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  1. #51

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    RE: Rossi .81 FIRE

    Finally had a chance to bench run this thing.
    5% Nitro, 20% oil, 10x12 CF prop. Rossi with 8mm carb.
    I include the numbers for the YS 60. Both on pipe. Both on same prop.
    Rossi .81: 13900 rpm
    YS 60: 11750 rpm
    I AM IMPRESSED.

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  2. #52
    speedracerntrixie's Avatar
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    RE: Rossi .81 FIRE

    I think the 8mm carb is really holding it back. Did you try a longer header? The header I use on my .61 is 6.5". I'm getting 13,000 + with an APC 11X11.



  3. #53

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    RE: Rossi .81 FIRE

    I tuned the pipe. I will try a bigger carb but I dont totally dislike the 13.9K. It is a heavy prop, the YS can only turn it 11.75K.

    Do you think I can get more out of it?




  4. #54

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    RE: Rossi .81 FIRE

    I would add one or two shims to head and then try some 20-25 percent nitro, I agree the larger carb is needed..nitromethane burns much slower than methanol so adding head shims wont degrade squish effect. most boaters in the pre 15 percent nitro days often used the standard head with shims and ran 30-45 percent nitro with excellent results

  5. #55
    speedracerntrixie's Avatar
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    RE: Rossi .81 FIRE


    ORIGINAL: Yak13

    I tuned the pipe. I will try a bigger carb but I dont totally dislike the 13.9K. It is a heavy prop, the YS can only turn it 11.75K.

    Do you think I can get more out of it?



    13.9K is a good number but with some more pipe length and a larger carb I think you can get that same number with a larger prop. I frequantly race airplanes that run in the 160-170 MPH range that are only turning 10-10.5K. Then again it is with an APC 13X13. Still I see no reason wht you wouldnt be able to spin an 11X13 in the 13K range with some more tuning.


  6. #56

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    RE: Rossi .81 FIRE

    OK, the OS 7D is set up un the .81. Tomorrow we'll see about the larger carb theory. I hope we get some decent rpm's with this setup.

    Will let you know!

    Thanks for all the great advice.

    Ed

  7. #57
    speedracerntrixie's Avatar
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    RE: Rossi .81 FIRE

    Very interested is seeing the results. Do you have a prop that would be more load as well? Maybe a 12X12. I think adding about 5" to the header and the larger prop woud net the same RPM but an overall higher top speed.

  8. #58

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    RE: Rossi .81 FIRE

    I will test the 10x12 and also have a 11x11, 11x12 and even a 11x14. But I think 11" is an overkill (and waste) for the small airframe. The numbers will be interesting anyway to understand this unique engine.

  9. #59
    speedracerntrixie's Avatar
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    RE: Rossi .81 FIRE

    Yes depending on the airframe 11" may be too much dia. Our requirements are a bit different I beleive. My airplanes being pylon racers that have to do 180 degree tuns at about a 30 ft radius need to have some pulling power to them. I can get more strait line speed by reducing dia but it gets lost in the turns and takes too long to get the engine back on step. I would be interested in seeing pictures of your airplane. I think your Rossi has the potential to spin the 11X12 but for your needs a 10X13 may be better. Did you measure the port timing on the 81? I'm still wondering if it has the same timing as the DF engine or pattern engine? Take a look inside the exhaust, is there about .070 of the liner visible at the top of the port? Not really a conclusive test but a good indicator.

  10. #60

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    RE: Rossi .81 FIRE

    Wow! what a great flying day!
    The Rossi effectively increased rpm's with the 7D carb. Using the same 10x12 prop it went up from 13,900 to 14,800. This is a great number, but I'm thinking it can still improve with a 10.5mm carb. Remember the YS60 piped only moved this prop at 11,750.

    I will measure the timing when I have a chance, but I'm almost certain that this is a pattern engine. It behaves really well at low end and transition.

  11. #61
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    RE: Rossi .81 FIRE

    Keep an eye open on Ebay for carbs. I see 12mm Picco and OPS marine carbs come up fairly often. They all have a 16mm bottom throat and will fit the Rossi. I have a Picco on mine and it works really well. I still think you could raise the exhaust port .030 to .040 and run a longer header. You would be amazed how much prop you can get it to spin. There was a reason I wanted to get that engine from you LOL

  12. #62

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    RE: Rossi .81 FIRE

    I flew the Weston uk magnum with a OS 91 df motor .It flew ONCE ith that motor . Its intended for a 55 high rpm motor . I used a 10x10 prop When I launched it it was like firing a arrow out of a cross bow.  When I looked down for a slit second to find the trims and looked back up  It was a tiny dot in the sky out of orientable sight.  All I could see was a tiny yellow dot crashing in the distance.  A few days later a tree farmer brought it bck to our club.  His farm was 8 miles away.  It went that far is not much more then a few hart beats. Im garenteeing it was faster then 200 mph  Whatever speed it was it was un flyable by the human computer brain.  Even for me who is used to fast pylon racers.  sick speeds It would have been a record holder if it wasn't TO fast for the brain.

  13. #63
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    RE: Rossi .81 FIRE

    A Magnum with .91 eh...that's daring, to say the least!

    Never ever look away...never! I learned that one when I was a teenager. I found it back though before it was too late.

    If you don't feel comfortable trimming it yourself, then have your launcher beside you adjust the trims.

    I guess a Magnum on that combo should come close too 200...since you basically have a flying engine...
    Revver Brother #33
    ...I think it needs more power...

  14. #64
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    RE: Rossi .81 FIRE


    ORIGINAL: gromuluss

    I flew the Weston uk magnum with a OS 91 df motor .It flew ONCE ith that motor . Its intended for a 55 high rpm motor . I used a 10x10 prop When I launched it it was like firing a arrow out of a cross bow.Â* When I looked down for a slit second to find the trims and looked back upÂ* It was a tiny dot in the sky out of orientable sight.Â* All I could see was a tiny yellow dot crashing in the distance.Â* A few days later a tree farmer brought it bck to our club.Â* His farm was 8 miles away.Â* It went that far is not much more then a few hart beats. Im garenteeing it was faster then 200 mphÂ* Whatever speed it was it was un flyable by the human computer brain.Â* Even for me who is used to fast pylon racers.Â* sick speeds It would have been a record holder if it wasn't TO fast for the brain.
    An experienced speedplane flyer never looks down to trim his plane.
    Never.
    WHO GUNNA FEED MAW KEEEIDS..???


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