Search the Community

Hi! I hope this will help other Bravo owners who struggle to run the TIO-540-AF1B at Peak or LOP TIT. But first, in full disclosure I am not an A&P and this is not advice. I am simply illustrating my experience with this engine, and it or may not apply to you. Always follow the POH when you are not sure that your deviation from that document is in your best interest. I am a lean of peak fan, always have been. It comes back from my days of working on non-aircraft internal combustion engines and proving that an engine run LOP operates cooler, cleaner and lasts longer than a similar engine run ROP. I have taken the Advanced Pilots Seminar course on advanced engine management http://www.advancedpilot.com and had numerous discussions with Lycoming engineers, the folks at GAMI and engine builders, and I have used this knowledge to come to a few conclusions about this engine that I would like to share. I am not poking the sleeping “ROP vs LOP” dog. :-) and I realize that Lycoming - in some instances but not all - does not recommend operating LOP. I also believe that if they could, they would revise that language to say: If you have a good engine monitor, tuned injectors, and a knowledge of how your engine operates, you should run LOP whenever your heart desires - except on take off. My opinion is that Mooney, when they introduced the TLS, continued their fine mission to make the fastest commercial SE piston airplane. To do this, they needed a lot of power -and- in a weight package that would not cause the flight envelope of the long body to get too forward on the CG, the TIO-540 was the answer. Bravo owners know that the airplane is already pushed forward CG and many have Charlie weight for aft ballast installed (which lowers the already skinny useful load). The TIO-540 is a complex high performance engine and should not be grouped with most other ground boosted engines for performance discussions, The reasons for this, IMHO, are due in part to two things: 1) a complicated (but effective) turbocharging controller system, and 2) the requirement that the engine runs at very high percentage of power levels to make book speeds. I did a post a few weeks ago on the Bravo’s power percentage here. Because this engine is normally operated at greater than 80% power during cruise by most people, this engine is very working hard and making a lot of heat for a lot of the time. It is also doing so with rather loose factory tolerances on the precision of fuel flow to the cylinders which makes it extremely difficult to run this engine in an wide and efficient range of power settings. The POH states only two settings: 1) ROP TIT by at least 125dF for “best power"; and 2) Peak TIT as long it’s below 1750dF (1650dF at high altitudes) for “best economy" - the latter is sometimes impossible to achieve with this engine at higher power levels (30” MAP and above) because of poor fuel distribution which causes engine roughness. When near peak TIT (or EGT) the roughness is normally due to some cylinders running leaner than others. The leaner cylinders produce less power than do the richer cylinders which give you the impression that there is something wrong because you feel that power imbalance as roughness. (Note: that slight roughness is not a bad thing, your engine won’t fly apart, it really doesn’t care, only you do.) Spark plugs play a key role in this too - more on that in a bit. Here’s the rub... Because most of the TIO-540-AF1Bs have unequal cylinder fuel distribution, when Bravo owners try to run the engine per the Sun Visor chart at Best Economy (Peak TIT) they may find an disconserting “roughness” and feel a slight loss of power. That combo causes some consternation, and when that happens, some operators I’ve spoken with will simply dial the Bravo’s red knob in just a little richer and go slightly rich of peak TIT just enough to cure the roughness. Thinking that they are now 'just fine’ they fly the engine at that setting - when in fact they are not “just fine." They are now operating the engine “slightly ROP TIT” at a mixture setting that causes the most cylinder head heat, the highest internal combustion pressures and at a place where the engine can easily begin to exhibit detonation. (See graph below, which was taken from the Lycoming Flyer publication) The Mooney POH does not say it is OK to run the engine “slightly” ROP TIT because both the factory and Lycoming know that is a very bad mixture setting. All of the experts I’ve spoken to agree that no internal combustion engine should be operated “slightly” (10-60dF) rich of peak. If you can’t make Peak TIT for whatever reason, better to just go greater than 80-100dF and accept the extra fuel costs and keep things in the engine cooler and happier. I have not found anyone who disagrees that sustained high heat weakens, fatigues and shortens the life of the metals used in engines, and that’s why we see all kinds of advice about keeping cylinder head temps below 400dF. The Bravo’s POH advises that you use a combination of gauges when setting power - TIT and CHT as the most prominent. The POH also says that the CHT redline for this engine is 500dF - which everyone (experts or not) agrees is simply ridicules. If you have an older Bravo, and especially one where a field AF1A to AF1B conversation was done, you may want to check to see on which cylinder the panel’s CHT temp probe is located. The AF1A probe was located on cylinder #5, and Mooney Service Instruction M20-101C states that it should be on cylinder #3 for the AF1B. Check yours, especially if you rely on the single panel CHT gauge, I’ve spoken to three Bravo owners where the CHT probe was still on #5 (mine was too). There is a big difference in the cooling between #3 and #5 - #3 being as much as 50dF hotter. That all said, in summary the TIO-540-AF1B is a hot running, high power, high performance engine, different from many others. In the M20M it is asked to operate at the top of its performance range in order to make POH (book) performance numbers, and us Mooney drivers like to go fast! Adjusting the mixture on this engine can be tricky due to engine’s generally unequal cylinder fuel distribution and, in many cases, the wrong type of spark plug being used. I wanted my Bravo to act like most other well-tuned and instrumented airplanes I’ve flown. While always keeping