flyboy0681 Posted January 12, 2023 Report Share Posted January 12, 2023 It's been a very long time since I've flown in cold temperatures in South Florida, but recently we've had some cold overnight temps. On those days that I fly after a cold night, the engine shakes for several minutes after startup and I was wondering what could be causing it. By the time that I start up, the outside temperatures are typically in the high 50's. 1 Quote Link to comment Share on other sites More sharing options...
201er Posted January 12, 2023 Report Share Posted January 12, 2023 That's not cold. 2 3 Quote Link to comment Share on other sites More sharing options...
flyboy0681 Posted January 12, 2023 Author Report Share Posted January 12, 2023 1 minute ago, 201er said: That's not cold. Mike, does Six One Hotel shake on mornings like that? Quote Link to comment Share on other sites More sharing options...
201er Posted January 12, 2023 Report Share Posted January 12, 2023 Just now, flyboy0681 said: Mike, does Six One Hotel shake on mornings like that? I can't tell cause my teeth are rattling more. There can be a couple burbles but if it's anything less than 40F, I'm preheating so I dunno. I usually run at 1000-1100 RPM with cowl flaps closed for a few mins until cylinder heads get into 200F+ and oil temp is over 90F. Then I'll go to 1200 RPM or taxi. I get the shakes when #4 is running way leaner. At colder temps, lower power, the fuel divider doesn't do a very good job and seems to starve #4 causing 100-200 higher EGT and that will cause a rumble. It goes away once things warm up or higher power. Quote Link to comment Share on other sites More sharing options...
DXB Posted January 12, 2023 Report Share Posted January 12, 2023 Not sure but overall story is pretty classic for "morning sickness" from a sticky exhaust valve guide. If so, the engine monitor would greatly help support the hypothesis and identify the offending cylinder (or develop a different hypothesis). Hopefully you have a data logging function on your engine monitor. Quote Link to comment Share on other sites More sharing options...
flyboy0681 Posted January 12, 2023 Author Report Share Posted January 12, 2023 16 minutes ago, DXB said: Not sure but overall story is pretty classic for "morning sickness" from a sticky exhaust valve guide. If so, the engine monitor would greatly help support the hypothesis and identify the offending cylinder (or develop a different hypothesis). Hopefully you have a data logging function on your engine monitor. I found an entry from one such morning... Quote Link to comment Share on other sites More sharing options...
DXB Posted January 12, 2023 Report Share Posted January 12, 2023 8 minutes ago, flyboy0681 said: I found an entry from one such morning... The initially reduced EGT on the purple cylinder seems to support that's where the problem is? CHT should be low there also. I'll let others weigh in on whether that's diagnostic of a sticky exhaust valve or a transient fuel issue could explain it (I suspect not but I don't understand the fuel injected systems very well). Sticky valve is no joke - I'd be hesitant to fly without it being address. Having it stick hard can lead to a very bad day. 2 Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 14, 2023 Report Share Posted January 14, 2023 If you suspect valve sticking, and shaking on cold mornings is certainly an indicator, do a wobble check on ALL cylinders, it’s not hard but why play wack a mole with valves, check them all, plus a sticking valve can honestly destroy an engine and possibly cause in flight engine failure. The set up to check / ream a valve guide is half the labor time, it’s very possible you may have more than one tight valve, with one sticking now, but another could be close. I’ve seen people clean one plug and just don’t understand the logic. Your engine is sending warning signs, listen to it. You may not have any tight valves, but the check is worth doing, you may have just flooded the thing Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted January 14, 2023 Report Share Posted January 14, 2023 If you suspect valve sticking, and shaking on cold mornings is certainly an indicator, do a wobble check on ALL cylinders, it’s not hard but why play wack a mole with valves, check them all, plus a sticking valve can honestly destroy an engine and possibly cause in flight engine failure. The set up to check / ream a valve guide is half the labor time, it’s very possible you may have more than one tight valve, with one sticking now, but another could be close. I’ve seen people clean one plug and just don’t understand the logic. Your engine is sending warning signs, listen to it. You may not have any tight valves, but the check is worth doing, you may have just flooded the thingI don’t know how a sticky valve can destroy an engine.If it sticks open and collides with the cylinder head the worst that can happen is the valve is broken and you’ll need to replace a cylinder.Liberal use of MMO on last flight before oil change can help clean the valve stems. Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 14, 2023 Report Share Posted January 14, 2023 51 minutes ago, ArtVandelay said: I don’t know how a sticky valve can destroy an engine. If it sticks open and collides with the cylinder head the worst that can happen is the valve is broken and you’ll need to replace a cylinder. Liberal use of MMO on last flight before oil change can help clean the valve stems. According to the pictures I saw yesterday, the push rod can jump completely out of the lifter pocket and ends up breaking the case, but that’s not at all worst case, if that’s all that happens you probably could still fly for awhile until oil loss becomes critical, but your buying, not overhauling on landing. Of course if the valve sticks open the piston can break the valve head off when it shoves the valve closed, especially on an angle valve engine, known as swallowing a valve, if you swallow a valve it’s very likely the engine is “destroyed” often resulting in a thrown rod when the piston disintegrates and nothing holds the small end of the rod in place. Rather than me trying to explain further, I found this article, scroll down to where “what happens when a valve sticks” And I thought I was bad at spelling? https://www.avweb.com/ownership/dealing-with-stuck-valves/ IF your an MMO fan, and I won’t weigh in on it other than to say that I’ve seen numerous R-1340’s that will stick valves without it, I’d say run it, one way is to add it as you need oil right from the beginning until of course your at 20% MMO. I’ve seen MMO work numerous times, but it’s not FAA approved. Back in the day when Big Radials ruled Delta Airlines bought it in 55 gl drums. My opinion only of course. Quote Link to comment Share on other sites More sharing options...
flyboy0681 Posted January 14, 2023 Author Report Share Posted January 14, 2023 Last night saw temps in the mid to high 40’s down here and I had asked my partner start the plane up today. He reported that she ran smoothly. I’m flying Monday morning when temps are forecasted to be in the 50’s, so we shall see. Quote Link to comment Share on other sites More sharing options...
PT20J Posted January 15, 2023 Report Share Posted January 15, 2023 9 hours ago, flyboy0681 said: Last night saw temps in the mid to high 40’s down here and I had asked my partner start the plane up today. He reported that she ran smoothly. I’m flying Monday morning when temps are forecasted to be in the 50’s, so we shall see. If I suspected it had stuck a valve once I wouldn't run it again until I did a wobble test. The risk of more expensive damage isn't worth it and the test isn't invasive. Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 15, 2023 Report Share Posted January 15, 2023 17 hours ago, ArtVandelay said: I don’t know how a sticky valve can destroy an engine. If it sticks open and collides with the cylinder head the worst that can happen is the valve is broken and you’ll need to replace a cylinder. Liberal use of MMO on last flight before oil change can help clean the valve stems. My O360 stuck a valve open… Something I wouldn’t want to repeat… At full power, about 500’ agl… the shaking is gigantic, and the power left is closer to 50% then the expected 75% Valve rod bent, dent in the piston crown… replaced with another cylinder assembly… (there are better solutions) I didn’t have an engine monitor to know it was only one cylinder… it felt like something more serious had happened…. Climb rate dropped to about zero fpm, near sea level with two people on board… If I had an engine monitor… I would be sharing the graphs here… And I would use Savvy to help do that… Once Savvy had the data… I would be asking them what they think is going on… (low cost, professional engine guys, opinion…) Cold in NJ is below 20°F… where engine heat is required to get the fuel to evaporate enough…. For the IO550… a cold start includes leaving the Lo boost pump running until the cylinders and fuel systems warm up enough to keep things running smoothly… If everything is operating properly… it may be a simple enrichment challenge…. If valves are sticking… wobble test, ream the carbon out…. Sticky valves are different from stuck valves… sticky is a rotation thing, you have time to get fixed… stuck valve is an up and down thing, I wouldn’t wish this on anyone…. Simple test… below 40°F… no