Can I run LOP?

[GeeBee]

36 minutes ago, bradp said:

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? 

For one year, you can order new injectors based on new data. I got mine within .4 gph, but I wanted better GAMI worked with me and shipped me a new #5 which brought me within .1 gph. After a year, they charge 199 for a new injector, if for instance you swap a cylinder. They are really quite easy to work with. 

[bradp]

That’s pretty cool.  Thanks @GeeBee

[Will.iam]

23 hours ago, Ulysse said:

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.

 

From what I’ve been told power prediction from efis or engine monitors in general are set to calculate power on the ROP operations and are not as accurate for LOP. Because your air (MP) is constant as you do the mixture pull to lean you will lose power. So you can accept a lower power setting than 65% or since you know the formula for LOP FF setting which is 10.4 so you can increase fuel to 10.4 but that would put you rich of peak IF you kept the table chart for ROP MP setting. In order to fly LOP 10.4 you have to increase your MP to above the charted ROP table setting. How much you increase the MP will dictate how far LOP you will go but only if you keep resetting your fuel flow to 10.4. I think where you are getting confused is that when you adjust your mixture to lean your MP stays constant. But if you adjust your MP your mixture adjusts too. And it has to or everytime you Applied takeoff thrust your engine would leanout and quit or if you where at cruise and pulled back to idle the engine would flood and die so its good for when you are changing power just not when you want to change your ratio of LOP. As an experiment set your power for say 60% out of the POH so you can’t hurt the engine.  Now instead of changing the mixture, change  the MP bY increasing it BUT constantly keep the fuel flow the same.   If you look on your engine monitor you will see the same thing as you did when you were adjusting the mixture. All that to say if you want 65% power while being LOP you have to have a higher MP than the charted ROP setting of MP. And how deep of LOP you want to go @ 65% can be controlled my MP so long as you keep the fuel flow at 10.4.  For example say your MP is at 25”  and FF at 10.4 gets you 10d LOP if you increase your MP to 27” AND readjust your FF back down to 10.4 you will see that your degrees LOP on your engine monitor will be showing 60 or 70d LOP now. 
I have the MB engine so only 210 compared to your 220 so my numbers are a little lower than yours but i find 2500rpm 25” MP and 9.5 fuel flow gives me 1550 TIT which is 100d below the limit on my TIT and works for all altitudes that i have flown.  Because LOP burns so much slower if you go too far LOP or to high rpm you will see the TIT rise too high due to the combustion still burning as the exhaust valve opens dumping flames down the exhaust manifold. By slowing down the RPMs to say 2400 or 2300 you allow the slower burning LOP mixture to complete more before the exhaust valve opens thus lowering your TIT temp. Problem is as you go up into the FL you need the faster turning prop due to the thin air and 2500 rpm is my prop’s best efficiency speed. 

[Ulysse]

thank you very much for the detailed explanation @Will.iam and @jlunseth. It all makes more sense now. I'll try this tomorrow

Edited August 9, 2021 by Ulysse

[carusoam]

Since the 90s… LOP and ROP have been equally important in Mooney aviation…

If for some reason… your engine monitor isn’t able to display the %BHP numbers for both ops…

It isn’t because it’s not important, or they think they’re is only one way…

It has taken a while for the %bhp calculation to be adopted…

absolute accuracy isn’t that critical… Key Numbers work pretty well…

Go Savvy!

Go MAPA PPP!

Best regards,

-a-

[squeaky.stow]

On 6/21/2021 at 1:58 AM, 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 ?

Ulysse, I have found that starting from a higher power setting works very well. I use a technique that many have described on this forum that is fairly reliable to set my LOP 65% power. I climb to cruise altitude at full throttle, full rich and prop at max rpm. Then as I level off I close the cowl flaps and set 75% power by first pulling back MP and then RPM to my desired cruise setting, leaving the mixture still at full rich. Then when established in cruise power, I pull the mixture smoothly back to my pre-calculated LOP fuel flow. For me with the MB engine that is 10 GPH but for your SB it should be 10.4 as @jlunseth and others have already mentioned. When I do this my JPI monitor shows the power coming back to 65% but I am not sure whether the G3X will accurately show you percentage power as you transition to LOP. It doesn’t matter however, because once you know the FF for 65% LOP it will always be the same. It doesn’t really make sense to start leaning from 65% because by the time you get LOP you will be well below 65% and then you have to start increasing MP and RPM to get back up there. Much easier to start about 10% higher, get your MP and RPM where you want them and then do “the big mixture pull” to your target FF. 

[carusoam]

Ulysse,

Are you familiar with the big pull technique?

Take lots of notes on every flight… sooner or later you have all your power settings and how you got there…

This will keep you from creeping through high TITs where you want to pass through them quickly…

PP thoughts only not a CFI…

Best regards,

-a-

[Stetson20]

3 hours ago, BalaGee69 said:

what is Lop?

Lean of Peak- type it in the search bar and you'll get many threads and posts on what LOP and ROP (rich of peak) mean.

