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At that density altitude, full rich is too rich. The overly rich mixture burns slower than a best power mixture which is why the CHTs are lower and the power is lower. When you go to one mag, the mixture burns even slower because there is only one point of ignition. That causes a larger than normal power drop which shows up as lower rpm. It's a good practice to lean to max rpm for the mag check regardless of altitude in a NA engine because then you are always testing under the same conditions. At density altitudes above 5000 feet, I always do a full power run up and lean to max power for best takeoff and climb performance.

Thank you guys for the good info and thoughts. I did speak to Brian Kendrick... On the original issue: he thought the mixture was likely too lean based on the story (assessment of the local guy) where we had all thought maybe too rich previously. Might also explain some marginally-higher TIT's on takeoff. The local guy just did a fuel check on my request, said all he had to adjust was mixture to get rid of stumbling. Flight testing pending. As for the cylinders, he thought lap #3 (hot spot, low compressions recently and intermittently in past) and flush #4 (lowish recent compressions). Anyhow, I did find a shop less than 2 hrs away recommended by a DPE. The guy I talked too was very open to valve lapping, suggested it de novo in fact. Oddly the place I'm looking to commute to soon. So hoping to get them to try that on the 2 low/lowish cylinders. Went to the shop yesterday evening. I can see and hear the compression findings. The cracks in the three cylinders (2,4,5) are not macroscopically visible but show on eddy current. Some say this is too sensitive (the local A&P works on a range of aircraft including turbines and has a lot of gear). He seems totally sincere that he thinks this is a real relevant crack but also says he replaces them right away and has never seen a failure and can't give me any predictive #s on failure rate. So... maybe ECI is too sensitive a test (several say yes), or my CB glasses? He's offered to advance the work, let me pay later, etc, so I think this is just his philosophy (shop is busy so I'm sure I'm not a cash cow, probably more of a sad idealistic foundling with a nice plane). I'm currently planning to fly the plane to the other site and have the less invasive things done first. At least a few knowledgebale, though remote, folks, encourage this and say the AC is flyable. Part of me thinks, hey 1450 hrs SNEW, the two problem cylinders still original... maybe order a few spares? Maybe talk myself into more? Still not yet had an oil analysis or scoping into the camshafts etc so I don't know how long replacing a bunch of cylinders (1-6) would extend things vs a full overhaul, vs going on-condition. If the bottom end is solid, I might be inclined to throw newer jugs on and let it ride (Mike Busch is having indigestion as I think this right now about the first part, probably approves of the second). Any thoughts appreciated, D

Hey all, tl;dr - New engine is running richer than the old one and I believe it is causing the mag checks to be rough I just had my IO-360-A3B6 major overhauled by an engine shop down in South Florida. They ran it 3 hours in the test cell and it's back on the airplane now and I've done a couple break-in flights, and fortunately things are mostly looking good so far, and my install shop has helped me fix a few gremlins w/ the (also freshly overhauled) governor, etc. However, one remaining issue is that my mag checks are considerably rougher than I would expect, dropping in some cases almost 200rpm. The mags seem timed close to each other, the split isn't much. Yesterday I decided to debug this issue a bit, and I noted that there is the proper rise of EGT on all 4 cylinders on both mags, so I don't think there is any issue with bad plugs. I had noticed that on my first takeoff (when I was watching all the indications quite closely) that my takeoff fuel flow was higher than normal, hitting around 20.5 gal/hr. My old engine hit around 18.5 gal/hr on takeoff. (From my research on the forum here, that seems to be the correct value, approximately) Takeoff power felt normal, and probably a bit stronger than the old engine, and I suspect my old engine was down a bit on performance, so a bit higher fuel flow isn't terribly surprising, but I didn't expect that much more flow. Anyway, based on this, I suspected that my full-rich mixture setting is a too rich. So I repeated the mag check with the mixture slightly pulled back, and the mag checks were totally normal. I also noted the full-rich runup RPM (2000) fuel flows were also higher than the old engine. I suspect the fuel flows are higher across the board. Based on my reading, this is basically not adjustable... so I think it's potentially an issue with the fuel servo and I guess I need to contact the engine shop for their opinion?

20 gph sounds a bit high, but if it is running well and climbing well I'm a bit puzzled. Does it make static rpm on the ground at full rich? If it is too rich it could be either the servo was not properly overhauled, or the injector nozzles are not the correct size. There aren't any field adjustments to correct either.