pre-heat, you get shaking…. Rent a pre-heater and see if the shaking goes away… This is most likely… the engine isn’t evaporating enough fuel… The simple fix… send the engine more fuel to evaporate… The risk… if you din’t have a Lo boost switch… you can flood the engine… PP guesses only, not a mechanic… Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 15, 2023 Report Share Posted January 15, 2023 About cold temps… in NJ… above 40°F… is an ordinary start…. Below 40°F… Pre-heat is desired… Below 20°F… Pre-heat is required… below 0°F… You start questioning your motivation to fly… But… wind speed is near zero, %bhp available is near 110%, wing efficiency is tremendous… plane performance is glorious… and there are no bumps… Rate of fuel evaporation is very temp related… mostly OAT at the time, but engine mass and its temperature does have a strong affect… Ask your airport if they have a pre-heater you can rent…. In NJ, this is an available service…. Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
takair Posted January 15, 2023 Report Share Posted January 15, 2023 Some stuff here on what Lycoming considers cold. At one point they mention -20F as extreme. https://www.lycoming.com/content/operating-cold-weather I have noticed that the amount of prime can change with cold weather and the amount of preheat. However, the effect of prime only lasts a few seconds, not minutes. Fouled plugs can play into it, but you would likely see issues at all temps. Many years ago, I had a fuel servo that would barely allow the engine to run until it warmed up. I didn’t have an engine analyzer back then, but I suspect that impact all cylinders. A single cylinder, for multiple minutes, would point at an injector or…as suggested, valve. I would think the injector would show up on a warm day too. 1 Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted January 17, 2023 Report Share Posted January 17, 2023 On 1/15/2023 at 2:39 AM, carusoam said: My O360 stuck a valve open… Something I wouldn’t want to repeat… At full power, about 500’ agl… the shaking is gigantic, and the power left is closer to 50% then the expected 7 Cold in NJ is below 20°F… where engine heat is required to get the fuel to evaporate enough…. If valves are sticking… wobble test, ream the carbon out…. Sticky valves are different from stuck valves… sticky is a rotation thing, you have time to get fixed… stuck valve is an up and down thing, I wouldn’t wish this on anyone…. Simple test… below 40°F… no pre-heat, you get shaking…. Rent a pre-heater and see if the shaking goes away… Cars don’t have a problem with fuel evaporation at lower temperatures, why do planes (especially fuel injection engines)? Why do sticky valves (non rotating) would result in no ignition? i definitely have starting issues below 40°, I figure it was because I don’t have much experience here in south Florida. Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 17, 2023 Report Share Posted January 17, 2023 20 minutes ago, ArtVandelay said: 1) Cars don’t have a problem with fuel evaporation at lower temperatures, why do planes (especially fuel injection engines)? 2) Why do sticky valves (non rotating) would result in no ignition? 3) i definitely have starting issues below 40°, I figure it was because I don’t have much experience here in south Florida. Temperature is everything… 1) Cars don’t use 100LL! Car gas also have winter formulations… 100LL has some magic properties that we don’t often discuss… like stability for years. Car gas has a tendency to detonate when CHTs get hot… The opposite is true as well… old car gas has the lighter, easy to evaporate part, leave the system… getting a car started in the winter… can be really hard with year old gas in it… 2) If a valve is stuck open, there is no compression, essentially skipping the compression stroke. Compression is needed for the whole process to work as expected… If the valve is stuck somewhat closed the exhaust stroke isn’t working as expected… 3) There is a chart for evaporation rate of 100LL vs temp… it is worth taking a look at. Cold start for the IO550 has two different priming times… to specifically cover the rate of evaporation… and once started, the low boost pump is used to supply a little extra fuel until things warm up… Adding extra fuel is an odd way to handle the evaporation rate change… especially when time is involved… but, it works… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
