Can I run LOP?

[Ulysse]

I did a Gami test and found that my EGT6 is almost flat on the LOP side and the engine starts to run a bit rough when that cylinder is 20deg LOP at 8gph FF. In these conditions can I run LOP and if yes at which settings?
2 pictures are attached: peak EGT6 and 20 LOP 

[Cruiser]

changes in EGT appears very uniform across the cylinders. Very good. 

What you need to do now is go back and review the data to find at what FF each of the cylinders reached peak EGT. Compare the first FF value to the last one for each cylinder at peak EGT. IF the difference is less than 1.0 gallons you should be able to operate LOP smoothly. (the lower the number the better)

I think you mean the CHT on #6 did not drop as much as the others, but it is low enough already (341), so not really a problem. You could check the baffling and fix any leaks, this will change CHT also. 

"rough" is not really a problem, it is the difference in power produced from each cylinder. A little rough will not hurt anything. 

Did you try this at different altitudes? 

Edited June 19, 2021 by Cruiser

[jlunseth]

I’ll take a stab. First, although the EGT of #6 is consistently lower than the others, we don’t care about that much. EGT’s value is as a relative number, not an absolute number - at what fuel flow does the EGT for a particular cylinder peak relative to the other cylinders. This can be the result of probe placement, or in the case of #6 which is up front and in the most unobstructed of your cooling intake holes, it can be better cooling flow. 

What I see, and it is a little difficult to analyze with precision because of the graph scaling, is that the EGT for #6 consistently peaks later, in other words, at a lower fuel flow, than the other five cylinders. The first five are fairly tightly packed, but the peak for #6 is shifted to the right, and then as you reach the bottom of your leaning and enrich the mixture it is shifted to the left. That is what makes the graph line for #6 look “flat,” but it is really not flat, it is just that #6 is peaking at a lower fuel flow so the two “humps” are closer together. It is peaking at about the same value both as you lean the fuel out and as you enrich the fuel flow again, and that is a lower value than the other cylinders.

GAMI says to aim to have the cylinders peak within .5 GPH of each other. Because of the graph scaling, it is a little difficult to determine how far the peak of #6 is from the other five cylinders, but it is distinctly different. Probably best to send your test data to GAMI or Savvy so they can analyze it.

As for your question about whether you can run LOP, the APS people teach that you can run anywhere you want so long as the power is at or below 65% HP. By my math, that is a fuel flow of 10.4 GPH so long as you are LOP, assuming you have the 220 HP engine. So as long as you stay under that GPH and are happy with the way the engine is running the answer is yes. If you want to make the engine smoother, or you want to run at a higher power setting, then a set of GAMI injectors that would make the fuel flows match up better (peak within .5 GPH of each other) might be in order.

[N201MKTurbo]

Your CHTs look fine, just increase your FF until it smooths out. 

Everybody overthinks these things.

If you get your spark plug gaps dead nuts equal, they will all go rough at the same time. If you have equal fuel flows.

[GeeBee]

1 hour ago, jlunseth said:

If you want to make the engine smoother, or you want to run at a higher power setting, then a set of GAMI injectors that would make the fuel flows match up better (peak within .5 GPH of each other) might be in order.

Absolutely agree. The GAMI's are the bomb for smooth running LOP. Takes a little time, a little work to get them all matched but once you do, it is really nice. Suggest you use the "GAMI" mode (that little circle "G" )to right on your graphing.  GAMI will work with you on getting them matched up.

 

[PilotX]

I think the only way I can get to 8 gph is to LOP off a couple cylinders. 

[A64Pilot]

I’m not much for graphs, but I’ve seen people swap injectors around to get them to peak closer together with good success.

‘The EGT temp that a cylinder peaks at is very often tied to compression, a higher compression engine will peak at lower EGT’s than a low compression engine will.

‘For many reasons the EGT that an engine peaks at is irrelevant, but it can sometimes be used in troubleshooting.

‘I’ll second that the condition of the plugs can greatly influence how well and how deep you can run LOP smoothly.