Not necessarily. The point I was making with this post (which is from AvWeb) is that if the turbo wasn't making pressure, it would automatically reduce the fuel flow. So the contention that if you had to restart your turbo engine at high altitude, it would be too rich, isn't true. With my turbo system, If I set cruise mixture, I can descend from the flight levels to the airport without adjusting the mixture and the FF and TIT will stay the same all the way down. Well actually, the TIT will drop a little. But My turbo system is a bit of a unicorn. there were only 35 of them made and I think some have been taken out of service.

Well what makes it more complicated for turbos is that mixture knob is set for turbo boosted air. You loose the plant and the turbo spools down so you also lost the air. Now that mixture you have set is way too rich. How lean do you need to go? Much easier to just cutoff the fuel and give as much air as you can with full throttle. As you slowly introduce fuel the mixture will get to a combustible mixture and start running the engine but real quickly that turbo is going to spoolup and give so much air it will lean out too much. Hince why reducing throttle immediately after engine starts running.

Next time you shut down, set it at idle (should be ~650rpm) and slowly pull mixture to ICO. Should see an rpm increase of 25-50 before it quits. If the increase is more than 50 rpm, the idle mixture is too rich.

@A64Pilot Let's say these are steady state temperatures and I achieve these temperatures by slowly approaching them from the 'cold' side of the curve, regardless of which side I'm on. (if I'm LOP, I approach it slowly from being too lean, and if I'm ROP I approach it slowly from being too rich) So there is no risk of anything from the lag between the actual in-cylinder or in-exhaust temperature and the measured temperature from the probe. If I do this, am I potentially damaging my engine despite the RPM& MP combo being an approved one and the CHTs and TIT are 'OK'?

The A/P who put it all back together is sticking to his guns and saying we need to adjust the carb saying it is too rich. Carb is new, less than 50hrs on it, FYI. My brain says if it is too rich, then it would make the popping regardless of the position of the mag check.

I decided to postpone the trip for several reasons, most notably that we got weathered out of my intended insurance checkout flights. I'm going to wait for my home airport's shop to get their equipment back from calibration. For what it's worth, during my search I located a company called Aircraft Structural Inspections out of Arkansas. They quoted me $375 plus 65 cents per mile for travel expenses. That would have added up to around $1100-ish. Way too rich for my blood, but it might be a good option if someone near Arkansas ends up in a jam with their pitot/static/transponder inspection.

I read that this technique was used with success by WWII fighter pilots to extend range without engine monitors. Introduced by a bold pilot (don't remember the name) who bucked the prevailing "LOP is BAD" thinking. I've played with this technique recently. Compared to the lean-find function on my engine monitor, it works out to run my IO-360 about 60-70F LOP in the leanest cyl., with the richest being about 30-40F LOP. So, I can run LOP pretty well by leaning to roughness, richening to smooth it out, then richen a tad more. The GAMI spread on my engine is 0.2 gph, which means the fuel injectors are well matched. @Flying Dutch an engine monitor is a great first upgrade for a "new to you" Mooney to help you manage your engine better. If you get a certified primary engine monitor, it can replace your Manifold Pressure and Tach gauges, plus your instrument cluster. This puts all engine info on one screen. Gives you much greater situational awareness in the case of a rough running engine at runup during the mag checks or in flight. I've dealt with both. I can run my IO-360 above 10kft on about 7.5 gph LOP and get 145 TAS. That's efficiency. Below 65% power, mixture setting cannot harm the engine. Too rich and you'll foul plugs. Too lean and it just stops making power.

Great conversation! NA or TN’d there are some differences… and many similarities… in my O1…. 1) I prefer to fly LOP. 2) Long body speeds as they are… I start slowing down a couple miles from the traffic pattern… 3) This gives the opportunity to have gear down, and T/O flaps deployed once in the white arc… 4) This is also the time I go into ROP mode… not full rich. 5) the LBs got a blue arc on the EGT gauge for climb power… a 100°F range… starting about 200°F ROP 6) the Acclaims have the G1000 with the white box instead… same range, same engine safety, same operability for the go-around… 7) Essentially my first Gumps occurs a bit earlier than the rest of the world… 8) And the mixture is now steady in the blue box… 9) In the traffic pattern the usual flaps and gumps checks… and full rich at my near SL airport…. Note: leaving the engine leaned from altitude… won’t be noticed until the plane is on the ground… it will stumble and die on roll out. if you are fast on the mixture control it runs easily… if the prop stops turning… you start to wonder if the next start will be a hot, cold, or warm start… wondering if the plane’s momentum will carry you to the next turn off… Note for Dan… this is my NA IO550 experience for my O3 powered O1. Consider using the white box on your G1000’s EGT/TIT sensor..(?) going full rich at sea level the EGT will be lower than the white box… in a slight too rich zone…. But, realistically when we are turning 2700 rpm full rich is considered 30gph… (310 hp discussion) it’s hard to get there even at full rich… The big difference from standard Mooneys… the EGT gauge is calibrated with real temperature readings, and an arc is ‘printed’ on the face of the instrument… that makes it really easy to put the engine in a safe ROP zone… not too rich, not too lean, no matter what altitude we are landing at… the IO550s got a standard EGT sensor location for this important ship’s gauge. A location machined in the exhaust’s 3 into 1 collector allowing for the calibration between sensor location and the instrument readings… where an 1/8” really changes the temp being displayed… Oddly, for years… the G1000’s EGT display in the Ovations was marked TIT… it took a while before the software ever got updated… PP thoughts only, not a mechanic… or CFI. Best regards, -a- Soooo many Mooneys currently have nice engine instruments, and their sensors installed in standard locations… it wouldn’t take much to have the blue box actually indicated on a JPI or EI device… making absolute EGT readings totally useable…