the cylinder head temps below 400dF, I want to be able to safely set the engine for maximum power when I want to go fast, and I want the ability to safely save fuel when fast doesn’t matter as much. I don’t want complicated instructions to do this, and I want to feel as if the engine is happy and smooth no matter what. Before I started this trek, I could not run my Bravo at Peak TIT at MAP higher then 29” without noticeable roughness and/or what I felt was unacceptable power loss. And there was no way this engine would run LOP. I would flow about 22 GPH of fuel in cruise at 100dF ROP TIT (on hot days I needed to to be richer to keep the CHTs below 400dF). Here’s what I did. I first ensured that magneto timing was correct. This is very important with high performance engines; you can often get away with inexact timing on lower power engines, but never on engines like the TIO-540. Mine were pretty close, but not exact - they are now. I had new Champion massive plugs installed about a hundred hours earlier, on inspection they looked okay and they passed the tester test. We gapped them at .016. I installed a new set of GAMI TurboInjectors. When I spoke with the factory rep John-Paul he cautioned me that this engine was a hard tune and that I should expect to have to work at, and that there might not be the success that others have with GAMIs on other engines. I love honesty - these guys at GAMI are true pros. The first set of injectors made a marked and clear difference. I was able to run at Peak TIT smoothly for the first time, but I was unable to run LOP without roughness. I did a GAMI lean spread test and found that my spread was about 1.4GPH, while better, it was not ideal. I contacted the factory and John-Paul immediately sent out two replacement injectors for a better match. After that a test flight or two it showed that I actually picked up about two knots at peak TIT and fuel flow was down a little. I could now get a little bit LOP with a GAMI spread of .9GPH. Also noticed CHT were generally cooler by about 20dF. This was due to the fact that the better fuel distribution was allowing all cylinders to run more equally, so at Peak TIT all cylinders were closer to their peak EGT. Fuel was saved for the same reason - unnecessary rich cylinders were now leaner for any given mixture setting. Because this engine seems finicky at different MAP/RPM settings, I decide to tune to a specific sweet-spot for the GAMI spread - I picked 29”/2400 for this as it is, according to the Lycoming power graphs, about 75% power on a standard day, at mid altitudes. This might have been the most important step I took in achieving success with this tune, on this engine to allow for good LOP performance. I sent the new GAMI lean test to John-Paul - not satisfied he sent me a single replacement for the one cylinder that was off a bit. (no charge for all of this and no questions asked). We installed that one injector and then did a test flight. The biggest change was that I could get more LOP without roughness, at 2400/29” I could get to about 20dF LOP. I would lose about 9 knots, but I was able to save almost 6 GPH of fuel. While I still couldn't get much past Peak TIT at higher power setting I was happy with the trade off; now I could achieve both fast and efficient settings. My GAMI lean spread was now a very comfortable .3GPH as you can see from the graph below. I thought that was all I needed to do but it wasn’t ... I have a Savvy Aviator account, I upload my JPI engine analyses data there, and I happily buy their yearly analysis service. I uploaded a flight and was looking at the graph and saw something on one of my lean spread tests that I could not understand. During a lean test, you should see all EGTs rise as you get leaner and leaner, then they should all peak (at slightly different times, that’s the fuel flow “spread”) and then they should drop off. On my test, there was a second peak? I submitted the flight for review at Savvy and Paul Kortopates wrote back and explained it, and as soon as I read his explanation I understood: He said "That second "peak" is actually what happens when the mixture goes lean enough to fire only one plug. You are seeing the same rise we would see if you switched off one of the magneto's so that there was only one plug firing- which is what we're seeing here. On one plug alone, combustion is slowed and therefore when the exhaust valve opens we are seeing more of the combustion event and the associated higher EGT because of it” That’s when we discussed the last step I needed to take to get this whole project right - new plugs - but specifically fine wire plugs. It seems as if the fine wire plugs work better than the massives in two instances 1) older wet and oily engines (not the case here) and; 2) in lean mixtures. They’re expensive, about $80 a shot, but they also are suppose to last hundreds of hours longer. After researching both Champion and Tempest, I opted for the Tempest Fine Wires and installed 12 of them. Paul was right on! From the moment I turned the key I could tell that something was different. The engine started better and ran smoother on the ground and in the air, and I am now able to run LOP at 32” MAP and below if I chose. My CHTs are generally 30dF cooler than when I started this project, and I am saving fuel at every power setting. Where I use to run 22GPH at 2400/32 ROP, I now run 20GPH with the same airspeed, and if I want to throttle back to 2400/29, I loose about 10 knots and run about 15GPH at about 20dF LOP. In all, I have about $2500 invested here, but in fuel savings alone that will pay back in short order and then keep paying back. The big benefit is that I have more power options now with the aircraft and my engine will be much cleaner with less carbon deposits on the heads, the values, the plugs and the exhaust system. My flight profiles are not religious LOP, and yours don’t have to be either to get a benefit from the cleaning and cooling aspects of running your engine with a proper mixture, which, for me includes LOP at times. Typically I will run lower power and LOP in tail winds of any speed, because why not? If I loose 10 knots true in LOP but I make up some or all with a tail wind, I’m saving 5-6GPH of fuel AND cleaning the engine as I go. Thanks for reading! I attached some pics - happy to try to answer any questions. Dave

