tried LOP for the first time - have some questions

[bd32322]

So I read a bunch about LOP operations and tried it yesterday - I was impressed with the fuel economy and speed. I have a few questions about LOP operation though:

1) To get into LOP mode at cruise, I did the GAMI big mixture pull. I went to where the engine was rough and then enriched it where the engine was smooth, hottest CHT was 340 - enriched mix to get hottest CHT to 360, EGTs were around 1380-1420 and fuel flow was at 8.5 gph - full throttle 7500 feet, 2500 rpm. So my question is do I really need to find the peak to see how far lean I am? I think I should be fine as long as CHTs are within safety limits (discovered from the forum here that 380 is a good number). I know at that height and the power setting there is no "red-box" - but I was wondering about flying down low at full throttle at power settings where there *IS* a red box of mixture settings.

2) As I was climbing I wanted to maintain the same EGT as takeoff. I checked the EGT at 1000 AGL and it was I think 1200 or so. Then I wanted to pull the mixture to maintain that EGT but all the way up to 7500 the EGT barely decreased much. I had to make maybe 1 tweak to get it back to 1200 on the climb (CHTs around 340). I think it had dropped to 1100. That tweak barely made any difference to fuel flow. I guess if I am climbing higher I would tweak more - but I am wondering if others see the same thing.

3) Once I had the engine settings all setup - half way into my 1.5 hour trip - I noticed that the hottest CHT had crept up from 360 to 370. So I leaned it a bit more and got it back - but wondering why that happened? Warmer air ? I was flying south

 

Thanks

[Parker_Woodruff]

At 7500 you can pull the fuel flow back slower and you're not going to hurt anything. At that altitude, you should be able to run Wide Open Throttle and 2600 RPM at 9 GPH and be I'm a pretty good place.

[Cruiser]

The IO 360 A3B6D has a compression ratio of 8.7:1 so your fuel flow multiplier is 15.13 to determine %power when LOP.

At 8.5 gph your were at 64% power.

I believe you should peak EGT at around 10 gph. so your approach the setting the mixture is the simpiliest way. IF you want to manage your engine based on CHT (which is a very wise method) you are doing everything you need to do.

[bd32322]

thanks for the responses - what about if i want to maintain full throttle at say 4500. Seems like I lean more until CHTs are acceptable and I can find out power from 15 times fuel flow as you say. Its probably going to be less than 75% if I want CHTs around 360 I think - I'll have to try it. But there is nothing stopping me from having 75 or greater % power as long as CHTs are okay...

 

I like this simple way of managing the engine rather than finding peak - I feel like I am staring at the JPI a lot more then - which makes me nervous - instead of looking out.

[WardHolbrook]

Quote: bd32322

thanks for the responses - what about if i want to maintain full throttle at say 4500. Seems like I lean more until CHTs are acceptable and I can find out power from 15 times fuel flow as you say. Its probably going to be less than 75% if I want CHTs around 360 I think - I'll have to try it. But there is nothing stopping me from having 75 or greater % power as long as CHTs are okay...

 

I like this simple way of managing the engine rather than finding peak - I feel like I am staring at the JPI a lot more then - which makes me nervous - instead of looking out.

[GeorgePerry]

concur with the advanced pilot recommendation.  But to simplify LOP operations, A good rule of thumb for NA engines is 65% or less and you can do whatever you want with the mixture and not hurt anything regardless of altitude.  Check the POH for MP / RPM combinations.

I always liked finding peak egt to get a baseline for that day's conditions and then lena to 30 deg LOP.  Some go more, some go less, 30 deg LOP seemed to work well for me.  Your mileage might vary.  The caveat of having GAMI's and a good engine monitor with individual probes and FF of course applies.

As for your climb question, I believe the best technique is to run the engine with everything full forward until passing about 1000 feet, then pull the rpm's back to 2600 just for noise levels.  Passing 3000 msl slowly pull the mixture back to maintain 150 deg ROP for climb.  You'll have to tweek the mixture periodically as you go up and always monitor temps and adjust to richer settings if required.  This technique reduces exsess Fuel flow during climbout and keeps the engine operating happily in it's max power range.

[KSMooniac]

You cannot rely on CHTs as a suitable point for leaning... you need to lean via EGT and verify that CHTs are acceptable.  At typical non-turbo cruise altitudes (say 7,000-9,000) I would lean for peak to 10 LOP, let things stabilize, and watch your CHTs.  If they stay below 380 dF, then you're fine, but if they creep up you can lean a little more until they settle down below 380 dF.  CHT will vary widely based on OAT and mixture setting, which is why it is not a good reference.

If you cruise lower, then you need to be *more* LOP, assuming you are still running wide open throttle, which is the only sensible thing to do.  

In the summer around here (and south to TX) I need to go further LOP than I do currently to stay below 380 dF.  

