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Too much consumption of fuel

in 912 / 914 Technical Questions 6 years ago
Too much consumption of fuel!
My 912ULS engine drink 20-24liters/hour !! on 4800Rpm, 20hgmm manyfold pressure. The plane/engine are just after 500hours big inspection: new pipes, ignition, pipes, folters, etc. The ballance of the plane is corrected, and the prop is brand new (Woodcomp hydraulic regulated constant speed). Carburators are syncronised.The airplane is just after the 500hours total big inspection
The power probebly less than normal, but the compression of the cylindrrs are ok. Indicated air speed is going down from 180km/h to 150 km/h after 1 hour operation instead of constant 220km/h like a normal TL-Sting S4 Rg ul carbon airplane. I can not push the trottle more than 20-22 hgmm manyfold presure, becouse than the consumption of fuel increasing to 25-27liter/hour !!!
How can it drink 22-24 liter/hours or more on 4800Rpm on 20hgmm manyfold presure.
Carburator problem?
Does have anybody idea?
I am new on this site. I do not know if I get alarm about your answers. My email addres is vattayp@gmail.com
Thanks for all any help.
IMG_20180630_105105_2018-07-01.jpg (You do not have access to download this file.)

  • Re: Too much consumption of fuel

    by » 6 years ago

    What is your WOT rpm in level flight. You may be just over proped and that’s why you’re burning all that fuel you should get a minimum of 5500+ WOT in level flight.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Vattay Peter
      
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  • Re: Too much consumption of fuel

    by » 6 years ago

    Dear Roger,
    Thanks. As we talked about it, I ask you for the best understsnding to give me your detail instructions by email for the operation of trotl and constant speed prop in the next situations:
    -Taking off
    -Climbing
    -Cruising
    Waiting for your email.
    Thanks and the best regards:
    Peter Vattay
    vattayp@gmail.com
    Tel.: +36-30-200-7099
      
    Report

  • Re: Too much consumption of fuel

    by » 6 years ago

    ..and Roger, the max Rpm with fully open trotle is in flight 5850-5900 Rpm.
    Peter Vattay
    vattayp@gmail.com
      
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  • Re: Too much consumption of fuel

    by » 6 years ago

    Hi Peter,
    Nice talking to you yesterday.
    Here is what I gathered from our talk.
    You get 5800+ rpm at takeoff. Then you adjust the prop to only get 5200 rpm in level flight at WOT and then reduce the rpm with the throttle to cruise at 4800 rpm.
    If this is true then you are over pitched at that max WOT setting of only 5200 and then just cruising at 4800. This will burn a lot of extra fuel compared to a proper prop pitch setup. An over pitched prop will always use more fuel than a properly set one.

    Try this:
    Climb at your 5800 rpm. Once at altitude adjust the prop pitch to get at least 5500 - 5600 WOT. Once the prop pitch is set then just reduce the throttle to cruise between 5000 - 5200 rpm. Don’t cruise all the time in the 4K rpm range.

    While flying in level flight you should be able to advance the throttle any time and get that 5500 - 5600 without touching the prop setting.

    If I misunderstood in our conversation please correct me.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Too much consumption of fuel

    by » 6 years ago

    Wow! I will test it.
    My process was a little bit different, probaly I told it not clearly.
    1, Taking off: full trottle, max rpm pitch. 5850-5900 for some seconds. (15-20 seconds)
    2, climbing: On 30meter (100 feet) I reduced the trottle to 26-28manyfold pressure, and the pitch back for 5200Rpm.
    3, cruising: I reduced the pitch for 4800Rpm, and I reduced the trottle till the manifold pressure is max 26, or lower due to the high fuel consumption. The end result: 4800Rpm, 20-22 manifold pressure, and average 18-20-24 liter/hour consumption of fuel. I did not use higger Rpm or manifold presure, becouse the consumption of fuel was too high. The consumption gived the limitation for the trottle an for the prop. pitch.

    And now Your instruction is, wich I will follow, ( if I understand yuo well) is:
    1, taking off: full trottle, on 5800 full Rpm. ( we have to make a reducing correction on the ground calibration of the prop, becouse now the max Rpm is 5850-5900Rpm/ min. We will reduce for max 5800Rpm at cruising level)
    2, climbing: pitch back to 5500-5600, on max trottle,
    3, cruising: trottle back to arrange 5000-5200Rpm. If it is necesarry, I can change the trottle till 5500-5600Rpm, instead of the prop. pitch. During the cruising I do not touch the prop.pitch.

    I have hidraulic pitch. My question, that your instruction is relevant for this?
    I thoought before your instructiom, that 5000Rpm/min. or higher Is not good for the engine, and this high Rpm reduce the long life of the engine. You mean, that the Rotax912 ULS3 engine is desined in cruising situation between 5000-5600Rpm/min.? This is very very close to the maximum 5800Rpm....

    On this site I do not find how to attach an excel table. I have a test result about the 2 blade Woidcomp prop. like mine. ( Rpm, manifold presure, speed, etc...If you send me your email address, I can send this test for you.
    Give me please reflection, if I understund well your instructions.
    Many many thanks and the best regards:
    Peter Vattay
      
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