My CFII insists that I add fuel flow (move the Red knob in) as I reduce MP at level flight during the "Slow Down" phase to get slow enough to drop the gear on an approach. Level flight at 4000 MSL, (LOP at cruise but he says that doesn't matter). This doesn't seem correct. I am at the same density altitude, not starting down yet. Opinions please, and references to actual data or expert's articles such as Mike at Savvy articles would be really appreciated. Thanks, -mark

There has been a lot of discussion lately on turbos, power settings, etc. I'm no expert on this subject and am still learning all I can. I fully intend to someday have @kortopates, or @donkaye, or Brian Lloyd, in other words, a true expert, ride with me in my 252 and teach me how to fly it properly. But in the mean time I document my flights and try to learn from experience. One of the ways I document my flights are to take pictures of the panel. My new panel layout lends its self well to this method. You can see in each picture the Aspen with all the air data and the JPI with all the engine parameters. The pictures are named based on ROP/LOP and the percentage of power at the time. The pics are here if anyone cares to take a look. https://drive.google.com/drive/folders/1BmxtvTtWAWXTqEkQ6lsq0t94zcQl0km7?usp=sharing I also upload all my flights to SavvyAnalysis. If I ever decided to sell this bird, a prospective buyer will be able to see every single flight I've made and what the engine parameters were for each. And if you see something you don't like here... by all means, let me know.

