carusoam Posted December 3, 2016 Report Share Posted December 3, 2016 I think this may be the first time I have seen EGT charts for an O360... 1) EGT #4 seems to be running a bit differently than the others. 2) the mag check occurs so quickly compared to the data acquisition speed, you can see a mag check happened but the results aren't very clear. (If you take more time, it will show two separate peaks and returns to normal with both mags running. It takes six seconds to acquire a datapoint on a standard JPI set-up... going 15 seconds per mag will collect more data (if you can stomach the rough ground run) 3) what I was hoping to discern was... the effects of the secondary fuel nozzle. It comes on at full throttle and comes off when the throttle is backed off just a bit. I think I see it happen... 4) Leaning... appears, but not incredibly visible. 5) If you annotate a time line, it may look something like this... 00:00 engine start, cylinders begin heating... 3:00 - 6:00 mag check and prop tests... 6:00 - 10:00 taxi to runway... 10:30 There is an interesting signature of the throttle all the way out for a few seconds. Or mixture going full rich... 11:00 Game-on... full throttle, EGTs go skywards. #4 leads the pack stronger than the others... 13:00 Something interesting is occurring... possibly the secondary fuel nozzle gets cut off. EGTs take a step higher and continue upwards as if the pilot is leaning the mixture... 14:00 - 18:00 Leaning appears to be going on in this time frame 18:00 - 29:00 Steady as she goes, mate... egt#4 runs noticeably colder than the other three. 29:00 - 33:00 Slight rise in all EGTs 33:00 - All EGTs begin to cool, throttle has been pulled for descent...? All but #4! Who is a bit chilly already... 36:00 - 38:00 traffic pattern activity, low throttle position, cool EGTs... GUMPS puts the mixture all the way in... 38:00 throttle pulled for landing procedure... Taxiing and shut down... Take a second look at EGT #4, it behaves differently than the others. Could be the oddness of a carburetor. Or might be an induction air leak adding to the behavior. It has some of the sawtooth I was expecting to match up with the photo of the mal-behaved valve. Take a second look at CHT #2, it is just running hotter than the others. Look for reasons airflow may be escaping... Always verify the EGT#s correlate with the cylinder numbers. PP thoughts, most liking missing the proper details. It would be interesting to take a flight and go through all of these steps again. Take notes at the time of each throttle and mixture adjustment, engine flaps open and close too... Best regard, -a- 1 Quote Link to comment Share on other sites More sharing options...
DXB Posted December 3, 2016 Author Report Share Posted December 3, 2016 On 12/2/2016 at 9:15 AM, Marauder said: Dev -- before I went whole hog on an aggressive approach, I would try to get better pizza pictures. I have a pretty decent borescope that articulates and will allow you to get a full picture of the valve. You are more than welcome to use it. Let me know. Here is a picture of one of my pizzas. Chris - thanks for the offer - your pix are beautiful. I actually got sick of my lousy $20 dental camera recently and got this: http://www.oasisscientific.com/vividia-va-400-rigid-usb-articulating-borescope-videoscope-inspection-camera.html I'm very happy with the pix it gives - I'm pretty confident in my exam of the valves now - I just haven't gotten good at capturing stills to show folks :). 14 hours ago, carusoam said: 1) EGT #4 seems to be running a bit differently than the others. 2) the mag check occurs so quickly compared to the data acquisition speed, you can see a mag check happened but the results aren't very clear. (If you take more time, it will show two separate peaks and returns to normal with both mags running. It takes six seconds to acquire a datapoint on a standard JPI set-up... going 15 seconds per mag will collect more data (if you can stomach the rough ground run) 3) what I was hoping to discern was... the effects of the secondary fuel nozzle. It comes on at full throttle and comes off when the throttle is backed off just a bit. I think I see it happen... 4) Leaning... appears, but not incredibly visible. 5) If you annotate a time line, it may look something like this... 00:00 engine start, cylinders begin heating... 3:00 - 6:00 mag check and prop tests... 6:00 - 10:00 taxi to runway... 10:30 There is an interesting signature of the throttle all the way out for a few seconds. Or mixture going full rich... 11:00 Game-on... full throttle, EGTs go skywards. #4 leads the pack stronger than the others... 