Well, the OP flies a turbocharged aircraft, not an NA. Reading through the answers, quite a few apply to NAs. For example, in an NA it would indeed be a problem at a high DA airport to go too rich. That is not relevant to turbo ops. The turbo needs all the fuel it can get at full power to keep the engine cool. Lots of answers from F and J folks. I don’t fly an Acclaim, I fly a 231, so it may be that the fuel setting issues are a little different between the two. But I am going to relate what I do in my 231 to the extent it is applicable to the Acclaim. Turbocharged engines are generally set to provide a very rich fuel flow at full power in order to keep the engine cool on takeoff and during a long climb to altitude. Mine is that way when set up properly. During landing the engine will burble if I make the fuel flow full rich. The burble is because the engine is drowning in fuel and not igniting consistently. The way to handle it is to keep the mixture lean during the landing phase. For that reason, I don’t make the mixture full rich unless I actually need to go around. Typically it is necessary to make the mixture a little richer after touch down. Once the aircraft’s descent is no longer helping the prop, the engine can die during rollout if it is very lean, so a little more fuel may be needed. The 231s induction system is not as sophisticated as the Acclaim, so it may be that the mixture issues are less pronounced, but advice applicable to leaning an NA engine is generally not applicable to a turbo and in fact can damage the turbo.

If you fly in high DA a lot there are times when it is a Bad Idea to go full rich. There've been accidents around here where an aircraft failed to climb out after takeoff or on a go-around that are thought to have been due to insufficient leaning (or full rich) settings. For me that just means special attention is always required to the mixture on approach and go around. It is often not "full rich" on go-around, but some estimate of about where it should be to not cause a significant decrease in power. It's a pretty wide window between "too rich" and "too lean", so a reasonable guess followed up by attention to EGTs is usually sufficient. It is more work, but can make a difference when needed. Otherwise I'm in the camp of leaving it alone until needed, which means pushing the mixture forward with the throttle in the event of a go-around. In any case, keeping an eye on EGTs is always a good idea.

It could also mean the mixture is it way too rich

Is it your contention that a naturally aspirated P&W 1340 with a compression ratio of 6.1 to 1 has the same FF/HP ratio requirements of a naturally aspirated O360 with a compression ratio of 8.5 to 1? I agree with everything you've said conceptually. However, at a more granular level, the general numbers you've given are just that, general. They must be fine tuned by application as the range of configurations of both NA and Turbo Charged engines vary significantly. Look at Mooney's apples to apples HP/FF ratio specifications in 1966 and 1968 for the same engine... 1966 M20C POH - 2600, 26inHg 90% (162HP) 13.4GPH= HP/FF ratio of .0827 1968 M20C POF =2600, 26inHg 91.2% (164.1hp) 16.5GPH = HP/FF ratio of .1005 Lets look at the specifications for F model IO360 with near perfect F/A distribution. 1968 M20F POH 2700, 28.4inHg 99.9% (198.8hp) 18.6GPH - HP/FF ratio of .09309 You cannot possibly believe that there are no other factors besides Turbo Supercharging and normally aspirated associated with FF, CHT and detonation margins? Do you think we can just throw thermal efficiency (HP/per unit of fuel) and the associated increases in ICP and reduced detonation margins out the window for a 1 size fits all for NA engines and a one size fits all for TSO/IO engines with a range of C/Rs, Piston speeds and boost levels? All of those variables affect CHTs and detonation margins. Fractional differences in HP/FF ratio have a profound effect on power, CHT and detonation margin but more so at the extreme lean and rich edges of ignitable mixtures. According to a widely published graph by P&W, best power mixture (highest ICP) is at .08. and too rich to ignite is at .125. According to P&Ws own graph the engine (assuming NA) will make full HP from ~.08 to ~.094. Help me understand how raising the FF of a 1964 O360 M20C from the HP/FF ratio of .0827 shown in it's POH to the FF/HP ratio of .105 shown in the 1968 POH for the same O360 M20C will cause cylinder scuffing? Lycoming and Continental have their own graphs mixture graphs and while they are conceptually identical to the P&W graph, the numbers are not.

