[Brantel]

I understand from reading all the papers from Lycoming that they recommend that you run 50? ROP with my setup....

My question is what do you consider peak? When the first cylinder peaks or the last one?

Also, which cylinder do you use for determining the 50?? The first to peak or the last?

On my engine, when the last one peaks, the first to peak is over on the LOP side. I assume this is because it is a Carb setup.

All I was ever taught was the old method of lean till rough and then richen it a turn to a turn and a half.....

My CHT's run within 20? of each other. My EGT's run close except #2 which is always 100-125? less than the other three. It tracks consistently there so I think it is a proble placement issue. Overall my EGT's run higher than what others say theirs do. I think I placed my probes higher than most apparently???? The engine runs great and makes great power so it must be placement.

 

[Radomir]

Answer to the question is first to peak...

But I'd look into alternatives before accepting those things blindly. I prefer LOP.... and had run it that way even when I was carbed..

What ignition do you have? If you don't have an EI.. go get one.. long term it'll be cheap.. a lot cheaper than a pair of mags..

 

[mahlon_r]

You lean and manage mixture to the leanest cylinder, which should be the first one to peak. That way any of the other cylinders are being operated richer or the same as the leanest one, which you are using as the cylinder you, are managing the engine off of.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

 

[n5lp]

I understand from reading all the papers from Lycoming that they recommend that you run 50° ROP with my setup....

This isn't my understanding. Here is a quote from the Lycoming "Key Reprints" web page.

For a given power setting, best economy mixture provides the most miles per gallon. Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting.


This is what I have been doing for over 40 years and still do. All the fancy instrumentation doesn't mean much when you have a carb. Just lean to rough then richen to smooth. Really really simple. I have all the fancy instrumentation so can see, if I choose to, that some cylinders are rich of peak, some are lean of peak and some are at peak. The solution to that is to not look at the fancy instrumentation.

Lycoming Web Page I reference

If you want to do something else, fine. I don't follow all off Lycoming's recommendations either, like what altitude to start leaning at.

 

[reak]

If you haven't already seen this Lycoming Flyer article, they address carborated engine leaning on page 37 paragraph 5.

http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key Operations.pdf

Basically Lycoming is saying EGT isn't very useful on a carb'ed engines, the best you can do is lean until rough then rich until smooth. I've following Lycoming's advice on my Superior O360.

regards,
Brad

 

[Brantel]

All good sources of info...

I used this doc as my reference:

http://www.lycoming.textron.com/support/troubleshooting/resources/SSP700A.pdf

Seems that even Lycoming has different opinions within their own organization and or over the years.....

During my testing of different methods, the lean till rough and richen till smooth method seems to fall right into the 100? to 50? ROP range so I guess in a round about way it is following their advice.

This isn't my understanding. Here is a quote from the Lycoming "Key Reprints" web page.

For a given power setting, best economy mixture provides the most miles per gallon. Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting.


This is what I have been doing for over 40 years and still do. All the fancy instrumentation doesn't mean much when you have a carb. Just lean to rough then richen to smooth. Really really simple. I have all the fancy instrumentation so can see, if I choose to, that some cylinders are rich of peak, some are lean of peak and some are at peak. The solution to that is to not look at the fancy instrumentation.

Lycoming Web Page I reference

If you want to do something else, fine. I don't follow all off Lycoming's recommendations either, like what altitude to start leaning at.

If you haven't already seen this Lycoming Flyer article, they address carborated engine leaning on page 37 paragraph 5.

http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key Operations.pdf

Basically Lycoming is saying EGT isn't very useful on a carb'ed engines, the best you can do is lean until rough then rich until smooth. I've following Lycoming's advice on my Superior O360.

regards,
Brad

 

[Brantel]

Maybe next year I will...I am thinking P/Emags at this point. Seems they have most of their growing pains behind them....

Answer to the question is first to peak...

But I'd look into alternatives before accepting those things blindly. I prefer LOP.... and had run it that way even when I was carbed..

What ignition do you have? If you don't have an EI.. go get one.. long term it'll be cheap.. a lot cheaper than a pair of mags..

