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Thread: EGT during Take Off - Do they look normal

  1. #1
    Junior Member
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    Default EGT during Take Off - Do they look normal

    Hi Folks Ive got a 2013 CC SS and I was after some feedback on recent EGT data. (Bearing in mind https://www.savvyanalysis.com/articl...myths-debunked )

    I had several instances of rough running after throttling back at circuit height in 12 months/100 hours -see other post this thread. So not often but annoying.

    Just recently I completed SB-22 (Upgrade to perforated fuel nozzle) by swapping out the original AvStar for a Marvel 5-6200 (MA-4SPA). Thanks to great support from Tac Aero maintenance. The new combo is running good but early days. I was hoping the Forum brains trust could venture an opinion of the engine monitor data around EGT since I have installed the new Marvel carby.

    Also attached is some cockpit video of when the engine data was generated - so you can see the actual engine monitor in HD video during the take off.

    www.youtube.com/watch?v=iYgIWXmU4e4&feature=youtu.be

    (Observation from video - after several seconds at full power you can see that I reduce the throttle slightly from 2480 to 2440/2450 - 31 sec into the video. Cylinder head temps for 3 and 4 start rising at this point.
    I wonder if this is enough of a reduction in richness to get the mixture to a more optimum lean setting for Cyl's 3 and 4 ?)

    EGT
    You can see that the EGT for cylinders for 3 and 4 rises but then does NOT increase in line with the increase in cylinders 1 and 2.

    Question
    1. Does this look normal ?
    2. If not - what does it indicate (mixture too rich ?, uneven fuel distribution ?, something else, nothing !!)

    Any insight welcomed.

    Engine monitor graph TO.jpg
    Last edited by CharlesTym; 11-11-2020 at 08:30 PM.

  2. #2
    Senior Member Clay Hammond's Avatar
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    Feb 2010
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    Hudson Valley, NY
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    Default Re: EGT during Take Off - Do they look normal

    I would run additional flight tests to gather more data. Assuming you can see similar results in a full power climb as you do immediately after take off in the climb, go out and do climbs starting from the same altitude each time where you slowly add power from the straight and level up to a point where you are WOT. hold steady for several seconds at each power setting before advancing again. Do this both by holding a constant airspeed and by a constant rate of climb. Then do it all again but at full power from the start and instead adjusting mixture by increments instead. Gather all that comparative data and then start making conclusions. Much of flight test is making small little changes and measuring them for comparative analysis. That's what you need to do here. Break down the flight and power regimes you are experiencing the anomaly in to as much of a minute degree as you can.
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    Clay Hammond

  3. #3
    Administrator Pete D's Avatar
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    Default Re: EGT during Take Off - Do they look normal

    EGT
    You can see that the EGT for cylinders for 3 and 4 rises but then does NOT increase in line with the increase in cylinders 1 and 2.

    Keep in mind, moving the throttle back from WOT changes the throttle plate in the carburetor from vertical to an angle which changes how the fuel/air mixture is split between the aft two cylinders vs the forward two cylinders. As the throttle plate moves away from vertical it causes swirls that change the fuel air ratio differently for Cyls 1 and 2 vs 3 and 4.
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

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