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  1. #1

    Join Date
    Aug 2004
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    zdz80 surges during idle

    I have a ZDZ80 with a 3W 26x10 which is about 1 years old with a little over 100 flights on it.
    Lately, the engine has been surging a bit at idle during flight. Example is when I am doing an inverted harrier and the throttle is pulled or kept slightly above idle, the engine surges and you can see it push the plane a bit. This is pretty new.

    Also, going from flight to stall to flat spin it sounds like it is going to die so I add throttle. It idles fast enough on the ground, but up in the air doing things like the flat spin or blender, or other 3D maneuvers it does not like so well. Tons of power in a hover, and picks up speed very well. High end is a rocket. Low end... not so good.

    Some extra information.. idle itself is not normal. It wants to die at lower RPM settings so I set it about 5 clicks higher when flying and when i want to land, lower it 5 clicks. Sometimes it slows down well, other times it still keeps the rpms pretty high, then comes down slowly.

    I adjusted the low end and found a spot where if you go from idle to full power it dies (lean I think) and the other end where it bogs down in the mid-range (rich). Neither of these seem to be doing the trick, though I am not a master of tuning the engine.

    The engine gets a bit hot maybe, though it is exposed on the front of a H9 Extra330S and the cylinder is in the airflow. I noticed the spinner is pretty warm (which I heard is not ideal). I richened the high speed needle just in case, but does not seem to make any difference.

    Sorry for the ton of info, but I wanted to paint as complete a picture as possible.

    --james vanwinkle

  2. #2

    RE: zdz80 surges during idle

    James, sounds like an airleak. Do you have oil residue on the engine anywhere?
    What oil and mix ratio are you using?
    Thanks,
    Mike Dooley
    RC Showcase

  3. #3

    Join Date
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    RE: zdz80 surges during idle

    I am using 32:1 Mobil 2XT oil.

    I will check the engine this evening for residue, but I don't think I have seen any.
    The air leak makes a lot of sense now that you mention it. It is also a bit harder to start the first flight and takes quite a few flips before it fires the first time.

    Thanks for your help. The last time I posted you helped me as well, and I really appreciate that.

    Best regards,
    James Vanwinkle


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