I've attached a picture of my panel so you can see what gauges I have and don't have. In short, I have an EDM 700, a digital tach, a JPI 450 for digital fuel flow and a manual MP gauge. I do not have GAMI's. This is in an 84 J model. Can I expect to fly LOP accurately and consistently with this setup but without GAMI's? If so, what would be the procedure to do so? How much does it cost to buy and have GAMI's installed? Thanks. Glen PS: I pick up my new-to-me J on Thursday!!

Great new youtube video on how to manage mixture and fly LOP and ROP: The most information dense filled video on the topic I can remember seeing in some time. The only real thing I would offer to add is Gami's recommend tablel on both how far to be LOP and ROP for any percent power; available here: afms gami injectors rev ir.pdf Incidentally the GAMI FAA approved mixture management is excellent guidance regardless of whether or not use Gami injectors or even if your not fuel injected. Its just that without good mixture distribution (<=0.5 GPH gami spread) an engine won't be able to fly very far LOP, if at all LOP (i.e. where all cylinders are LOP). But virtually any IO-360 can and most of the higher performance Continentals can but may require a little help. But otherwise Martin does a great job of both communicating and illustrating a wealth of information on the subject matter.

Hello all. Over the last 4 or 5 months, I have noticed my CHT's have been steadily rising and the spread from the hottest to the coolest is increasing as well. (Used to be 30 degrees, now it varies between 35 & 40) It is to the point where I can't fully close the cowl flaps. This hasn't been an issue for the last 250+ hours on the plane over the past year and a half. This is when I started running LOP. I have an M20K/231. Inner-cooler and 'automatic' wastegate & GAMI injectors. I took the first picture this morning while flying from Phoenix to San Diego. LOP, 12k, Cowl flaps in tow (Fully closed and CHT's go over 400) The second pic is almost a year ago to date. LOP, Cowl flaps closed, not sure altitude but probably pretty close to 12k. I know It was running about 45 degrees more LOP a year ago, but the CHT's are much cooler with the cowl flaps closed than they are now. What could/would have changed over the last year? (Compression check 2 weeks ago showed about same as annual in Nov. Any help would be appreciated!

For all you ROP v. LOPers out there, https://www.advancedpilot.com/livesignup.html. Coming up mid-March. Go. See an actual engine running on an actual test stand and then make up your mind. The food and company are pretty good too. And you thought I was going to start an argument, er, debate, er, discussion. You know what I mean.

I have a small number of Auto-Lean kits available at a discount. The kits list for $899.00 and I have offered them at discounted prices to MooneySpace members in the past. The price for the remaining kits, to MooneySpace members, is $650.00. I am selling at a discount to make room for our soon to be approved AML-STC kit. You can get more info at http://Www.flightenhancements.com or contact me. These are STC-PMA approved kits for Mooney M20 A-J with in line mixture controls. Quadrant equipped and turbocharged aircraft will be approved as a part of the AML-STC.

Wondering what suggestions I can get on this. A little back ground first. '78 M20J 201 IO-360 ~1500 hours SMHO fly ROP per POH cylinder #3 plug fowled out a week ago (see picture) all new plugs and now I am seeing Cylinder 3 EGT highest and CHT lowest (see pictures) in all phases of flight. Oil consumption, maybe a quart every 6-8 hours and all oil analysis come back with excellent results. I am thinking bad injector and going to Gami. Thoughts and comments much appreciated.

