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Thread: Cylinder Head Temp Variation - comments appreciated

  1. #1

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    Default Cylinder Head Temp Variation - comments appreciated

    So, with my newfound information on EGT and CHT from my new digital EI gauge during flight, and; being somewhat tuned-up by the wise folks on this forum, I focused on my CHT numbers during a recent 1.5 hour flight around the patch. Up and down the beach from Cape Canaveral, over Patrick AFB and down to Melbourne airport, and the heading out east for some fun maneuvers and then back to Titusville with a couple touch and goes at Merritt Island I watched my CHT numbers carefully.

    Summary: my number ONE cylinder is living in a very cool and comfortable environment and my number FOUR cylinder is suffering.

    Number 2 and 3 are in between but closer to suffering with number 4.

    Here are the steady state (7 minutes - full rich) cruise -2,400 RPM, 117 mph (Air speed and ground speed average), 58 inch prop on a stock PA22 - numbers at 3,000 feet on an 83F degree day with somewhat high (86%) r-humidity (for the other states it's high, but a very nice day here) and low winds (7-12 mph at 120deg), blue skies with beautiful clouds in the distance.

    EI digital Cylinder Head Temps: 1) 266 2) 311 3) 330 4) 346 degrees F. Oil temps were well inside the green arc on my original mechanical gauge, but didn't record the numbers...230deg F comes to mind.

    Please advise what to do to try to get these CHT numbers in a tighter spread during flight. And, lower is better where I come from.

    Steve, if you want to combine this with some earlier threads on CHT and EGT for shortwings, that would be fine with me. So you know, I searched on EGT and CHT and combinations of that and got nothing. Zilch. CamTom has had a series of pertinent comments on this topic, as have others. I think you need a major title with EGT / CHT in SHORTWINGS.ORG. Don't know how to do that other than start another thread and I would prefer if someone else did that.

    In my short period of study, I find that the two things that kill engines in shortwings are internal corrosion and extreme spreads in CHT's. Just my research here, so do your own if you don't accept that.

    My argument for a separate subject is that there are so many variations in the way people are adjusting their engine cooling environments on their individual planes, (Cowlings, Baffles, Ducting, Oil cooler locations, Exhaust), I think it might be of interest. Just my opinion. Maybe a it's a summer vacation project for you (compiling all the contextual comments on this topic) when the storms are pounding us?

    I'd read it all.

    Thanks,
    Subsonic

  2. #2
    Pacerfgoe's Avatar
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    Default Re: Cylinder Head Temp Variation - comments appreciated

    I think the first thing you need to do is an evaluation of your baffling and pre-existing holes in the cowl.....Pics always help us nitpic...LOL. If you can limit the amount of air that gets into the lower cowl without either going through the cylinder fins or through a rear oil cooler that would help.
    I just spent about 2 weeks fitting new baffles to my cowl and I've pretty much got it tight as as you can get it, so it will be interesting what results I get.

    It's been said before, but these new engine monitors are terrible for us wanting to get all cylinder temps exactly perfect......when all we had was oil temp, nobody cared!
    Forrest Miller

  3. #3
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    Default Re: Cylinder Head Temp Variation - comments appreciated

    Yes, and I'll be interested to see what my plane will do...once it's back in the air, that is.... I've also been thinking about one of those digital temp gauges for CHT and EGT. How was your install, Subsonic? A hassle or not too bad? Cost...?

    In any case, now that I have new baffle seals, a couple new or repaired broken baffles, my handy-dandy gold-plated Univair carb air intake scoop.. etc. etc. I'm curious about how 57A will do; it certainly ought to at least be better than it was!

    (Battery now in, time to call the avionics guy -- closer and closer!)

    Walt

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    Administrator Steve Pierce's Avatar
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    Default Re: Cylinder Head Temp Variation - comments appreciated

    Those numbers look fine to me. We have used foil tape on the front of #1 and #2 to bring the temps up in line with the other cylinders and once we figured out where then I used a piece of aluminum bent 90 degrees and screwed to the front baffle. It is hard to closely balance an O-320 because the intake tubes are not of equal length. The cross vanes in the throat of the airbox is there to straighten the air out as it comes into the intake tubes and ven it out and some have installed the peppered fuel nozzle to get the temps closer. I think what you have looks good, might use foil tape to get #1 up a bit. I went and picked up an FX2 Carbon Cub a few days ago with just over 100 hours on it. It kept bumping 404-406 on #3 but finally settled in at just under 400 degrees and that is in the green.
    IMG_20200611_083148.jpg
    Last edited by Steve Pierce; 06-13-2020 at 06:37 AM.

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    Default Re: Cylinder Head Temp Variation - comments appreciated

    My #3 appears to the be hot one hitting 390 on climb out on a hot day. My coldest is number 2 (I believe) and it has been around 290-300, so my spread is hovering around 80-90. After climb out I believe that spread narrowed, but I will have to pay better attention in the future to give more accurate numbers throughout a full flight.

    my baffling might be the one part of my plane that seems to have been done mostly right, however I am missing the carb intake nose fork baffle.

