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Thread: carburetor heat recommendation for 912 ULS?

  1. #11

    Join Date
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    Default Re: carburetor heat recommendation for 912 ULS?

    yes for mandatory carb heat systems for Canadian home builts,
    so I put 600 hours on a Rans 912uls and twice the engine stumbled, the only explanation being carb ice must have been starting, they're cheap compared to being scared or damaging your plane. you/ll feel wonderful about that $ still in your bank account as the engine struggles to breath .... both times the rough running was almost hard to detect (like could have been missed by a passenger not tuned in to mechanics) and short lived, but what would it have been without the hot water jackets?
    and this reminds me, there is a new system with electric heat, improved from the earlier failure version that used a probe, and they are only 40 miles away, so I'll update when I confirm there service record - good timing for my K3 912ul rebuild project

  2. #12

    Join Date
    Jan 2015
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    Michigan
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    Default Re: carburetor heat recommendation for 912 ULS?

    Iíve seen the electric kits on the internets. Iím guessing they work off of the thermoelectric Peltier principal. Note that any carbíd motor is subject to carb ice this includes any Lycoming. I was nearly killed in a C-150 that iced up on takeoff (Continental O-200). Per the NTSB my Mooney went down in NM in the 70ís due to the O-360-A1D icing up and they were unable to restart the engine in the air. I suppose it is a factor of the temperature, humidity, AND induction system. There is no way I would run without some sort of carb ice detection and mitigation system. Note that even the snowmobiles have carb ice mitigation systems built in (electric).

  3. #13
    Senior Member jrevens's Avatar
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    Default Re: carburetor heat recommendation for 912 ULS?

    Quote Originally Posted by chipjumper View Post
    ... Note that even the snowmobiles have carb ice mitigation systems built in (electric).
    I can imagine that snowmobiles might potentially be sucking up as much snow as air on occasion. Seems like "carb ice mitigation systems" would be standard equipment on them alright.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE

  4. #14

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    Default Re: carburetor heat recommendation for 912 ULS?

    Quote Originally Posted by hallschuch View Post
    Does anyone have any recommendations for adding carb heat to a 912 ULS? thanks in advance
    Hi, well for those who donít think you get carb ice on the 912 instalation on a Kitfox. I have to say are wrong because you do!
    I have a standard instillation where the heat is drawn from the exhaust shroud And directed to the carbs by selection. Now before I fitted a carb temperature probe too the carbs I would get rough running during selection of hot air ie top of descent or in cruise. I was suspicious of ice but couldnít be sure as the hangar chat was oh itís probably running richer when carb heat applied.
    So with that uncertainty I installed a carb temperature probe. Ahaa guess what carb ice, big time
    No more rough running keep that sucker warm, so as I said I have the old selection system however have fitted too other kitfoxes, the electrical heaters and water jacket type.

    The electrical version does draw a high load when selecting the highest setting watch you donít pull to many amps from the generator. Found strobes non essentials needed switching off when on high.

    2 the water jacket type does move the carbs further back which can cause the air filters to contact the fire wall so ensure your filters donít rub. Heat wise when the engines up to temp the carbs stay warm period so you canít select it on or off, this doesnít appear to effect performance.
    we operate in a rather wet environment in Scotland, moist air.
    Stay safe, Mike

  5. #15
    Senior Member Dorsal's Avatar
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    Default Re: carburetor heat recommendation for 912 ULS?

    When you say "standard installation" where is the air drawn from when heat is not selected?
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  6. #16

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    Default Re: carburetor heat recommendation for 912 ULS?

    Sorry should have mentioned that the filter is left of the gearbox
    at the front of the engine as per installation Manuel fitted to the carb heat box!
    scat tube to each carb.

  7. #17
    Senior Member jrevens's Avatar
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    Default Re: carburetor heat recommendation for 912 ULS?

    Sturdee,

    So, you are drawing air directly from outside the engine compartment when not using carb heat. It is a very different situation when the air is drawn from the relatively warmer top rear area of the engine compartment.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE

  8. #18
    Senior Member Dorsal's Avatar
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    Default Re: carburetor heat recommendation for 912 ULS?

    As John mentions, for many "standard installation" is filters directly on the back of the carbs or on an airbox located inside the top rear of the engine compartment. I believe this is a bit like running medium carb-heat all the time. I have not heard of anyone having carb-ice with this setup. If I were drawing outside air directly to the carbs I would include a heat option.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  9. #19

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    Default Re: carburetor heat recommendation for 912 ULS?

    Quote Originally Posted by jrevens View Post
    Sturdee,

    So, you are drawing air directly from outside the engine compartment when not using carb heat. It is a very different situation when the air is drawn from the relatively warmer top rear area of the engine compartment.
    Morning jrevens,
    the air box and filter are inside the top cowl as per the build Manuel Mk4 912 1993.
    Believe me ice is forming inside the carb. Have had manifold drop due too it before carb temp probe installed.
    the amount of air flowing through the round cowl in principal you would expect to be warmer after flowing over the engine however someone should measure that. As we know the carb temperature will be colder due to the mechanics of fuel vaporizing.
    I think most of the airflow travels down and out the bottom cowl as there is no baffles inside the cowl or need for them as water cooled heads, only air cooled barrels.
    I was sceptical until I had seen the probe temps so believe carb heat is nessecary especially in this climate.
    I can select on or off. Stay safe
    Sturdee

  10. #20
    Senior Member jrevens's Avatar
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    Default Re: carburetor heat recommendation for 912 ULS?

    Quote Originally Posted by sturdee View Post
    Morning jrevens,
    the air box and filter are inside the top cowl as per the build Manuel Mk4 912 1993.
    Believe me ice is forming inside the carb. Have had manifold drop due too it before carb temp probe installed.
    the amount of air flowing through the round cowl in principal you would expect to be warmer after flowing over the engine however someone should measure that. As we know the carb temperature will be colder due to the mechanics of fuel vaporizing.
    I think most of the airflow travels down and out the bottom cowl as there is no baffles inside the cowl or need for them as water cooled heads, only air cooled barrels.
    I was sceptical until I had seen the probe temps so believe carb heat is nessecary especially in this climate.
    I can select on or off. Stay safe
    Sturdee
    Thanks, Sturdee. Just to clarify, I believe that you have said that your outside air intake is adjacent to the gearbox, basically right at the front opening of the cowl. Your points are all well taken, but people have measured the air temp (as per a previous post on this thread) at the back of the engine near the firewall, and an increase in temperature of 10 deg. C over ambient was mentioned. I think it may be, & probably is higher with the smooth cowls that many of us are using now. However, many builder/owners with round cowls and carburetors with air filters directly mounted on them have never experienced carb ice over many thousands of hours of combined experience. I have a friend who has flown his Kitfox Mod. IV to every state in the United States except Hawaii, and almost every province in Canada, in all types of weather, and I don't think that he's encountered carb ice. I believe he is approaching 3,000 hrs. flight time in that airplane. He doesn't have carb heat. I have no doubt that you experience carb ice with your situation. Kitfox owners need to do what they feel is safe, all things being considered, and I respect your need for carb heat.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE

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