[RoundTwo]

On 6/20/2021 at 1:11 AM, carusoam said:

…clean it following the procedure and Hopp’s #9…

As in gun cleaning solvent? Love the smell. :-)

[carusoam]

4 hours ago, RoundTwo said:

As in gun cleaning solvent? Love the smell. :-)

Yes…

Good for cleaning lead deposits for some reason….  

Best regards,

-a-

[Ulysse]

a little feedback on this topic:

After months of waiting for my plane to be available again, I had the opportunity to fly long enough flights to try LOP settings.

It actually was much simpler than I thought and I soon could see 8.7 gph @ 165kt TAS at 14000 feet, all the CHTs below 370° at about 35° LOP! This was amazing for me.

However, the numbers do not match the discussions above.

I have a 220HP engine. If I apply the formula given in this thread, I should need 10.4gph for 65% power. 

My g3x/EIS display gives me 65% @8.7gph., 28.2" MAP and 2480 RPM.

Is the algorithm for computing power incorrect? or some settings on my system which generates this error?

As per the formula 13.7*FF/HP, 8.7gph should give me just 54% power, but if this were true then I don't think I could get 165kt TAS. Actually from the graph in the POH, 65%ROP should give about 165kt of TAS. Since 65% is 65% LOP or ROP, then the speed I am getting LOP (165kt) seems to indicate that the power is indeed 65%. Then why 8.7gph only ?

Thank you for your comments.

[Tom 4536]

36 minutes ago, Ulysse said:

a little feedback on this topic:

After months of waiting for my plane to be available again, I had the opportunity to fly long enough flights to try LOP settings.

It actually was much simpler than I thought and I soon could see 8.7 gph @ 165kt TAS at 14000 feet, all the CHTs below 370° at about 35° LOP! This was amazing for me.

However, the numbers do not match the discussions above.

I have a 220HP engine. If I apply the formula given in this thread, I should need 10.4gph for 65% power. 

My g3x/EIS display gives me 65% @8.7gph., 28.2" MAP and 2480 RPM.

Is the algorithm for computing power incorrect? or some settings on my system which generates this error?

As per the formula 13.7*FF/HP, 8.7gph should give me just 54% power, but if this were true then I don't think I could get 165kt TAS. Actually from the graph in the POH, 65%ROP should give about 165kt of TAS. Since 65% is 65% LOP or ROP, then the speed I am getting LOP (165kt) seems to indicate that the power is indeed 65%. Then why 8.7gph only ?

Thank you for your comments.

About two months ago I posted (I can't find the post) the same concern with a friend's 252 that has a new GI275 EIS. It seems that the LOP algorithm might be incorrect or the EIS is not recognizing that the engine is being run LOP.  Fortunately we can calculate %HP from the LOP fuel flow if the fuel flow is calibrated correctly. It would be nice if Garmin would provided some info, but no such luck.

[Will.iam]

40 minutes ago, Ulysse said:

a little feedback on this topic:

After months of waiting for my plane to be available again, I had the opportunity to fly long enough flights to try LOP settings.

It actually was much simpler than I thought and I soon could see 8.7 gph @ 165kt TAS at 14000 feet, all the CHTs below 370° at about 35° LOP! This was amazing for me.

However, the numbers do not match the discussions above.

I have a 220HP engine. If I apply the formula given in this thread, I should need 10.4gph for 65% power. 

My g3x/EIS display gives me 65% @8.7gph., 28.2" MAP and 2480 RPM.

Is the algorithm for computing power incorrect? or some settings on my system which generates this error?

As per the formula 13.7*FF/HP, 8.7gph should give me just 54% power, but if this were true then I don't think I could get 165kt TAS. Actually from the graph in the POH, 65%ROP should give about 165kt of TAS. Since 65% is 65% LOP or ROP, then the speed I am getting LOP (165kt) seems to indicate that the power is indeed 65%. Then why 8.7gph only ?

Thank you for your comments.

Are you sure your fuel flow is accurate? My fuel totalizer is not software programable for the k factor got to take it apart but my JPI unit is and they are both connected to the same fuel transducer. After flying multiple times with just 5 gallons in one tank, i got the JPI dialed in that it would run out of gas right when the JPI showed 5 gallons used. The hopskins totalizer showed 5.8 gallons used. Once i started doing LOP to the JPI ff instead of my old totalizer, the performance numbers started agreeing to book values. Just as a side note you can always verify if you are LOP or not by increasing ff all the EGT’s should increase if one doesn’t or they all decrease you where not fully lop to start with. 

[PT20J]

Airspeed is the final arbiter of power. If all the instruments are accurate, and your speed and power settings match the POH, then they are most likely correct. I seem to remember a post on Beechtalk where George Braly said he developed the power algorithms for Garmin, but I could be wrong about that.

It would be interesting to compare numbers with other 252 owners.