You're on the right track for leaning in the climb, but I would check your full-power EGT on cyl #1 during a takeoff from sea level (or as close as possible) and use that as a reference.  I suspect you'll be closer to 1300 than 1200, but that varies based on probe position.  Fuel Flow should be around 18 GPH as well.  

Taking the Advanced Pilot seminar is the single best thing you can do as an aircraft owner to learn all about managing engines and diagnosing issues.

[jetdriven]

Scoot, excellently put.  CHT is a nice long term trend but leaning to a value and verifying it with good CHT is a better method. We also have to run >50 LOP at lower alttude in the texas summer heat to keep CHT under 380.

FWIW our Peak EGT value at a lower altitude and high power setting is around 1600. Full power std day temp sea level takeoff is 1350 with a FF of 18-18.5 GPH.  From what I have read here, that is exactly what it should be at.  Leaning to that 1350 target works well ((even on takeoff with a DA over 3k)  until around 3-5K feet, where you can go leaner, to something like 1400-1450.  Its below 75% power by then anyways.

[aviatoreb]

Quote: KSMooniac

Taking the Advanced Pilot seminar is the single best thing you can do as an aircraft owner to learn all about managing engines and diagnosing issues.

[Hank]

Quote: aviatoreb

Is there a lot more to learn in the seminar than can be learned by self study?  Including Deakin's own many many writings on the subject in his Pelikan's perch, but many other reputable sources.

[KSMooniac]

Quote: aviatoreb

Is there a lot more to learn in the seminar than can be learned by self study?  Including Deakin's own many many writings on the subject in his Pelikan's perch, but many other reputable sources.

[fantom]

Quote: KSMooniac

[MARZ]

"While a monitor would be nice, or even fuel flow, this year will be a reseal instead."

I managed to pull off both this year JPI had a heck of a deal on the fuel flow at OSH 480 with a 200 dollar rebate.....

I'd have to say if I had to choose from one to the other I'd go with the egt first and the fuel flow second.   Remember at 5+ a gallon that investment pays back dividends...... (at least that was how I got one over my conscience to make the purchase )

[KSMooniac]

fantom, I understand that sentiment, believe me, as I've been in many engineering courses that just convey info that is purely of academic interest and not practically useful in the real world.  This course is 100% practical for us owner/operators, and incredibly useful in conveying knowledge that helps us operate the engines properly as well as diagnosing and troubleshooting various maladies.  It is not just a "learn how to fly LOP" course...far from it!

[Shadrach]

I second what Scott has said. I've never taken either course. However, I cannot imagine a faster way to gain a working understanding of what is going on in your engine's combustion chamber and how it relates to FF, EGT, CHT, Range and Engine Health. I came into aviation with a basic knowledge of engines and engine tuning. Even though I'd personally built up 2 small engines (old British inline twins) and tuned /repaired a number of other interesting engines I had 0 experience with constant flow injection systems and how they operate.  I've learned a lot from Deakin, Braly, Atkinson et al... via forums, articles and in the early days they would personally answer emails. A group of more patient and forth coming guy would be hard to find. True gentleman.

[bd32322]

i got back to check on this thread a bit later - but here is what I got in summary:

Lean by EGT - try 10 LOP and see if it CHTs are in line - if not in line, lean more to keep CHTs in line. So how is that not leaning with CHT in mind? You are going to keep varying your degree of "LOP-ness" until CHTs are in-line. By starting with 10 LOP you are trying to get the most power out with the best fuel consumption and with CHTs in limit. The way I see it now is that the red knob is just being used as a power knob because I am running WOT.

 

Basically control mixture to control power - and control CHT using power/mixture. Also can someone explain to me what EGT really means? The hotter the EGT the more complete the combustion process is? Always confused by this.. I tried LOP at 18 MP at 3000 feet - my EGT went to 1500 or so ! But up at 7k or above i barely ever see 1450 or so.

Anyway I am now a big fan of the GAMI big pull in terms of simplicity of in-flight operations especially for the mooney. By getting the engine to go rough, I am pretty much starting leanest first - checking if CHTs and ground speed are good enough and then enriching until CHTs are in-line (i try 360 F because of a chart of metal characteristics that shadrach posted) and there is a good tradeoff of speed and fuel consumption etc etc. Less fiddling with the JPI and less head-down time too !

Need to do more experiments with periodic oil inspections and borescope inspections. My engine has 1800 hours on it - so I dont mind experimenting on it a bit now

[jetdriven]

Quote: bd32322

i got back to check on this thread a bit later - but here is what I got in summary:

Lean by EGT - try 10 LOP and see if it CHTs are in line - if not in line, lean more to keep CHTs in line. So how is that not leaning with CHT in mind? You are going to keep varying your degree of "LOP-ness" until CHTs are in-line. By starting with 10 LOP you are trying to get the most power out with the best fuel consumption and with CHTs in limit. The way I see it now is that the red knob is just being used as a power knob because I am running WOT.