It only takes one long or too rich idle to foul the bottom plugs.

The after firing, burbling in the muffler is from mix being too rich. If you lean lean aggressively, so much that you can’t attempt a takeoff, or I promise you one day you eventually will takeoff leaned out and that’s killed people in the past. You can’t hurt an engine at all at taxi power with mixture, many even promote it to keep plugs clean. The roughness after starting is most likely vapor lock, it’s hot now so of course it’s worse, depending on where the vapor lock is occurring boost may help, pressure raises the boiled point of a liquid and vapor lock is of course the liquid fuel boiling.

I need to go either way too rich or very lean to keep temps < 400F in cruise with cowl flaps trailing. Anyway, the baffling was not in the best condition, so my idea is to get that in the best shape possible, so if temps are still high I will look somewhere else.

So here’s the situation. I am at 8000 feet today at 75% power in my M20J. I have a 30 knot headwind so I’m running it hard for best speed. I’m at 2600 rpm and 24 inches. My cylinder head temperatures started creeping up close to the 400 mark. I tried running lean of peak, 8.7 GPH and the CHT’s stayed high. I tried running rich of peak at 13.5 GPH and my CHT’s still stayed high. The only way I could bring my cylinder head temperatures down would be to open the cowl flaps to their first notch. That brought the CHT’s down to 350, But I also lost about five or six knots. The outside temperature today was hot. On the ground it was 90+. Do others have this problem? My baffling looks good to me but I am not a mechanic. Any thoughts?

At the Cessna factory they taught us to lean on landing because of this. Even though the poh says full rich it’s far too rich in the turbo engines. They said the turbos are set up to be extra rich partly to allow for go around a without the engine stumbling as the turbo spins up. Go around is 50% throttle then rich then full throttle

Many things we are taught during PPL about operating an engine apply to NA engines only, which is what the great majority of school planes have. For example, we may have been taught to lean in the climb, which works in an NA to keep the mixture from going overly rich because the ambient pressure is decreasing. The turbo wants to be full rich when at full power in a climb to keep the engine cool and the input pressure can be held to a full power pressure like 36-38” all the way to critical altitude; no reason at all to lean in a climb. The “full rich for landing” is another. During the descent on final the engine will not quit when too rich or too lean because the movement of the aircraft is helping the prop. But during the rollout when the help stops and the engine is on its own, either too rich or too lean will cause the engine to stop. The “make the engine full rich for landing” lesson we are taught is another OWT better left to school plane operation. There is no great trick to pushing two knobs in for a go around instead of just one. Haven’t heard of a pilot crashing because he/she had to push in two knobs. The turbo engines need to be set rich to keep the engine cool. It does seem to be tricky to perfectly balance the idle setting and the full power setting. Paul K. can explain it better than me. But the pilot has full control over this problem. I operate LOP quite a bit. But whether I was cruising at LOP or ROP I make my final approach at a lean setting. There is a “perfect” point for this, which is idle rise. On the ground, with the engine at idle, if you pull the mixture slowly out, the RPMs will rise about 75 until they start to fall again. Remember approximately how far out the stick was and use that for your landing setting. I personally go even further, I will make my final approach at a much leaner setting and just put in some mixture immediately before or after touchdown. It is not hard to do. Changing plugs will help whether you are making your approach lean or rich, if the new plugs are generating a stronger spark. The whole point of a LOP or a ROP setting is that the mixture is harder to ignite, resulting in a slower flame front during the combustion cycle. Make the spark better and the mixture will ignite more readily. That said, if you are burbling during landing or rollout you are operating the engine too rich, which eventually is going to gunk up the plugs. Just find a better setting, which is one that is leaned out somewhat. Not to say there are not some more exotic engine issues that could cause a stoppage on rollout. But the most common one is just that the pilot was taught to operate a school plane in a particular way, and now is driving a different engine entirely. I wish when I first started flying my Mooney that there had been someone around to tell me these things. One dark night some 13 years ago I was flying pattern practice. This was when the landing lights were still incandescent and drew a ton of current, more than the 231 alternator makes at idle, and before I had a good engine monitor that would tell me how bad the electrical situation was. I came in for a landing, taxied toward the little operations building my FBO had back then, and the engine stopped dead right in front of it. No battery left to restart. All the instructors came out and helped me push my “new” plane in. They had a lot of fun with that! Now we have Mooneyspace.