‘I’ve run GAMI’s on two different engines an IO-520 and an IO-540, and on both of those motors fine wire plugs made more of a difference than the injectors did.

‘The IO-520 was a fresh factory zero timed motor and the IO-540 I did the field overhaul with new Millenium’s.

On edit. I don’t mean to say you need fine wires, you don’t, but you do need an ignition system to be in good order, it’s harder to ignite a lean mixture,and plugs are often the first to go.

Edited June 19, 2021 by A64Pilot

[GeeBee]

If I was planning LoP operation, I would square away ignition, meaning good mags and fine wire plugs, before turning attention to injectors.

[Ulysse]

4 hours ago, GeeBee said:

Suggest you use the "GAMI" mode (that little circle "G" )

thank you! I didn't know that.
I only run the test at 4500ft. Going from 65% power and about 12gph, all my EGTs peaked at 9.4-9.3 gph except EGT6 which peaked at 9. So the spread is .4
but then I do not understand :

5 hours ago, jlunseth said:

the power is at or below 65% HP. By my math, that is a fuel flow of 10.4 GPH so long as you are LOP,

How can I be at 10.4 LOP if the peak is at 9.4 , and by leaning FF can only go down? Unless 10.4 gph is for a higher power setting ? (or my power went down in the process of leaning ?)
 

[GeeBee]

https://www.advancedpilot.com/downloads/GAMI Lean Test.pdf

[A64Pilot]

When your LOP the amount of power that can be made is determined by fuel flow. On edit it’s determined by fuel flow ROP too, just it’s a variable if ROP, but a set number if LOP.

So therefore if your LOP, apparently the fuel flow you were given will be less than the percent power that can hurt the engine.

‘I don’t know the formula off the top of my head, but every engine can produce x amount of power per unit volume of fuel consumed, so fuel flow can be used to determine power output, that number can vary if ROP. but if LOP it’s flat, so you can say for each GPH = X horsepower if the formula is known.

Edited June 19, 2021 by A64Pilot

[jlunseth]

The formula for determining %HP when LOP, in our TSIO360’s, is 13.7 x FF (in GPH) divided by rated HP. The 13.7 is a constant that is derived from the compression ratio of the engine. Your graphs did not show what Manifold Pressure you were using for the lean test. LOP is a fuel/air ratio, “x” molecules of oxygen to “y” molecules of fuel. The ratio where the number of molecules of air is exactly that needed to burn the available molecules of fuel is called a stoichiometric mix. We don’t have instruments that measure in molecules, we have manifold pressure and fuel flow, and we use the technique of “finding peak,” which is reflected in the GAMI lean test, as a way of determining that the mixture is leaner than stoichiometric, and we use the drop in temperature to determine how far lean of peak the engine is running. Stoichiometric is about 2% cooler than peak EGT. If you have followed so far, you can run lean of peak at 65% by starting with a higher MP than you used to run your lean test. Since I don’t have the 220 HP engine I don’t know exactly what MP would be best, because it is not particularly important as long as the MP is high enough to keep the mixture well lean. I would suggest trying 27 - 30 inches and that 10.4 GPH fuel flow. If the perfect MP for this is 27” and you use 30” it does not materially effect the 65% power because when lean of peak, fuel flow determines power, not MP, but if the engine runs a little rough, then try the same fuel flow but a little lower MP.  @gsxrpilot runs his 210 HP 252 engine at 65%. Perhaps he can say what he uses for an MP. If I recall correctly he uses 26”. You would want to use an MP a little higher than his because your engine has a higher rated HP.

[carusoam]

It takes some practice…

Everyone can run LOP…

You have a strong indication that the EGT6 is peaking before the others…

Know that .4gph isn’t terrible… but, your other five cylinders are very close together… so work on that…

Learn to grab data…

Share data…

Review data…

Use the savvy site and push the share button…

Copy the link here…

Read up on things like the baby jar test

See what it takes to clean a fuel injector…

 

if it is really one FI messing with the fuel flow in that cylinder… pull it out and clean it following the procedure and Hopp’s #9…

Catch anything that was stuck in the FI… share a pic.

