one, make sure you change the oil every 25 hours.)

[Davidv]

@LANCECASPER, thanks, we re-checked the timing today and it was exactly where it's supposed to be.  That means that it's either the boost that was turned higher to give higher manifold on takeoff (recommended by Phil Jimenez who did the work) or the internal mag timing.  However, I'm not sure the internal mag timing could be responsible for almost a 100 degree indicated difference from where my temps should be.  We also flew the aircraft the other day and found that it peaked above the redline for TIT.  We obviously didn't stay there for very long but not sure what that could mean...

[carusoam]

Two things that have been known to raise EGTs...

1) Delayed Timing can shift the time available to burn the fuel, before the exhaust valve opens...

2) Often, a faulty spark plug doesn’t initiate the burn properly... sending a percentage of raw fuel towards the exhaust valve...

3) Verify the TIT indicator to see if it has the same temp as all the other TCs before engine start... changing out a sensor can have a couple of surprises associated with it... the old one may have some calibration still in the system...

So... do you have EGT data to go along with TIT data?

A dud plug will be given away by the JPI graph...

Speaking of JPI graphs...

During the run-up if the timing of one mag is different other... the EGTs will peak with one higher than the other...

Want to download the data and send it to the savvy site?  

Best regards,

-a-

[Davidv]

On 2/26/2020 at 1:27 AM, carusoam said:

Two things that have been known to raise EGTs...

1) Delayed Timing can shift the time available to burn the fuel, before the exhaust valve opens...

2) Often, a faulty spark plug doesn’t initiate the burn properly... sending a percentage of raw fuel towards the exhaust valve...

3) Verify the TIT indicator to see if it has the same temp as all the other TCs before engine start... changing out a sensor can have a couple of surprises associated with it... the old one may have some calibration still in the system...

So... do you have EGT data to go along with TIT data?

A dud plug will be given away by the JPI graph...

Speaking of JPI graphs...

During the run-up if the timing of one mag is different other... the EGTs will peak with one higher than the other...

Want to download the data and send it to the savvy site?  

Best regards,

-a-

Thanks @carusoam for the usual valuable insights.  Despite being cleaned at annual less than 6 hours ago, we found some small amounts of lead in a few of the plugs we pulled so we are pulling all of them and re-cleaning.  This is odd since I definitely don't run too rich and lean during taxi as well. However, after talking to some very knowledgeable people including @philiplane in person, we think most of this is due to the adjustment that was made on the controller.  I'm also going to remove the mags and have them inspected at a shop near the field to see if anything needs changing internally.  I've been told that even with 250 hours, some of the components can prematurely wear on the slicks very easily.

Unfortunately, I have one of the very early JPI's that doesn't export data...

I'll let everyone know what I find in case anyone has this issue in the future.

Edited February 27, 2020 by Davidv

[carusoam]

Is your JPI a 700 from the early 90s?  (Mine is)

There may be a cable and parts that can be purchased to enable getting the data out of it...

Some installs were done in the 90s when data collection wasn’t popular... and the cables and plugs just weren’t purchased at the time...

Today...

We find things like dead plugs, and blocked injectors... simply by downloading the data...

 

Some MSers have found a data port in their panel and have asked what is that? Looks like a 1/8” headphone plug receptacle...

 

PP thoughts only, not a mechanic...

Bestr regards,

-a-

 

 

 

 

[Davidv]

43 minutes ago, carusoam said:

Is your JPI a 700 from the early 90s?  (Mine is)

There may be a cable and parts that can be purchased to enable getting the data out of it...

Some installs were done in the 90s when data collection wasn’t popular... and the cables and plugs just weren’t purchased at the time...

Today...

We find things like dead plugs, and blocked injectors... simply by downloading the data...

 

Some MSers have found a data port in their panel and have asked what is that? Looks like a 1/8” headphone plug receptacle...

 

PP thoughts only, not a mechanic...

Bestr regards,

-a-

 

 

 

 

Yes, it's one of the original ones.  After I bought the plane I purchased the JPI data cable so I could download the data but it didn't seem to be working correctly so I called JPI.  They did some troubleshooting and then had me read the version off the device.  It turns out mine was one of the original few that does not have the data record capability (despite having a label on the panel next to a plug that says JPI DATA".  I'm going to be updating this gauge soon...