 

[n5lp]

All good sources of info...

I used this doc as my reference:

http://www.lycoming.textron.com/support/troubleshooting/resources/SSP700A.pdf...

Brian, the document is a little vague but it seems to refer to injected engines and in particular the companies that promote balanced injectors.

There are many ?experts? today with new products and techniques to help customers in the operation of their engines. One that is receiving public attention by way of aggressive advertising is a company manufacturing fuel injection nozzles and espousing an operating technique that is ?better? than that recommended by the engine manufacturer.

I don't think it supersedes the recommendations for carbureted engines operated at 75% power or less.

 

[Brantel]

Yep, most likely. It is date 2000 as well...

Brian, the document is a little vague but it seems to refer to injected engines and in particular the companies that promote balanced injectors.

There are many ?experts? today with new products and techniques to help customers in the operation of their engines. One that is receiving public attention by way of aggressive advertising is a company manufacturing fuel injection nozzles and espousing an operating technique that is ?better? than that recommended by the engine manufacturer.

I don't think it supersedes the recommendations for carbureted engines operated at 75% power or less.

 

[Chino Tom]

Lean till rough then richen to smooth is what I do also. But having the info
on all 4 cylinders is heplful. When I was running two mags, leaning till rough
was only one cylinder going past peak EGT. Continueing to lean until the
2nd cylinder peaked, had the first on the lean side and the engine really running rough.
After installing one LSE Plasma II electronic Ignition, the engine would actually run with
all the cylinders having peaked. But there is no way my carbed O-360 could ever run
lean of peak. I usually cruise at 65% or less and always pretty high (8K+, mostly 9.5 - 10.5)
and leaning rough to smooth works out that the first cylinder to peak is #1 then going
to the lean side where its starting to run rough (sometimes #2 peaks but not always)
then richen to smooth brings #1 back to peak or slightly rich (<25 deg rich). The other
cylinders never peaked. This is still leaner than when I had two mags. My CHTs are
within 15 deg of each other (usually around 375) and although I tried my best to position
the EGT probes the same distance from the exhaust port, the right side runs as much
at 75 deg hotter than the left (specifically #1 where the exhuast pipe bend is closer to the head)
at about 1300-1375.

 

[L.Adamson]

As of now, I only have CHT & EGT on cylinder #3. I do use the lean to rough, & 1 1/2 - 3 turns in on the mixture method. EGT's on the #3, will usually range from 1300 - 1350 F. I don't try for those 1300 F settings as any exact set point, but they always let me know I'm in the ball park. When I first began running this engine, I had a few instances of fowled plugs on the mag runup due to operating at high altitudes and not agressively leaning enough. I'd see exhaust temps in the upper 1100 & 1200's. At least with EGT around 1325 & the engine running smooth, it all works well, and plugs never fowl. I have no exact idea of what the actual ROP is, as well as any LOP because of the one cylinder setup. A monitor for all four cylinders is next on the list.........someday. In the meantime, I tend to think about leaning a lot, and fiddle quite often. Most flights are in the 7500 - 10,500' msl bracket.

L.Adamson --- RV6A

 

[N941WR]

What I found to be odd is that if you lean until it is rough and then push the red knob in until it smoothes out you will run right where Lycoming doesn't recommend.

My problem with Lycoming's comments about running 50* ROP is that is where thousands of Cessna and Pipers run every day and still make it to TBO.

So why is this all of a sudden bad for your engine? Anyone?

 

[Toobuilder]

Also keep in mind that the "lean until rough" method can result in a wildly different EGT depending upon ignition type or condition. It's likely that the same engine will stumble with weak mags and old plugs long before it will with electronic and new plugs (EGT wise). Altitude also plays a major part. The -8 I fly can barely manage 35 LOP at 10.5k with mags... I expect to see a major improvement when it flies again with the two Pmags. I expect it will still be pulling strong even at 50 LOP (rather than "dead", as it would at 50 with the mags).

 

[erich weaver]

What I found to be odd is that if you lean until it is rough and then push the red knob in until it smoothes out you will run right where Lycoming doesn't recommend.

