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Thread: Mixture Control Creep

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    Senior Member kiwibob's Avatar
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    Default Mixture Control Creep

    The mixture control on my FX-3 has started to creep rich in the cruise (I lean LoP using Fuel Flow per the manual).

    Anyone know if there's a simple fix to this?
    Bob Gray, FX-3 #38, ZK-FXC

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    Senior Member Andy's Avatar
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    Default Re: Mixture Control Creep

    Quote Originally Posted by kiwibob View Post
    The mixture control on my FX-3 has started to creep rich in the cruise (I lean LoP using Fuel Flow per the manual).

    Anyone know if there's a simple fix to this?
    Would you please give a reference to any CubCrafters recommendation or procedure for LOP operation. All AFM settings are for 50 deg F ROP

    By "creep" do you mean the mixture control actually moves or that the mixture changes for a fixed mixture control position? I have never seen the mixture control move, or the fuel flow change, from what I have set.

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    Senior Member kiwibob's Avatar
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    Default Re: Mixture Control Creep

    Quote Originally Posted by Andy View Post
    Would you please give a reference to any CubCrafters recommendation or procedure for LOP operation. All AFM settings are for 50 deg F ROP

    By "creep" do you mean the mixture control actually moves or that the mixture changes for a fixed mixture control position? I have never seen the mixture control move, or the fuel flow change, from what I have set.
    Hi Andy, I follow Superior XP360 Operators Manual (XPOM360) 4.10 Leaning to Flowmeter, there's a bunch of graphs for different power settings. Aero Sport Power supplied me with the manual.

    By creep it's the mixture control gradually moving in (more rich).....
    Bob Gray, FX-3 #38, ZK-FXC

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    Senior Member Andy's Avatar
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    Default Re: Mixture Control Creep

    Quote Originally Posted by kiwibob View Post
    Hi Andy, I follow Superior XP360 Operators Manual (XPOM360) 4.10 Leaning to Flowmeter, there's a bunch of graphs for different power settings. Aero Sport Power supplied me with the manual.

    By creep it's the mixture control gradually moving in (more rich).....

    Thanks for the reference. My FX-3 (serial 0100) has the Lycoming built engine so I assume that explains the difference. My mixture control has multiple fixed detents and there is no way it could slip or creep. I understand that a vernier mixture control was offered as an option. Was there an earlier, non vernier, mixture control that had no detents?

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    Senior Member Andy's Avatar
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    Default Re: Mixture Control Creep

    Quote Originally Posted by kiwibob View Post
    Hi Andy, I follow Superior XP360 Operators Manual (XPOM360) 4.10 Leaning to Flowmeter, there's a bunch of graphs for different power settings. Aero Sport Power supplied me with the manual..

    Well I tried to find that document but couldn't. Superior seems to combine installation and operation of the O-360 and IO-360 in this document - https://www.superiorairparts.com/fil...42/SVIOM01.pdf.

    I only found one reference to LOP operation "Do not lean beyond 50įF lean of peak on fuel injected engines" and no fuel flow plots for LOP operation. Did I miss something or has Superior changed their recommendations?

    BTW I have no intention of opening a discussion on the merits of LOP operation. I am well aware of the conflicting advice on the subject.

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    Senior Member kiwibob's Avatar
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    Default Re: Mixture Control Creep

    Quote Originally Posted by Andy View Post
    Thanks for the reference. My FX-3 (serial 0100) has the Lycoming built engine so I assume that explains the difference. My mixture control has multiple fixed detents and there is no way it could slip or creep. I understand that a vernier mixture control was offered as an option. Was there an earlier, non vernier, mixture control that had no detents?
    That's interesting, the CC website still talks about the CC363i, is this no longer Aero Sport Power's engine?

    My mixture is a simple pull knob, it does have detents in the sens that it clicks but there's no vernier.