PT20J Posted January 17, 2023 Report Share Posted January 17, 2023 1 hour ago, ArtVandelay said: Cars don’t have a problem with fuel evaporation at lower temperatures, why do planes (especially fuel injection engines)? Why do sticky valves (non rotating) would result in no ignition? i definitely have starting issues below 40°, I figure it was because I don’t have much experience here in south Florida. Great questions. The first thing to think about is that engines cannot burn liquid gasoline. The fuel must be vaporized and well mixed with the appropriate amount of air to combust. The carburetor or fuel injector nozzle does not vaporize the fuel but instead breaks it up into tiny droplets in the proper proportion to the airflow which vaporize and mix with air more readily. Once the engine is running the cylinders warm up and provide the heat to vaporize the fuel. During starting when the engine is cold, the only heat source is the compression heating in the cylinder. To prevent vapor lock at high altitude, avgas doesn't vaporize quite as readily as mogas so it is harder to get the fire going than in your car. Also, automobile engines generally have higher compression ratios than aircraft engines, and the higher the compression ratio, the more heat generated by the compression stroke. Sticky valves are caused by deposits on the valve guides. Burned valves are caused by failure to rotate. If a valve sticks open, the cylinder will have no compression and will not generate power. If a valve sticks closed, exhaust gasses cannot escape and will dilute the incoming mixture charge to the point where it will not burn. Depending on the cylinder design, if a valve sticks open, it may contact the piston. If a valve sticks closed, it can result in a bent pushrod. Skip 1 1 Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 17, 2023 Report Share Posted January 17, 2023 A valve really can’t stick closed and block exhaust gasses from escaping, without engine damage. A mechanical force is transmitted to the valve to open it, it MUST open, if it doesn’t then something will either bend or break, often the pushrod, but sometimes the cam follower or even the rocker arm or bosses on the head for the rocker shaft, but something must give. A spring is what closes a valve so a valve can stick partially open without damage and this is what usually happens in our stuck valve scenarios as the spring is weaker than the valve train, but if it sticks at the fully open point, then it WILL be closed by the piston, which particularly on angle valve engines isn’t pushing the valve closed in line with the valve but to the side, this is likely to bend the valve and worst case break off the head of the valve as Lycoming valves are two piece valves and break more easily than one piece, but even one piece valves (Continental) can break. Most often it’s the exhaust valve as it’s hottest and most likely to build up deposits, Lycomings are more likely to stick as they are cooled with sodium, this cooling is through the valve stem, which means the stem is hotter than an uncooled valve A valve head is a big chunk of metal, laid on its side it won’t fit in the space left when a piston is at TDC, so it destroys the piston and head. Remember at 2,000 RPM that piston is making a full stroke 40 times per second, so it doesn’t take long to be destroyed, this frees up the small end of the rod to bang around and the piston wrist pin too, if the rod breaks, then the portion still connected to the crank can start punching holes in the engine case etc. Many engines have been built that intentionally deactivate the valves and run quite happily on fewer cylinders in the search to save fuel, so a closed valve on its own won’t cause any damage, remember the Caddy 8-6-4 engine of the 70’s? So, treat a suspicion of a sticking valve VERY seriously, plus the cure isn’t real expensive and it’s easy to check for a sticking valve, called a wobble check, something that Lycoming recommends we do on a 400 hr interval, but don’t quote me on that, there are probably exceptions, and I think there might even be an improved valve guide that may not need inspecting, but I don’t know how you determine if you have that valve guide. https://www.lycoming.com/sites/default/files/Procedure to Determine Exhaust Value and Guide Condition.pdf Quote Link to comment Share on other sites More sharing options...
PT20J Posted January 17, 2023 Report Share Posted January 17, 2023 New valve guides have tight clearances and there is not much room for deposits to build up. As the guides wear, they become more susceptible to deposits and sticking. The motion of the rocker arm puts a side load on the valve stem which causes them to wear in a bell-mouth pattern. The 400 hr Lycoming wobble test (SB 388) is for pre-1996 valve guides. The newer higher chrome guides wear better and per SI 1485 can go to 1000 hrs before inspection. Skip 1 Quote Link to comment Share on other sites More sharing options...
