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Thread: Fast Fred's Secrets of the OMC MOD50's Thread #1

  1. #31
    FFX-61
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    Thumbs up

    was thinkin along the lines of a longer conrod, a trick piston,(same jug and crank) and two 7or 8mm carbs, on that pipe. top end would be similer, but the low and mid pull would go way up.
    good stuff

  2. #32
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    Smile dyno charts

    Unless the rules for measuing horspower have changed the first chart is in error. Horse power is a function of torque and rpm and the accepted formula is torque(in foot pounds) multiplied by RPM divided by the constant 5252. So go anywhere on the dyno chart torque curve and use this formula and you will see the HP numbers are incorrect. It is not possible to have more torque than horsepower above 5252rpm. In practical terms, the reason horsepower falls off at higher rpms is the declining ability of the engine to process air and therefore torque. If the torque was able to remain constant from its peak figure to an infinite rpm level the horsepower would also rise to an infinite level. An engine making 10ft lbs of torque at 5252 also makes 10HP at that rpm but at 25000rpm it would produce a healthy 47.6HP with that same small 10 FT lbs of torque. Until the advent of "powervalves"in high performance two stroke racing engines (which alters the exhaustport timing) most racing two strokes had a very narrow or "pipey" power delivery indeed waiting for all of the sonic pulsation to come together at a precise moment to get a cylinder full of something that will actually make pressure.
    This not a criticism of the person starting this thread in any way and I hope it may help someone who dosn't know how any of this suff works have a little better understanding. You feel torque in the seat of your pants! horsepower is but a function of that and rpm and is a way of measuring how much "work" is being done.

    sasbenson

  3. #33
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    Steve you would be correct if the first diagram was typical, but it is not.

    The charts are both correct, but the torque scale is not the same on each ... and the first one is certainly not typical with its non 1:1 ratio shown between torque & hp. Look at the torque number scale on the right - not the same as the hp scale on the left.

    That was probably done to clarify the chart where the lines ran concurrently. But it would probably have been better just to make sure an easy to read line fell on top of a heavier bold line instead of changing one scale, changing the ratio between the lines and making it weird to read
    Since 1925, about 150 different racing outboards have been made.


  4. #34
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    torque starts losein out hard at about 5grand, just like you said, but looks like
    it's pullin on nitro compaired to hp on the chart, that what ya mean?

  5. #35
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    OK, important news..."tooling and rights to the three-cylinder OMC Formula 3 race engines which had been built and distributed by Vander Velden since the late 1980s. Those engines and associated gear cases and center sections will be evaluated for production."thats this Moda, the FR-31M the last OMC genaration.

  6. #36
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    Ok then, wanted to talk about pistons and rods in the Mod50's and how it works hear we got a stocker piston and right next to it we got a Mod50 one ringer ( both factory made pistons), the diamiter and the hight are the same But the wrist pin location is closer to the crown in the one ring
    mod50 bullet , this is key to let the long rod run

  7. #37
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    hear we see both pistons and rod combos, thare overall hights are the same.


    crown stroke is the sameya it makes it biger,but what 's really important
    is the piston stays at T and B, DC longer ( thats ware the long stroke gos)
    which makes More torque.

  8. #38
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    then the next generation was called the "straight in"


  9. #39
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    Special die cast blocks were made by using inserts to form the ports. These inserts were later machined out and sleeves pressed in place.

  10. #40
    Sam Cullis Mark75H's Avatar
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    Does the straight in front use V-8 reed blocks?
    Since 1925, about 150 different racing outboards have been made.


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