100LL addivtives to reduce plug fouling

Discussion in 'Flight Following' started by Scott MacKie, Feb 2, 2021.

  1. Scott MacKie

    Scott MacKie Pre-Flight

    Joined:
    Oct 24, 2020
    Messages:
    50
    Location:
    Woodstock, GA
    Display Name:

    Display name:
    sbmackie
    Have a mogas STC, not always available, is there an additive that can help reduce lead fouling of plugs if using 100LL?

    Thanks
     
  2. GeorgeC

    GeorgeC Administrator Management Council Member PoA Supporter

    Joined:
    Dec 5, 2010
    Messages:
    3,606
    Display Name:

    Display name:
    GeorgeC
    TCP. Also, lean aggressively on the ground. Also also, UREM37BY plugs.
     
    Last edited: Feb 2, 2021
  3. SoonerAviator

    SoonerAviator Final Approach

    Joined:
    Jul 21, 2014
    Messages:
    6,280
    Location:
    Broken Arrow, OK
    Display Name:

    Display name:
    SoonerAviator
    Not so much of an additive, but pull red knob toward you until engine stumbles, then push in slightly. Plug fouling now minimized.
     
  4. Hang 4

    Hang 4 Cleared for Takeoff

    Joined:
    Aug 18, 2017
    Messages:
    1,103
    Display Name:

    Display name:
    Hang 4
    All of the above plus fine wire plugs for an expensive, but really works, solution
     
    Omalley1537 and WannFly like this.
  5. EdFred

    EdFred Taxi to Parking

    Joined:
    Feb 25, 2005
    Messages:
    26,056
    Location:
    Michigan
    Display Name:

    Display name:
    Ed Frederick
    Air. Cheapest additive there is.
     
  6. Magman

    Magman Pre-takeoff checklist

    Joined:
    Oct 30, 2020
    Messages:
    228
    Display Name:

    Display name:
    Magman
    Lycoming published an SI that addressed fouling in the O-235L2C S in a 152.

    During your Post Flight Run -up ( you do them?) at about 1800 RPM for 30 secs

    you lean mixture.

    Great time to check mags too!

    One Flight School had issues and the technique eliminated the problem.
     
  7. Scott MacKie

    Scott MacKie Pre-Flight

    Joined:
    Oct 24, 2020
    Messages:
    50
    Location:
    Woodstock, GA
    Display Name:

    Display name:
    sbmackie
    OK fella's I understand leaning. Do it all the time, lean before takeoff for density altitude, etc. I'll go find some Tom Cat ****.
     
  8. EdFred

    EdFred Taxi to Parking

    Joined:
    Feb 25, 2005
    Messages:
    26,056
    Location:
    Michigan
    Display Name:

    Display name:
    Ed Frederick
    REALLY lean it out. Like to the point that adding any RPM kills the engine.
     
    denverpilot likes this.
  9. mondtster

    mondtster En-Route

    Joined:
    Nov 25, 2011
    Messages:
    3,327
    Display Name:

    Display name:
    mondtster
    It may seem obvious but make sure the engine is well maintained and running the best it can. I have had very little plug fouling trouble with any of the common flat engines that most people fly when they are properly cared for. That is with only a mediocre effort to lean the mixture as well.

    And before someone feels the urge to point it out, yes I am aware that some engine models are more fussy than others. Some of the ones I am referring to are the fussy ones and they were in a training environment too.
     
  10. FastEddieB

    FastEddieB Touchdown! Greaser!

    Joined:
    Oct 14, 2013
    Messages:
    10,073
    Location:
    Lenoir City, TN/Mineral Bluff, GA
    Display Name:

    Display name:
    Fast Eddie B
    Decalin is used by many ROTAX owners when forced to use 100LL, myself included.

    Not sure it’s applicability to “legacy” engines.
     
    mcdewey likes this.
  11. eman1200

    eman1200 Touchdown! Greaser!

    Joined:
    Mar 10, 2013
    Messages:
    13,162
    Display Name:

    Display name:
    eman1200
    how does one "add air"?
     
  12. LesGawlik

    LesGawlik Pre-takeoff checklist

    Joined:
    May 6, 2006
    Messages:
    108
    Display Name:

    Display name:
    Les
    The iridium plugs have been magic for me. Instant starts, smooth running and less wet dog shakes on shutdown.
     
  13. IK04

    IK04 Pattern Altitude

    Joined:
    Nov 6, 2018
    Messages:
    2,282
    Location:
    Copperas Cove, Texas
    Display Name:

    Display name:
    LNXGUY
    The O-235 in the Early C-152s was the worst case for plug fouling. Even with TCP and constant leaning and the high RPM shutdown, the low-compression pistons made removal and cleaning of all eight plugs every 20-25 hour necessary.
     
