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  1. #1

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    Tuned Muffler header length adjustments.

    Hi all,
    Ihave a MVVS 49 now with a tuned silencer (thanks Pe&acute intended for control line stunt use and will probably target only 9000 rpm in flight, depending on prop choice but certainly no more than 10 000.
    Now as the factory says these pipes state of tune kicks in at 13 000rpm and that is with the standard length header pipe.

    So ............ would it be possible to lower the tuned point of the pipe to suit the intended rev range of the engine by simply lengthening the header?

    Iknow that some latitude is given in respect to which engine that tuned silencer works with since the one size works with the 40, 45 and 49 and its only the header length that varies.
    I know that the Akrobat silencer has the internal pipe a bit shorter than any other 'tuned silencer.'
    I also know that my stunt MVVS 51 wil run at about 10 500 rpm and has a standard tuned silencer with no header pipe length at all and it runs without 'tuned' benefit quite well.
    And I have read about MVVS engines using a smaller than standard tuned silencer and working at a higher rev range.

    So perhaps an experiment is in order and Iwas thinking that double the header length may be a good place to start.

    Thoughts?

  2. #2

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    RE: Tuned Muffler header length adjustments.

    while it is possible to adjust the peak point of a tuned pipe. are you talking about the short approx 6-7 inch muffler or a true tuned pipe with muffled expansion chamber? if it is the muffler it is almost impossible to properly "detune" down in rpm. i would recommend a standard expansion style muffler as the detuned one will actually rob power from the motor.

  3. #3

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    RE: Tuned Muffler header length adjustments.


    ORIGINAL: resourcecapital

    while it is possible to adjust the peak point of a tuned pipe. are you talking about the short approx 6-7 inch muffler or a true tuned pipe with muffled expansion chamber? if it is the muffler it is almost impossible to properly "detune" down in rpm. i would recommend a standard expansion style muffler as the detuned one will actually rob power from the motor.
    Hi mate,
    I refer to the tuned silencer that MVVS make or the mini pipe as it may be known to others, not the full length pipe that the speed and pattern guys use.

    A 'detuned' MVVS mini pipe is of no detriment to the engine for control line stunt use, in fact its a definite plus as it controls the engine run by way of back pressure.

    What I was wondering about is if Ican use that back pressure control AND still get the engine to pick up some power by finding a way to get the pipe on tune at the revs I intend to use.


  4. #4

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    RE: Tuned Muffler header length adjustments.

    that is the pipe that i thought you were speaking of. just could not think of the name mini pipe. the timing of the return pulse is multifold and works generally only for a very small rpm range. it can be adjusted just like the full tuned pipe but as i said generally it is designed for the higher rpms.
    first select the prop you want to use along with the fuel that you plan to run. keeping the same fuel is critical as the flame front pulse changes from brand to brand, oil mix, and nitro content.
    run engine without any muffler, port adapters etc. peak engine and get rpm. write it down as your base referance.
    install mini pipe re-run engine get rpm (most likely rpm will drop significantly)
    this is where it gets tedious and can get expensive
    1 inch at a time lengthen distance from center of glow plug following the curve of the adapter to the muffler. it may take 5-8 inches to get the rpm change into the correct area.
    the correct area is determined by a rise in rpm, flattening out and then dropping again.
    once it drops start shortning the extension by 1/8 inch at a time till it peaks. this is the sweet spot for that fuel, day, engine, glow plug (yes they do make a major difference)
    all of this testing needs to be done in a fairly short period of time as all weather variables combine to screw things up.

    many years ago i was a sponsered r/c boat racer with full tuned pipes runnng 70%nitro at 30k rpm+ using ops engines up at a rate of 4 or 5 engines in a day. (do we say pushed to the max)
    good luck i hope you can make the adjustments work at those low rpms.

  5. #5

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    RE: Tuned Muffler header length adjustments.

    Ok, 5 to 8 inches - that's what I will work from then.

    Probably easier to start at 8 and trim it back down but what concerns me is the volume of the canister may not be large enough to resonate at those lower rpm.

    And by the way, full length pipes can be tuned as a means of control at control line stunt rpm so here is hoping that the MVVS folded pipe can be too!

  6. #6

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    RE: Tuned Muffler header length adjustments.

    if as you are shortning the additional pipe length if rpm drop it is still to short.

    i tried this on a 45 size motor and it would not work.

    timing on the exhaust port was not correct.

    and yes the volume of the mini pipe is also a factor in generating the correct return wave pulse.

    good luck let me know if you can get it to work



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