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  1. #1

    Boost Pressure and Engine RPM

    I see a lot of questions like "How much boost will I get if I use XXXX Blower"

    Here is the boost I get with a good cold air intake, Fizzle intercooler and a stock X blower. All numbers are at near full throttle.

    __RPM_____Max Boost
    2000 RPM - Close to none
    3500 RPM - 1.3 LBS Boost
    4500 RPM - 2.3 LBS Boost
    5500 RPM - 4.1 LBS Boost
    6500 RPM - 6.1 LBS Boost
    7500 RPM - 8.5 LBS Boost
    8500 RPM - 11.8 LBS Boost

    As you can see, Max boost is very dependent on the RPM of the motor with a Seadoo style blower. When you go to a different size blower, the curve simply shifts up a little. How fast do you want to spin the motor and how much boost do you want at that RPM?

    Have fun tuning

    Andy
    Last edited by whittlebeast; 06-02-2015 at 02:59 PM.


  2. #2
    imp0ster's Avatar
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    nuh uhh. I see 1psi @ 6K.

    Those are turbo numbers

  3. #3
    I am talking Max possible boost at each RPM when at full throttle. I bet you are thinking the boost that you see at 6000 RPM when holding a constant speed like riding up the river. The numbers I am quoting all happen in 1/10s of a sec as the motor sweeps very fast thru this part of the map.

    I am talking about the areas near red line and in the green circle in this plot. I bet you are thinking about what happens in the blue box.

    http://www.nbs-stl.com/CMD/AreaOfMapControl.PNG

    Andy
    Last edited by whittlebeast; 06-02-2015 at 04:13 PM.

  4. #4
    This happens to be data off a bigger blower but the effect is the same. WOT boost climbs with RPM.

    http://www.nbs-stl.com/RxpxTuning/TypCCRacePlot_WOT.png

    On the left plot, throttle position is shown. WOT is shown in red. The right plot shows AFR in color.

    Andy
    Last edited by whittlebeast; 06-02-2015 at 04:14 PM.

  5. #5

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    Quote Originally Posted by imp0ster View Post
    nuh uhh. I see 1psi @ 6K.

    Those are turbo numbers

    If they are its a reallllllllllllllllllllly big one with a wastegate set higher than it make boost or shit control...

    Your names not Noel is it??

  6. #6
    Boost addict hotbird's Avatar
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    Quote Originally Posted by Spanners View Post
    Quote Originally Posted by imp0ster View Post
    nuh uhh. I see 1psi @ 6K.

    Those are turbo numbers

    If they are its a reallllllllllllllllllllly big one with a wastegate set higher than it make boost or shit control...

    Your names not Noel is it??
    Maybe with a aftermarket ecu running launch control.

  7. #7
    Here is what a turbo plot looks like. Notice how things are far less "clear"

    http://www.nbs-stl.com/RxpxTuning/TurboScatterPlots.png

    Note that this motor is holding 19.5 PSI at 8525 RPM accelerating hard in smooth water. The rider did not top out the speed on the log I had.

    Andy
    Last edited by whittlebeast; 06-02-2015 at 04:14 PM.

  8. #8
    hkss's Avatar
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    8500 RPM - 11.8 LBS Boost - that is not so much, than I had to expect.
    I see some threats discussing about stock fuel pressure and injektors....
    With 11,8 LBS boost at may (in my case) it seems not so (very) bad with stock fuel pump and vt1100.
    Thanks for this post Andy!

  9. #9
    imp0ster's Avatar
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    hmmmm I'ma have to go replicate this and break something on my ski now

  10. #10
    Here is a little pair of screen shots as to why the high speed guys love these turbo motors but the closed course guys find them a little difficult to race. Hang with me on this one....

    Closed course guys need total control of the power as everything around them is trying to kill them. Jet wash from the guy they are trying to pass, rough water, or simply trying to get the motor to pull off a corner and still hang on. They like very predictable power based on where their finger is.

    Keep in mind that the throttle is the drivers request of power and MAPxRPM is essentially power. Here is a very common CC pattern.

    http://www.nbs-stl.com/RxpxTuning/Th...owerBlower.png

    Any given finger position for the most part gives a Power Delivery

    Now look at the turbo motor, everything below about 25% throttle looks fairly predictable but above 25% throttle, all hell breaks loose. Where your finger is has very little to how much power the motor is making.

    http://www.nbs-stl.com/RxpxTuning/Th...PowerTurbo.png

    Have fun tuning

    Andy

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