  14. mondtster

    mondtster En-Route

    Joined:
    Nov 25, 2011
    Messages:
    3,327
    Display Name:

    Display name:
    mondtster
    Take away fuel.
     
    Huckster79 likes this.
  15. eman1200

    eman1200 Touchdown! Greaser!

    Joined:
    Mar 10, 2013
    Messages:
    13,162
    Display Name:

    Display name:
    eman1200
    right, because I have one of those "take away fuel" levers but I don't have an "add air" lever.
     
    Omalley1537 and Scott MacKie like this.
  16. Bell206

    Bell206 En-Route

    Joined:
    Oct 6, 2017
    Messages:
    4,056
    Display Name:

    Display name:
    Bell206
    And the throttle does what..........;)
     
  17. eman1200

    eman1200 Touchdown! Greaser!

    Joined:
    Mar 10, 2013
    Messages:
    13,162
    Display Name:

    Display name:
    eman1200
    it makes the plane make loud zoomy zoom engine noises
     
  18. mondtster

    mondtster En-Route

    Joined:
    Nov 25, 2011
    Messages:
    3,327
    Display Name:

    Display name:
    mondtster
    Think about it. Fuel has mass and takes up space. If you remove some fuel from the intake port there is more room for air.

    This is a big problem in high horsepower port injected applications and one advantage to direct injected engines.
     
  19. eman1200

    eman1200 Touchdown! Greaser!

    Joined:
    Mar 10, 2013
    Messages:
    13,162
    Display Name:

    Display name:
    eman1200
    so then we agree, the action taken is to reduce the fuel..........
     
  20. mondtster

    mondtster En-Route

    Joined:
    Nov 25, 2011
    Messages:
    3,327
    Display Name:

    Display name:
    mondtster
    Which is what I said from the beginning.
     
  21. EdFred

    EdFred Taxi to Parking

    Joined:
    Feb 25, 2005
    Messages:
    26,056
    Location:
    Michigan
    Display Name:

    Display name:
    Ed Frederick
    it is a it is a seesaw of stoichiometry
     
  22. SoonerAviator

    SoonerAviator Final Approach

    Joined:
    Jul 21, 2014
    Messages:
    6,280
    Location:
    Broken Arrow, OK
    Display Name:

    Display name:
    SoonerAviator
    Supercharger/turbocharger? :)
     
  23. MauleSkinner

    MauleSkinner Final Approach

    Joined:
    Oct 25, 2005
    Messages:
    8,873
    Location:
    Wichita, KS
    Display Name:

    Display name:
    MauleSkinner
    Say that three times real fast. ;)
     
  24. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    7,257
    Display Name:

    Display name:
    Dan Thomas
    We had a Citabria 7ECA with the O-235 and had to clean the plugs that often. Lots of time in the circuit made it like that. I finally replaced all eight plugs with UREM37BYs and the problem instantly disappeared. I also put those plugs in the other engines for which they were approved. The engine even runs better with them, since the spark is farther out in the air/fuel mix. I've sometimes wondered if there are sometimes exhaust gases lingering in the plug well of ordinary plugs that can inhibit ignition performance.
     
  25. mondtster

    mondtster En-Route

    Joined:
    Nov 25, 2011
    Messages:
    3,327
    Display Name:

    Display name:
    mondtster
    Ive always used 37BYs as well and have had similar results. Some of the old mechanics I’ve worked with refused to use them and thought I was dumb for doing so but I’ve always had good results even on engines known for fouling plugs.

    The recess in which Lycoming likes to put their spark plugs is a mystery to me. It’s as if they went out of their way to create a collection point for oil and lead and intentionally reduce power and efficiency.
     
    Dan Thomas likes this.
  26. LesGawlik

    LesGawlik Pre-takeoff checklist

    Joined:
    May 6, 2006
    Messages:
    108
    Display Name:

    Display name:
    Les
    If you don't want to buy 8 iridium plugs, just get 4 and put them in the lower holes. That's what I did, and it worked perfectly. I also used TCP, and that helped but not nearly as much as the plugs.
     
    Hang 4 likes this.
  27. Ghery

    Ghery Touchdown! Greaser!

    Joined:
    Feb 25, 2005
    Messages:
    10,521
    Location:
    Olympia, Washington
    Display Name:

    Display name:
    Ghery Pettit
    Lean the mixture. Pull the red knob out a bit.
     