Here's a new one for the LOP/ROP argument. I flew up to International Falls last night for dinner from Minneapolis (KFCM->KINL). I have been flying my aircraft LOP quite a bit for the last year, but I could not do it last night. The cylinders just ran too cold for my comfort. #6 is the coldest cylinder in my aircraft because it is at the front and has an unobstructed airflow from the cowl opening. The conditions were otherwise perfect for LOP, I was at 5,000, so not too high. The problem was that #6 ran so cold I had to make a change. The graph line on my JPI 930 for CHT starts at 224. When the CHT on #6 stopped graphing I got a little worried, and when it slowly drifted down to 219 (I get a number displayed even if there is no graph line) I figured I needed to do something, so I ran ROP and with some extra power and everything was fine. Part of the problem was that the cowl flaps were stuck in the half open position, and I could not fully close them. But the bigger problem was that it was -22C at low altitude where the air is dense, and the cooling combined with LOP ops was just too good. I don't know, probably that was just fine, I don't think there is a minimum CHT in my manual. But I was not going to tempt fate. Besides, it was getting really cold in the cabin with all the cylinders in the 200-somethings. That is at 75% power (11.5 GPH and about 33 MAP @ 2450). LOP ain't perfect in my aircraft. I can't usually fly LOP above 12,000 in the summer, the temps are just too hot. It sure works well most of the time, below 12. Just was too cold this time, which is a new one on me.

I am looking for response from anyone flying a turbo or turbo-normalized aircraft. Most of the engines have a max manifold pressure based on continuous ROP max power settings. Have any of you experimented with trying to attain high horsepower numbers on the lean side of peak? I am assuming that running 80-90% HP while LOP may in some cases require MP in excess if not over redline. I know of more than a few TAT modded Bonanzas that are regularly operated at 85-90% power with excellent CHT numbers, however it does require enough MP to get to 70 to 100LOP. I would ask that those of you that use the POH recipe please refrain judging those who operate outside those parameters. I'd like to focus on engine ops and theory, so please keep the "you'll shoot your eye out" comments to a minimum unless they're accompanied by data or experience.

I just read this this morning. It's a light read with just enough technical information to make it interesting. The engineer's name was Frank Walker and he helped to pioneer water injection. From what I gleaned from the profile, he was also instrumental in discovering how to use super lean efficiency ratios (LOP). Sorry for the crude link; I can't embed links with an iPad. http://www.enginehistory.org/Frank%20WalkerWeb1.pdf

Well, I tested out my bladder this weekend flying from Las Vegas (KVGT) to San Antonio (KCVB) in my '84 M20J (N5759B). My overall route was 945 NM and we made the trip nonstop. One would think that I must have had a great tailwind. However, this never seems to be the case for me. I can fly a 360 degree circle and find a headwind the whole time. So, my secret to success was 11,000 MSL, ~151 KTAS, and 8.6 gph. It was pretty cool to be able to fly the entire trip without a fuel stop. My total flight time 6:14:13. Yep, that is the longest nonstop flight I've ever made in the Mooney. Hope y'all enjoy the few pics. -Dan

I'm making up my own checklists for my 1962 M20C, and as I'm writing them up, I'm cross referencing them with the POH. As I read through the manuals they specify running the Carbureted O-360 engine Lean of Peak, as far as I can tell! I have always understood that this was a VERY questionable idea, pretty much asking for trouble. I cross referenced this with the manual for a 1967 M20C, and the advice was the same. Does anyone run 25 Deg LOP as the manual describes? Here is the paragraph in question: Lean the mixture for smooth operation (reference Lycoming's Operators Manual.) The Exhaust Gas Temperature Indicator is to be used only as an aid in setting the mixture during cruse at powers up to 75% power, but not take-off, climb, or descent. For lean-out procedures at 75% power or lower, lean to peak temperature, then lean until temperature drops 25 Deg F. minimum. In the '67 manual, it continues talking about Best Power Setting: To obtain a best power (maximum airspeed) setting, lean to peak temperature and then enrich mixture (push control forward) until the indicator shows a 100 Deg F. drop (four marks on the gauge) from the peak temperature. This has probably been discussed before, but I couldn't find it in a search. Thanks, James

