JPI data analyses.

[Lood]

The #2 CHT on my engine is running a bit hotter than the rest. I thought that I had a bad probe on #2 and replaced it with a new one, but the higher temp persisted. Although still way below the limit, it bothers me and even more so because it's one of the front cylinders.

What could be the cause? A partly clogged injector, or maybe a bad spark plug? I would appreciate any advice.

 

As additional information, I always fly WOT and 2500rpm at 75 deg ROP, except when loitering low level around the patch. I have brand new baffling all round that is in perfect condition. My engine has now done about 130 odd hours SMOH and the break in went very well.
I've attached a .PDF with cruise flight extracts from 3 different flights.

 

JPI Engine data.pdf

[Cruiser]

Are you certain the probe wires are connected to the proper cylinders? i.e. is #1 reading actually #1 cylinder etc.

Have you done a leaning peak test to determine the spread of fuel flow between the cylinders. 

How are you determining 75°F ROP? Which cylinder and what are the others running at?

 

Perhaps you could post the actual JPI file or upload it to the Savvy Aviators site https://www.savvyanalysis.com/home its free.

[Shadrach]

On my 67 F # 2 is the richest cylinder (it's the one I use to set power LOP).  Are you setting #2 to 75ROP?  It's conceivable that your other cylinders are running closer to peak or even slightly LOP wich is a much cooler place to run... What happens when you run the engine at a less abusive mixture setting like peak or say 125ROP?

[Lood]

@Cruiser:

The probes have been verified to be connected correctly.

I have not done the test on the new engine (new injectors) to determine the spread.

75ROP is determined by using the normal "Lean find" function and prescribed procedure on the EDM700.

 

@Shadrach:

Using the EDM700, #3's dot is the first to flicker when I start to lean - sometimes #1. I'm really not sure which cylinder actually peaks first.

The spread on my previous set of standard injectors were 0.5 and although I haven't done the test on the new set, I doubt whether they would be so bad that some of the cylinders could be LOP while one is 75ROP. Certainly possible, but highly unlikely.

I'll attach an extract of a climb where the mixture is probably close 150ROP, or at target EGT. I've never cruised at 125ROP, because temperature wise, my engine is actually running exceptionally cool at 75ROP and the only reason why I don't fly it leaner than 75ROP is to avoid high pressures and possible damage at say 50ROP, for instance.

 

I have flown LOP on one flight for about 30 minutes and although it ran perfectly well at -15LOP, I'm just not comfortable with LOP. But let's leave that there. I don't want it to become another LOP vs ROP debate.

I will try and do the Gami lean test this coming weekend and post the results here. That would certainly help a lot towards determining what's up with #2 on my engine.

[Shadrach]

Max power according to GAMI occurs at ~80ROP max CHT occurs ~30ROP.  I'm not trying to debate where you run your engine. I still have not determined which cylinder your leaning on. One thiing you could do to get more info is find out precisely where #2 is running. Set it up in cruise as you normally would and then wait for temps to stabilize, then select number 2; note EGT and the slowly enrichen to peak. If it's around 30 or 40 ROP, then you've just discovered that you've been running that cylinder without problem at what should be about the hottest place possible. At that point you can look for other problems or rethink you SOP.

[Lood]

Attached below, the climb data. Sorry about some of the data being cut off in my attachment above, I've changed the page layout and all data is now shown.

 

JPI Climb data.pdf

[Lood]

Below are data from 3 different flights. The extracts are taken at the exact point where the JPI determines peak and it seems that #1 is always the first to peak. If my assumption is correct, the other 3 cylinders are all running richer, no?

 

JPI Peak data.pdf

[Shadrach]

OK so if I'm reading your data correctly, you're running ~ 9GPH, your 2 hottest cylinders are 2 and 4 which are running 37 ROP and 26 ROP (respectively). Your coolest cylinder (#1) is 114 ROP and you next coolest cyl  (#3) is running 51 ROP. Is that correct? I see nothing that shows 75ROP... Perhaps I'm reading it wrong. At 9GPH with those numbers I have to assume you are pretty high or you pulled back the MAP...  

[pinerunner]

@Cruiser:

The probes have been verified to be connected correctly.

I have not done the test on the new engine (new injectors) to determine the spread.

75ROP is determined by using the normal "Lean find" function and prescribed procedure on the EDM700.