    I'll PM you about the manual.
    Bob Gray, FX-3 #38, ZK-FXC

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    Default Re: Mixture Control Creep

    In this post on my forum thread, I have several attached files at the bottom you can download.

    http://forum.cubcrafters.com/showthr...ll=1#post23102

    This is the correct manual they said to use for the 363i that was made by Superior and assembled by Aerosport. The newer engines being shipped now (which I havenít run yet) are done by Lycoming.

    file:///Users/davidembry/Downloads/Superior%20O360%20Engine%20Manual.pdf

    Note..... their manual (page 39 & 40) says to NEVER run engine between peak EGT and 75 ROP. 50 ROP is the WORST place for an engine and they state this in the manual. For more info, research Savvy Aviation, Mike Busch articles and videos on the RED BOX. Here is one link to an article but go to savvy aviation and Youtube for many more articles, etc on the subject.

    https://resources.savvyaviation.com/...ox-red-fin.pdf

    For performance cruise at or above 75%; 75 ROP. For economy cruise at 75% or less...... lean to peak EGT or -50 LOP.

    On the 363i (once broken in) I have found it best to use the LEAN ASSIST function (or just watch EGT's) and just lean while watching EGT's. Once they peak and start to fall again, continue leaning to 20-30 LOP while watching the CHT's. Continue LEANING until you get the CHT's where you want them. The more you lean, the more the CHT's will drop (once you are lean enough for the CHT's to start to drop). I like to keep them 370-390ish. I've never had a problem with these engines running very LOP. The carburetor engines (like 340) can get touchy running LOP and go rough many times before you can get them lean enough.

    Contrary to old wives tale, you can't hurt an engine going lean. Rough maybe and loose power.....but you can't hurt it (otherwise we wouldn't be shutting it down going lean).

    Once I start up, I immediately lean back to where it will just idle at 1,000 - 1,200 rpm so that if I give it more power (like to taxi) it might stumble. Then I enrichen only enough to taxi. These plugs can foul when idling at full rich for very long.

    Also by being VERY lean.....if you happen to forget to enrighen before run-up or take-off......you'll know it quick when it won't run up! (safety factor)


    Quote Originally Posted by Andy View Post
    Well I tried to find that document but couldn't. Superior seems to combine installation and operation of the O-360 and IO-360 in this document - https://www.superiorairparts.com/fil...42/SVIOM01.pdf.

    I only found one reference to LOP operation "Do not lean beyond 50įF lean of peak on fuel injected engines" and no fuel flow plots for LOP operation. Did I miss something or has Superior changed their recommendations?

    BTW I have no intention of opening a discussion on the merits of LOP operation. I am well aware of the conflicting advice on the subject.
    Last edited by Daveembry; 02-16-2021 at 06:42 PM.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

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    Senior Member Andy's Avatar
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    Default Re: Mixture Control Creep

    Quote Originally Posted by kiwibob View Post
    That's interesting, the CC website still talks about the CC363i, is this no longer Aero Sport Power's engine?

    My mixture is a simple pull knob, it does have detents in the sens that it clicks but there's no vernier.

    I'll PM you about the manual.
    CC363i is the CubCrafters engine designation but it doesn't indicate who built it. At one time CubCrafters was using two suppliers but all recent FX-3 registrations seem to show engine as Lycoming. Mine is Lycoming built and came with Lycoming test documentation. The AFM and Lycoming documentation suggest leaning to 50 deg F rich of peak which is a much disputed technique.

    Sound like you have the same mixture control as I do. I don't understand how it could slip unless it is defective. The detents in my mixture control are very positive.

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    Senior Member kiwibob's Avatar
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    Default Re: Mixture Control Creep

    Quote Originally Posted by Daveembry View Post
    On the 363i (once broken in) I have found it best to use the LEAN ASSIST function (or just watch EGT's) and just lean while watching EGT's. Once they peak and start to fall again, continue leaning to 20-30 LOP while watching the CHT's. Continue LEANING until you get the CHT's where you want them. The more you lean, the more the CHT's will drop (once you are lean enough for the CHT's to start to drop). I like to keep them 370-390ish. I've never had a problem with these engines running very LOP. The carburetor engines (like 340) can get touchy running LOP and go rough many times before you can get them lean enough.

    Contrary to old wives tale, you can't hard an engine going lean. Rough maybe and loose power.....but you can't hurt it (otherwise we wouldn't be shutting it down going lean).

    Once I start up, I immediately lean back to where it will just idle at 1,000 - 1,200 rpm so that if I give it more power (like to taxi) it might stumble. Then I enrichen only enough to taxi. These plugs can foul when idling at full rich for very long.