13:00 Something interesting is occurring... possibly the secondary fuel nozzle gets cut off. EGTs take a step higher and continue upwards as if the pilot is leaning the mixture... 14:00 - 18:00 Leaning appears to be going on in this time frame 18:00 - 29:00 Steady as she goes, mate... egt#4 runs noticeably colder than the other three. 29:00 - 33:00 Slight rise in all EGTs 33:00 - All EGTs begin to cool, throttle has been pulled for descent...? All but #4! Who is a bit chilly already... 36:00 - 38:00 traffic pattern activity, low throttle position, cool EGTs... GUMPS puts the mixture all the way in... 38:00 throttle pulled for landing procedure... Taxiing and shut down... Take a second look at EGT #4, it behaves differently than the others. Could be the oddness of a carburetor. Or might be an induction air leak adding to the behavior. It has some of the sawtooth I was expecting to match up with the photo of the mal-behaved valve. Take a second look at CHT #2, it is just running hotter than the others. Look for reasons airflow may be escaping... Interesting and accurate analysis Anthony - I've also puzzled over why #4 EGT behaves at it does. My interpretation is a major change in mixture distribution between climb and leaned cruise power settings - leanest at takeoff WOT, settles out much richer in cruise after leaning. An induction leak on that one would lean the mixture and make EGT rise when MP gets lower (relative to atmospheric) as power is reduced. BTW the flight I posted was at low altitude (2500 ft, 23 squared, not aggressively leaned). Interestingly, when I fly higher (e.g. 7500 ft, 2500 rpm, leaned aggressively), I get a completely different pattern: https://www.savvyanalysis.com/flight/1623585/82403f65-d1a7-4781-9837-fb3274916a6f There is also a lot of variability in pattern between flights, making me think mixture distribution is a fickle thing with the carb. But since you bring up the question of induction leak, I will fly the test profile recommended by Savvy for induction leak detection before it goes in the shop: https://www.savvyanalysis.com/articles/in-flight-diagnostics You are correct also on #2 CHTs - consistently runs 20-30 degrees hotter in cruise, regardless of leaning - and it is never the leanest cylinder. I attribute to a gap in the baffle to the prop side of my starter, as I've tightened up the rest pretty well - getting to that one requires dropping the bottom cowl though. It will definitely get taken care of at annual this month and may be more reachable with #2 taken off. Also just for fun, here's a flight where I did in flight mag checks: https://www.savvyanalysis.com/flight/1586170/e46a28ef-72f3-4545-96a3-91170d13b954 That one made me clean and gap my plugs based on the unstable EGTs on a single mag - it fixed the issue. On 12/2/2016 at 10:45 AM, Marcopolo said: Going with the theory of not pulling multiple jugs simultaneously, why not pull them one at a time meaning only having one jug off at a time. This should keep the case torqued and aligned properly but it will increase your downtime. You could even buy a cylinder up front to put on as you take one off and then only wait on the second one. Just a thought...or two. I'm reading a little deeper into this issue. Seems like the greatest risk is ending up with a spun bearing if the work is not done meticulously: https://www.cirruspilots.org/copa/tech/m/magazine_articles/563618/download.aspx Quoting Mike Busch from the article linked above: "The Right Way to Pull a Jug...The correct way to remove multiple cylinders is to remove one cylinder at a time, then retorque the associated pair of through-bolts (using a “torque plate” or a stack of washers in place of the missing cylinder flange) before moving on to the next cylinder. By doing it this way, six of the eight through bolts are always in a torqued state, firmly clamping the crankcase halves together and making it far less likely that any of the main bearings will shift in their saddles. In addition, the crankshaft should never be rotated while any through bolts are in an untorqued state. The mechanic should position a piston, then remove the eight hold-down nuts and the cylinder, then re-torque the two through-bolts (so all eight are torqued) before rotating the crankshaft to position the next piston." I think it may be worth quizzing the shop that will do the work on their standard practice for pulling multiple jugs. What do the A&P's here think? Am I contributing to my own safety or undermining it by being a nosy and obnoxious client? 1 Quote Link to comment Share on other sites More sharing options...
