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  1. #1
    BOOSTED's Avatar
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    Question stg III SC how much boost??

    How much boost does the Riva Stg III SC push with the stock ECU???

    and what about the RR high boost?


  2. #2
    Site Admin Green Hulk's Avatar
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    Boost figures are misleading, its volume of air that is most important. Even so, the RR makes 9+ at 8100 and the Riva will make 10+, but move a greater volume of air.

  3. #3

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    The performance difference is not noticable at 8100.

  4. #4
    Site Admin Green Hulk's Avatar
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    It was for me

  5. #5
    BOOSTED's Avatar
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    thx for the info jerry

  6. #6
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    Thumbs up

    Quote Originally Posted by jawz View Post
    The performance difference is not noticable at 8100.
    Wanna bet. Its noticeable below that.

  7. #7
    cyoungesq's Avatar
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    s/c boost & volume

    Proving my ignorance, I gotta know anyway . . . isn't boost & volume directly related in the context of our superchargers? I understand you can have 10 lb boost in a straw or 10 lb. boost in a tube and the tube will move more volume than the straw. BUT, with our engines, isn't the size of the "tube" a constant? The diameter of the hose/pipe from the supercharger to the intake manifold is the same/universal, no?

  8. #8
    Vern's Avatar
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    'Boost' only measures back pressure, both from the compression of air (desirable) but also due to the expansion of air due to heating of the air (byproduct of compression and bad). So if a supercharger is spun beyond its 'efficiency window' the gauge might register 'more boost' but the dyno may show LESS horsepower since the supercharger is not effectively compressing air, but simply heating it up, making it LESS dense (less HP) rather than more dense. A good supercharger, sized correctly to the engine and operated within the right rpms will pressurize air in the intake and not generate excessive heat; a supercharger that is too small and spun faster than optimal might register higher boost, but way less HP.

    There is far more to it, including that high boost might (even with a good supercharger) only indicate poor flowing heads and cam. Two V8 motors with the exact same supercharger and carburetor, one with great heads and cam, one with stock head and cam - the stock-headed motor will show more boost (due to restrictive heads and cam), but much less HP than the one with great heads and cam.

    Way oversimplified, but boost is not necessarily a great indicator of much other than backpressure. Then there are the different type of superchargers and how they work too ...

  9. #9

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    This takes me back to my fun days modifying turbo cars. Comprehending the different performance factors of a turbo/supercharger takes some research. The previous post does a good job. Once you get close to the max efficiency point of the charger a good IC will allow you to push the limit a bit.

  10. #10
    Quote Originally Posted by Vern View Post
    'Boost' only measures back pressure, both from the compression of air (desirable) but also due to the expansion of air due to heating of the air (byproduct of compression and bad). So if a supercharger is spun beyond its 'efficiency window' the gauge might register 'more boost' but the dyno may show LESS horsepower since the supercharger is not effectively compressing air, but simply heating it up, making it LESS dense (less HP) rather than more dense. A good supercharger, sized correctly to the engine and operated within the right rpms will pressurize air in the intake and not generate excessive heat; a supercharger that is too small and spun faster than optimal might register higher boost, but way less HP.

    There is far more to it, including that high boost might (even with a good supercharger) only indicate poor flowing heads and cam. Two V8 motors with the exact same supercharger and carburetor, one with great heads and cam, one with stock head and cam - the stock-headed motor will show more boost (due to restrictive heads and cam), but much less HP than the one with great heads and cam.

    Way oversimplified, but boost is not necessarily a great indicator of much other than backpressure. Then there are the different type of superchargers and how they work too ...
    Yep but if the air is hotter than it is not as dense it would be less HP and less boost.I talked to my freind that builds Turbo's and he said there would be very little change by the effinciency in your boost pressure if it is filling the same volume.That said every little bit does count.

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