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#11
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TBO Advisor recommends the peak EGT method of leaning for the O-470 series
(except O-470-U), but it also warns that "In some engines, such as the O-470-R, it may not be possible to operate smoothly at peak EGT (when EGT is measured from a single probe that averages one bank of cylinders), since mixture maldistribution can cause lean misfire to appear in the leanest cylinders before peak EGT for the engine-as-a-whole has been reached." It also says that running at peak EGT also means that detonation protection is at its lowest. What does your POH say? Continental does not recommend leaning to peak EGT at settings above 65% power for normally-aspirated engines. "Jeffrey" wrote in message . com... Greeting to all; I own a 1964 Cessna 182 with a Continental O-470-R25 engine. This is equipped with an E.I. 6 pt EGT gauge. Typical cruise power setting is 20" manifold pressure 2300 RPM. I seem to have a plug fouling issue. Can someone please give me the proper leaning procedure for both cruise flight and ground operations (taxing)? I'd really appreciate some experienced input. Thanks in advance! Jeffrey |
#12
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In article ,
"Jeffrey" wrote: What's your technique Scott? Leeeaaaaannnn - on the ground until it almost quits, and in the air - be aggressive - a cht/egt monitor helps! I recommend ECI. Tony -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE "Scott Skylane" wrote in message ... RST Engineering wrote: Then you will have plug fouling issues with the O-470 for the rest of your airplane's life. Bulls**t. I've put almost 500 exclusively 100LL hours on my O-470R with nary a single plug fouled. Happy Flying! Scott Skylane N92054 |
#13
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In article ,
Scott Skylane wrote: RST Engineering wrote: Then you will have plug fouling issues with the O-470 for the rest of your airplane's life. Bulls**t. I've put almost 500 exclusively 100LL hours on my O-470R with nary a single plug fouled. Same here....around 800 hours and no fouling problems. Usually leaned on the ground. Leaned at cruise regardless of altitude. Had an EI engine scanner/monitor with 6 leads EGT/CHT. -- Dale L. Falk There is nothing - absolutely nothing - half so much worth doing as simply messing around with airplanes. http://home.gci.net/~sncdfalk/flying.html |
#14
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Jeffrey wrote:
What's your technique Scott? Well it's a very detailed, scientifically validated protocol, and I'll attempt to outline the specifics he For ground operation, I'll pull the mixture out, oh, about an inch and a half or so, give or take. Full rich for takeoff and climb, up to about 5000 ft or so (home base is at sea level). Lean it a little for climbs above 5000 ft. For cruise, pull the mixture out, oh, about an inch and a half or so, give or take depending on altitude (pull out more at higher alt). I have no engine monitor, so I used to pull the mix untill power loss, then enrich slightly for cruise, but it always ended up in the same place, so see above. Thats it, as far as leaning goes. I cruise at 23 square, get about 150 mph on 12 gph. I try to keep manifold pressure as high as possible. After takeoff, I leave the throttle full, and pull back RPM to 2450. For power reduction approaching the traffic pattern, I pull the RPM's down with the MP, down to 2000 RPM and about 18" for pattern entry. My theory is, higher combustion chamber pressures should help scavenge the lead better. This theory is based on nothing but my gut. Happy Flying! Scott Skylane N92054 |
#15
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Jeffrey,
Well I didn't think it was too low a power setting. What do you prefer to use? 75 percent as long as it's available, all that's there when not. And yes, it could be too low a power setting influencing the scavenging process through lower temps and pressures. But the main culprit is likely not enough leaning on the ground. As for Deakin's articles, I've not read them, thanks for the tip on that! But which one should I start on? There's a trio in succesion dealing with Mixture, Prop and Manifold Pressure, IIRC. The latter is easy to recognize by its title, which is "Manifold Pressure Sucks" (get it? - if not, you will after reading). There's a general one dealing with engine management older than those. These are the foundation. But basically, you'll be ok if you read all of them in chronological order. It's a lot to read, but well worth it. -- Thomas Borchert (EDDH) |
#16
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Juan,
It also says that running at peak EGT also means that detonation protection is at its lowest. Which is probably not so. Some people have had good results with a little addition of carb heat to even out the mixture distribution across cylinders, it seems. -- Thomas Borchert (EDDH) |
#17
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Hi Scott
Are you at Arlington this year? Tony -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE Happy Flying! Scott Skylane N92054 |
#18
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At power settings above 65% you need to be concerned about running too