Marauder Posted December 3, 2016 Report Share Posted December 3, 2016 1 hour ago, DXB said: Chris - thanks for the offer - your pix are beautiful. I actually got sick of my lousy $20 dental camera recently and got this: http://www.oasisscientific.com/vividia-va-400-rigid-usb-articulating-borescope-videoscope-inspection-camera.html I'm very happy with the pix it gives - I'm pretty confident in my exam of the valves now - I just haven't gotten good at capturing stills to show folks :). Interesting and accurate analysis Anthony - I've also puzzled over why #4 EGT behaves at it does. My interpretation is a major change in mixture distribution between climb and leaned cruise power settings - leanest at takeoff WOT, settles out much richer in cruise after leaning. An induction leak on that one would lean the mixture and make EGT rise when MP gets lower (relative to atmospheric) as power is reduced. BTW the flight I posted was at low altitude (2500 ft, 23 squared, not aggressively leaned). Interestingly, when I fly higher (e.g. 7500 ft, 2500 rpm, leaned aggressively), I get a completely different pattern: https://www.savvyanalysis.com/flight/1623585/82403f65-d1a7-4781-9837-fb3274916a6f There is also a lot of variability in pattern between flights, making me think mixture distribution is a fickle thing with the carb. But since you bring up the question of induction leak, I will fly the test profile recommended by Savvy for induction leak detection before it goes in the shop: https://www.savvyanalysis.com/articles/in-flight-diagnostics You are correct also on #2 CHTs - consistently runs 20-30 degrees hotter in cruise, regardless of leaning - and it is never the leanest cylinder. I attribute to a gap in the baffle to the prop side of my starter, as I've tightened up the rest pretty well - getting to that one requires dropping the bottom cowl though. It will definitely get taken care of at annual this month and may be more reachable with #2 taken off. Also just for fun, here's a flight where I did in flight mag checks: https://www.savvyanalysis.com/flight/1586170/e46a28ef-72f3-4545-96a3-91170d13b954 That one made me clean and gap my plugs based on the unstable EGTs on a single mag - it fixed the issue. I'm reading a little deeper into this issue. Seems like the greatest risk is ending up with a spun bearing if the work is not done meticulously: https://www.cirruspilots.org/copa/tech/m/magazine_articles/563618/download.aspx Quoting Mike Busch from the article linked above: "The Right Way to Pull a Jug...The correct way to remove multiple cylinders is to remove one cylinder at a time, then retorque the associated pair of through-bolts (using a “torque plate” or a stack of washers in place of the missing cylinder flange) before moving on to the next cylinder. By doing it this way, six of the eight through bolts are always in a torqued state, firmly clamping the crankcase halves together and making it far less likely that any of the main bearings will shift in their saddles. In addition, the crankshaft should never be rotated while any through bolts are in an untorqued state. The mechanic should position a piston, then remove the eight hold-down nuts and the cylinder, then re-torque the two through-bolts (so all eight are torqued) before rotating the crankshaft to position the next piston." I think it may be worth quizzing the shop that will do the work on their standard practice for pulling multiple jugs. What do the A&P's here think? Am I contributing to my own safety or undermining it by being a nosy and obnoxious client? Dev -- that is the camera I have. Works great. Several apps will work with it. Quote Link to comment Share on other sites More sharing options...