 

@Shadrach:

Using the EDM700, #3's dot is the first to flicker when I start to lean - sometimes #1. I'm really not sure which cylinder actually peaks first.

The spread on my previous set of standard injectors were 0.5 and although I haven't done the test on the new set, I doubt whether they would be so bad that some of the cylinders could be LOP while one is 75ROP. Certainly possible, but highly unlikely.

I'll attach an extract of a climb where the mixture is probably close 150ROP, or at target EGT. I've never cruised at 125ROP, because temperature wise, my engine is actually running exceptionally cool at 75ROP and the only reason why I don't fly it leaner than 75ROP is to avoid high pressures and possible damage at say 50ROP, for instance.

 

I have flown LOP on one flight for about 30 minutes and although it ran perfectly well at -15LOP, I'm just not comfortable with LOP. But let's leave that there. I don't want it to become another LOP vs ROP debate.

I will try and do the Gami lean test this coming weekend and post the results here. That would certainly help a lot towards determining what's up with #2 on my engine.

I think your responses are quite sensible and heartily endorse your wish to avoid an ROP/LOP debate.  I think some here, myself included, think of those issues first when any temperature problem comes up. My bet is on air flow. I notice that the right side is 20 degrees colder than the left side. I seems to me that any change in configuration in the engine compartment can have effects on the CHT's that are sometimes hard to predict or explain. Quite a bit of wind in there after all and the two sides aren't quite identical in what's in the flow path. The numbers you're seeing may be within the normal, acceptable range. Maybe there are adjustments your mechanic can make to your cowl flaps to balance the flow on both sides with cowl flaps closed.

 

For added information my M20E gave #1 265, #2 300, #3 280, #4 290 running 7.1 GPH LOP (23in MP, 2500RPM probably) during one flight last summer. I grabbed those numbers off my computer at work so I can't spend much time with them. Similar pattern to yours I think though cooler since I had a low power setting and maybe cool Maine air.

[mikesalman]

I noticed all your exhaust temps were way over 1400 and even reached 1500. My flight instructor told me to never let your exhaust temperature exceed 1400. I am confused, I know I'm a new pilot with my first airplane. Could Cessna's be different from Mooney's. I was running in the mid to high 300 cylinder temps and high 1300 on the exhaust getting 12.5 gal per hour. No Gammi's ether. I would love to see 9 gal per hour. That would have saved me 24 gallons on my flight to Tampa and back last week.

[Shadrach]

I noticed all your exhaust temps were way over 1400 and even reached 1500. My flight instructor told me to never let your exhaust temperature exceed 1400. I am confused, I know I'm a new pilot with my first airplane. Could Cessna's be different from Mooney's. I was running in the mid to high 300 cylinder temps and high 1300 on the exhaust getting 12.5 gal per hour. No Gammi's ether. I would love to see 9 gal per hour. That would have saved me 24 gallons on my flight to Tampa and back last week.

You're fight instructor may be a great pilot/instructor, but if what you've stated about EGT is truly his advice, I would seek my engine operation information elsewhere. Your flight instructor may have a reason for what he's told you, but it's a flawed (to put it nicely) approach to engine management... You're not doing your engine any favors running it that way (probably not hurting anything either).  Ask him to explain his advice. My guess is that it's his experience that most EGTs peak around 1450 to 1500. He's figuring that his advice will keep people in what he considers to be the 50-100 ROP range.  That's fine, but it's not optimal for all scenarios and a student is much better off learninf the "whys" behind the procedure then a cook book recipe for mixture management...

[jlunseth]

I routinely run with EGT's in the 1400's at cruise.  I have several hundred hours on my engine that way.  It is not an issue, 1300's would be too cold in my engine.

[Shadrach]

I hope your instructor never looses a mag in flight...The engine may blow up when those EGTs climb into the 1600s... 

[rahawk]

For one one of your cylinders, I would assume that you used a spark plug sensor?  If so that cylinder will probably read cooler that a bayonet sensor.  The primary CHT will use a bayonet, while the JPI will most likely use the spark plug sensor.

[Shadrach]

Spark plug thermocouples typically read 30-50df hotter than bayonets...