Sounds just like what we do.  Thats logical thinking. The lowet BSFC starts about 10-15 LOP and goes to about 50 LOP.

 

 

Basically control mixture to control power - and control CHT using power/mixture. Also can someone explain to me what EGT really means? The hotter the EGT the more complete the combustion process is? Always confused by this.. I tried LOP at 18 MP at 3000 feet - my EGT went to 1500 or so ! But up at 7k or above i barely ever see 1450 or so.

Down low you can make more power, therefore a higher peak EGT.  Peak is roughly where all oxygen and all fuel are used up. A little bit leaner is a little more efficient from a BSFC standpoint.

 

Anyway I am now a big fan of the GAMI big pull in terms of simplicity of in-flight operations especially for the mooney. By getting the engine to go rough, I am pretty much starting leanest first - checking if CHTs and ground speed are good enough and then enriching until CHTs are in-line (i try 360 F because of a chart of metal characteristics that shadrach posted) and there is a good tradeoff of speed and fuel consumption etc etc. Less fiddling with the JPI and less head-down time too !

Need to do more experiments with periodic oil inspections and borescope inspections. My engine has 1800 hours on it - so I dont mind experimenting on it a bit now

Ours went from using a quart in 5 hours to a quart in 12-14.  Canrt blame it on the LOP maybe its the MMO or 2400 RPM cruise, but I like it.

[bd32322]

thanks jetdrive - yeah my engine is drinking oil at about 1 quart every 5 hours or so - hoping it comes down with LOP - altho like you said I am not sure of the correlation

[bd32322]

Oh one more question - is there a red-line for peak EGT?

I saw 1500 in the flight i mention above at 3000 feet - and thought that was a pretty darn high number compared to what i usually see - so I took immediate action

[carusoam]

Bd,

Can I recommend experimenting at a higher altitude?  Where hp is limited by mp.

Lop ops are about cruising efficiently.  3,000' is where Cessna training occurs more, not so much mooney cruising.

As you mention 7k and above. ..

Is your JPI set up for Lop?  Set lop using EGT.  This shouldn't be so hard as you seem to be describing that you know what you are doing....

 

CHTs are the final check to make sure you are not over heating things.

 

Use your JPI to lean lop, at altitude, using EGTs, check CHTs and oil temp as a result.

If this is not making sense, go to JPI website to learn how to set JPI to LOP mode.  You can then measure if you are 10 deg lop or 50 deg lop or anywhere in between....

 

The secret is learning the JPI magic buttons before committing to flight.

 

"big pulls" are for turbo guys that know where they want to be with minimal transition to get there.

You have 200 hrs left (before your oh decision), no need to throw them away

Best regards,

-a-

Did I push too hard?

[jetdriven]

We pull to 8 GPH (WOT, 2400 RPM, and 3-7K) and then richen to find peak, then lean back to 10-15 LOP.  Less time to set the final mixture.

[bd32322]

carusoam - i normally cruise at high altitudes when I am going somewhere. That 3000 feet experiment was a one off thing - i was limited by ceilings and cloud chasing around my airport

I dont have the JPI set for LOP though - I do know how to set it - but I find it very annoying to use the JPI to lean the mixture. It just seems to take forever - and altho i have my eyes out while turning the mixture knob during the leanFind process - I really doubt whether I am actually "seeing" anything. My attention seems to be elsewhere Plus the JPI manual lists many different reason you can find false peaks etc etc - so I am never quite sure if I have done the process right :|

Hence the big pull - it did give me a scare the first time I did it tho - did rather more than a big pull and was sure it was gonna quit Have learned better since then

 

jetdriven: your numbers sorta agree with me - I think i end up seeing numbers around 8.4-8.5 gph at WOT, 7.5k feet ...

[carusoam]

 

JetD,

You know this because you already did the experiments.

Finding peak going one way or the other...15 seconds or 30?  You still want to be looking out the window while you do it.

You still use egt, and then check cht and oil t.

Becca is the only mooney driver cruising at 3k or below, right?  And she is running ROP.....

 

Again, trying to help out bd...experiment at alt until it is second nature.

 

Then cruise at 3k lop, using big pull or whatever works for you...

Still not magic...just good cents whichever way you get there...

Or if you are daveydog pour it on, stay ROP,fly fast!

Best regards,

-a-

I agree JPI did not make it "Cirrus easy" to use. It is a good tool worth learning.  The hints it gives to engine health are even more difficult to ascertain then LOP mode, but worthwhile nonetheless.

nobody said it was going to be easy at first.  It will be rewarding......when you are good at... And you will be....

 

[jetdriven]

ROP is the only way possible to develop 95% HP without melting the engine down.  18 GPH for 45 minutes is tolerable once in a while.

[201er]

Could someone explain this "big pull" concept? I was just accustommed to pulling the mixture to where I'd guess 50ROP is and letting it stabilize. The slowly leaning with the vernier to peak and then either in or more out to get to where I want to be.