kortopates Posted December 3, 2016 Report Share Posted December 3, 2016 1 hour ago, DXB said: I think it may be worth quizzing the shop that will do the work on their standard practice for pulling multiple jugs. What do the A&P's here think? Am I contributing to my own safety or undermining it by being a nosy and obnoxious client? Absolutely I would. The reason being is that I have yet to see Continental publish a bulletin on the importance on torquing the 2 through bolts as soon as the cylinder is removed. Their documentation only specifically addresses single cylinder replacement or overhaul - it doesn't really discuss these added issues for multiple cylinder replacement or performing tops. Another related issue is that even if just one cylinder is removed the through bolts must be torqued from both sides of the engine. This has gotten into their recent Service Bulletins (SB')s and now part of their M-O Maintenance Manual (A generic standard practices for all piston engines) but its still not present in the original engine specific maintenance manuals (some say to just hold the opposite side of the through bolt - which is a far cry from torquing the opposite side). Until the manufacturers document this need for multiple cylinder replacement I think it very wise to have the conversation in light of the several failures we've seen from improper torquing procedures. Many mechanics are using cut off cylinder flanges to make this easy. But just using washer gets the job done and with only two through bolts per cylinder, its not much effort to do it right. 1 Quote Link to comment Share on other sites More sharing options...
DXB Posted December 20, 2016 Author Report Share Posted December 20, 2016 Ok - I'm continuing this thread as I start to bleed some amu in annual on my O-360-A1D. Here's a brief recap plus pix: 1. The engine now has 920hrs SMOH in 2000, when it got new Millennium cylinders. #1 was IRAN'd after my pre-buy 2 years ago because of an exhaust leak. Compression on #1 was in high 70s today. 2. In the last year, oil consumption has gone up dramatically (from 1qt /7-10 hrs to 1 qt/ 3 hrs or less), and the oil now turns black quickly (<5 hrs). 3. #2 exhaust valve looked burnt on borescope. Compression today was in 50's. The #2 cylinder came off today and will get sent out for IRAN. See valve pix below. I could feel the slop in the guide when I move the valve by hand on the bench. The valve isn't warped at all though - A&P says that it can be simply be reground in the seat and reused after swapping the guide. Does this sound kosher? 4. #3 bottom plug gets oil on it - I'd cleaned it and rechecked several times. I've also rotated plugs and also done in flight mag checks leaned out, so I know it's not a bad ignition system or plug that is causing it. I'm guessing #4 is the one with all the blow by, giving me my high oil consumption and black oil, despite a compression check in the low 70's. So it also got pulled today and is getting sent out for IRAN. However there was nothing obviously wrong with the rings or cylinder walls on it, which makes me worry it was not worth pulling. 5. Cam and lifters look ok after taking off #2 and #3. Whew. Neither jug has any cracks and likely will be within spec for IRAN given that they are first run. 6. So now only #4 has not been removed since overhaul. Its compression is in the mid 70s and doesn't create oily plugs. Its valves look fine on borescope. Bottom line: I'm hoping that I pulled the right two jugs for IRAN. In particular, I will be upset if I still have high oil consumption after re-break in because the blow by was not on #2 or #3. Question: Did I do the right thing? The wrong thing? The foolishly cheap thing? The stupidly expensive thing? I'm learning a lot here and am open to harsh critique. PIX of #2 exhaust issues: Quote Link to comment Share on other sites More sharing options...
Yetti Posted December 20, 2016 Report Share Posted December 20, 2016 So what we found in my A1A was that the rings are loose down low, but the compression is fine. That is causing the plugs to oil foul. So we put and REM37BY on the bottom since it is a different design and it sticks up a little more. Here is the approved spark plug chart. https://www.lycoming.com/sites/default/files/SI1042AB Approved Spark Plugs.pdf Once we get the plane together we will see. I had a spare cylinder and number 4 seems to be the bad actor but we decided not to change it at this time. Soon it will probably be swapped out. I think swapping cylinders is just part of the continuous maintenance program. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted December 20, 2016 Report Share Posted December 20, 2016 I've been told that #4 cylinder is the hardest to replace, and Murphy's law says it will always be #4. Quote Link to comment Share on other sites More sharing options...