My problem with Lycoming's comments about running 50* ROP is that is where thousands of Cessna and Pipers run every day and still make it to TBO.

So why is this all of a sudden bad for your engine? Anyone?

It isnt NECESSARILY bad. Its just that 50* ROP (measured on EGT) happens to be about the the point where your CHTs and internal pressures will reach their maximums. These maximums can be completely acceptable if you are running at a moderate or low power setting. They can be UNACCEPTABLE if you are running at a high power setting. Your 4-cylinder engine monitor will tell the story. If you dont have one, you are only guessing at what is going on.

erich

 

[bryan12]

So what your saying,,

is that when I lean to roughness then richen to smooth that point is a really bad point to be at in high power settings. So where should I be when I am at altitude leaned out then want to climb and put in full power?

While we are on the subject, at what temp/ altitude do most of you lean on the ground? I fly from sea lever to 1300 ft max on the ground all summer.

 

[lostpilot28]

They can be UNACCEPTABLE if you are running at a high power setting. Your 4-cylinder engine monitor will tell the story. If you dont have one, you are only guessing at what is going on.

erich

Right, this is what I read in the aforementioned articles by Deakin. But, they don't explain how the internal pressures are bad. I'm just curious about this because I've always used the "lean 'til rough, then rich until smooth" rule. My engine is carbed, and I was hoping to keep things simple. It seems that this is an enormously complicated subject, however.

So, I have an MGL EFIS that monitors CHT/EGT for all cylinders...what exactly am I supposed to be looking at that tells me I'm running too rich or lean for high(er) power settings? The only thing I ever recall was that I can follow my simple rule as long as CHTs don't go above 400 F. I take it that's wrong?

 

[erich weaver]

The only thing I ever recall was that I can follow my simple rule as long as CHTs don't go above 400 F. I take it that's wrong?

Not at all - you may be over thinking this. We dont have gauges to measure the pressures inside our cylinders so forget about that and focus on temps as an indicator of engine stress. The rate at which aluminum starts losing its strength goes up dramatically somewhere around 500*F. 400* CHT is a good conservative place to start thinking about taking action, but certainly no need to panic yet.

Can you set your monitor to automatically identify when you go LOP on each cylinder? Very handy - other wise you will need to watch the EGTs closely until you gain experience with the fuel flow monitor. For my IO360, I find that I go LOP somewhere around 9.5 gph, and typically end up crusing at a little over 7 gph.

Anyway, if your temps are on the high side, you can (1) lower your nose and get more air cooling (2) richen the mixture to go more ROP (3) lean the mixture to go more LOP. For the latter two, you better know which side of peak you are currently on and by how much or you may make things worse rather than better.

If you are making a signficant climb at high power, the simplest thing is to use a very rich setting to keep things cool and then futz with mixture at cruise altitude to go LOP. If your temps start going up too high, lower the nose until it gets under control. If you are in a relatively high power cruise situation and your temps are too high, its likely a mixture issue - as in not lean enough if you are of the LOP persuasion, or too lean if you are ROP.

Our engines are actually pretty forgiving - you just dont hear about detonation problems often. The engine monitor and fuel injection just gives you the ability to explore mixture ranges that werent previously possible. Play with the mixture settings when you are in a nice comfortable cruise setting and watch the effects as you go from rich to leaner and leaner until it stumbles. Mentally tie that in with your fuel flows and you are on your way.

hope that helps?

erich

PS see now that you are carbed. LOP not as easy to achieve for carbs, but worth trying. You may be limited in your ability to go leaner - when it starts running rough, you are pretty much done with LOP. Suposedly, cocking the throttle a bit can help a little with this - you will have to experiment.