Or… clean them all… then start collecting the real data…

It really helps to have a few flights to look at… set your JPI to collect data as quickly as possible…

Take extra time during your run-ups to allow the data to stabilize for a second or six…

PP thoughts only, not a mechanic…

Best regards,

-a- 

[Ulysse]

here is the link to the flight
https://apps.savvyaviation.com/flights/4957870/54c3da88-9453-4b14-8b56-60574e5fec9e

I followed the test procedure suggested by savvy. They recommend doing this at 65% power setting. https://resources.savvyaviation.com/resources/other-documents/flight-test-profile/

I do not understand @jlunseth comment regarding MP: 
My understanding is that at a given pressure altitude and OAT, when ROP, power is determined by a combination of MAP+RPM. at 2500RPM,  If I increase the MAP then the power will no longer be 65%. 
Anyway, attached is another graph with MAP and %power. MAP remains constant throughout the test at about 25.8-26". So does power until I get LOP which is consistent with the fact that when LOP, power is a function of FF.
In my test in the LOP region, power goes down from 64% to 56%. Supposing that decrease in percentage remains the same at a different setting, then if I wanted 65% power LOP, I would need to start the test at about 73% ROP which would have been in this case 29" MAP. This would probably lead to the 10.4gph FF mentionned by jlunseth. Is this reasoning correct ?

[Ulysse]

[carusoam]

Follow closely what JL is saying…

It is a complex subject… and every detail counts…

+1 When JL writes about operating a TC’d engine… there is a lot to be learned…

Some of the best engine ops paragraphs around MS…

And… thanks for posting the JPI links and data… 

MS Rocks!

Best regards,

-a-

[carusoam]

When it comes to engine data…

Some snapshots really help…

Others can be just TMI…

So…

I start simple… like looking for the two humps where the run-up occurs…

if you speed through the run-up like a student pilot in a C152 paying by the hour…

You won’t be able to find the two humps…

I did see the prop get tested thrice… 

Engines aren’t digital… they don’t flop immediately to the next status…

Turbos add some lag…

Expect some trial and error to find what works…

See if you can help me find the run-up in these… data sets…

Great collection of data in your JPI… lots o variables!

Expect some leaning data got lost by the speed of which you were leaning…

I takes some waiting once you get close… the instruments have a few seconds of lag to catch up…

Best regards,

-a-

 

 

[carusoam]

When it comes to leaning see if you can show the five minutes of activity where you leaned and what you got…

It is incredibly challenging to look through a flight of data… and be talking about the exact event that you are seeing…

Some people will describe the sections of the flight along their time line…

We can all see what is happening, but only the PIC knows what knobs were touched when…

Best regards,

-a-

[Ulysse]

I agree, I did not let time to the engine to settle. The reason is that I did not see a significant decrease in egt6 from its peak value while the FF had dropped to 8gph and the engine started to run rough.

It means that if I wanted to run LOP, cylinder #6 would be almost at peak EGT. Is this a problem?

[carusoam]

4 minutes ago, Ulysse said:

I agree, I did not let time to the engine to settle. The reason is that I did not see a significant decrease in egt6 from its peak value while the FF had dropped to 8gph and the engine started to run rough.

It means that if I wanted to run LOP, cylinder #6 would be almost at peak EGT. Is this a problem?

When kept below 65% bhp… technically, not a problem… from a red box point of view…

Followed by… what is CHT6 doing at the time?

if all cylinders are a few degrees LOP… some more than others… are you still feeling roughness?

Roughness is typically caused by something not running very well..

Find the point on the graph where that happened… look for spikes in EGT… where something has caused incomplete burning of fuel in that cylinder… skipping of a spark plug or two…

Too late for me to hang out… big day tomorrow….  
-a-

[jlunseth]

Ulysse, I think you ran the test just fine. You started at a rich of peak power setting of 65% and got what appear to be valid readings. Stick with that.