Skip

[Will.iam]

19 minutes ago, PT20J said:

Airspeed is the final arbiter of power. If all the instruments are accurate, and your speed and power settings match the POH, then they are most likely correct. I seem to remember a post on Beechtalk where George Braly said he developed the power algorithms for Garmin, but I could be wrong about that.

It would be interesting to compare numbers with other 252 owners.

Skip

I’m a 252 owner but with the MB engine at 210HP OP said he had 220 so must me a 252 with encore conversion. 
i run 9.5 FF and get 150kias at 3000 160kts at 10000 and 170kts at 17000 i think but not sure as i was more concerned about O2 and didn’t pay much attention that one flight. 8.7 at 165 seems very efficient even at 14000. 

[Will.iam]

Also my engine is at TBO so my engine is probably less efficient than a lower time engine. 

[Ulysse]

On 5/13/2022 at 10:13 PM, Will.iam said:

k factor

I do not know what the k factor is, I suppose some calibration parameter. Is there such a user settable parameter for the Garmin EIS ? Maybe @PT20J knows?

If the formula is wright then FF could indeed be underestimated, or maybe the formula (13.7 factor) is incorrect?

Another question is that when approach peak and go LOP, I clearly feel that the engine has sometimes a "hesitation" that I suppose is a misfire. Is this a normal behavior that I shouldn't worry about ?

 

Edited May 15, 2022 by Ulysse

[aviatoreb]

I know the formula, and I use it in my own thinking on this topic.  But it can't be entirely exact.  Since it refers to the max power of an engine when trying to describe power at low power settings say 50%.  But consider that say an Acclaim can be purchased at 270hp but its power output can be increased by STC by increasing the max rpm to 310hp.  I don't expect that increases the power produced at a fixed fuel flow at 50% in any way.  So the formula must just be a rough estimate.

[Fly Boomer]

4 hours ago, Ulysse said:

engine has sometimes a "hesitation"

CAVEAT:  I only know what I read -- I'm not a mechanic.  This advice is worth exactly what you paid.

Everything needs to be nearly perfect:

- plugs - most prefer fine-wire but some run massive
      clean
      gapped accurately and identically
      resistance tested
      new plug gaskets every time they come out
      precise torque

- harness - may be hard to diagnose a marginal harness

- mags - "recent overhaul" isn't enough.  Point gap and E-gap need to be near-perfect.  External timing identical and near-perfect.

- fuel system - most prefer GAMIjectors but some get good "GAMI spread" without them

- induction system

- everything else

We all wish our mechanics, like our doctors, were god-like in their knowledge, skill, and dedication to doing the best job humanly possible.  Sadly, that isn't the case for either.  The confidence inspired by new plugs at your last annual, or knowing that your mags were gone through only 200 hours ago, or knowing that the harness "looks good" isn't enough.  Everything in, on, and around your engine must be nearly perfect to get smooth LoP operation.

Braced for flame.
 

[PT20J]

10 hours ago, Ulysse said:

I do not know what the k factor is, I suppose some calibration parameter. Is there such a user settable parameter for the Garmin EIS ? Maybe @PT20J knows?

If the formula is wright then FF could indeed be underestimated, or maybe the formula (13.7 factor) is incorrect?

Another question is that when approach peak and go LOP, I clearly feel that the engine has sometimes a "hesitation" that I suppose is a misfire. Is this a normal behavior that I shouldn't worry about ?

 

The K factor is the the number of pulses (in thousands, hence the 'K') that the transducer emits per gallon of flow. Flowscan transducers are usually around 29. In a perfect world, you would set the G3X/EIS to match the number marked on the transducer. But that never seems to give the right fuel burn and so some tweaking is required to adjust the EIS K-factor to get the most accurate results. This can be done by measuring the reported fuel consumption over several tanks and comparing to the pump readings. In my case, the transducer has a calibrated K-factor of 28.898 and I set my EIS to 30.00. Interestingly, with the same installation of transducer, the EDM 700 K-factor for most accuracy was 30.5.

[Will.iam]

9 hours ago, aviatoreb said:

I know the formula, and I use it in my own thinking on this topic.  But it can't be entirely exact.  Since it refers to the max power of an engine when trying to describe power at low power settings say 50%.  But consider that say an Acclaim can be purchased at 270hp but its power output can be increased by STC by increasing the max rpm to 310hp.  I don't expect that increases the power produced at a fixed fuel flow at 50% in any way.  So the formula must just be a rough estimate.

I think the FF is very exact. That acclaim engine at 270 is really a 310 just derated to 270.
 
for my engine once i get the encore conversion the engine to chance from 210 to 220 all they do is turn up the boost on my manifold from 36 to 39 and increase the fuel flow from 24 to 26. Rpm gets reduced 100rpm interestingly enough.  So my engine right now is like doing a reduced power takeoff compared to what the components could be subject to if i had more air and fuel going through it. 

so instead of 9.5 ff being 62% power after the conversion, that same ff will be 59% power. So i can keep the same wear and tear or bump up my ff to 62% of the encores max HP but I’ll be wearing out the engine that much faster.