 

[DaveMC]

Question:

 

When Leaning ROP using a JPI 900 they tell you to Pre- lean.  I am curious about other Bravo owners..... What TIT do you pre lean to?  before starting your ROP leaning process?

[carusoam]

Answers to be found in the other thread...

 

-a-

[Davidv]

Just to follow up on this issue, I’ve done the following and unfortunately I feel like I’m way too hot (my airplane obv):

1. Had internal mag timing adjusted (right was odd but left was OK)

2. Re-installed mags and timed to recommended engine timing 

3. Cleaned all spark plugs 

4. Verified that density controller set correctly 

Does anyone have any ideas? As you’ll see in the photos below I need to have a crazy high fuel rate at 29/24 to achieve a TIT that I believe most of you get at around 18-19 GPH.  Pics taken at 9K feet, 150 IAS with OAT of 20 degrees C.  While I don’t completely trust my factory gauges the numbers are pretty well supported by my JPI which shows EGTs around 50-100 degrees lower than the TIT depending on cylinder.

Or maybe I’m making too big of a deal and others see similar numbers in their bravo?

[carusoam]

How old is the TIT sensor?

They live in the harshest environment...  

so... if something unexplained is going wrong... that thing is worth a look... the next time the cowl is open...

PP thoughts only...

Best regards,

-a-

[Davidv]

Thanks Anthony, it was actually just replaced at annual but I don’t think it’s the issue since my EGTs from my JPI are also about 100 degrees hotter than everyone else’s it seems...

[LANCECASPER]

9 hours ago, Davidv said:

Just to follow up on this issue, I’ve done the following and unfortunately I feel like I’m way too hot (my airplane obv):

1. Had internal mag timing adjusted (right was odd but left was OK)

2. Re-installed mags and timed to recommended engine timing 

3. Cleaned all spark plugs 

4. Verified that density controller set correctly 

Does anyone have any ideas? As you’ll see in the photos below I need to have a crazy high fuel rate at 29/24 to achieve a TIT that I believe most of you get at around 18-19 GPH.  Pics taken at 9K feet, 150 IAS with OAT of 20 degrees C.  While I don’t completely trust my factory gauges the numbers are pretty well supported by my JPI which shows EGTs around 50-100 degrees lower than the TIT depending on cylinder.

Or maybe I’m making too big of a deal and others see similar numbers in their bravo?

You either have a fuel leak (look for staining) or a massive air leak around your baffles. In the latter case you're cooling an air-cooled engine with fuel. Take some pictures without your upper and lower cowling and see if the Mooney braintrust can offer some suggestions. Were your cowl flaps open or closed?

[nfonville]

My CHTs go way up if I don't position the baffling correctly.  The front baffles on mine need to be pulled forward.  They tend to move backward when reinstalling the lower cowling.  The problem one is just below the alternator on the passenger side.  Makes my CHTs go up by 25-30 degrees.

[Davidv]

20 minutes ago, LANCECASPER said:

You either have a fuel leak (look for staining) or a massive air leak around your baffles. In the latter case you're cooling an air-cooled engine with fuel. Take some pictures without your upper and lower cowling and see if the Mooney braintrust can offer some suggestions. Were your cowl flaps open or closed?

Thanks Lance, I'll do that but I don't think it's an air issue.  I just put on the silicone geebee baffles last year and my cylinder temps never go over 375-380 at these power settings (with one cylinder around 340).  No signs of a fuel leak but I'll still take some photos.  I'm going to compare my totalizer to actual fuel used at my next fillup to see if it's a hoskins issue (which I doubt, since my plan isn't far off from actual usually).

Edited March 30, 2020 by Davidv

[Pissed_'Ole_Pete]

On 2/17/2020 at 7:31 PM, Davidv said:

Thanks, what kind of EGT’s are you seeing when running 100 LOP? 

If you are running LOP, you are operating your engine outside Lycoming's specifications. You are in fact voiding your warantee