  28. Dana

    Dana Pattern Altitude

    Joined:
    Oct 19, 2016
    Messages:
    1,983
    Location:
    CT & NY
    Display Name:

    Display name:
    Dana
    As I understand it, it works fine on older engines but unlike TCP it's not approved for use on standard category aircraft, experimental only.
     
  29. Daleandee

    Daleandee Cleared for Takeoff

    Joined:
    Mar 4, 2020
    Messages:
    1,101
    Display Name:

    Display name:
    Dale Andee
    In my uncertified air cooled conversion engine I use Decalin (for experimental only - certified requires TCP) and the dreaded Marvel Mystery Oil in the fuel. I've even been known to use a bottle of engine cleaner containing P.E.A. (polyether-amine) every once in a while to help keep the engine clean.

    Other than that it's about very aggressive leaning and the use of Iridium plugs. I use Mogas when I can get it but the octane requirement for my engine usually requires me to use some 100LL also.
     
  30. chemgeek

    chemgeek Pattern Altitude

    Joined:
    Dec 5, 2009
    Messages:
    2,349
    Display Name:

    Display name:
    chemgeek
    TCP works.
     
  31. Magman

    Magman Pre-takeoff checklist

    Joined:
    Oct 30, 2020
    Messages:
    228
    Display Name:

    Display name:
    Magman
    Spark Plugs were just one of the lead issues on the O-235L2C.

    Lead would build up on Piston Tops and strike the Cylinder Head!

    You could feel and hear the contact .

    Lycoming developed a procedure to blast the build up with wheat or rice

    with the cylinders installed.
     
  32. denverpilot

    denverpilot Tied Down PoA Supporter

    Joined:
    Nov 8, 2009
    Messages:
    54,856
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Nobody is pointing out that if it's an STC then the engine was designed to run on leaded fuel to start with. If it's fouling technique or something else is wrong. MoGas isn't the as solution, it's just masking the problem.
     
  33. Dana

    Dana Pattern Altitude

    Joined:
    Oct 19, 2016
    Messages:
    1,983
    Location:
    CT & NY
    Display Name:

    Display name:
    Dana
    Not necessarily. 100LL has a lot more lead than the 80/87 many older engines were designed to run on. An engine designed to run on 80 or lower (the A-65 in my T-Craft specified 73 octane minimum) will have lead fouling issues on 100 even if it's in perfect shape.
     
    Magman likes this.
  34. MBDiagMan

    MBDiagMan En-Route

    Joined:
    May 8, 2011
    Messages:
    4,211
    Location:
    NorthEast Texas
    Display Name:

    Display name:
    Doc
    The best medicine is leaning as much as possible without killing the engine while on the ground. My first reaction to an additive that claimed to prevent spark fouling would be to think of it as snake oil.
     
  35. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    7,257
    Display Name:

    Display name:
    Dan Thomas
    Yup. From memory, when I taught Aircraft Systems in college:

    80/87 (now known as 80) had 0.5 ml/gallon of TEL (note the silly mix of metric and US measures). 73 octane would have had even less lead.
    100/130 (known as 100) had 4.0 ml/gallon. That stuff really fouled plugs in little low-compression engines. Eight times the lead of 80/87.
    100LL has 2.0 ml/gallon.

    I looked up current all-metric numbers on Wiki:

    80 .14 g/l
    100LL 1.12 g/l
    100 .56 g/l
    115/145 (115), the old warbird fuel, had 1.29 g/l. Seems to me there are racing fuels still available with that chemistry.
     
  36. denverpilot

    denverpilot Tied Down PoA Supporter

    Joined:
    Nov 8, 2009
    Messages:
    54,856
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Most were listed as not only the 80/87 but also the purplish stuff in the POH. Unless they were some 70s newcomer to the block that wasn't originally a 1930s tractor engine.

    This stuff is ancient.

    People were putting total garbage fuels thru them before I was born.

    It's mainly technique as others have pointed out. Lean aggressively on the ground means enough the engine will die if you advance the throttle.

    All the oldsters knew this. Their other equipment and their cars needed it when they were kids.

    It ain't the MoGas. That's all I was saying. These engines barely care at all what's put thru them if they aren't a turbo model. Especially carbed ones.

    As my altitude aggressive leaning is pretty much always a requirement.
     
  37. Mooney Fan

    Mooney Fan Line Up and Wait

    Joined:
    Sep 17, 2017
    Messages:
    920
    Location:
    Indian Mound, TN
    Display Name:

    Display name:
    Mooney Fan
    A little dab of Marvel Mystery oil will do ya
     
    denverpilot likes this.