[EFI] Re: Building a Flow bench

[Daniel Houlton]

Greg Hermann wrote:
> 
> At 2:32 PM 1/31/02, Eric Fahlgren wrote:
> >pressure ratio at which this flow occurs.  The leaf blower specs
> >are for free air on both sides of the turbine, which is probably
> >a pressure ratio of 1.2:1 or something really low.  When you
> >go to put it on a flow bench you want (iirc from a previous
> >post on this thread) about 25 in/Hg, or about 17 kPa absolute,
> >giving a pressure ratio across the turbine of about 6:1 or
> >higher; it just ain't gonna happen.
> 
> It was 25 or 28 inches of H2O, not Hg, but _BINGO_. Not gonna happen with
> any standard fan or blower wheel !!
> 

Ok, I know I must be missing something fundamental on how
a flow bench works, but...

If it's 25 in/Hg you need, that's around 12.5 psi/1.8:1
pressure ratio.

If it's 25 in/water, that's absurdly less, less than 1 psi.  

If you're flowing a head that typically has engine vacuum
inside, and atmospheric pressure outside, why is 25 in/water
even remotely enough pressure.  And if it is enough, why is 
is so hard for a leaf blower to do?  It is, after all, less
than 1 psi.


--Dan
houlster at inficad.com

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