The second question I was addressing was your question about how you would achieve a 65% lean of peak power setting at 10.4 and why the peak you found during the test was about 9.4 and not 10.4. Please note, I am assuming you have the 220 HP Encore engine, if you have a 210 HP engine the fuel flow would be lower for 65%.

I think you did the test correctly. But you are assuming that once you set the power at 65% ROP at the start, the power setting then does not change during the test. In fact, the power setting is being changed through the course of the test. If you start at a 65% ROP power setting and then lean the mixture, you are changing the power setting, no? So when you find peak EGTs during the test that does not mean that at that point you are still at 65% power, rather, you are at some lower power. The point of the test is to find out where each of the six cylinders reaches peak EGT relative to each other and it is not necessary for that purpose that the power must remain constant during the course of the test.

So what I am trying to tell you, is that if you want to run at a LOP cruise power setting of 65% that would not be 9.3 or .4 GPH for a 220 HP TSIO360, that would be 10.4, and to be lean of peak you would probably need a manifold pressure a little higher than 26”, say 27, 28 or 29. Since the power when LOP is based solely on fuel flow, it does not matter which of these manifold pressures you use so long as it is one where the engine runs smoothly.

A LOP power setting at 9.4 GPH for a 220 HP engine is about 58% rated HP.

I would not run the test again as you describe, it is not necessary. There is no need. You ran it correctly the first time. 

[Ulysse]

Yes, I have the 220HP engine. So, to achieve 65% LOP, I should start ROP at a higher power setting in order to reach 65% when power starts to drop after peak EGT or should I start 65% ROP and once LOP increase MP and FF ?

[N201MKTurbo]

27 minutes ago, Ulysse said:

Yes, I have the 220HP engine. So, to achieve 65% LOP, I should start ROP at a higher power setting in order to reach 65% when power starts to drop after peak EGT or should I start 65% ROP and once LOP increase MP and FF ?

It doesn’t matter where you start. I normally reduce the MP, then lean until there is a pronounced power drop, then increase MP to where you want it, then slowly richen the mixture until I get the FF or TIT I’m looking for.

[Ulysse]

On 6/19/2021 at 3:39 PM, jlunseth said:

By my math, that is a fuel flow of 10.4 GPH so long as you are LOP

When I set power to 65% ROP (with FF=11.3 GPH according to the POH) and then lean, my EGTs peak at around 9.4 GPH. So, if enrich to 10.4 GPH, would'nt I be running ROP? Unless my fuel flow sensor is not accurate. Thus the question: How do I know it is accurate? I have garmin EIS with the g3x. I do not know if the sensor comes calibrated from the factory or if it is done by the installer on the field.

Anyway, I tried running LOP based on the indications of the EIS. 

I set power to 65% ROP as per the POH then leaned until the last cylinder (#6) went 10 deg LOP. The first EGT peaked at 9.4 GPH and the last one at 8.9 GPH. In order to get 10 deg LOP, the FF was down to 8.6 GPH. The engine run smoothly with low cylinder tempertures and 1575 deg TIT but I lost about 10 knots of speed. However, the power computed by garmin had dropped to 60% although I did not adjust the MAP. So the second question is how accurate is the power computation? and if it is accurate, then should I increase MAP to return to 65% once LOP? In that case how would it affect the whole process of leaning etc.

 

[bradp]

On 6/19/2021 at 10:50 AM, GeeBee said:

Absolutely agree. The GAMI's are the bomb for smooth running LOP. Takes a little time, a little work to get them all matched but once you do, it is really nice. Suggest you use the "GAMI" mode (that little circle "G" )to right on your graphing.  GAMI will work with you on getting them matched up.

 

One thing I never understood with the gamis is that they are dependent on a dynamic state whenever you order them.  So say you have a small induction leak in a cyl that gets fixed down the road, you’ve now changed you cyl AF mix.  So either things need to be spot on tuned when ordering or do they swap out restrictors if your spread isn’t perfect or changes later on?