There is something missed on this thread so far regarding diagnosing a turbo charger failure in flight. I learned this the scary way - I had a turbo charger failure in flight! If you are at altitude where the turbo charger is making pressure well above ambient pressure - which is usually - then your engine will likely be too rich if the charger fails and this will cause the engine to turn off. I.e., I was in cruise at 16.5k running 30'' 2200 which is 18gph. Without the turbo - the pressure is so low inside the cylinders that 18gph is waaaaay too rich and it causes the engine to flood and shut off. So then it was very obvious something was wrong. I didn't figure out what until I had landed. There was also smoke because the turbo had started burning oil in the last minutes. So I assumed I had a fire and didn't correctly diagnose a turbo failure - a restart would have required a much leaner mixture to match the percent power of running without turbo MP at 16.5k. I think there is also a danger of a fuel fire with that much fuel pumping into a dead but hot engine? In any case, in my case I made a successful on airport landing, dead stick as there is plenty of glide range at that altitude. So I learned a lot that day....

Actually due to the overhead of the turbo, the loss of MAP is going to even bigger than @rbp example above by an 1-2". But your FF & pressure will be fine showing its not a fuel pump issue. But what's even more important to recognize is that with the loss of MAP the mixture is going to be way too rich and you'll have to lean the mixture to get power back and in the process see the EGTs come back up - leaning by EGT. Although its possible to figure things out without it, a good engine monitor is really helpful in recognizing what's going on quickly so you can restore power to some degree. The other main turbo power losses are due to fuel where the monitor comes in again to tell you what to do. Many of the turbo failures I see, and I see quite a few, were actually preventable if the pilot noticed his declining oil pressure before the turbo seized. One nice if you will with a turbo is its actually the sacrificial part that fails first due to declining oil pressure saving the rest of the engine - if the pilot pulls back power at that point and glides it in to an airport assuming you have the altitude.

Edit: 1998 M20J I recently completed a "Top" overhaul. During the break-in, it became apparent that my injector setup was no longer valid. We swapped out an injector on the #4 cylinder that solved the biggest problem we were seeing with the #4 cylinder which was it was running too rich. Now with this swapped out injector, it is still running too rich but not quite as bad. It's still hard to manage though because if I try to run LOP, by the time #4 gets to 10 degree LOP, the other three cylinders have started flaming out. I did a GAMI lean test and sent the data to GAMI. It turns out they want to change out three of the injectors so they sent me three new ones. Before we install them, I wanted to ask a question here about CHT. The #4 CHT is hard to manage. (never was before) I normally target a maximum of 380 for CHT. Currently, as I start to lean out the mixture, the EGT for #4 peaks first and the CHT easily will overshoot 380 if I don't hurry up and get to the lean side. I'm not currently flying this way though because like I said, the other 3 cylinders start to get rough at this point. I am staying on the rich side and the #4 CHT is hard to manage there too. If I lean the engine such that the EGTs rise above 1300, #4 CHT goes over 380. So, I have to keep it pretty rich, burning about 13.5 GPH @ 7500 to to not exceed 380 on #4 CHT. Everything lean of this, gets me into the problem of the #4 CHT or if I keep leaning such that #4 CHT comes back down, the other three cylinders are just running too rough So, here is my question. Do you think the injector swap out will fix this? Is there something else we should be looking for? I noticed that barely cracking open the cowl flaps has a huge effect on the CHTs. I can do this and lean further. However, I don't really want to fly around like that. I can hear it. And, it might take a knot off. I'm not sure about that. I have looked at the baffling and it looks good. Flashlight test and all. There is nothing about the baffling material that leads me to believe it's kinked or anything. I never had to work hard to manage temps before and I'd like to get back to not having to do it now. I'm definitely going to swap out the injectors as prescribed by GAMI. Just thought I'd check in here to see if there were any other thoughts on it. I've been told that sometimes a cylinder runs hotter due to differences in airflow. Maybe that's it. Also, maybe once I swap the injectors, and get get all the cylinders peaking at the same time, it'll be easier. Here is a pic of my engine monitor with me ROP. Notice I am already pushing the 380 and barely have EGTs 1300+. Here is another pic with me trying to get LOP. Notice that by the time #4 gets to 10 degrees LOP, the other EGTs especially #3 are already much cooler. (60-70 degrees LOP for #3) I really want to have the option to fly LOP but it's not really even an option right now. Currently, I'm about ~50 into the Top overhaul and oil consumption is very stable at about 1 qt every 8-10 hours.