Shadrach Posted January 17, 2023 Report Share Posted January 17, 2023 On 1/14/2023 at 2:52 PM, flyboy0681 said: Last night saw temps in the mid to high 40’s down here and I had asked my partner start the plane up today. He reported that she ran smoothly. I’m flying Monday morning when temps are forecasted to be in the 50’s, so we shall see. I start all the time in sub freezing temps with the engine preheated and in moderate temps (<60°) without preheat. It starts like a Guillow's rubber band model, often on the first blade. No abnormal vibration. A wobble test is not super invasive or expensive and will rule out a the simplest explanation. Quote Link to comment Share on other sites More sharing options...
Parker_Woodruff Posted January 17, 2023 Report Share Posted January 17, 2023 On 1/12/2023 at 10:12 AM, DXB said: I'll let others weigh in on whether that's diagnostic of a sticky exhaust valve or a transient fuel issue could explain it (I suspect not but I don't understand the fuel injected systems very well). This isn't the norm with a Lycoming IO-360. Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted January 17, 2023 Report Share Posted January 17, 2023 1 hour ago, Shadrach said: I start all the time in sub freezing temps with the engine preheated and in moderate temps (<60°) without preheat. It starts like a Guillow's rubber band model, often on the first blade. No abnormal vibration. A wobble test is not super invasive or expensive and will rule out a the simplest explanation. If you pre-heat, it’s not really cold starting, cold starting is when the engine is cold soaked. WWII the Germans couldn’t get their engines going, but the Russians could, story is from captured Russians the Germans learned how to dilute their oil with fuel. At just about any temp you can get a spark ignition engine going if the oil isn’t jello, may be tougher and require a lot more fuel than you would expect, the carburetor guys may have to slowly pump the primer once it lights as an example. Sticky valve is not one that’s not rotating, it’s one that sticks intermittently, usually when cold. Not rotating is a whole other thing, a completely free valve may not rotate and a tight one that sticks may rotate just fine. Guy who built my engine along with other things hones the valve guides to very tight tolerances, reaming leaves a rougher finish, think drilling a hole as opposed to reaming one, honing is even finer / smoother. ‘Our fuel injection is really very primitive compared to cars and at very low pressures so fuel doesn’t atomize well. Modern cars vary fuel quantity by how long the injector is open and keep high fuel pressure, an airplane varies fuel quantity by fuel pressure as the injector is always open, so at low RPM / starting it doesn’t atomize fuel well at all. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted January 17, 2023 Report Share Posted January 17, 2023 4 minutes ago, A64Pilot said: If you pre-heat, it’s not really cold starting, cold starting is when the engine is cold soaked. WWII the Germans couldn’t get their engines going, but the Russians could, story is from captured Russians the Germans learned how to dilute their oil with fuel. At just about any temp you can get a spark ignition engine going if the oil isn’t jello, may be tougher and require a lot more fuel than you would expect, the carburetor guys may have to slowly pump the primer once it lights as an example. Sticky valve is not one that’s not rotating, it’s one that sticks intermittently, usually when cold. Not rotating is a whole other thing, a completely free valve may not rotate and a tight one that sticks may rotate just fine. Guy who built my engine along with other things hones the valve guides to very tight tolerances, reaming leaves a rougher finish, think drilling a hole as opposed to reaming one, honing is even finer / smoother. Nothing is truly cold soaked in Florida when the OAT is in the mid 50s. That is prime flying weather in my neck of the woods. I don't preheat above 40° and the plane starts beautifully. In fact it will start sans prime in a few blades simply by cranking it with the mixture at full rich. Diluting oil with fuel is fine for war stories and bush pilots in extreme situations but with modern oils anyone in the lower 48 ought to easily be able to ready an engine for start under temp conditions that won't cause it run poorly. 1 Quote Link to comment Share on other sites More sharing options...
flyboy0681 Posted January 17, 2023 Author Report Share Posted January 17, 2023 I flew up to the northern part of the state and last night temperatures were in the low 40's. This morning the plane started on one blades and ran super smooth. At this time I'm going to consider the rough start a one-off event. Quote Link to comment Share on other sites More sharing options...
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