[mikesalman]

You're fight instructor may be a great pilot/instructor, but if what you've stated about EGT is truly his advice, I would seek my engine operation information elsewhere. Your flight instructor may have a reason for what he's told you, but it's a flawed (to put it nicely) approach to engine management... You're not doing your engine any favors running it that way (probably not hurting anything either).  Ask him to explain his advice. My guess is that it's his experience that most EGTs peak around 1450 to 1500. He's figuring that his advice will keep people in what he considers to be the 50-100 ROP range.  That's fine, but it's not optimal for all scenarios and a student is much better off learninf the "whys" behind the procedure then a cook book recipe for mixture management...

Thank you for the advice, I actually feel better now since the last 23 hours I was leaning more aggressively (with a different instructor) and he never mentioned anything about the egt's being too hot. This time I had a 4 hour flight in IFR conditions so I needed a safety pilot to go with me on that business trip and back.

It was a great experience flying in the clouds.

[Lood]

OK so if I'm reading your data correctly, you're running ~ 9GPH, your 2 hottest cylinders are 2 and 4 which are running 37 ROP and 26 ROP (respectively). Your coolest cylinder (#1) is 114 ROP and you next coolest cyl  (#3) is running 51 ROP. Is that correct? I see nothing that shows 75ROP... Perhaps I'm reading it wrong. At 9GPH with those numbers I have to assume you are pretty high or you pulled back the MAP...  

 

Shadrach, I can see where you're going with this and it makes perfect sense - thanks. It seems crucial that I do the Gami lean test to determine exactly where each cylinder is running and when each actually peaks.

 

Wrt the 75ROP, my procedure is as follows:

After settled in the cruise, I hit the LF button on the JPI and start leaning immediately. Soon after, the #3 cylinder (on my engine) dot will normally start to flicker, which just confirms that the JPI is in "Leanfind mode" and has detected the leanest cylinder in the engine, which readings it will use to determine peak.

Normally, at around 8 gal/hr, the JPI display flashes the "LEANEST" message which implies that I peak has been found.

I now hit the "LF" button again and the JPI will display the actual degrees that the leanest cylinder is at. As there is a minor time lapse in the analyzer, my leanest cylinder is normally at -15LOP at that stage and then I start to richen the mixture. During this process, the JPI displays the actual degrees of the leanest cylinder and I lean that to 75ROP.

As I understand it, the other 3 cylinders must thus be richer than 75ROP as the LF (ROP) process on the JPI works using the leanest cylinder.

 

The confirmation in this will lie in doing the lean test and writing down the actual numbers and fuel flows for each cylinder. Each cylinder will peak at a different EGT and its number of degrees ROP will be determined from its own peak EGT and not that of another cylinder.

 

That's my understanding. If your interpretation above is indeed correct, I am now VERY worried about the 37- and 26ROP on cylinders 2 & 4.

[pinerunner]

Shadrach, I can see where you're going with this and it makes perfect sense - thanks. It seems crucial that I do the Gami lean test to determine exactly where each cylinder is running and when each actually peaks.

 

Wrt the 75ROP, my procedure is as follows:

After settled in the cruise, I hit the LF button on the JPI and start leaning immediately. Soon after, the #3 cylinder (on my engine) dot will normally start to flicker, which just confirms that the JPI is in "Leanfind mode" and has detected the leanest cylinder in the engine, which readings it will use to determine peak.

Normally, at around 8 gal/hr, the JPI display flashes the "LEANEST" message which implies that I peak has been found.

I now hit the "LF" button again and the JPI will display the actual degrees that the leanest cylinder is at. As there is a minor time lapse in the analyzer, my leanest cylinder is normally at -15LOP at that stage and then I start to richen the mixture. During this process, the JPI displays the actual degrees of the leanest cylinder and I lean that to 75ROP.

As I understand it, the other 3 cylinders must thus be richer than 75ROP as the LF (ROP) process on the JPI works using the leanest cylinder.

 

The confirmation in this will lie in doing the lean test and writing down the actual numbers and fuel flows for each cylinder. Each cylinder will peak at a different EGT and its number of degrees ROP will be determined from its own peak EGT and not that of another cylinder.

 

That's my understanding. If your interpretation above is indeed correct, I am now VERY worried about the 37- and 26ROP on cylinders 2 & 4.

Ah but none of your CHT's are very high. The highest I saw posted was 350 which isn't bad (though check your climb). So I wouldn't be VERY worried. Busch makes the point strongly that CHTs are that thing you want to watch most since they track so well with internal pressure that can lead to detonation.  You can probably learn more and treat your engine kinder but it looks like its not too bad if the CHT's aren't headed for 400 F. 