Yetti Posted December 20, 2016 Report Share Posted December 20, 2016 actually it is the last screw or bolt you try and remove will always be the hardest one. Do number 4 first Quote Link to comment Share on other sites More sharing options...
rbridges Posted December 20, 2016 Report Share Posted December 20, 2016 On 12/2/2016 at 7:15 AM, Marauder said: Dev -- before I went whole hog on an aggressive approach, I would try to get better pizza pictures. I have a pretty decent borescope that articulates and will allow you to get a full picture of the valve. You are more than welcome to use it. Let me know. Here is a picture of one of my pizzas. Sent from my iPad using Tapatalk What scope do you have? I bought a cheapo from Home Depot but it doesn't articulate and the images aren't as good as yours. It has been helpful but I'd like a better one. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 20, 2016 Report Share Posted December 20, 2016 1) the halo around the valve is the sealing surface... if something isn't right with that surface, the seal is no longer 100% 2) how much does a new valve cost? In spec is in spec, re-use it. But since it cost money to swap out, swap it out while the old one has been pulled already... 3) compression and oil leaking are not really related to each other. Pistons have compression rings and oil rings... good compression and leaking oil is probably a problem with the oil ring being worn or broken. 4) oil getting dark is caused by exhaust blow-by. If your nose is working, the oil will be smelling like exhaust. It isn't 'burning' as much as it is just going out with the exhaust... oil burning on the sparkplug can turn to a crusty coating interfering with the fuel's access to the spark energy. Bottom spark plugs have the oil run away from the hot tip so burning and crust coating becomes less of a common result. 5) everything but the case has been swapped out... PP thoughts, not a mechanic... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
RobertGary1 Posted December 20, 2016 Report Share Posted December 20, 2016 Yes on an inflight mag check you keep your hand on the throttle and quickly pull to idle if one cyclinder doesn't fire. Turning back to both with the throttle forward will cause explosive holes. But with a jpi you'd already know if one mag isn't firing -Robert Quote Link to comment Share on other sites More sharing options...
Marauder Posted December 20, 2016 Report Share Posted December 20, 2016 What scope do you have? I bought a cheapo from Home Depot but it doesn't articulate and the images aren't as good as yours. It has been helpful but I'd like a better one. This one: https://www.amazon.com/gp/product/B00GY7C9ZW/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1Same one as Dev. Sent from my iPad using Tapatalk 1 Quote Link to comment Share on other sites More sharing options...
rbridges Posted December 21, 2016 Report Share Posted December 21, 2016 Thanks! 1 Quote Link to comment Share on other sites More sharing options...
DXB Posted December 21, 2016 Author Report Share Posted December 21, 2016 22 hours ago, carusoam said: oil getting dark is caused by exhaust blow-by. If your nose is working, the oil will be smelling like exhaust. It isn't 'burning' as much as it is just going out with the exhaust... oil burning on the sparkplug can turn to a crusty coating interfering with the fuel's access to the spark energy. Bottom spark plugs have the oil run away from the hot tip so burning and crust coating becomes less of a common result. Yeah I'm still coming to terms with some of these concepts Anthony. I now get how a plugged oil control ring leads to extra oil in he cylinder and oily bottom plugs, not bad compression rings. I'm told there's also a way to flush the cylinder to clear the oil control ring? If so, pulling #3 may have been premature. Oh well. I had assumed my oil loss and black oil were both from blowby pressuring the crankcase. But I guess the oil loss could be out the exhaust and not past the rings, and it's turning dark fast based on burnt oil coming back to the crankcase via the oil return tube by the exhaust port. Yet I don't see any unusual residue at the tailpipe. Confusing stuff ! Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 21, 2016 Report Share Posted December 21, 2016 Dev, Still thinking through the possibilities... does sound like blow-by... -a- Quote Link to comment Share on other sites More sharing options...
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