    Also by being VERY lean.....if you happen to forget to enrighen before run-up or take-off......you'll know it quick when it won't run up! (safety factor)
    Thanks Dave, A most helpful post.

    I don't have a lean assist function (or if I do I don't know about it, I have the EI engine monitor) and have been leaning to fuel flow. This results in CHT around 320-360F, cyls 2&4 are always 20-30F hotter for some reason. I pretty much always run economy cruise 23"x2300 as the performance cruise only give an extra 5-10kts and burns a lot more gas.

    The tip about leaning for idle is most welcome, I've been running full rich until after t/o as I've been concerned about accidently "giving it the gravy" without going to full rich.
    Bob Gray, FX-3 #38, ZK-FXC

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    Default Re: Mixture Control Creep

    Bob,

    Yes, going by fuel flow works well once you know where the sweet spot is so you can just lean to it. The "Lean Assist" function is on the G3X and simply tracks egt's by having all egt columns green as they go up but once they drop off the peak, they turn blue and show how many degrees LOWER than peak......either ROP or LOP you are as determined whether you are leaning or enriching after peak. It just eliminated your addition/subtraction and tallies it for you also showing on your fuel flow, a separate triangle for the fuel flow at the PEAK. If your fuel flow triangle on that same gauge is HIGHER than this PEAK triangle....then you are running ROP and vice versa.

    Excuse me if I go too elementary here but if you do have an EGT probe (or more), then from full rich just begin slowly leaning (1 click at a time) and watch egt's. They will rise until one cylinder starts to drop from peak. Now, if you continue leaning.....you will notice the egt's will continue to drop (no matter which way you go from here.....rich or lean). The CHT's may stay the same or even go up a bit at first but then as you continue to lean, the CHTs (which lag EGTs a good bit) will start to drop. The power also will drop and you may need to add more throttle if you want to keep the power up. You can continue leaning until the cht's are where you want them or the engine runs rough (or you loose too much power). Here you will notice a HUGE difference in fuel flow (way less) with the same power. On the lean side of peak (LOP), pretty much anywhere is OK..... 30-50% being the most common. Why not?

    Now also, once you reach the peak EGT, if you now RICHEN the mixture.....the EGT's will also begin to drop but you are now ROP and CHT's will be high at the peak and as you richen the mixture now, the cht's will again drop as will the EGT's and the FUEL FLOW WILL GO UP. So here you are..... EGT down from PEAK.....CHT's lower than PEAK (but still much higher than running LOP) ......same % of power.... BUT BUT BUT..... WAAAAAAAAAY higher fuel flow. Why would you???

    It's recommended if you run ROP (like for best performance cruise at 75% power or more or while breaking in a new rings), you should GO BIG OR GO HOME. Run it 75% or more ROP if are running ANY ROP. So on the ROP side, go 75% or more ROP and nothing in between. You will probably notice that even at full rich, when running ROP.....your CHT's will still stay much higher than when running LOP.

    Like you said, once you have determined what fuel flow at what power setting works for you, then you just just pull back the mixture in cruise to the fuel flow and you should be there without having to go through the discovery process again.

    If you read about the RED BOX....that is the area ROP from PEAK EGT to 50% ROP. This area is a DON'T GO THERE RED BOX. Don't even linger there any more than you have to.

    This is also for the fuel injected engine as the fuel flows/air mixtures normally are just not good enough between the cylinders to let it not run "Rough" = different in each cylinder.

    Every 363i engine I've run does exceptionally well LOP without roughness to as lean as I want to go. The induction air (intake manifold) is no doubt flow tested and custom made out of the carbon fiber and really flows even and true (as do the injectors), making this a very good engine that runs extremely smooth with consistent temps.




    Quote Originally Posted by kiwibob View Post
    Thanks Dave, A most helpful post.

    I don't have a lean assist function (or if I do I don't know about it, I have the EI engine monitor) and have been leaning to fuel flow. This results in CHT around 320-360F, cyls 2&4 are always 20-30F hotter for some reason. I pretty much always run economy cruise 23"x2300 as the performance cruise only give an extra 5-10kts and burns a lot more gas.

    The tip about leaning for idle is most welcome, I've been running full rich until after t/o as I've been concerned about accidently "giving it the gravy" without going to full rich.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

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