 

[49clipper]

49clipper

The different peaks of your egt is most likely not the placement of your probe, but the mixture distribution of you intake from the carb. Lycoming and TCM are notorious in having poor mixture distribution. It simply means that the air going thru the carb past the venturi is not mixed well enough and some cylinders get a slightly richer mixture and they peak later than the lean ones. I have done a lot of experimenting with this and found I could change the distribution by creating turbulence in fron t of the carb, therefore making the air and fuel mix more thoroughly before entering the intake tubes.
Jim

 

[nomocom]

"Experts"

the papers from Lycoming

Reading the Lycoming papers are great for context and discussion, but these days, the "experts" are not the manufacturers but the folks that are doing GAMI, Tornado Alley, and Advanced Pilot Seminars. I'd suggest spend some time with the Deakin articles, they've been mentioned many times in various threads.

Why go to someone other than the manufacturer for advice? When Cirrus wanted to run their turbo conti's at high power up into the 20's, the Tornado Alley/Gami folks were who they went to for the technology. LOP, cooler cht's, lower fuel flows, etc. http://cirrusaircraft.com/turbo/learn/turbotech.aspx

What does that mean for a carb'ed 4 cylinder lycoming? Here's a link, check out the course prep material http://www.advancedpilot.com/assist.html
Much of the discussion has to do with fuel flow balanced engines but your carb'ed cylinders don't "know" how the fuel get's added! If you can use tools like carb heat, throttle butterfly cocking, and other tricks to achieve balance, the same rules apply. Deakin has described how to improve cooling, economy, efficiency, and longevity many times. I'm not going to try and do the same. I'll just encourage you to read and decide for yourself.

 

[elippse]

mixture distribution

The different peaks of your egt is most likely not the placement of your probe, but the mixture distribution of you intake from the carb. Lycoming and TCM are notorious in having poor mixture distribution. It simply means that the air going thru the carb past the venturi is not mixed well enough and some cylinders get a slightly richer mixture and they peak later than the lean ones. I have done a lot of experimenting with this and found I could change the distribution by creating turbulence in fron t of the carb, therefore making the air and fuel mix more thoroughly before entering the intake tubes.
Jim

We found on my friend's O-320 that we got pretty-even EGTs at WOT, but the front cylinders would run richer and the rear cylinders leaner at part throttle. We assumed that was occuring because at part throttle the throttle plate slants up and forward which would cause the flow to favor the front two ports at the top of the riser above the carburetor, especially the wet, un-evaporated fuel droplets. He used a Vans-style filter and box on the bottom of the carb.

 

[Finley Atherton]

Tried some LOP settings yesterday in my 0-320 (carb) and got some unexpected results. I have not been able to run true LOP before and generally run around peak and use carb heat to even out the EGTs.

I leaned to roughness and then in to just smooth. As you can see from the graph I got good peaks on all cylinders with all cylinders eventually stabilizing between 50 and 56 degrees LOP. What was surprising is that this was achieved with no carb heat and relatively cool air:

8,500 ft density altitude
2,250 rpm (Hartzell C/S)
WOT
OAT, 38 degrees F
Carb air temp, 40 degrees F

I leaned slowly to allow the probes to accurately show the EGT. Fuel flow at peak EGT was about 6.8 gal which according to Lycomings, Part Throttle Fuel Consumption Curve for 2,250 rpm would be around 93 hp or 58% power for a standard Lycoming engine (mags, 8.5:1 CR). My engine is not standard with one LS Plasma III, 9:1 CR and Vettermans efficient, no muffler exhaust and is probably capable of around 170 hp. So using some maths and guess work I would suspect I am putting out more like 99 hp or about 62% for a standard engine. This is below 65% at peak EGT and should keep me out of the danger area.

Fuel Flow at 50 to 56 degrees LOP dropped to about 5.5 gal hr and CHTs stabilised at 290 to 312 degrees. I normally cruise around peak EGT and CHTs are usually between 350 to 370 degrees. I did a rough two way speed check and got about 146 kts TAS. I know my FF for 146 kts at peak EGT is also about 5.5 gal hr so there was no real fuel saving going LOP but CHTs were considerably lower. This is in line with Lycomings, Representative Effect of Leaning graph which shows the Specific Fuel Consumption pretty much bottoming out between peak and 70 degrees LOP.
So it seems my engine likes cold air into the carb.

Fin
9A