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Optimum intake bellmouth shape

Discussion in 'Normally Aspirated Forum' started by RobT, Mar 3, 2010.

  1. RobT

    RobT Full throttle trip

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  2. RobT

    RobT Full throttle trip

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    Just read it more thoroughly. Take home messages are:

    Optimum length of a bellmouth = exit diameter
    Optimum entry daimater = 2.13x exit diameter
    eliptical profile
    corner radius = 0.08x entry diameter

    for a 45mm throttle body:
    exit diameter=45mm
    length of curved section of rampipe=45mm (then it goes into straight pipe)
    front of rampipe diameter=95.85mm
    radius on front of bellmouth=7.66mm

    best design for an eliptical bellmouth had 1.5% more air mass flow than a simple radius'd pipe
    doesn't sound like much, but this is 3hp in 200....worth having

    fully radiused end had next to no effect over a half radius
    rectangular bellmouths are best avoided
     
  3. RobT

    RobT Full throttle trip

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    [​IMG]

    If you dont have a bellmouth on the end of an air intake pipe, the effective size of the pipe is reduced by a narrowing of the air flow called the 'vena contracta' (seen here in the top pic)

    If a bellmouth is fitted, the vena contracta is effectively the same width of the intake pipe = best flow

    This is quite useful also:

    [​IMG]
     
    #3 RobT, Mar 3, 2010
    Last edited: Mar 3, 2010
  4. Fl@pper

    Fl@pper Back older greyer and less oilier but always hope
    Moderator

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    someone forgot to pass that on to TVR then it seems - link to lazyness:whistle:

    my first try just been radiused at 45 degrees so far like this

    might have to go back to plan A and use a block of poly and rethink the curve profile maybe even mill it so the mouths are raised instead of flush mind you wouldn't the plenum volume and flow need to be added into the equation ? no point it racing in at high speed if there's a lack of volume behind it for supply, mind you i'm trying to feed 8 cyl's else - eek


    off for a read - nice link
     
    #4 Fl@pper, Mar 3, 2010
    Last edited: Mar 3, 2010
  5. RobT

    RobT Full throttle trip

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    thats pretty shoddy from TVR.

    45 deg has got to be better than straight pipe surely so good effort. I cannot imagine anything that you do to the bellmouths will greatly affect the plenum volume?
     
  6. old 'uns

    old 'uns Modern Life is Rubbish...

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    that looks like the TVR coffee cup tray!

    now i know why my old F400-4 went slower than with an airbox :redface:
     

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