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Discussion in 'Normally Aspirated Forum' started by RobT, Mar 3, 2010.
Just read it more thoroughly. Take home messages are:
Optimum length of a bellmouth = exit diameter
Optimum entry daimater = 2.13x exit diameter
corner radius = 0.08x entry diameter
for a 45mm throttle body:
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
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:
someone forgot to pass that on to TVR then it seems - link to lazyness
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
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?
that looks like the TVR coffee cup tray!
now i know why my old F400-4 went slower than with an airbox