  6. #6

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    Default Re: Cylinder Head Temp Variation - comments appreciated

    Sometimes more info isn’t really a good thing. When I had the Howard, I was having oil temperature issues. I called one of my friends that runs an ag business and asked him how he kept the oil temperature within limits on his R985 powered AgCats. His response was “masking tape”! What you can’t see won’t bother you. He further explained - just put masking tape over the gage!

    Like many, I’m a gadget nut, but these engines have been running fine for 70+ years. I’ve run O-320s as high as 7000 hours without overhaul in glider towing operations, perhaps the worst environment they could be in with full power to altitude and rapid descent. I’ve also run them for similar times in banner tow operations running full power or close to it for hours on end at 60mph or less. These engines like to be run hard! None of these airplanes had more than a single cht probe and oil temperature. Only one airplane (my TriPacer) had an EGT.

    Yes, these engine monitors are great tools, but too much info can cause you to over think the 1930 tractor technology that is what makes these engines as good as they are. Go fly the airplane, put that couple thousand $ into gas and fly more. Engines that fly over 300 hours a year will last much longer than engines that only fly 50 hours a year. I do ~50 annual a year. The average time on all those airplanes is less than 30 hours with some less than 10. If you want your engine to last, fly it more and run it hard!


    Sent from my iPad using Tapatalk

  7. #7
    CamTom12's Avatar
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    Default Cylinder Head Temp Variation - comments appreciated

    I disagree about hiding the info.

    I think 320-380 are ideal CHTs for cruise. In climb, I like to keep mine below 400, but usually end up with #1 around 405° on a hot day.

    If your CHTs are too cold, you might not be getting the lead scavenging you need to keep deposits from building in the cylinder or on the valves/stems/guides.

    I think your #1 is too cold and would experiment with foil tape to mask the front of that cylinder. I’m betting that’ll help bring your #4 down as well. If it doesn’t, you can mask #2 a little to balance the temperature spread on that side of the engine. Once you find the height, you can build metal plates like Steve recommended.

    In all though, your cruise CHTs look cool enough to not worry much about cowl sealing and whatnot. Just need to get #1 warmer in my opinion.

    EDIT: Just noticed your oil temp, it’s in the green but a little warm. Keep an eye on that but I don’t know that I’d stress it too much now. What’s it normally run on a hot day?

    What’s it look like if you lean? Do you normally lean or fly full rich?
    Last edited by CamTom12; 06-13-2020 at 10:48 AM.

  8. #8

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    Default Re: Cylinder Head Temp Variation - comments appreciated

    Quote Originally Posted by CamTom12 View Post
    I disagree about hiding the info.

    I think 320-380 are ideal CHTs for cruise. In climb, I like to keep mine below 400, but usually end up with #1 around 405° on a hot day.

    If your CHTs are too cold, you might not be getting the lead scavenging you need to keep deposits from building in the cylinder or on the valves/stems/guides.

    I think your #1 is too cold and would experiment with foil tape to mask the front of that cylinder. I’m betting that’ll help bring your #4 down as well. If it doesn’t, you can mask #2 a little to balance the temperature spread on that side of the engine. Once you find the height, you can build metal plates like Steve recommended.

    In all though, your cruise CHTs look cool enough to not worry much about cowl sealing and whatnot. Just need to get #1 warmer in my opinion.

    EDIT: Just noticed your oil temp, it’s in the green but a little warm. Keep an eye on that but I don’t know that I’d stress it too much now. What’s it normally run on a hot day?

    What’s it look like if you lean? Do you normally lean or fly full rich?

    I actually agree about not hiding the data.

    Now to the concept of adding or subtracting stuff to baffles beyond actually repairing what Piper put there, you do realize that per Part 43 Appendix A, that is a major alteration. Not saying it isn’t a good idea, just realize when you do it you are outside what the regulations allow.


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  9. #9
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    Cool Re: Cylinder Head Temp Variation - comments appreciated

    Mike Bausch has an interesting article on CHT's in the recent AOPA. He recommends 350 to 400 for Lycoming's as ideal. Cooler temps wear valve guides and lead to sticking valves. He says prolonged over 420 will shorten engine life.

    I usually exceed 400 on 3 and 4 during climb out. At cruise my 3 and 4 run in the high 300's. My oil temp run at 180 to 190, which is good.

    I know what is meant by too much information. All those years flying 150's, then my J3, I never had a CHT issue.....
    Last edited by Stephen; 06-13-2020 at 12:02 PM.
    "You can only tie the record for flying low."

  10. #10
    CamTom12's Avatar
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    Default Cylinder Head Temp Variation - comments appreciated

    Here’s my latest “high-power” cruise numbers:

    RPM: 2450

    OAT: 71° F

    Pressure Altitude: 1800’

    Density Altitude: 2990’

    Power: ~68%, maybe 109hp?

    CHTs:
    1: 389° F
    2: 365° F
    3: 383° F
    4: 381° F

    Oil Temp: 197° F

    EGTs:
    1: 1530° F
    2: 1545° F
    3: 1490° F
    4: 1570° F

    That’s leaned pretty good.



    Finally got the picture uploaded.
    Last edited by CamTom12; 06-13-2020 at 03:34 PM.

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