[jlunseth]

Shad, I don't think we can determine degrees from peak based on the data strip that was posted (JPI Peak Data.pdf).  I saw how you determined the "degrees ROP" numbers (line three from line two), but saw a couple of other things that didn't make sense so I re-read the post and Lood said the three records (the three lines of data) were from three different flights.  They are the moment in time when the leanest cylinder peaks.  In other words, line three is one flight (at roughly 13 minutes into the flight) and line two is a different flight (roughly 5 minutes into the flight).  My only reaction to the data strip is that the CHT's are very cool.  I am going to guess that MP is back quite far, maybe 65% power?

[Shadrach]

I thought that might be the case after looking at the time signatures. The data does not tell us very much other than giving a snap shot of CHTs at an unknown power setting... 

[Lood]

Cruise power settings are always WOT, 2500rpm and 75ROP.

Climb power settings are always WOT, 2700rpm, target EGT (1250 deg on #1)

I fly mostly from strips at around 4000ft AMSL and I normally cruise between 6500ft - 9500ft. This may explain the "low" power.

The peak data.PDF is indeed extracts from 3 different flights and were taken after the climb, when leaning from the richer climb mixture setting to cruise.

The times in the left most column of the .PDF are actually ZULU time and not flight time.

 

I've read through the leaning part in the JPI manual again and I quote:

 

"... by tapping the LF button. This tells the EDM to begin looking for a 15deg rise in EGT for any cylinder. Begin leaning the mixture without pausing. When a 15deg rise occurs, eliminating false peaks, the LeanFind mode becomes activated, shown when the cylinder dot above the hottest cylinder begins flashing."

 

"Continue leaning slowly without pausing... / ... Eventually, one cylinder will reach peak before any of the other cylinders. The EDM will determine this automatically. Note that this cylinder does not necessarily have the hottest EGT."

 

The way I read it is that the EDM will calculate and execute the whole leaning process by determining and working solely on the leanest cylinder. This will thus prevent one from leaning on the wrong cylinder and leaving the rest running leaner. So, according to JPI and regardless of the EGT difference between the cylinders, my mixture setting is 75ROP on the leanest cylinder, leaving the other three richer than 75ROP.

 

My engine's leanest cylinder is #1, but it also runs the coldest of all ito CHT. Reading through all the replies, looking at the data again and having the hotter CHT's on the same side, tends to have me leaning towards a cooling or airflow difference.

Could it be that the oil cooler, together with its oil lines that run just above and inside the cowl flap may cause some restriction, resulting in less air being able to flow through the left side of my engine?

Quite possible, I suppose.

[Cruiser]

It is very easy to confirm your settings (75°F ROP etc) by reviewing the data file from the EDM700. Open the file and click on the DATA icon which will open a spreadsheet style listing of data the engine monitor collected during the flight. You can scroll through the lines by time to find the peak EGT on each cylinder and then step through each line to find the point where the temps are stable. Subtract the two and you get the degrees from PEAK each cylinder is operating. 

 

If you feel more comfortable using the graphics from the chart, use the mouse to click and drag the bright yellow bar from the left side of the graph to the point you are interested in during the flight. Read the values listed on the right side of the graph for each of the EGTs and CHTs for that point in time. Continue to move the yellow bar to any other point and read the values to compare. 

[jlunseth]

Lood you are correct in your understanding of how the Lean Find function works. 

 

JPI provides a piece of software called EZ Trends that allows opening, viewing and analyzing data files.  It is fun to play with and can be downloaded from their website.  Maybe that is what you used to open the data file.

 

The front cylinders are indeed usually colder than the back, but if your baffles are failing just about anything can happen.  Cooling air can actually reverse flow and spill out the opening at the front of the cowling, which is not very effective cooling.  I think you are correct that there are two candidates for what you are seeing.  One is that your fuel flows are off from cylinder to cylinder.  EZ Trends has a function that can determine that by the way, and I noticed that the GAMI people are actually now asking for raw data files rather than the paper and pencil lean test, because they can run an analysis on the data and find the differences in fuel flow between cylinders.  You can do the same if you want, with the JPI software.  The other candidate is poor cooling because of interruptions in the air flow. 

 

I would say you are on the right track.

[BigTex]

I'd also recommend uploading it to Savvy Analysis and trend it there.  It's a free service that I actually like better than EZ Trends.  Here's the website:

 

https://savvyanalysis.com/home