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  1. #1

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    Rossi 45 Engine performance tuning

    Hi all

    Recently i bought a Rossi 45 Engine from USA, i try to tune the engineer to reach it peak RPM which is the factory specification at 19000RPM with 11*6. i test data is below

    Byron 10 % Castro and synthetic mixed with R4 Rossi Grow Plug

    Marc Pipe @ 10*6 = 16400RPM = provide the best result with thrust and speed
    Marc Pipe @ 10*7 = 15500RPM = Lesser speed and thrust.
    Marc Pipe @ 8.8*8.75 = 17800RPM = Poor Speed and thrust, engine just scream like hell
    Jett Speed Muffler @ 10*6 = 15800RPM
    Jett Speed Muffler @ 10*7 = 14500RPM
    Jett Speed Muffler @ 8.8*8.75 = 16800RPM = Poor Speed and thrust, engine just scream like hell

    no matter how i tune and adjust the length or change the prop to smaller size. the RPM just cant reach t 1800 and above, any one who have experience on this engineer please share you experience with me about what is the best combination setting for this engineer to get the top performance.

  2. #2
    speedracerntrixie's Avatar
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    RE: Rossi 45 Engine performance tuning

    Not sure what version you have but I have been using a Rossi .45 VP that I got from SG Model Engines. The VP version has had some smoothing of intake ports and some work done on the crankshaft and comes equipped with a 10mm carb. First off, you will never get 19,000 rpms out of this engine. Even if you did you will be well past the power band. I don't know why engine manufacturers state these very high rpm ratings as they just don't mean anything. Maybe it's that the engine is capable of running that rpm without failure. You posted this in the Q500 forum so I am going to assume you are putting it on a Q500. My warbird racer is close to the same weight and drag as a Q500 so my setup should work out well for you or at least get you in the ball park. For a prop I have found the APC sport 9X7 to work well. The 9.5X7N pylon prop works well too and may work even better for you due to a slightly cleaner airplane. I use the Nelson Ultra Thrust muffler with 15% fuel and either an OS#8 or K&B 1L plug. 15%is a little high nitro content for a Rossi so if you find yourself blowing plugs, you are too lean or need to add another head gasket.


    This is where I step out of the box. I can't tell you RPM figures as I don't beleive in using a tach. The reason for this is I have seen too many people doing exactly what you are doing and that is going for as much RPM as possible thinking this is going to lead you to more speed. You need to prop an engine to get an RPM within the engines power band while unloaded ( In flight ). This takes some experimentation. For my airplane the 9X7 works the best. A cleaner airplane and you can decrease prop dia and increase pitch where on an airplane with more drag you will want to go bigger dia and less pitch.

  3. #3

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    RE: Rossi 45 Engine performance tuning

    hi speedracerntrixie , i using Rossi .45 VP that I got from SG Model Engines too. i will try to use 9 x 7 and see what is the result, so far 10 x 6 with Marc Pipe is the best i get from this engine but i never try 9 x 7 Prop. by the way what is the difference between Rossi 45 VP and Rossi 45 Speed VP?

  4. #4
    speedracerntrixie's Avatar
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    RE: Rossi 45 Engine performance tuning

    Not really sure what the difference is internally. From the outside other then the blue head, the speed version comes with an 8mm carb wereas the black head comes with a 10mm.

  5. #5

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    RE: Rossi 45 Engine performance tuning

    10mm carb should be better than 8mm carb right?

  6. #6

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    RE: Rossi 45 Engine performance tuning

    Hi!
    Is it possible that you has misinterpreted the text?
    No .45-.46 engine is ever going to rew 19000 rpm with a 11x6 prop. It's more likely they ment a 9x6 APC or a small thin APC pylon racing 8,75x8 prop.
    Jan Karlsson - Supplier MVVS Products

  7. #7

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    RE: Rossi 45 Engine performance tuning

    Hi Jaka

    I don't think i misinterpreted the text, you can read my first post, i did use 8,75x8 but i with Marc Pipe i can make it 18000RPM on the ground. so i suppose to reach nearly 19000RPM unloaded in the air. but the thrush is really bad. so i think what speedracerntrixie mention make sense, the engine is pass the power band. but if anyone who have the combination data to share will be appreciated. i need to know how other people setup this engine such as prop size, pipe type and so on.

    Kelvin Koh

  8. #8

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    RE: Rossi 45 Engine performance tuning

    >Exhaust timing to be lifted above 185 dregees (no sub-piston induction)
    >Add head shim 0.004 thou
    >Change carby to 11mm webra, available from axiengines
    >Dub jett short black version Q500 pylon pipe with adaptor, you must smooth/flow the sharp internal edges to aid exhaust flow, use no gaskets, draw file flat all exhaust mating surfaces, use hightemp red RTV silicon on mating surfaces - just a small bead is suficient
    >K&B 1L plug
    >APC 8.8x8.75 pylon prop
    >Coolpower 20% nitro all synthetic (rossi engines do not like castor - not even 2%)

    = 19K 19.5K rpm or better (depending on how fresh your motor is) on the ground -

  9. #9
    speedracerntrixie's Avatar
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    RE: Rossi 45 Engine performance tuning

    By lifting exaust timing, do you mean raising the top edge via a mill? If yes how much? I was going to do this and start with taking off .015

  10. #10

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    RE: Rossi 45 Engine performance tuning

    Hi scoeroo

    i dont understand this

    "Exhaust timing to be lifted above 185 dregees (no sub-piston induction) "

    kelvin Koh

  11. #11

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    RE: Rossi 45 Engine performance tuning

    First make sure there are no shims under the liner, if there is.... take them out and make sure the liner is ALL the way DOWN,
    Looking thru the exh. port, use a scribe and mark the liner to the highest point and width,
    Remove the liner and useing a dremel, remove material upto the scribed line and to the max width you marked earlier
    This is where a degree wheel is now needed.....time out the exhaust (no 0.004 gasket) and see what you have, you will more than likely have to do more dremeling but this time it must be at an upward angle of aprox 30 degree, do this in small steps to creep up on the timing of 185 dgrees,
    Once at 185 clean all parts thoroughly, now install the 0.004 liner shim,
    This modification i have personely found wakes up a ROSSI with out standing results,
    I have a crappy old viper with a second hand rossi bought from RCU, i have no more than $200-250 in this thing and it will boogie at 160 + mph with good throttle reliability,
    I have many rossi spares that i R&D with to get the most go-go, plus i've been playing with rossi's for over 20 years.

    Hope this helps -


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