One of the things that Busch and Deakins reccomend that I haven't seen discussed here is setting the mixture for maximum power during the low-power, landing phase of flight. After some agonizing I've incorporated that advice, along with some practice at altitude for advancing mixture first, then power for go-around; it didn't seem too complicated. Basicly as I approach entry into downwind I drop the power until the prop comes out of governance with the prop full forward and then set it to 2500 RPM. Then mixture comes back until slight decrease of RPM and move back ahead until it maximizes. Then I leave it (the mixture) alone for the rest of the landing, treating it like a fixed-pitch prop and controlling everything with just the throttle. I practiced once at altitude giving it full throttle with the mixture set like this to be sure the engine wouldn't quit like it does when aggresively leaned for idle; that wouldn't do if I reverted to just going for the throttle in a go-around situation 10 feet off the runway. It gave power fine; I didn't leave it like that but gave full mixture after a couple seconds of course. The point is to help keep the temperatures up and minimize lead and carbon deposits. It is obviously in the low-power regime where detonation isn't an issue. The only criticism for it I can think of is what might happen in a go-around if I forget to go full rich. While I was trained 40 years ago to basicly ignore the mixture control, I've been implementing newer leaning procedures cautiously since I purchased my M20E two years ago. As a chemist Busch and Deakins made sense to me and they were quoting a lot of good data. It also made sense things were done the way they were "back in the day" when we didn't have such good engine monitors so I can see where two separate "churchs" have evolved around leaning. For me a big question mark was "What about my habits and training". Its one thing to understand something and another to implement it. I've slowly convinced myself to trust myself and these day use of the mixture is part of my SOP in all phases of flight (full rich for take-off at sea level where I live). Dave

Two questions/ comments here... With the frigid winter temps here in the midwest my coolest CHT gets down to 290-300 while running LOP. The other 3 are in the 330 range. Other than running ROP I really don't see how this can be changed. Secondly my oil temp doesn't get over the magic 180 degree mark in cruise to burn off the moisture the Lycomings hate so much. It does get over the 180 mark in climb but cools down to 176-178 or so once cruise configuration is reached. Does this make my 3 hour cross country flights as useless for engine longevity as a ground run?

I see a lot of LOP believers here in Mooneyspace and count myself in as kind of a poor cousin (GAMI spread 0.8 GPH and still haven't bought GAMI's yet; tight budget). One thing I've heard is the the typical examiner in a check ride is likely to grief (or even fail you) you if he sees you using LOP techniques to manage your plane. I'll be taking my IFR check ride in the next year with any luck and I wonder if any of you have run into this. Dave

I'm an avowed LOP flyer, enjoying the fuel economy and lower CHTs that result. But there's no doubt that EGTs are higher, which leads to my current situation. Plane is in for annual, and we knew the muffler baffles were showing signs of stress and probably needing work, plus ever since I bought the plane the muffler shroud had a little gap on one end. We decided to send the whole exhaust stack off for inspection, and the word is it essentially needs a full overhaul, with pitting and metal loss in many of the pipes. I'll have to look at the logs to see when the last maintenance was done, but I suspect it might date to the last engine overhaul which was 13 years/1200 hours ago. So my question is twofold. For those who've had their planes long enough, what is the expected life of an exhaust sytem? And secondarily, is there any evidence that the higher temps of LOP operations can shorten this life, or are the systems designed to handle these temps?

I've been messing around with running LOP and like the results as far as GPH (8.5 at 7-8k) and CHT temps ( -30 degrees) go. My question is regarding my EGT's. While running 100 degrees ROP the highest and lowest are on average only 10 degrees apart. LOP they are 80-90 degrees apart and overall about 75-100 degrees hotter with the hottest being in the mid to high 1400's. Is this consistent with running LOP vs ROP? Engine runs smooth, although it did feel a little weird pull back so much the first few times.