Building a Flow bench, was: Measuring air flow

[The Dupuis]

I'm not sure he's looking for WOT calibration, instead relying on the finer
accuracy of the area most of us drive in.  However, this puts another piece
into a puzzle for me:  I'd like to build a flow bench but I've never seen
one in the flesh.  I had it all figured out except for two things - the fans
and the flow measuring device.  The flow measuring device could be as simple
as a known orifice and a manometer, but a discarded AFM might work too.
Assuming these can flow 200 or 250 hp worth of air, that will be TONS more
than I plan on measuring through each intake/exhaust port.

I've got two residential furnace fans with motors kicking around - I don't
know how much air they flow or how much water column they'll produce, but my
3 month old furnace filter gets pretty handily sucked against the side of
the housing...  Aftermarket standard to flow bench testing is 28" h20, or 1
psi.  Manufacturer's is 25", and lots of smaller shops use 10".  There are
charts to compare flow rates from 10" to 28" depressions, but since I'll be
looking at a similar port over and over again, what it ACTUALLY flows by
aftermarket standards is of little importance to me, so long as it flows
better than it did.

The bench will be designed for vacuum, not pressure, and I guess that's okay
with some creative mounting and measuring tactics.  There is a commercially
available measuring device that uses a shop-vac as it's vacuum source, and
it measures the observed airflow versus the observed depression and
calculates the airflow at 28" - it's $600 USD.  One day at the porter's
table might cost that much.  If anyone has any suggestions, I'd love to hear
them.  Also, Bruce mentioned that the values for LT MAF sensor were in the
archives - the only archives I can find are the monthly discussions and I'm
loathe to look through THERE.  Anyone have somewhere they can point me?

Thanks.
Matt

> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Eric Fahlgren
> Sent: January 24, 2002 3:22 PM
> To: diy_efi at diy-efi.org
> Subject: Re: Measuring air flow
>
>
> Greg Hermann wrote:
> >
> > At 11:39 AM 1/24/02, Greg S Larson wrote:
> > >He said per hour
> > >
> > >On Thu, 24 Jan 2002 07:30:32 -0500 Eric Fahlgren <efahl at adams.com>
> > >writes:
> > >> 944Technologist wrote:
> > >> >
> > >> > I am looking for a bench setup capable of measuring air flow of up
> > >> to 500
> > >> > m"/hr accurately. Within 1% anyway. Use will be calibration check
> > >> of AFMs.
> > >> > What kind of gauges are out there that won't cost an arm and leg.
> > >>
> > >> Do you have your units right?  500 m^3 is over 17,000 cfm (good
> > >> for roughly 12,000 HP).
> >
> > Mind your units, Eric !! :-)
> >
> > That was 500 M^3/_HOUR_--or about 293 cfm !!
>
> Ah, that's better.  Now I think it's not big enough. :)
>
> --
> Eric Fahlgren
> Mechanical Dynamics, Inc
> efahl at adams.com                                         Ann
> Arbor, Michigan, USA
>
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