lean, thus too hot. With monitoring all 6 cylinders it should be possible to run 50 to 100 rich of peak at these high power settings. You will have to lean until you hit peak, then richen. Use this EGT as a guide. I would use 100 degrees rich of peak on power settings above 75%. This is on your hottest cylinder. At power settings below 65%, you do not need to worry about running too lean, so just lean until it runs rough and richen slightly. Note the EGT on the hottest cylinder and use this EGT all the time. Most of us pilots lean to a specific EGT. I use 1350, but I only have one probe on one cylinder. The exact temperature varies with probe installation. On my carb Lycoming 360, 1350 is all the way lean at 50% power and maybe 100 degrees rich of peak at 75% power and 50 degrees rich at 65% power. I have an engine that is well over TBO and still going strong using this technique. One thing you can do is lean all the way to roughness while at full throttle at 10,000' then richen till smooth. Note the EGT and use this as a target setting at all power settings. This will give you rich of peak at higher power settings and all the way lean at 50% power. You will read articles about running lean of peak, but most of this only applies to engines with fuel injection and GAMI injectors. They run these engines lean of peak at high power settings to help cooling and fuel economy. It usually wont work with carbureted engines as you will have uneven air and fuel distribution. Lean on the ground for taxi as much as possible. Lean for takeoff at airports above 3000'. Don't go full rich on landing unless landing at airports below 3000'. Leaning for takeoff involves doing a runup and leaning until you get an rpm drop, then richen 3 half turns on the mixture knob. This works well. For landing, just lean to the takeoff setting judging on how far out the mixture knob was set on takeoff. This is all for airports above 3000'. Hope that helps. |
#19
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Doug,
At power settings above 65% you need to be concerned about running too lean, thus too hot. Uhm, no, not at all. He'd have to be concerned to run not lean enough, actually, since the temps decrease again when running leaner and leaner. The point is: You have to worry to run at the right point in relation to peak. With monitoring all 6 cylinders it should be possible to run 50 to 100 rich of peak at these high power settings. 50 rich is about the worst point to run at. Most of us pilots lean to a specific EGT. Well, I sure don't. I don't know ANY other pilot (apart from you) who does. Those numbers are completely irrelevant. The relation to peak is key. I have an engine that is well over TBO and still going strong using this technique. I can't see any curvature of the earth from the ground, so it must be flat. Or, in other words: What proof do you have of a correlation? Lean on the ground for taxi as much as possible. Lean for takeoff at airports above 3000'. Density altutide, not actual altitude, I'd like to add. VERY important! -- Thomas Borchert (EDDH) |
#20
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Jeffrey wrote:
: I own a 1964 Cessna 182 with a Continental O-470-R25 engine. This is : equipped with an E.I. 6 pt EGT gauge. Typical cruise power setting is 20" : manifold pressure 2300 RPM. I seem to have a plug fouling issue. : Can someone please give me the proper leaning procedure for both cruise : flight and ground operations (taxing)? I can't comment directly on the O-470 Cont in the 182 (My Cherokee has an O-360 180hp Lyc). I've read through as much leaning info as I could get my hands on, and the Deakin articles on Avweb as others have suggested are the best around. Bottom line: - You cannot hurt the engine by *ANY* leaning below 65-75% power (depending on brand). - You must run much richer than 50 ROP if above 75% At least 100 or more, or you very well may damage the engine. - You will foul plugs if too rich for too long and/or not hot enough. - CHT is what really determines if you have to run really rich or can run lean... as long 65-75% or less. If you're running at 65% and you lean as far as you can (roughness) but your CHT's go above 400 (spark-plug type), you'd better not run there for too long. Too hard on the jugs. I would hazzard to say that if you're running 100LL in the 182, there is probably a huge detonation margin since the octane rating is much more than necessary. You probably couldn't even *get* it to detonate at sea level full power if you tried... not that'd I'd try it. If possible, run mogas in it for a cleaner, happier engine... unless you live where you can't get alcohol-free gasoline. If you live there, move. My personal procedures (which will be attacked by many as crazy) are as follows: - Lean aggressively on the ground. Although it's difficult to get the mixture right since it changes when you throttle-jockey for taxi, you want to run it so lean it's impossible to runup without stumbling. You can't hurt it on the ground, and you can't forget to go full rich for takeoff. If you just lean it a little on the ground because you're worried about too lean, you could takeoff with it leaned out that "safe inch or so"... which *ISN'T* safe for takeoff. - Lean in a long climb to whatever EGT was at full-rich, low-altitude takeoff. On mine, peak EGT is 1550 or so, and full-rich takeoff on a standard day is about 1400. I'll continuously pull the mixture in a long climb to hold 1400 degrees. If I get high enough so full throttle is less than 70%, I'll lean to peak even in a climb so long as the CHT's don't go over 400. - In cruise at 70% or less, lean as far as it will go and leave it there. Monitor CHT's and make sure it never gets over 400. All my CHT temps are referenced to spark-plug probes. They read 50-75 degrees hotter than the cylinder barrel probes (I've got one of those too and have verified it). If using those types, 350 would be my max comfortable, continuous cruise CHT. I've been running 93 A.K.I mogas in my 180 hp for about 250 hours now. Always clean plugs, very little combustion chamber buildup, never fouled, etc, etc. Flame on! -Cory -- ************************************************** *********************** * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * ************************************************** *********************** |
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