A64Pilot Posted October 8, 2022 Report Share Posted October 8, 2022 1 hour ago, Shadrach said: It’s true that e.g. tees track compression but I don’t think the differences are significant enough to amount to more than noise. Probe position alone can have a significant effect on the actual number. As for cylinder reference for leaning, The cylinder with the lowest margins is the one with the most aggressive mixture setting. If setting mixture on the rich side of peak EGT, the leanest cylinder (first to peak) is the safest cylinder to reference as all others will be richer. If mixture setting is peak or leaner, the richest cylinder (last to peak) is the safest cylinder to reference as all others will be leaner. Whatever the mixture setting, it’s best if the remaining cylinders are known to be at a setting that is equal to or more conservative with regards to detonation margins than the referenced cylinder. I knew you would disagree, but if you have decent distribution, it’s all in the noise band, but compression is at least as likely to get you into detonation as mixture, if we are talking about being close to it anyway. But you know I’m a proponent of running power settings where any mistake can’t lead to detonation, cause people do make mistakes One day someone will market a detonation sensor, surely it would be a hot seller. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted October 8, 2022 Report Share Posted October 8, 2022 54 minutes ago, A64Pilot said: I knew you would disagree, but if you have decent distribution, it’s all in the noise band, but compression is at least as likely to get you into detonation as mixture, if we are talking about being close to it anyway. But you know I’m a proponent of running power settings where any mistake can’t lead to detonation, cause people do make mistakes One day someone will market a detonation sensor, surely it would be a hot seller. The only place to run where mistakes won’t cause potentially harmful mixture settings is full rich (provided the fuel system is set up properly ) or on the lien side of peak (on your riches cylinder)…that is it. Any other mixture setting has the potential to put some cylinders in a harmful place, particularly 100° Rich of peak which is spitting distance from the hottest, highest pressure combustion event that there is. ROP operations are fraught with potential problems, yet Pilots rarely melt pistons. I don’t think how you run he engine is nearly as important as knowing how it’s running. Nevertheless, these little engines drone on. My airplane didn’t have an engine monitor until the year 2000. It flew for 33 years and cruised at 50° ROP on a single cylinder gauge. It did swallow valve at 1600hrs but I can’t attribute that to power/mixture settings. George Braly has had aircraft detonation sensors for some time but certification seams to have stalled. The system is called PRISM (Pressure Reactive Intelligent Spark Management). He has modified spark plugs on his test stand that incorporate pressure transducers. He can see and graph detonation in real time. I don’t think either of the major engine manufacturer’s have that capability. That is the test stand he used to develop G1000UL and how he is able to make direct comparisons 100LL. I am sure that he is able to switch back-and-forth seamlessly between the two fuels and compare their combustion event profiles without shutting down the engine. Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted October 8, 2022 Report Share Posted October 8, 2022 Yes at least Lycoming can and does have the capability to test for detonation, has for a long time. The Piezo pressure spark plugs have been around for a long time, usually used just to measure pressures not so much detonation, but as it’s a pressure spike they could be used for that too, but they are one off pretty expensive things, doubt that would be usable in a GA aircraft. People will of course say an aircraft engine is too noisy to use sound sensors, but it’s been done successfully before. If you follow the engine manufacturers recommendation for leaning, no you can’t hurt an engine by following their directions, they say don’t lean until your below a power where any mixture is safe, for Lycoming I believe that’s 75%, which coincidentally just happens to be max cruise power. If you read and follow the manual, you won’t hurt the engine Personally if I’m above 75%, I’m full rich although if climbing high enough and if cyl head temps allow I’ll lean to just below initial climb EGT if she’s getting just too rich. Then Lycoming has said for max engine longevity operate at or less than 65% power, so that’s what I do, cause I don’t plan on ever overhauling this motor, I only have about 1500 hours of flying left in me probably 100 ROP is about POWER, it’s not about anything else, the further you get away from 100 ROP either lean or rich the more power you lose This is a 40 year old AC telling you how to do a detonation survey, but it was done well before this AC too. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_33_47-1.pdf 1 Quote Link to comment Share on other sites More sharing options...
kortopates Posted October 8, 2022 Report Share Posted October 8, 2022 Definition of Max cruise power by both TCM and Lyc is the highest %power where the engine can be aggressively leaned i.e. leaning more than just for high density altitude takeoff and climb. Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted October 8, 2022 Report Share Posted October 8, 2022 Operators manual defines it as 75% for Lycoming Then read para 7 if N/A and 9 if turbo https://www.lycoming.com/sites/default/files/Fuel Mixture Leaning Procedures.pdf Now we all know if your engine will, LOP is just fine, but I feel it’s prudent to do so at a power that you can’t hurt the motor, as I’m at 65% or less for max life that’s where I run LOP, now you can run LOP full throttle and full MP down low, but you can hurt the motor if your not careful and you can’t make as much power as ROP so why do it. Quote Link to comment Share on other sites More sharing options...
kortopates Posted October 8, 2022 Report Share Posted October 8, 2022 Operators manual defines it as 75%. Then read para 7 if N/A and 9 if turbo https://www.lycoming.com/sites/default/files/Fuel Mixture Leaning Procedures.pdfyep, it’s also in the performance curves of each engine in each operators manual. the percent power isn’t strictly 75%, it varies by the engine but 75% is very typical with NA engines.Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
Fly Boomer Posted October 9, 2022 Report Share Posted October 9, 2022 On 10/7/2022 at 4:30 PM, kortopates said: Mike’s redline MAP is only 32”. That makes it much easier to stay at redline than most other Turbo’s; especially the highly boosted TSIO-360’s! But very easy to do on any NA engine. Sent from my iPhone using Tapatalk The TSIO-520NB is 38. I’m surprised to learn that his 520s are 32. That would make it easier for sure. Quote Link to comment Share on other sites More sharing options...
carusoam Posted October 10, 2022 Report Share Posted October 10, 2022 It’s really cool when somebody quotes a guru of engine ops… and… one of the guru’s partners comes along and explains some additional finer details…. Back to the OP on this one… All Mooneys have been documented to operate ROP…. It’s in the POH… perfectly acceptable… A few of the Continental powered Mooneys have been documented to run LOP as well… also in their POH…. Even better for some… Where is the confusion coming from? There isn’t a time you want to fly full rich… with the mixture always pushed all the way in… like a trainer. This can be an expensive lesson in ROP flight… less than favorable… In an O1… we have a calibrated EGT gauge… with a blue box. This has a defined meaning that can be read about in the POH…. In newer Os with G1000 systems… they have a white box instead of a blue one… same meaning… explained on their POH… Sooo…. Fly around ROP if you like… but in accordance with your POH… lean properly for T/O, climb, cruise…descent, and landing…. Then during taxi… Did I mention leaning prior to taxi, right after start-up? The cool thing about IO550s…their EGT sensors are calibrated… and have real meaning… to go along with their real numbers… PP thoughts only, see if you can add more detail to your question… The G1000 white box is the ROP window for climb… somewhere 2-300°F ROP wide… cruise will be slightly leaner possibly 100°F ROP… Leaning anywhere you like is often done below 65%bhp… above 8k’ is easy to be in a safe spot for NA engines… In cruise… stay below 65%bhp… lean anyway you like… maintain CHTs using additional FF…. @12k’, the IO550 uses about 12.5gph LOP, 15gph ROP… using 2500rpm, slightly more when using 2550 when able… PP thoughts only, not a CFI… or mechanic… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
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